UFC 3-250-11 16 January 2004

UNIFIED FACILITIES CRITERIA (UFC)

SOIL STABILIZATION FOR

PAVEMENTS

APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED

UFC 3-250-11 16 January 2004

1

UNIFIED FACILITIES CRITERIA (UFC)

SOIL STABILIZATION FOR PAVEMENTS

Any copyrighted material included in this UFC is identified at its point of use. Use of the copyrighted material apart from this UFC must have the permission of the copyright holder. U.S. ARMY CORPS OF ENGINEERS (Preparing Activity) NAVAL FACILITIES ENGINEERING COMMAND AIR FORCE CIVIL ENGINEER SUPPORT AGENCY Record of Changes (changes are indicated by \1\ ... /1/) Change No. Date Location

This UFC supersedes TM 5-822-14, dated 25 October 1994. The format of this UFC does not conform to UFC 1-300-01; however, the format will be adjusted to conform at the next revision. The body of this UFC is the previous TM 5-822-14, dated 25 October 1994.

UFC 3-250-11 16 January 2004

2

FOREWORD \1\ The Unified Facilities Criteria (UFC) system is prescribed by MIL-STD 3007 and provides planning, design, construction, sustainment, restoration, and modernization criteria, and applies to the Military Departments, the Defense Agencies, and the DoD Field Activities in accordance with USD(AT&L) Memorandum dated 29 May 2002. UFC will be used for all DoD projects and work for other customers where appropriate. All construction outside of the United States is also governed by Status of forces Agreements (SOFA), Host Nation Funded Construction Agreements (HNFA), and in some instances, Bilateral Infrastructure Agreements (BIA.) Therefore, the acquisition team must ensure compliance with the more stringent of the UFC, the SOFA, the HNFA, and the BIA, as applicable. UFC are living documents and will be periodically reviewed, updated, and made available to users as part of the Services’ responsibility for providing technical criteria for military construction. Headquarters, U.S. Army Corps of Engineers (HQUSACE), Naval Facilities Engineering Command (NAVFAC), and Air Force Civil Engineer Support Agency (AFCESA) are responsible for administration of the UFC system. Defense agencies should contact the preparing service for document interpretation and improvements. Technical content of UFC is the responsibility of the cognizant DoD working group. Recommended changes with supporting rationale should be sent to the respective service proponent office by the following electronic form: Criteria Change Request (CCR). The form is also accessible from the Internet sites listed below. UFC are effective upon issuance and are distributed only in electronic media from the following source: • Whole Building Design Guide web site http://dod.wbdg.org/. Hard copies of UFC printed from electronic media should be checked against the current electronic version prior to use to ensure that they are current. AUTHORIZED BY: ______________________________________ DONALD L. BASHAM, P.E. Chief, Engineering and Construction U.S. Army Corps of Engineers

______________________________________DR. JAMES W WRIGHT, P.E. Chief Engineer Naval Facilities Engineering Command

______________________________________ KATHLEEN I. FERGUSON, P.E. The Deputy Civil Engineer DCS/Installations & Logistics Department of the Air Force

______________________________________Dr. GET W. MOY, P.E. Director, Installations Requirements and Management Office of the Deputy Under Secretary of Defense (Installations and Environment)

ARMY TM 5-822-14AIR FORCE AFJMAN 32-1019

SOIL STABILIZATION FOR PAVEMENTS

APPROVED FOR PUBLIC RELEASE; DISTRIBUTION IS UNLIMITED

DEPARTMENT OF THE ARMY, THE NAVY, AND THE AIR FORCEOCTOBER 1994

TM 5-822-14/AFJMAN 32-1019

REPRODUCTION AUTHORIZATION/RESTRICTIONS

This manual has been prepared by or for the Government and, exceptto the extent indicated below, is public property and not subject tocopyright.

Copyrighted material included in the manual has been used with theknowledge and permission of the proprietors and is acknowledged assuch at point of use. Anyone wishing to make further use of anycopyrighted material, by itself and apart from this text, should seeknecessary permission directly from the proprietors.

Reprints or republications of this manual should include a creditsubstantially as follows: “‘Joint Departments of the Army and AirForce, USA, TM 5-822-14/AFMAN 32-8010, Soil Stabilization forPavements,” 25 October 1994.

If the reprint or republication includes copyrighted material, thecredit should also state: ‘Anyone wishing to make further use ofcopyrighted material, by itself and apart from this text, should seeknecessary permission directly from the proprietors.”

i

ATM 5-822-14/AFJMAN 32-1019

TECHNICAL MANUAL HEADQUARTERSNO. 5-822-14 DEPARTMENTS OF THE ARMY,AIR FORCE MANUAL AND THE AIR FORCENO. 32-1019 WASHINGTON, DC, 25 October 1994

SOIL STABILIZATION FOR PAVEMENTSParagraph Page

CHAPTER 1. INTRODUCTIONPurpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1 1-1Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2 1-1References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3 1-1Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4 1-1Uses of Stabilization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5 1-1

CHAPTER 2. SELECTION OF ADDITIVEFactors to be Considered . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1 2-1Use of Stabilized Soils in Forst Areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2 2-2Thickness Reduction for Base and Subbase Courses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3 2-4

CHAPTER 3. DETERMINATION OF STABILIZER CONTENTStabilization with Portland Cement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1 3-1Stabilization with Lime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2 3-3Stabilization with Lime-Fly Ash (LF) and Lime Centment-Fly Ash (LCF) . . . . . . . . . . . . . . . . . . 3-3 3-5Stabilization with Bitumen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4 3-6Stabilization with Lime-Cement and Lime-Bitumen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5 3-8Lime Treatemt of Expansive Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6 3-8

CHAPTER 4. DETERMINATION OF STABILIZER CONTENTConstruction with Portland Cement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1 4-1Construction with Lime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2 4-10Construction with Lime-Fly Ash (LF) and Lime-Cement-Fly Ash (LCF) . . . . . . . . . . . . . . . . . . . 4-3 4-20Construction with Bitumen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4 4-20

CHAPTER 5. QUALITY CONTROLGeneral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1 5-1Cement Stabilization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2 5-1Lime Stabilization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3 5-1Lime-Fly Ash (LF) and Lime-Cement-Fly Ash (LCF) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4 5-2Bituminous Stabilization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5 5-2

APPENDIX A. REFERENCES A-1

APPENDIX B. pH TEST ON SOIL-CEMENT MIXTURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-1

APPENDIX C. DETERMINATION OF SULFATE IN SOILS, GRAVIMETRIC METHOD . . . . . . . . . . . . . . . C-1

APPENDIX D. pH TEST TO DETERMINE LIME REQUIREMENTS FOR LIME STABILIZATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-1

List of Figures

Figure 2-1. Gradation triangle for aid in selecting a commercial stabilizing agent. 2-23-1. Chart for the initial determination of lime content. 3-44-1. Transverse single-shaft mixer processing soil cement in place. Multiple passes are required. 4-24-2. Multiple-transverse-shaft mixer mixing soil, cement, and water in one pass. 4-24-3. Windrow-type traveling pugmill mixing soil-cement from windrows of soil material. 4-24-4. Twin-shaft, continuous-flow central mixing plant mixing soil, cement, and water. 4-24-5. Batch-type central plant used for mixing soil-cement. 4-24-6. Rotary-drum central mixing plant. 4-24-7. Bulk portland cement being transferred pneumatically from a bulk transport truck to a job

truck. 4-34-8. Mechanical cement spreader attached to a job dump truck spreading cement in regulated

quantities. 4-34-9. Windrow-type mechanical spreader is used to place cement on the top of a slightly flattened

windrow of borrow soil material. 4-34-10. Sketch of soil-cement processing operations with windrow-type traveling pugmill. 4-54-11. Plan for processing with windrow-type traveling pugmill. 4-6

APPROVED FOR PUBLIC RELEASE; DISTRIBUTION IS UNLIMITED

TM 5-822-14/AFJMAN 32-1019

ii

List of Figures (cont*d)Page

Figure 4-12. Sketch of soil-cement processing operations with multiple-transverse-shaft traveling mixing machine. 4-6

4-13. Plan for processing with multiple-transverse-shaft traveling mixing machine. 4-74-14. Sketch of soil-cement processing operations with single-transverse shaft mixers. 4-84-15. In-place mixing of lime with existing base and paving material on city street. 4-114-16. Off-site mixing pads for Mississippi River levee repair project. 4-114-17. Deep stabilization after lime spreading the plow cuts 24 inches deep. 4-114-18. Root plow for scarifying to a depth of 18 inches. 4-114-19. Scarifying existing clay subgrade with lime on city street project. 4-114-20. Lime-treated gravel with lime fed by screw conveyor. 4-124-21. Lime-cement-fly ash aggregate base course. 4-124-22. Enclosed soil holds lime for adding to marginal crushed stone base material. 4-124-23. Lime slurry pressure injection (LSPI) rig treating a failed highway slope. 4-124-24. Application of lime by the bag for a small maintenance project. 4-134-25. Application of lime by a bulk pneumatic truck. 4-134-26. Bulk pneumatic truck spreading lime from bar spreader. 4-134-27. Distribution of quicklime from mechanical spreader on city street. 4-134-28. Spreading of granular quicklime. 4-154-29. Slurry mixing tank using recirculating pump for mixing hydrate and water. 4-164-30. Jet slurry mixing plant. 4-164-31. Spreading of lime slurry. 4-164-32. Recirculation pump on top of a 6,000-gallon wagon agitates slurry. 4-164-33. Grader-scarifier cutting slurry into stone base. 4-164-34. Portabatch lime slaker. 4-164-35. Watering of lime-treated clay on airport project. 4-184-36. Mixing with a disc harrow. 4-184-37. Rotary mixer. 4-184-38. Train of rotary mixers. 4-184-39. Rotary mixer on primary road project. 4-184-40. Self-propelled sheepsfoot roller. 4-194-41. Double sheepsfoot roller. 4-194-42. Pneumatic roller completes compaction of LCF base. 4-204-43. Vibrating roller completes compaction of subgrade. 4-204-44. Windrow-type pugmill travel plant. 4-214-45. Hopper-type pugmill travel plant. 4-214-46. Multiple rotary mixer. 4-214-47. A processing chamber of a multiple rotary mixer. 4-214-48. Single-shaft rotary mixer with asphalt supply tank. 4-224-49. Single-shaft rotary mixer without asphalt. 4-224-50. Mixing with motor grader. 4-224-51. Distributor applying asphalt. 4-224-52. Spreading and compacting train. 4-254-53. Stationary cold-mix plant. 4-264-54. Flow diagram of a typical cold-mix continuous plant. 4-264-55. Spreading cold mix with conventional paver. 4-264-56. Spreading cold mix with full-width cutter-trimmer modified for paving. 4-264-57. Jersey spreader. 4-274-58. Towed-type spreader. 4-27C-1. Example standard curve for spectrophotometer. C-3

List of Tables

Table 2-1. Guide for selecting a stabilizing additive. 2-32-2. Minimum unconfined compressive strength for cement, lime, lime-cement, and lime-cement-

fly ash stabilized soils. 2-42-3. Durability requirements. 2-43-1. Gradation requirements for cement stabilized base and subbase courses. 3-13-2. Cement requirements for various soils. 3-23-3. Gradation requirements for lime stabilized base and subbase courses. 3-33-4. Gradation requirements for fly ash stabilzed base and subbase courses. 3-53-5. Recommended gradations for bituminous stabilized subgrade materials. 3-73-6. Recommended gradations for bituminous stabilized base and subbase materials. 3-73-7. Emulsified asphalt requirements. 3-83-8. Swell potential of soils. 3-9

TM 5-822-14/AFJMAN 32-1019

CHAPTER 1

INTRODUCTION

1-1. Purpose. This manual establishes criteriafor improving the engineering properties of soilsused for pavement base courses, subbase courses,and subgrades by the use of additives which aremixed into the soil to effect the desired im-provement. These criteria are also applicable toroads and airfields having a stabilized surfacelayer.

1-2. Scope. This manual prescribes the appropri-ate type or types of additive to be used withdifferent soil types, procedures for determining adesign treatment level for each type of additive,and recommended construction practices for incor-porating the additive into the soil. It applies to allelements responsible for Army and Air Forcepavement and design construction.

1-3. References. Appendix A contains a list ofreferences used in this manual.

1-4. Definitions.a. Soils. Naturally occurring materials that are

used for the construction of all except the surfacelayers of pavements (i.e., concrete and asphalt) andthat are subject to classification tests (ASTM D2487) to provide a general concept of their engi-neering characteristics.

b. Additives. Manufactured commercial productsthat, when added to the soil in the proper quanti-ties, improve some engineering characteristics ofthe soil such as strength, texture, workability, andplasticity. Additives addressed in this manual arelimited to portland cement, lime, flyash, and bitu-men.

c. Stabilization. Stabilization is the process ofblending and mixing materials with a soil toimprove certain properties of the soil. The processmay include the blending of soils to achieve adesired gradation or the mixing of commerciallyavailable additives that may alter the gradation,texture or plasticity, or act as a binder for cemen-tation of the soil.

d. Mechanical stabilization. Mechanical stabili-zation is accomplished by mixing or blending soilsof two or more gradations to obtain a materialmeeting the required specification. The soil blend-ing may take place at the construction site, acentral plant, or a borrow area. The blendedmaterial is then spread and compacted to requireddensities by conventional means.

e. Additive stabilization. Additive stabilizationis achieved by the addition of proper percentagesof cement, lime, fly ash, bitumen, or combinationsof these materials to the soil. The selection of typeand determination of the percentage of additive tobe used is dependent upon the soil classificationand the degree of improvement in soil qualitydesired. Generally, smaller amounts of additivesare required when it is simply desired to modifysoil properties such as gradation, workability, andplasticity. When it is desired to improve thestrength and durability significantly, larger quan-tities of additive are used. After the additive hasbeen mixed with the soil, spreading and compac-tion are achieved by conventional means.

f. Modification. Modification refers to the stabi-lization process that results in improvement insome property of the soil but does not by designresult in a significant increase in soil strength anddurability.

1-5. Uses of Stabilization. Pavement design isbased on the premise that minimum specifiedstructural quality will be achieved for each layerof material in the pavement system. Each layermust resist shearing, avoid excessive deflectionsthat cause fatigue cracking within the layer or inoverlying layers, and prevent excessive permanentdeformation through densification. As the qualityof a soil layer is increased, the ability of that layerto distribute the load over a greater area isgenerally increased so that a reduction in therequired thickness of the soil and surface layersmay be permitted.

a. Quality improvement. The most common im-provements achieved through stabilization includebetter soil gradation, reduction of plasticity in-dex or swelling potential, and increases in durabil-ity and strength. In wet weather, stabilizationmay also be used to provide a working platformfor construction operations. These types of soilquality improvement are referred to as soil modifi-cation.

b. Thickness reduction. The strength and stiff-ness of a soil layer can be improved through theuse of additives to permit a reduction in designthickness of the stabilized material compared withan unstabilized or unbound material. Proceduresfor designing pavements that include stabilizedsoils are presented in TM 5-822-5/AFM 88-7,Chap. 3, TM 5-825-2/AFM 88-6, Chap. 2, TM

1-1

TM 5-822-14/AFJMAN 32-1019

5-825-3/AFM 88-6, Chap. 3. The design thickness strength, stability, and durability requirementsof a base or subbase course can be reduced if the indicated in this Technical Manual for the particu-stabilized material meets the specified gradation, lar type of material.

1-2

TM 5-822-14/AFJMAN 32-1019

CHAPTER 2

SELECTION OF ADDITIVE

2-1. Factors to be Considered. In the selectionof a stabilizer, the factors that must be consideredare the type of soil to be stabilized, the purpose forwhich the stabilized layer will be used, the type ofsoil improvement desired, the required strengthand durability of the stabilized layer, and the costand environmental conditions.

a. Soil types and additives. There may be morethan one candidate stabilizer applicable for onesoil type, however, there are some general guide-lines that make specific stabilizers more desirablebased on soil granularity, plasticity, or texture.Portland cement for example is used with a vari-ety of soil types; however, since it is imperativethat the cement be mixed intimately with thefines fraction (< .074 mm), the more plastic materi-als should be avoided. Generally, well-graded gran-ular materials that possess sufficient fines toproduce a floating aggregate matrix (homogenousmixture) and best suited for portland cement sta-bilization. Lime will react with soils of medium tohigh plasticity to produce decreased plasticity,increased workability, reduced swell, and in-creased strength. Lime is used to stabilize avariety of materials including weak subgrade soils,transforming them into a “working table” orsubbase; and with marginal granular base materi-als, i.e., clay-gravels, “dirty” gravels, to form astrong, high quality base course. Fly ash is apozzolanic material, i.e. it reacts with lime and istherefore almost always used in combination withlime in soils that have little or no plastic fines. Ithas often been found desirable to use a smallamount of portland cement with lime and fly ashfor added strength. This combination of lime-cement-flyash (LCF) has been used successfully inbase course stabilization. Asphalt or bituminousmaterials both are used for waterproofing and forstrength gain. Generally, soils suitable for asphaltstabilization are the silty sandy and granularmaterials since it is desired to thoroughly coat allthe soil particles.

b. Selection of candidate additives. The selectionof candidate/stabilizers is made using figure 2-1and table 2-1. The soil gradation triangle in figure2-1 is based upon the soil grain size characteris-tics and the triangle is divided into areas of soilswith similar grain size and therefore pulverizationcharacteristics. The selection process is continuedwith table 2-1 which indicates for each areashown in figure 2-1 candidate stabilizers and

restrictions based on grain size and/or plasticityindex (PI). Also provided in the second column oftable 2-1 is a listing of soil classification symbolsapplicable to the area determined from figure 2-1.This is an added check to insure that the properarea was selected. Thus, information on grain sizedistribution and Atterberg limits must be knownto initiate the selection process. Data required toenter figure 2-1 are: percent material passing theNo. 200 sieve and percent material passing theNo. 4 sieve but retained on the No. 200 (i.e., totalpercent material between the No. 4 and the No.200 sieves). The triangle is entered with these twovalues and the applicable area (1A, 2A, 3, etc.) isfound at their intersection. The area determinedfrom figure 2-1 is then found in the first columnof table 2-1 and the soil classification is checkedin the second column. Candidate stabilizers foreach area are indicated in third column andrestrictions for the use of each material are pre-sented in the following columns. These restrictionsare used to prevent use of stabilizing agents notapplicable for the particular soil type under consid-eration. For example, assume a soil classified as aSC, with 93 percent passing the No. 4 and 25percent passing the No. 200 with a liquid limit of20 and plastic limit of 11. Thus 68 percent of thematerial is between the No. 4 and No. 200 and theplasticity index is 9. Entering figure 2-1 with thevalues of 25 percent passing the No. 200 and 68percent between the No. 4 and No. 200, theintersection of these values is found in area 1-C.Then going to the first column of table 2-1, wefind area 1-C and verify the soil classification, SC,in the second column. From the third column allfour stabilizing materials are found to be potentialcandidates. The restrictions in the following col-umns are now examined. Bituminous stabilizationis acceptable since the PI does not exceed 10 andthe amount of material passing the No. 200 doesnot exceed 30 percent. However it should be notedthat the soil only barely qualifies under thesecriteria and bituminous stabilization probablywould not be the first choice. The restrictionsunder portland cement indicate that the PI mustbe less that the equation indicated in footnote b.Since the PI, 9, is less than that value, portlandcement would be a candidate material. The restric-tions under lime indicate that the PI not be lessthan 12 therefore lime is not a candidate materialfor stabilization, The restrictions under LCF stabi-

2-1

TM 5-822-14/AFJMAN 32-1019

PERCENT BY WEIGHT, FINES(MATERAIL PASSING NO. 200 SIEVE)

Figure 2-1. Gradation triangle for aid in selecting a commercial stabilizing agent.

lization indicate that the PI must not exceed 25,thus LCF is also a candidate stabilizing material.At this point, the designer must make the finalselection based on other factors such as availabil-ity of material, economics, etc. Once the type ofstabilizing agent to be used is determined, samplesmust be prepared and tested in the laboratory todevelop a design mix meeting minimum engineer-ing criteria for field stabilization.

2-2. Use of stabilized soils in Frost Areas.a. Frost considerations. While bituminous, port-

land cement, lime, and LCF stabilization are themost common additives other stabilizers may beused for pavement construction in areas of frostdesign but only with approval obtained from theHQUSACE (CEMP-ET), Washington, DC 20314-1000 or the appropriate Air Force Major Com-mand.

2 - 2

b. Limitations. In frost areas, stabilized soil isonly used in one of the upper elements of apavement system if cost is justified by the reducedpavement thickness. Treatment with a lower de-gree of additive than that indicated for stabiliza-tion (i.e., soil modification) should be used in frostareas only with caution and after intensive tests,because weakly cemented material usually hasless capacity to endure repeated freezing andthawing than has firmly cemented material. Apossible exception is modification of a soil that willbe encapsulated within an impervious envelope aspart of a membrane-encapsulated-soil-layer pave-ment system. A soil that is unsuitable for encapsu-lation due to excessive moisture migration andthaw weakening may be made suitable for suchuse by moderate amounts of a stabilizing additive.Materials that are modified should also be testedto ascertain that the desired improvement is dura-

TM 5-822-14/AFJMAN 32-1019

Table 2-1. Guide for selecting a stabilizing additive.

ble through repeated freeze-thaw cycles. The im-provement should not be achieved at the expenseof making the soil more susceptible to ice segrega-tion.

c. Construction cutoff dates. Materials stabil-ized with cement, lime, or LCF should be con-structed early enough during the constructionseason to allow the development of adequatestrength before the first freezing cycle begins. Therate of strength gain is substantially lower at 50degrees Fahrenheit than at 70 or 80 degrees

Fahrenheit. Chemical reactions will not occurrapidly for lime-stabilized soils when the soiltemperature is less than 60 degrees Fahrenheitand is not expected to increase for one month, orcement-stabilized soils when the soil temperatureis less than 40 degrees Fahrenheit and is notexpected to increase for one month. In frost areas,it is not always sufficient to protect the mixturefrom freezing during a 7-day curing period asrequired by the applicable guide specifications,and a construction cutoff date well in advance of

2 - 3

TM 5-822-14/AFJMAN 32-1019

the onset of freezing conditions (e.g. 30 days) may lime, LF, and LCF are indicated in tables 2-2be essential. and 2-3, respectively. For bituminous stabilized

2-3. Thickness Reduction for Base and SubbaseCourses. Stabilized base and subbase course mate-rials must meet certain requirements of grada-tion, strength, and durability to qualify for re-duced layer thickness design. Gradation require-ments are presented in the sections covering de-sign with each type of stabilizer. Unconfinedcompressive strength and durability requirementsfor bases and subbases treated with cement,

materials to qualify for reduced thickness, theymust meet strength requirements in TM 5-825-21AFM 88-6, Chap. 2. All stabilized materials ex-cept those treated with bitumen must meet mini-mum durability criteria to be used in pavementstructures. There are no durability criteria forbituminous stabilized materials since it is assumedthat they will be sufficiently waterproof if properlydesigned and constructed.

Table 2-2. Minimum unconfined compressive strength for cement, lime, lime-cement, and lime-cement-fly ash stabilized soils

Minimum Unconfined Compressive strength, psia

Stabilized Soil Layer Flexible pavement Rigid pavement

Base course 750 500Subbase course, select material or subgrade 250 200

a Unconfined compressive strength determined at 7 days for cement stabilization and 28 days for lime, lime fly ash, or lime-cement-flyash stabilization.

Table 2-3. Durability requirements

Type of Soil Stabilized

Granular, PI < 10Granular, PI > 210SiltClays

Maximum Allowable Weight Loss After 12 Wet-Dry orFreeze-Thaw Cycles Percent of Initial Specimen Weight

11886

2 - 4

TM 5-822-14/AFJMAN 32-1019

CHAPTER 3

DETERMINATION OF STABILIZER CONTENT

3-1. Stabilization with Portland Cement. Port-land cement can be used either to modify andimprove the quality of the soil or to transform thesoil into a cemented mass with increased strengthand durability. The amount of cement used willdepend upon whether the soil is to be modified orstabilized.

a. Types of portland cement. Several differenttypes of cement have been used successfully forstabilization of soils. Type I normal portland ce-ment and Type IA air-entraining cements wereused extensively in the past and gave about thesame results. At the present time, Type II cementhas largely replaced Type I cement as greatersulfate resistance is obtained while the cost isoften the same. High early strength cement (TypeIII) has been found to give a higher strength insome soils. Type III cement has a finer particlesize and a different compound composition than dothe other cement types. Chemical and physicalproperty specifications for portland cement can befound in ASTM C 150.

b. Screening tests for organic matter and sul-fates. The presence of organic matter and/or sul-fates may have a deleterious effect on soil cement.Tests are available for detection of these materialsand should be conducted if their presence is sus-pected.

(1) Organic matter. A soil may be acid, neu-tral, or alkaline and still respond well to cementtreatment. Although certain types of organic mat-ter, such as undecomposed vegetation, may notinfluence stabilization adversely, organic com-pounds of lower molecular weight, such as nucleicacid and dextrose, act as hydration retarders andreduce strength. When such organics are presentthey inhibit the normal hardening process. A pHtest to determine the presence of organic material

is presented in appendix B. If the pH of a 10:1mixture (by weight) of soil and cement 15 minutesafter mixing is at least 12.0, it is probable thatany organics present will not interfere with nor-mal hardening.

(2) Sulfates. Although sulfate attack is knownto have an adverse effect on the quality of hard-ened portland cement concrete, less is knownabout the sulfate resistance of cement stabilizedsoils. The resistance to sulfate attack differs forcement-treated coarse-grained and fine-grainedsoils and is a function of sulfate concentrations.Sulfate-clay reactions can cause deterioration offine-grained soil-cement. On the other hand, gran-ular soil-cements do not appear susceptible tosulfate attack. In some cases the presence of smallamounts of sulfate in the soil at the time ofmixing with the cement may even be beneficial.The use of sulfate-resistant cement may not im-prove the resistance of clay-bearing soils, but maybe effective in granular soil-cements exposed toadjacent soils and/or ground water containing highsulfate concentrations. A procedure for determin-ing the percent SO4 is presented in appendix C.The use of cement for fine-grained soils containingmore than about 1 percent sulfate should beavoided.

c. Water for hydration. Potable water is nor-mally used for cement stabilization, although seawater has been found to be satisfactory.

d. Gradation requirements. Gradation require-ments for cement stabilized base and subbasecourses are indicated in table 3-1.

e. Cement content for modification of soils.(1) Improve plasticity. The amount of cement

required to improve the quality of the soil throughmodification is determined by the trial-and-errorapproach. If it is desired to reduce the PI of thesoil, successive samples of soil-cement mixtures

Table 3-1. Gradation requirements for cement stabilized base and subbase courses

Type Course Sieve Size Percent Passing

Base

Subbase

1½ in.¾ in.No. 4No. 40No. 200

1½ in.No. 4No. 40No. 200

10070-10045-7010-400-20

10045-10010-500-20

3-1

TM 5822-14 /FJMAN 32-1019

must be prepared at different treatment levels andthe PI of each mixture determined. The RefereeTest of ASTM D 423 and ASTM D 424 procedureswill be used to determine the PI of the soil-cementmixture. The minimum cement content that yieldsthe desired PI is selected, but since it was deter-mined based upon the minus 40 fraction of thematerial, this value must be adjusted to find thedesign cement content based upon total sampleweight expressed as

A = 100BC (eq 3-1)where

A = design cement content, percent totalweight of soil

B = percent passing No. 40 sieve size, ex-pressed as a decimal

C = percent cement required to obtain thedesired PI of minus 40 material, ex-pressed as a decimal

(2) Improve gradation. If the objective of modi-fication is to improve the gradation of a granularsoil through the addition of fines then particle-sizeanalysis (ASTM D 422) should be conducted onsamples at various treatment levels to determinethe minimum acceptable cement content.

(3) Reduce swell potential. Small amounts ofportland cements may reduce swell potential ofsome swelling soils. However, portland cementgenerally is not as effective as lime and may beconsidered too expensive for this application. Thedetermination of cement content to reduce theswell potential of fine-g-rained plastic soils can beaccomplished by molding several samples at vari-ous cement contents and soaking the specimensalong with untreated specimens for 4 days. Thelowest cement content that eliminates the swellpotential or reduces the swell characteristics to theminimum is the design cement content. Proceduresfor measuring swell characteristics of soils arefound in MIL-STD-621A, Method 101. The cementcontent determined to accomplish soil modificationshould be checked to see whether it provides anunconfined compressive strength great enough toqualify for a reduced thickness design in accord-ance with criteria established for soil stabilization.

(4) Frost areas. Cement-modified soil may alsobe used in frost areas, but in addition to theprocedures for mixture design described in (1) and(2) above, cured specimens should be subjected tothe 12 freeze-thaw cycles prescribed by ASTM D560 (but omitting wire-brushing) or other applica-ble freeze-thaw procedures. This should be followedby determination of frost design soil classificationby means of standard laboratory freezing tests. Ifcement-modified soil is used as subgrade, its frost-susceptibility, determined after freeze-thaw cy-

3 - 2

cling, should be used as the basis of the pavementthickness design if the reduced subgrade designmethod is applied.

f. Cement content for stabilized soil. The follow-ing procedure is recommended for determining thedesign cement content for cement-stabilized soils.

(1) Step 1. Determine the classification andgradation of the untreated soil following proce-dures in ASTM D 422 and D 2487, respectively.

(2) Step 2. Using the soil classification selectan estimated cement content for moisture-densitytests from table 3-2.

Table 3-2. Cement requirements for various soils

Soil Classification

Initial EstimatedCement Content

percent dry weight

GW, SWGP, GW-GC, GW-GM, SW-SC, SW-SM

GC, GM, GP-GC, GP-GM, GM-GC, SC,SM, SP-SC, SP-SM, SM-SC, SP

CL. ML, MH 9

CH 11

(3) Step 3. Using the estimated cement con-tent, conduct moisture-density tests to determinethe maximum dry density and optimum watercontent of the soil-cement mixture. The procedurecontained in ASTM D 558 will be used to preparethe soil-cement mixture and to make the necessarycalculations; however, the procedures outlined inMIL-STD 621, Method 100 (CE 55 effort), orASTM D 1557 will be used to conduct the moisturedensity test.

(4) Step 4. Prepare triplicate samples of thesoil-cement mixture for unconfined compressionand durability tests at the cement content selectedin step 2 and at cement contents 2 percent aboveand 2 percent below that determined in step 2.The samples should be prepared at the density andwater content to be expected in field construction.For example, if the design density is 95 percent ofthe laboratory maximum density, the samplesshould also be prepared at 95 percent. The samplesshould be prepared in accordance with ASTM D1632 except that when more than 35 percent of thematerial is retained on the No. 4 sieve, a 4-inch-diameter by &inch-high mold should be used toprepare the specimens. Cure the specimens for 7days in a humid room before testing. Test threespecimens using the unconfined compression testin accordance with ASTM D 1633, and subjectthree specimens to durability tests, either wet-dry(ASTM D 559) or freeze-thaw (ASTM D 560) testsas appropriate. The frost susceptibility of the

TM 5-822-14/AFJMAN 32-1019

treated material should also be determined as indi-cated in appropriate pavement design manuals.

(5) Step 5. Compare the results of the uncon-fined compressive strength and durability testswith the requirements shown in tables 2-2 and2-3. The lowest cement content which meets therequired unconfined compressive strength require-ment and demonstrates the required durability isthe design cement content. If the mixture shouldmeet the durability requirements but not thestrength requirements, the mixture is consideredto be a modified soil. If the results of the speci-mens tested do not meet both the strength anddurability requirements, then a higher cementcontent may be selected and steps 1 through 4above repeated.

3-2. Stabilization with lime. In general, alllime treated finegrained soils exhibit decreasedplasticity, improved workability and reduced vol-ume change characteristics. However, not all soilsexhibit improved strength characteristics. Itshould be emphasized that the properties of soil-lime mixtures are dependent on many variables.Soil type, lime type, lime percentage and curingconditions (time, temperature, moisture) are themost important.

a. Types of lime. Various forms of lime havebeen successfully used as soil stabilizing agents formany years. However, the most commonly usedproducts are hydrated high-calcium lime, monohy-drated dolomitic lime, calcitic quicklime, and dolo-mitic quicklime. Hydrated lime is used most oftenbecause it is much less caustic than quicklime,however, the use of quicklime for soil stabilizationhas increased in recent years mainly with slurry-type applications. The design lime contents deter-mined from the criteria presented herein are forhydrated lime. If quicklime is used the design limecontents determined herein for hydrated limeshould be reduced by 25 percent. Specifications forquicklime and hydrated lime may be found inASTM C 977.

b. Gradation requirements. Gradation require-ments for lime stabilized base and subbase coursesare presented in table 3-3.

c. Lime content for lime-modified soils. Theamount of lime required to improve the quality ofa soil is determined through the same trial-and-error process used for cement-modified soils.

d. Lime content for lime-stabilized soils. Thefollowing procedures are recommended for deter-mining the lime content of lime stabilized soils.

(1) Step 1. The preferred method for determin-ing an initial design lime content is the pH test.In this method several lime-soil slurries are pre-

Table 3-3. Gradation requirements for lime stabilized baseand subbase courses

Type Course Sieve Size Percent Passing

Base

Subbase

1½ in.¾ in.No. 4No. 40No. 200

1½ in.No. 4No. 40No. 200

10070-10045-7010-400-20

10045-10010-500-20

pared at different lime treatment levels such as 2,4, 6, and 8 percent lime and the pH of each slurryis determined. The lowest lime content at which apH of about 12.4 (the pH of free lime) is obtainedis the initial design lime content. Procedures forconducting the pH test are indicated in appendixD. An alternate method of determining an initialdesign lime content is by the use of figure 3-1.Specific values required to use figure 3-1 are thePI and the percent of material passing the No. 40sieve.

(2) Step 2. Using the initial design lime con-tent conduct moisture-density tests to determinethe maximum dry density and optimum watercontent of the soil lime mixture. The procedurescontained in ASTM D 3551 will be used to preparethe soil-lime mixture. The moisture density testwill be conducted following procedures inMIL-STD 621 Method 100 (CE 55 effort) or ASTMD 1557.

(3) Step 3. Prepare triplicate samples of thesoil lime mixture for unconfined compression anddurability tests at the initial design lime contentand at lime contents 2 and 4 percent above designif based on the preferred method or 2 percentabove at 2 percent below design if based on thealternate method. The mixture should he preparedas indicated in ASTM D 3551. If less than 35percent of the soil is retained on the No. 4 sieve,the sample should be approximately 2 inches indiameter and 4 inches high. If more than 35percent is retained on the No. 4 sieve, samplesshould be 4 inches in diameter and 8 incheshigh. The samples should be prepared at thedensity and water content expected in field con-struction. For example, if the design density is95 percent of the laboratory maximum density,the sample should be prepared at 95 percentdensity. Specimens should be cured in a sealedcontainer to prevent moisture loss and lime car-bonation. Sealed metal cans, plastic bags, and soforth are satisfactory. The preferred method ofcuring is 73 degrees F for 28 days. Accelerated

3 -3

TM 5-822-14/AFJMAN 32-1019

Figure 3-1. Chart for the initial determination of lime content.

curing at 120 degrees F for 48 hours has also beenfound to give satisfactory results; however, checktests at 73 degrees for 28 days should also beconducted. Research has indicated that if acceler-ated curing temperatures are too high, the pozzola-nic compounds formed during laboratory curingcould differ substantially from those that woulddevelop in the field.

(4) Step 4. Test three specimens using theunconfined compression test. If frost design is aconsideration, test three specimens to 12 cycles offreeze-thaw durability tests (ASTM D 560) exceptwire brushing is omitted. The frost susceptibilityof the treated material should be determined asindicated in appropriate design manuals.

3 - 4

(5) Step 5. Compare the results of the uncon-fined compressive strength and durability testswith the requirements shown in tables 2-2 and2-3. The lowest lime content which meets theunconfined compressive strength requirement anddemonstrates the required durability is the designlime content. The treated material also must meetfrost susceptibility requirements as indicated inthe appropriate pavement design manuals. If themixture should meet the durability requirementsbut not the strength requirements, it is consideredto be a modified soil. If results of the specimenstested do not meet both the strength and durabil-ity requirements, a higher lime content may beselected and steps 1 through 5 repeated.

TM 5-822-14/AFJMAN 32-1019

3-3. Stabilization with Lime-Fly Ash (LF) andLime-Cement-Fly Ash (LCF). Stabilization ofcoarse-grained soils having little or no tines canoften be accomplished by the use of LF or LCFcombinations. Fly ash, also termed coal ash, is amineral residual from the combustion of pulver-ized coal. It contains silicon and aluminum com-pounds that, when mixed with lime and water,forms a hardened cementitious mass capable ofobtaining high compressive strengths. Lime andfly ash in combination can often be used success-fully in stabilizing granular materials since the flyash provides an agent, with which the lime canreact. Thus LF or LCF stabilization is often appro-priate for base and subbase course materials.

a. Types of fly ash. Fly ash is classified accord-ing to the type of coal from which the ash wasderived. Class C fly ash is derived from theburning of lignite or subbituminous coal and isoften referred to as “high lime” ash because itcontains a high percentage of lime. Class C fly ashis self-reactive or cementitious in the presence ofwater, in addition to being pozzolanic. Class F flyash is derived from the burning of anthracite orbituminous coal and is sometimes referred to as“low lime” ash. It requires the addition of lime toform a pozzolanic reaction.

b. Evaluation of fly-ash. To be acceptable qualityfly ash used for stabilization must meet the re-quirements indicated in ASTM C 593.

c. Gradation requirements. Gradation require-ments for LF and LCF stabilized base and subbasecourse are indicated in table 3-4.

Table 3-4. Gradation requirements for fly ashstabilized base and subbase courses

Type Course

Base

Subbase

Sieve Size Percent Passing

2 in. 100¾ in. 70-1003/8 in. 50-80No. 4 35-70No. 8 25-55No. 16 10-45No. 200 0-15

1½ in. 100No. 4 45-100No. 40 10-50No. 200 0-15

(1) Step 1. The first step is to determine theoptimum fines content that will give the maxi-mum density. This is done by conducting a seriesof moisture-density tests using different percent-ages of fly ash and determining the mix level thatyields maximum density. The initial fly ash con-tent should be about 10 percent based on dryweight of the mix. It is recommended that mate-rial larger than ¾ in. be removed and the testconducted on the minus ¾ in. fraction. Tests arerun at increasing increments of fly ash, e.g. 2percent, up to a total of about 20 percent. Moisturedensity tests should be conducted following proce-dures indicated in MIL-STD 621, Method 100 (CE55 effort) and ASTM D 1557. The design fly ashcontent is then selected at 2 percent above thatyielding maximum density. An alternate methodis to estimate optimum water content and conductsingle point compaction tests at fly ash contents of10-20 percent, make a plot of dry density versusfly ash content and determine the fly ash contentthat yields maximum density. The design fly ashcontent is 2 percent above this value. A moisturedensity test is then conducted to determine theoptimum water content and maximum dry density.

d. Selection of lime-fly ash content for LF and (2) Step 2. Determine the ratio of lime to flyLCF mixtures. Design with LF is somewhat differ- ash that will yield highest strength and durability.ent from stabilization with lime or cement. For a Using the design fly ash content and the optimumgiven combination of materials (aggregate, fly ash, water content determined in step 1, prepare tripli-and lime), a number of factors can be varied in the cate specimens at three different lime-fly ashmix design process such as percentage of lime-fly ratios following procedures indicated in MIL-STDash, the moisture content, and the ratio of lime to 621 Method 100 (less effort) or ASTM D 1557. Usefly ash. It is generally recognized that engineering LF ratios of 1:3, 1:4, and 1:5. If desired about 1

characteristics such as strength and durability aredirectly related to the quality of the matrix mate-rial. The matrix material is that part consisting offly ash, lime, and minus No. 4 aggregate fines.Basically, higher strength and improved durabilityare achievable when the matrix material is able to“float” the coarse aggregate particles. In effect,the fine size particles overfill the void spacesbetween the coarse aggregate particles. For eachcoarse aggregate material, there is a quantity ofmatrix required to effectively fill the availablevoid spaces and to “float” the coarse aggregateparticles. The quantity of matrix required formaximum dry density of the total mixture isreferred to as the optimum fines content. In LFmixtures it is recommended that the quantity ofmatrix be approximately 2 percent above theoptimum fines content. At the recommended finescontent, the strength development is also influ-enced by the ratio of lime to fly ash. Adjustment ofthe lime-fly ash ratio will yield different values ofstrength and durability properties.

3 -5

TM 5-822-14/AFJMAN 32-1019

percent of portland cement may be added at thistime.

(3) Step 3. Test three specimens using theunconfined compression test. If frost design is aconsideration, subject three specimens to 12 cyclesof freeze-thaw durability tests (ASTM D 560) ex-cept wire brushing is omitted. The frost suscepti-bility of the treated material shall also be deter-mined as indicated in appropriate design manual.

(4) Compare the results of the unconfinedcompressive strength and durability tests with therequirements shown in tables 2-2 and 2-3. Thelowest LF ratio content, i.e., ratio with the lowestlime content which meets the required unconfinedcompressive strength requirement and demon-strates the required durability, is the design LFcontent. The treated material must also meet frostsusceptibility requirements as indicated in theappropriate pavement design manuals. If the mix-ture should meet the durability requirements butnot the strength requirements, it is considered tobe a modified soil. If the results of the specimenstested do not meet both the strength and durabil-ity requirements, a different LF content may beselected or additional portland cement used andsteps 2 through 4 repeated.

e. Selection of cement content for LCF mixtures.Portland cement may also be used in combinationwith LF for improved strength and durability. If itis desired to incorporate cement into the mixture,the same procedures indicated for LF designshould be followed except that, beginning at step2, the cement shall be included. Generally, about 1to 2 percent cement is used. Cement may be usedin place of or in addition to lime however, the totaltines content should be maintained. Strength anddurability tests must be conducted on samples atvarious LCF ratios to determine the combinationthat gives best results.

3-4. Stabilization with Bitumen. Stabilizationof soils and aggregates with asphalt differs greatlyfrom cement and lime stabilization. The basicmechanism involved in asphalt stabilization offine-grained soils is a waterproofing phenomenon.Soil particles or soil agglomerates are coated withasphalt that prevents or slows the penetration ofwater which could normally result in a decrease insoil strength. In addition, asphalt stabilization canimprove durability characteristics by making thesoil resistant to the detrimental effects of watersuch as volume. In noncohesive materials, such assands and gravel, crushed gravel, and crushedstone, two basic mechanisms are active: water-proofing and adhesion. The asphalt coating on thecohesionless materials provides a membrane which

prevents or hinders the penetration of water andthereby reduces the tendency of the material tolose strength in the presence of water. The secondmechanism has been identified as adhesion. Theaggregate particles adhere to the asphalt and theasphalt acts as a binder or cement. The cementingeffect thus increases shear strength by increasingcohesion. Criteria for design of bituminous stabi-lized soils and aggregates are based almost en-tirely on stability and gradation requirements.Freeze-thaw and wet-dry durability tests are notapplicable for asphalt stabilized mixtures.

a. Types of bituminous stabilized soils.(1) Sand bitumen. A mixture of sand and

bitumen in which the sand particles are cementedtogether to provide a material of increased stabil-ity.

(2) Gravel or crushed aggregate bitumen. Amixture of bitumen and a well-graded gravel orcrushed aggregate that, after compaction, providesa highly stable waterproof mass of subbase or basecourse quality.

(3) Bitumen lime. A mixture of soil, lime, andbitumen that, after compaction, may exhibit thecharacteristics of any of the bitumen-treated mate-rials indicated above. Lime is used with materialthat have a high PI, i.e. above 10.

b. Types of bitumen. Bituminous stabilization isgenerally accomplished using asphalt cement, cut-back asphalt, or asphalt emulsions. The type ofbitumen to be used depends upon the type of soilto be stabilized, method of construction, andweather conditions. In frost areas, the use of tar asa binder should be avoided because of its high-temperature susceptibility. Asphalts are affectedto a lesser extent by temperature changes, but agrade of asphalt suitable to the prevailing climateshould be selected. As a general rule, the mostsatisfactory results are obtained when the mostviscous liquid asphalt that can be readily mixedinto the soil is used. For higher quality mixes inwhich a central plant is used, viscosity-gradeasphalt cements should be used. Much bituminousstabilization is performed in place with the bitu-men being applied directly on the soil or soil-aggregate system and the mixing and compactionoperations being conducted immediately thereaf-ter. For this type of construction, liquid asphalts,i.e., cutbacks and emulsions, are used. Emulsionsare preferred over cutbacks because of energyconstraints and pollution control efforts. The spe-cific type and grade of bitumen will depend on thecharacteristics of the aggregate, the type of con-struction equipment, and climatic conditions. Gen-erally, the following types of bituminous materialswill be used for the soil gradation indicated:

3 - 6

(1) Open-graded aggregate.(a) Rapid- and medium-curing liquid as-

phalts RC-250, RC-800, and MC-3000.(b) Medium-setting asphalt emulsion MS-2

and CMS-2.(2) Well-graded aggregate with little or no

material passing the No. 200 sieve.(a) Rapid and medium-curing liquid as-

phalts RC-250, RC-800, MC-250, and MC-800.(b) Slow-curing liquid asphalts SC-250 and

SC-800.(c) Medium-setting and slow-setting asphalt

emulsions MS-2, CMS-2, SS-1, and CSS-1.(3) Aggregate with a considerable percentage

of fine aggregate and material passing the No. 200sieve.

TM 5-822-14/AFJMAN 32-1019

(a) Medium-curing liquid asphalt MC-250and MC-800.

(b) Slow-curing liquid asphalts SC-250 andSC-800.

(c) Slow-setting asphalt emulsions SS-1,SS-01h, CSS-1, and CSS-lh.The simplest type of bituminous stabilization isthe application of liquid asphalt to the surface ofan unbound aggregate road. For this type ofoperation, the slow- and medium-curing liquidasphalts SC-70, SC-250, MC-70, and MC-250 areused.

c. Soil gradation. The recommended soil grada-tions for subgrade materials and base or subbasecourse materials are shown in tables 3-5 and 3-6,respectively.

Table 3-5. Recommended gradations for bituminousstabilized subgrade materials

Sieve Size Percent Passing

3 in. 100No. 4 50-100No. 30 38-100No. 200 2-30

Table 3-6. Recommended gradations for bituminous-stabilized base and subbase materials

Sieve Size

1½-in.l-in.¾-in.M-in.3/8-in.No. 4No. 8No. 16No. 30No. 50No. 100No. 200

1½ in. 1-in. ¾-in. ½-in.Maximum Maximum Maximum Maximum

100 - - -8 4 ± 9 100 - -76 ± 9 83 ± 9 100 -66 ± 9 73 ± 9 82 ± 9 10059 ± 9 64 ± 9 72 ± 9 83 ± 945 ± 9 48 ± 9 54 ± 9 62 ± 935 ± 9 36 ± 9 41 ± 9 47 ± 927 ± 9 28 ± 9 32 ± 9 36 ± 920 ± 9 21 ± 9 24 ± 9 28 ± 914 ± 7 16 ± 7 17 ± 7 20 ± 79 ± 5 11 ± 5 12 ± 5 14 ± 55 ± 2 5 ± 2 5 ± 2 5 ± 2

d. Mix design. Guidance for the design ofbituminous-stabilized base and subbase courses iscontained in TM 5-822-8/AFM 88-6, Chap. 9. Forsubgrade stabilization, the following equation maybe used for estimating the preliminary quantity ofcutback asphalt to be selected:

p = 0.02(a) + 0.07(b) + 0.15(c) + 0.20(d) X 100 (eq 3-2)(100 - S)

wherep = percent cutback asphalt by weight of dry

aggregatea = percent of mineral aggregate retained on

No. 50 sieveb = percent of mineral aggregate passing No.

50 sieve and retained on No. 100 sieve

c = percent of mineral aggregate passing No.100 and retained on No. 200 sieve

d = percent of mineral aggregate passing No.200

S = percent solventThe preliminary quantity of emulsified asphalt tobe used in stabilizing subgrades can be determinedfrom table 3-7. The final design content of cutbackor emulsified asphalt should be selected basedupon the results of the Marshal Stability testprocedure (MIL-STD 620A). The minimum Mar-shall Stability recommended for subgrades is 500pounds. If a soil does not show increased stabilitywhen reasonable amounts of bituminous materialsare added, the gradation of the soil should be

3 - 7

TM 5-822-14/AFJMAN 32-1019

Table 3-7. Emulsified asphalt requirements

Percent PassingNo. 200 Sieve

Pounds of Emulsified Asphalt per 100 pound of Dry Aggregate at Percent Passing No. 10 Sieve

<50 60 70 80 90 100

0 6.0 6.3 6.5 6.7 7.0 7.22 6.3 6.5 6.7 7.0 7.2 7.54 6.5 6.7 7.0 7.2 7.5 7.76 6.7 7.0 7.2 7.5 7.7 7.98 7.0 7.2 7.5 7.7 7.9 8.2

10 7.2 7.5 7.7 7.9 8.2 8.412 7.5 7.7 7.9 8.2 8.4 8.614 7.2 7.5 7.7 7.9 8.2 8.416 7.0 7.2 7.5 7.7 7.9 8.218 6.7 7.0 7.2 7.5 7.7 7.920 6.5 6.7 7.0 7.2 7.5 7.622 6.3 6.5 6.7 7.0 7.2 7.524 6.0 6.3 6.5 6.7 7.0 7.225 6.2 6.4 6.6 6.9 7.1 7.3

modified or another type of bituminous materialshould be used. Poorly graded materials may beimproved by the addition of suitable tines contain-ing considerable material passing the No. 200sieve. The amount of bitumen required for a givensoil increases with an increase in percentage of theliner sizes.

3-5. Stabilization with Lime-Cement and Lime-Bitumen. The advantage in using combinationstabilizers is that one of the stabilizers in thecombination compensates for the lack of effective-ness of the other in treating a particular aspect orcharacteristics of a given soil. For instance, in clayareas devoid of base material, lime has been usedjointly with other stabilizers, notably portlandcement or asphalt, to provide acceptable basecourses. Since portland cement or asphalt cannotbe mixed successfully with plastic clays, the limeis incorporated into the soil to make it friable,thereby permitting the cement or asphalt to beadequately mixed. While such stabilization prac-tice might be more costly than the conventionalsingle stabilizer methods, it may still prove to beeconomical in areas where base aggregate costsare high. Two combination stabilizers are con-sidered in this section: lime-cement and lime-asphalt.

a. Lime-cement. Lime can be used as an initialadditive with portland cement or the primarystabilizer. The main purpose of lime is to improveworkability characteristics mainly by reducing theplasticity of the soil. The design approach is to addenough lime to improve workability and to reducethe plasticity index to acceptable levels. The de-sign lime content is the minimum that achieves

desired results. The design cement content isarrived at following procedures for cement stabi-lized soils presented in paragraph 3-1.

b. Lime-asphalt. Lime can be used as an initialadditive with asphalt as the primary stabilizer.The main purpose of lime is to improve workabil-ity characteristics and to act as an anti-strippingagent. In the latter capacity, the lime acts toneutralize acidic chemicals in the soil or aggregatewhich tend to interfere with bonding of the as-phalt. Generally, about 1-2 percent lime is all thatis needed for this objective. Since asphalt is theprimary stabilizer, the procedures for asphalt sta-bilized materials as presented in paragraph 3-4shall be followed.

3-6. Lime Treatment of Expansive Soils. Ex-pansive soils as defined for pavement purposes arethose that exhibit swell in excess of three percent.Expansion is characterized by heaving of a pave-ment or road when water is imbibed in the clayminerals. The plasticity characteristics of a soiloften are a good indicator of the swell potential asindicated in table 3-8. If it has been determinedthat a soil has potential for excessive swell, limetreatment may be appropriate. Lime will reduceswell in an expansive soil to greater or lesserdegrees depending on the activity of the clayminerals present. The amount of lime to be addedis the minimum amount that will reduce swell toacceptable limits. Procedure for conducting swelltests are indicated in MIL-STD 621 Method 101 orASTM D 1883. The depth to which lime should beincorporated into the soil is generally limited bythe construction equipment used. However, 2 to 3feet generally is the maximum depth that can betreated directly without removal of the soil.

3 - 8

TM 5-822-14/AFJMAN 32-1019

Table 3-8. Swell potential of soils

Liquid Limit Plasticity Index Potential Swell

>6050-60<50

>3525-35<25

HighMarginal

Low

3 - 9

TM 5-822-14/AFJMAN 32-1019

CHAPTER 4

CONSTRUCTION PROCEDURES

4-1. Construction with Portland Cement.a. General construction steps. In soil-cement con-

struction the objective is to thoroughly mix apulverized soil material and cement in correctproportions with sufficient moisture to permitmaximum compaction. Construction methods aresimple and follow a definite procedure:

(1) Initial preparation(a) Shape the area to crown and grade.(b) If necessary, scarify, pulverize, and pre-

wet the soil.(c) Reshape to crown and grade.

(2) Processing(a) Spread portland cement and mix.(b) Apply water and mix.(c) Compact.(d) Finish.(e) Cure.

b. Mixing equipment. Soil, cement, and watercan be mixed in place using traveling mixingmachines or mixed in a central mixing plant. Thetypes of mixing equipment are

(1) Traveling mixing machines.(a) Flat-transverse-shaft type:

1 Single-shaft mixer (fig 4-1).2 Multiple-shaft mixer (fig 4-2).

(b) Windrow-type pugmill (fig 4-3).(2) Central mixing plants.

(a) Continuous-flow-type pugmill (fig 4-4).(b) Batch-type pugmill (fig 4-5).(c) Rotary-drum mixers (fig 4-6).

Whatever type of mixing equipment is used, thegeneral principles and objectives are the same.Some soil materials cannot be sufficiently pulver-ized and mixed in central mixing plants because oftheir high silt and clay content and plasticity.Almost all types of soil materials, from granular tofine grained, can be adequately pulverized andmixed with transverse-shaft mixers. The exceptionis material containing large amounts of highlyplastic clays. These clays may require more mix-ing effort to obtain pulverization. Revolving-bladecentral mixing plants and traveling pugmills canbe used for nonplastic to slightly plastic granularsoils. For coarse, nonplastic granular materials, arotary-drum mixer can provide a suitable mix;however, if the material includes a small amountof slightly plastic fines, mixing may not be ade-quate.

c. Equipment for handling and spreading ce-ment. There are a number of methods of handling

cement. On mixed-in-place construction using trav-eling mixing machines, bulk cement is spread onthe area to be processed in required amounts bymechanical bulk cement spreaders (fig 4-7). Bagcement is sometimes used on small jobs. Cementspreaders for mixed-in-place construction are oftwo general types: those that spread cement overthe soil material in a blanket (fig 4-8) and thosethat deposit cement on top of a partially flattenedor slightly trenched windrow of soil material (fig4-9). Cement meters on continuous-flow centralmixing plants are of three types: the belt withstrikeoff, screw, or vane. Cement for batch-type-pugmill mixers and rotary drum-mixers is batch-weighed.

d. Construction. Construction with soil cementinvolves two steps-preparation and processing.Variations in these steps, dictated by the type ofmixing equipment used, are discussed in thischapter. Regardless of the equipment and methodsused, it is essential to have an adequately com-pacted, thorough mixture of pulverized soil mate-rial and other proper amounts of cement andmoisture. The completed soil-cement must be ade-quately cured.

(1) Preparation. Before construction starts,crown and grade should be checked and any finegrading should be completed. Since there is littledisplacement of material during processing, gradeat the start of construction will determine finalgrade to a major extent. If borrow material is to beused, the subgrade should be compacted andshaped to proper crown and grade before theborrow is placed. Any soft subgrade areas shouldbe corrected. To avoid later costly delays, allequipment should be carefully checked to ensure itis in good operating condition and meets construc-tion requirements of the job. Guide stakes shouldbe set to control the width and guide the operatorsduring construction. Arrangements should bemade to receive, handle, and spread the cementand water efficiently. The number of cement andwater trucks required depends on length of haul,condition of haul roads, and anticipated rate ofproduction. For maximum production, an adequatecement and water supply is essential. The limits ofthe different materials and their correspondingcement requirements should be established by theproject engineer. Prewetting by adding moisturebefore cement is applied often saves time duringactual processing. Friable granular materials,

4-1

TM 5-822-14/AFJMAN 32-1019

Figure 4-1. Transverse single-shaft mixer processingsoil-cement in place. Multiple passes are required.

Figure 4-2. Multiple-transverseshaft mixer mixing soil,cement, and water in one pass.

Figure 4-3. Windrow-type traveling pugmill mixingsoil-cement from windrows of soil material.

4 - 2

TM 5-822-14/AFJMAN 32-1019

Figure 4-7. Bulk portland cement being transferredpneumatically from a bulk transport truck to a job truck.

Figure 4-8. Mechanical cement spreader attached to ajob dump truck spreading cement in regulated quantities.

Figure 4-9. Windrow-type mechanical spreader placingcement on windrow.

which are most commonly used, require little or noscarification or pulverization. Silty and clayeysoils may require extra effort to pulverize them,particularly if they are too dry or too wet. Soilsthat are difficult to pulverize when dry and brittlecan be broken down readily if water is added andallowed to soak in; whereas, sticky soils can bepulverized more easily when they have been driedout a little. Most specifications require that thesoil material be pulverized sufficiently so that atthe time of compaction 100 percent of the soil-cement mixture will pass a l-inch sieve and aminimum of 80 percent will pass a No. 4 sieve,exclusive of any gravel or stone. Gravel or stoneshould be no more than 2-inches maximum size.The final pulverization test should be made at theconclusion of mixing operations. When borrowmaterial is specified, it should be distributed on anaccurately graded, well-compacted roadway in aneven layer or uniform windrow, depending on thetype of mixing equipment to be used. It should beplaced by weight or volume as required by thespecifications.

(2) Processing. For maximum efficiency and tomeet specification time limits, a day’s work shouldbe broken down into several adjacent sectionsrather than one or two long sections. This proce-dure will result in maximum daily production andwill prevent a long stretch of construction frombeing rained out in case of a sudden severerainstorm.

(a) Handling and spreading cement. Bulkcement is normally trucked to the jobsite in bulktransport trucks or shipped to the nearest railroadsiding in enclosed hopper cars. Compressed air orvibrators are used to loosen the cement in thehopper cars during unloading. Transfer to cementtrucks is done pneumatically or by a screen or beltconveyor. The trucks are usually enclosed or fittedwith canvas covers. The cement is weighed intruckloads on portable platform scales or at anearby scale. Soil materials that contain excessiveamounts of moisture will not mix readily withcement. Sandy soils can be mixed with a moisturecontent at optimum or slightly above; whereas,clayey soils should have a moisture content belowoptimum when cement is spread. Cement shouldnot be applied onto puddles of water. If the soilmaterial is excessively wet, it should be aerated todry it before cement is applied. Handling andspreading procedures for different types of equip-ment are presented below.

1. Mechanical cement spread, mixed-in-place construction. A mechanical cement spreaderis attached to the dump truck. As the truck movesforward, cement flows through the spreader, which

4 - 3

TM 5-822-14/AFJMAN 32-1019

regulates the quantity of cement placed on theprepared soil. To obtain a uniform cement spread,the spreader should be operated at a constant,slow speed and with a constant level of cement inthe hopper. A true line at the pavement edgeshould be maintained with a string line. Themechanical spreader must have adequate tractionto produce a uniform cement spread. Traction canbe aided by wetting and rolling the soil materialbefore spreading the cement. When operating inloose sands or gravel, slippage can be overcome bythe use of cleats on the spreader wheels or byother modifications; sometimes, the spreader ismounted on a tractor or high lift. The mechanicalcement spreader can also be attached directlybehind a bulk cement truck. Cement is thenmoved pneumatically from the truck through anair separator cyclone that dissipates the air pres-sure, and falls into the hopper of the spreader.Forward speed must be slow and even. Sometimesa motor grader or loader pulls the truck to main-tain this slow, even forward speed. Pipe cementspreaders attached to cement transport truckshave been used in some areas with variableresults. Improvements in this type of equipmentare being made.

2. Bagged-cement spread, mixed-in-placeconstruction. When bags of cement are used onsmall jobs, a simple but exact method for properlyplacing the bags is necessary. The bags should bespaced at approximately equal transverse andlongitudinal intervals that will ensure the properpercentage of cement. Positions can be spotted byflags or markers fastened to chains at proper inter-vals to mark the transverse and longitudinal rows.When the bags are opened, the cement should bedumped so that it forms fairly uniform transversewindrows across the area being processed. A spike-tooth harrow, a nail drag, or a length of chain-linkfence can be used to spread the cement evenly.The drag should make at least two round tripsover the area to spread the cement uniformly.

3. Cement application, central-mixing-plant construction. When a continuous-flow centralmixing plant is used, the cement is usually me-tered onto the soil aggregate and the two materi-als are carried to the pugmill mixer on the mainfeeder belt. Variations in moisture and in grada-tion of the soil aggregate will result in variationsin the amount of material being fed onto thefeeder belt. A high bulkhead placed in front of thesoil hopper will help to obtain a more uniform flowthrough the soil material feeder. The chance ofloss of cement due to wind can be minimized bythe use of a small plow attachment that will forma furrow for the cement in the soil aggregate.

4 - 4

After the cement is added, a second plow attach-ment a little farther up on the main feeder beltcloses the furrow and covers the cement. A coveron the main feeder belt will also minimize cementloss due to wind. One of three types of cementmeters-belt, screw, or vane-can be used to pro-portion the cement on a volumetric basis. Eachrequires a 450- to 750-pound capacity surge tankor hopper between the cement silo and the cementfeeder. This tank maintains a constant head ofcement for the feeder, thus providing a moreuniform cement discharge. Compressed air of 2- to4-pounds per square inch pressure should be usedto prevent arching of cement in the silo and thesurge tank. Portable vibrators attached to thesurge tank can be used instead of air jets. Apositive system should be included to stop theplant automatically if the cement flow suddenlystops. The correct proportion of cement, soil mate-rial, and water entering the mixing chamber mustbe determined by calibrating the plant beforemixing and placing operations begin.

(b) Mixing and application of water. Proce-dures for applying water and mixing depend onthe type of mixing machine used. A thoroughmixture of pulverized soil material, cement, andwater must be obtained. Uniformity of the mix iseasily checked by digging trenches or a series ofholes at regular intervals for the full depth oftreatment and inspecting the color of the exposedsoil-cement mixture. Uniform color and texturefrom top to bottom indicate a satisfactory mix; astreaked appearance indicates insufficient mixing.Proper width and depth of mixing are also impor-tant. Following are methods of applying water andmixing for the different types of mixing machines.

1. Windrow-type traveling mixing ma-chine. Windrow-type traveling mixing machineswill pulverize friable soil materials. Other soils,however, may need preliminary pulverizing tomeet specification requirements. This is usuallydone before the soil is placed in windrows forprocessing. The prepared soil material is bladedinto windrows and a proportion pulled along tomake them uniform in cross section. When borrowmaterials are used, a windrow spreader can beused to proportion the material. Nonuniform wind-rows cause variations in cement content, moisturecontent, and pavement thickness. The number andsize of windrows needed depend on the width anddepth of treatment and on the capacity of themixing machine. Cement is spread on top of thepartially flattened or slightly trenched, preparedwindrow. The mixing machine then picks up thesoil material and cement and dry-mixes them withthe first few paddles in the mixing drum. At that

point water is added through spray nozzles and theremaining paddles complete the mixing. A strike-off attached to the mixing machine spreads themixed soil-cement. If a motor grader is used tospread the mixture and a tamping roller is usedfor compaction, the mixture should first be loos-ened to ready it for compaction. If two windrowshave been made, the mixing machine progresses350 to 500 feet along one windrow and then isbacked up to process the other windrow for 700 to1,000 feet. The cement spreading operation is keptjust ahead of the mixing operation. Water issupplied by tank trucks. A water tank installed onthe mixer will permit continuous operation while

TM 5-822-14/AFJMAN 32-1019

the tank trucks are being switched. As soon as thefirst windrow is mixed and spread on one sectionof the roadway, it is compacted. At the same timea second windrow is being mixed and spread. It inturn is then compacted. Finishing of the entireroadway is completed in one operation. Waterrequirements are based on the quantity of soilmaterial and cement per unit length of windrow.See figures 4-10 and 4-11 for construction se-quences for windrow-type operations.

2. Multishaft traveling mixing machine.Since most multi-shaft traveling mixing machineshave a high-speed pulverizing rotor, preliminarypulverization is usually unnecessary. The onlypreparation required is shaping the soil material

Figure 4-10. Sketch of soil-cement processing operations with windrow-type traveling pugmill.

4 - 5

TM 5-822-14/AFJMAN 32-1019

2 WINDROWS

3 WINDROWS

Figure 4-11. Plan for processing with windrow-typetraveling pugmill.

to approximate crown and grade. If an old roadbedis extremely hard and dense, prewetting and scari-fication will facilitate processing. Processing isdone in lanes 350 to 500 feet long and as wide asthe mixing machine. Cement is spread on the soilmaterial in front of the mixing machine. Cement

spreading should be completed in the first workinglane and under way in the second lane beforemixing operations are begun. This ensures a full-width cement spread without a gap between lanesand keeps spreading equipment out of the way ofmixing equipment. See figures 4-12 and 4-13 foran illustration of the construction sequence.

3. Single-shaft traveling mixing machine.Soil-cement construction with single-shaft travel-ing mixers differs from the preceding examples inthat more than one mixing pass is required. Thebasic principles and objectives are the same, how-ever. Shaping, scarifying, and pulverizing theroadway are the first steps of preparation, asdescribed previously in this chapter. Since mostsingle-shaft traveling mixers were not designed toscarify, the soil material may need to be loosenedwith a scarifier. Prewetting the soil material iscommon practice. Applying water at this stage of

Figure 4-12. Sketch of soil-cement processing operations with multiple-transverse-shaft traveling mixing machine.

4-6

2 LANES 3 LANES

Figure 4-13. Plan for processing withmultiple-transverse-shaft traveling mixing machine.

construction saves time during actual processingoperations because most of the required water willalready have been added to the soil material. Invery granular materials, prewetting prevents ce-ment from sifting to the bottom of the mix bycausing it to adhere more readily to the sand andgravel particles. Mixing the soil material andcement is easier if the moisture content of the rawmaterial is two or three percentage points belowoptimum. However, very sandy materials can bemixed even if the moisture content is one or twopercentage points above optimum. Moisture shouldbe applied uniformly during prewetting. By mix-ing it into the soil material, evaporation losses arereduced. Because of the hazard of night rains,some prefer to do the prewetting in the earlymorning. After scarifying and prewetting, theloose, moist soil material is shaped to crown andgrade. Cement is spread by a mechanical cementspreader or from bags. Occasionally, the prewetsoil material becomes compacted by cement-spreading equipment. In such cases, mixing can behastened by loosening the material again aftercement is spread, usually with the scarifier on amotor grader. The scarifier teeth should be set sothat the cement will flow between them and not becarried forward or displaced by the scarifier frame.The mixer picks up the soil material and cement

TM 5-822-14/AFJMAN 32-1019

and mixes them in place. Water, supplied by atank truck, is usually applied to the mixture by aspray bar mounted in the mixing chamber, or itcan be applied ahead of the mixer by waterpressure distributors. The soil material and ce-ment must be sufficiently blended when watercontacts the mixture to prevent the formation ofcement balls. The number of mixing passes de-pends on the type of soil material and its moisturecontent and on the forward speed of the mixer. Seefigure 4-14 for construction sequences.

(c) Central mixing plant. Central mixingplants are often used for projects involving borrowmaterials. The basic principles of thorough mixing,adequate cement content, proper moisture content,and adequate compaction apply. Friable granularborrow materials are generally used because oftheir low cement requirements and ease in han-dling and mixing. Pugmill-type mixers, eithercontinuous flow or batch, or rotary-drum mixersare used for this work. Generally the twin-shaftcontinuous-flow pugmill is used on highwayprojects. Facilities for efficiently storing, handling,and proportioning materials must be provided atthe plant. Quantities of soil material, cement, andwater can be proportioned by volume for weight.Mixing is continued until a uniform mixture ofsoil material, cement, and water is obtained. Toreduce evaporation losses during hot, windy condi-tions and to protect against sudden showers, haultrucks should be equipped with protective covers.To prevent excessive haul time, not more than 60minutes should elapse between the start of moist-mixing and the start of compaction. Haul time isusually limited to 30 minutes. The mixed soil-cement should be placed on the subgrade withoutsegregation in a quantity that will produce acompacted base of uniform density conforming tothe specified grade and cross section. The mixtureshould be spread to full roadway width either byone full-width spreader or by two or more spread-ers operating in staggered positions across theroadway. Less preferable is the use of one piece ofspreading equipment operating one lane at a timein two or more lanes. No lane should be spread sofar ahead of the adjoining lane that a time lapse ofmore than 30 minutes occurs between the time ofplacing material in adjoining lanes at any loca-tion. The subgrade should be damp when thesoil-cement is placed. Bituminous pavers havebeen used for spreading soil-cement although mod-ification may be necessary to increase volumecapacity before they can be used. Compactionequipment should follow immediately behind thespreader. When compacting the first lane, a nar-row compacted ridge should be left adjacent to the

4 - 7

TM 5-822-14/AFJMAN 32-1019

Figure 4-14. Sketch of soil-placement processing operations with single-transverse-shaft mixers.

second lane to serve as a depth guide when placingthe mix in the second lane. Water spray equip-ment should be available to keep the joint areasdamp. The amount of water needed to bring thesoil-cement mixture to required moisture contentin continuous-flow-type mixing plants is based onthe amount of soil material and cement cominginto the mixing chamber per unit of time. Theamount of water required in batch-type centralmixing plants is similarly calculated, using theweights of soil material and cement for each batch.

(3) Compaction. The principles governing com-paction of soil-cement are the same as those forcompacting the same soil materials without ce-ment treatment. The soil-cement mixture at opti-mum moisture should be compacted to maximumdensity and finished immediately. Moisture loss byevaporation during compaction, indicated by agreying of the surface, should be replaced withlight applications of water. Tamping rollers are

generally used for initial compaction except for themore granular soils. Self-propelled and vibratorymodels are also used. To obtain adequate compac-tion, it is sometimes necessary to operate therollers with ballast to give greater unit pressure.The general rule is to use the greatest contactpressure that will not exceed the bearing capacityof the soil-cement mixture and that will still“walk out” in a reasonable number of passes.Friable silty and clayey sandy soils will compactsatisfactorily using rollers with unit pressures of75 to 125 pounds per square inch. Clayey sands,lean clays, and silts that have low plasticity canbe compacted with 100- to 200-pounds per squareinch rollers. Medium to heavy clays and gravellysoils required greater unit pressure, i.e., 150 to300 pounds per square inch. Compacted thicknessup to 8 or 9 inches can be compacted in one lift.Greater thicknesses can be compacted with equip-ment designed for deeper lifts. When tamping

4 - 8

TM 5-822-14/AFJMAN 32-1019

rollers are used for initial compaction, the mixedmaterial must be in a loose condition at the startof compaction so that the feet will pack the bottommaterial and gradually walk out on each succeed-ing pass. If penetration is not being obtained, thescarifier on a motor grader or a traveling mixercan be used to loosen the mix during start ofcompaction, thus allowing the feet to penetrate.Vibratory-steel-wheeled rollers and grid and seg-mented rollers can be used to satisfactorily com-pact soil-cement made of granular soil materials.Vibratory-plate compactors are used on nonplasticgranular materials. Pneumatic-tired rollers can beused to compact coarse sand and gravel soil-cement mixtures with very little plasticity andvery sandy mixtures with little or no bindermaterial, such as dune, beach, or blow sand. Somepermit rapid inflation and deflation of the tireswhile compacting to increase their versatility.Pneumatic-tired rollers pulled by track-type trac-tors equipped with street plates can be used tocompact cohesionless sand mixtures. The weightand vibration of the tractor aid in compaction.Heavy three-wheeled steel rollers can be used tocompact coarse granular materials containing lit-tle or no binder material. Gravelly soils thatcontain up to about 20 percent passing the No. 200sieve and have low plasticity are best suited forcompaction with these rollers. Tandem-steel-wheeled rollers are often used during final rollingto press down or set rock particles and to smoothout ridges. There are two general types of roadcross section: trench and featheredge. Both can bebuilt satisfactorily with soil-cement. In trench-typeconstruction, the shoulder material gives lateralsupport to the soil-cement mixture during compac-tion. In the featheredge type of construction, theedges are compacted first to provide some edgestability while the remaining portion is beingcompacted. The edge slope should not be steeperthan 2:1 to facilitate shaping and compacting.Shoulder material is placed after the soil-cementhas been finished. Occasionally, during compactionand finishing, a localized area may yield under thecompaction equipment. This may be due to one ormore causes: the soil-cement mix is much wetterthan optimum moisture; the subsoil may be wetand unstable; or the roller may be too heavy forthe soil. If the soil-cement mix is too damp, itshould be aerated with a cultivator, travelingmixer, or motor grader. After it has dried to nearoptimum moisture, it can be compacted. For bestresults, compaction should start immediately afterthe soil material, cement, and water have beenmixed. Required densities are then obtained more

readily; there is less water evaporation; and dailyproduction is increased.

(4) Finishing. There are several acceptablemethods for finishing soil-cement. The exact proce-dure depends on equipment, job conditions, andsoil characteristics. Regardless of method, the fun-damental requirements of adequate compaction,close to optimum moisture, and removal of allsurface compaction planes must be met to producea high quality surface. The surface should besmooth, dense, and free of ruts, ridges, or cracks.When shaping is done during finishing, all smoothsurfaces, such as tire imprints and blade marks,should be lightly scratched with a weeder, naildrag, coil spring, or spiketooth harrow to removecleavage or compaction planes from the surface.Scratching should be done on all soil-cement mix-tures except those containing appreciable quanti-ties of gravel. The surface should be kept dampduring finishing operations. Steel-wheeled rollerscan be used to smooth out ridges left by the initialpneumatic-tired rolling. Steel-wheeled rollers areparticularly advantageous when rock is present inthe surface. A broom drag can sometimes be usedadvantageously to pull binder material in andaround pieces of gravel that have been set by thesteel-wheeled roller. Instead of using a steel roller,surfaces can be shaved with the motor grader andthen rerolled with a pneumatic-tired roller to sealthe surface. Shaving consists of lightly cutting offany small ridges left by the finishing equipment.Only a very thin depth is cut and all materialremoved is bladed to the edge of the road andwasted. The final operation usually consists of alight application of water and rolling with apneumatic-tired roller to seal the surface. Thefinished soil-cement is then cured.

(5) Curing. Compacted and finished soil-cement contains sufficient moisture for adequatecement hydration. A moisture-retaining cover isplaced over the soil-cement soon after completionto retain this moisture and permit the cement tohydrate. Most soil-cement is cured with bitumi-nous material, but other materials such as water-proof paper of plastic sheets, wet straw or sand,fog-type water spray, and wet burlap or cottonmats are entirely satisfactory. The types of bitumi-nous materials most commonly used are RC-250,MC-250, RT-5, and emulsified asphalt SS-1. Rateof application varies from 0.15 to 0.30 US gallonsper square yard. At the time of application, thesoil-cement surface should be free of all dry, looseand extraneous material. The surface should alsobe moist when the bituminous materials are ap-plied. In most cases a light application of water is

4 - 9

TM 5-822-14/AFJMAN 32-1019

placed immediately ahead of the bituminous appli-cation.

(6) Construction joints. After each day’s con-struction, a transverse vertical construction jointmust be formed by cutting back into the completedsoil-cement to the proper crown and grade. This isusually done the last thing at night or the firstthing the following morning, using the toe of themotor-grader blade or mixer. The joint must bevertical and perpendicular to the centerline. Afterthe next day’s mixing has been completed at thejoint, it must be cleaned of all dry and unmixedmaterial and retrimmed if necessary. Mixed moistmaterial is then bladed into the area and com-pacted thoroughly. The joint is left slightly highuntil final rolling when it is trimmed to gradewith the motor grader and rerolled. Joint construc-tion requires special attention to make sure thejoints are vertical and the material in the jointarea is adequately mixed and thoroughly com-pacted. When bituminous material is used as acuring agent, it should be applied right up to thejoint and sanded to prevent pickup.

(7) Multiple-layer construction. When the spec-ified thickness of soil-cement base course exceedsthe depth (usually 8 or 9 inches compacted) thatcan be compacted in one layer, it must be con-structed in multiple layers. No layer should be lessthan 4 inches thick. The lower layer does not haveto be finished to exact crown and grade, nor dosurface compaction planes have to be removedsince they are too far from the final surface to beharmful. The lower layer can be cured with themoist soil that will subsequently be used to buildthe top layer-which can be built immediately, thefollowing day, or some time later. With mixed-in-place construction, care must be taken to elimi-nate any raw-soil seams between the layers.

e. Special construction problems.(1) Rainfall. Attention to a few simple precau-

tions before processing will greatly reduce thepossibility of serious damage from wet weather.For example, any loose or pulverized soil should becrowned so it will shed water, and low places inthe grade where water can accumulate should betrenched so the water will drain off freely. Asshown by the construction of millions of squareyards of soil-cement in all climates, it is unlikelythat rainfall during actual construction will be aserious problem to the experienced engineer orcontractor. Usually construction requires the addi-tion of water equivalent to 1 to 1½ inches of rain.If rain falls during cement-spreading operations,spreading should be stopped and the cement al-ready spread should be quickly mixed into the soilmass. A heavy rainfall that occurs after most of

4-10

the water has already been added, however, can beserious. Generally, the best procedure is to obtainrapid compaction by using every available piece ofequipment so that the section will be compactedand shaped before too much damage results. Insuch instances it may be necessary to completefinal blading later; any material bladed from thesurface is wasted. After the mixture has beencompacted and finished, rain will not harm it.

(2) Wet soils. Excessively wet material is diffi-cult to mix and pulverize. Experience has shownthat cement can be mixed with sandy materialswhen the moisture content is as high as 2 percentabove optimum. For clayey soils, the moisturecontent should be below optimum for efficientmixing. It may be necessary to dry out the soilmaterial by aeration. This can be done by usingsingle-shaft traveling mixers with the hood in araised position, or by cutting out the material withthe tip of a motor grader blade and working andaerating with a disc. The maintenance of goodcrown and surface grade to permit rapid runoff ofsurface water before soil-cement processing is thebest insurance against excessive amounts of wetmaterial.

(3) Cold weather. Soil-cement, like othercement-using products, hardens as the cementhydrates. Since cement hydration practicallyceases when temperatures are near or below freez-ing, soil-cement should not be placed when thetemperature is 40 degrees F or below. Moreover, itshould be protected to prevent its freezing for aperiod of 7 days after placement, and until it hashardened, by a suitable covering of hay, straw, orother protective material.

4-2. Construction with lime.a. Lime stabilization methods. Basically, there

are three recognized lime stabilization methods;in-place mixing, plant mixing, and pressure injec-tion.

(1) In-place mixing.(a) In-place mixing may be subdivided into

three methods: mixing lime with the existingmaterials already a part of the construction site orpavement (fig 4-15); off-site mixing in which limeis mixed with borrow and the mixture is thentransported to the construction site for final ma-nipulation and compaction (fig 4-16); and mixingin which the borrow source soil is hauled to theconstruction site and processed as in the firstmethod.

(b) The following procedures are for in-placemixing:

One increment of lime is added to clays orgranular base materials that are easy to pulverize.

TM 5-822-14/AFJMAN 32-1019

Figure 4-15. In-place mixing of lime with existing baseand paving material on city street.

Figure 4-16. Off-site mixing pads for Mississippi Riverlevee repair project.

The material is mixed and compacted in oneoperation, and no mellowing period is required.

One increment of lime is added and themixture is allowed to mellow for a period of 1 to 7days to assist in breaking down heavy clay soils.(The term mellow refers to the reaction of the limeon clay to make it more friable and easier topulverize.)

One increment of lime is added for soil modifi-cation and pulverization before treatment withcement or asphalt.

One increment of lime is added to produce aworking table. Proof rolling is required instead ofpulverization and density requirements.

Two increments of lime are added for soilsthat are extremely difficult to pulverize. Betweenthe applications of the first and second incrementsof lime, the mixture is allowed to mellow.

(c) Deep stabilization may be accomplishedby one of two approaches.

One increment of lime is applied to modify soilto a depth of 24 inches (fig 4-17 through fig 4-19).Greater depths are possible but to date have notbeen attempted. A second increment of lime is

Figure 4-17. Deep stabilization after lime spreadingthe plow cuts 24 inches deep.

Figure 4-18. Root plow for scarifying to a depth of 18 inches.

Figure 4-19. Scarifying existing clay subgrade with lime oncity street project.

added to the top 6 to 12 inches for completestabilization. Plows and rippers are used to breakdown the large clay chunks in the deep treatment.Heavy disc harrows and blades are also used inpulverization of these clay soils. In frost zones, the

4-11

TM 5-822-14/AFJMAN 32-1019

use of small quantities of lime for soil modificationunder some circumstances may result in a frostsusceptible material that in turn can produce aweak sublayer.

One increment of lime is applied for completestabilization to a depth of 18 inches. Mechanicalmixers are now available to pulverize the lime-clay soil to the full depth by progressive cuts asfollows: first-pass cut to a depth of 6 inches, secondto 9 inches, third to 12 inches, fourth to 15 inches,and then a few passes to a depth of 18 inches toaccomplish full pulverization. The full 18 inches iscompacted from the top by vibratory and conven-tional heavy rollers.

(2) Plant mixing. The plant-mix operation usu-ally involves hauling the soil to a central plantwhere lime, soil, and water are uniformly mixedand then transported to the construction site forfurther manipulation (fig 4-20 through fig 4-22).The amount of lime for either method is usuallypredetermined by test procedures. Specificationsmay be written to specify the actual strength gainrequired to upgrade the stabilized soil, and nota-tions can be made on the plans concerning theestimated percent of lime required. This noteshould also stipulate that changes in lime contentmay be necessary to meet changing soil conditionsencountered during construction.

(3) Pressure injection. Pressure injections oflime slurry to depths of 7 to 10 feet, for control ofswelling and unstable soils on highways (fig 4-23)and under building sites, are usually placed on5-foot spacings, and attempts are made to placehorizontal seams of lime slurry at 8- to 12-inchintervals. The top 6- to 12-inch layer should becompletely stabilized by conventional methods.

b. Construction steps.

Figure 4-21. Lime-cement-fly ash aggregate base course.

Figure 4-22. Enclosed soil holds lime for adding tomarginal crushed stone base material.

Figure 4-23. Lime slurry pressure injection (LSPI) rigtreating a failed highway slope.

Figure 4-20. Lime-treated gravel with lime fed byscrew conveyor.

(1) Soil preparation. The in-place subgrade soilshould be brought to final grade and alignment.The finished grade elevation may require someadjustment because of the potential fluff action ofthe lime-stabilized layer resulting from the factthat some soils tend to increase in volume whenmixed with lime and water. This volume change

4-12

TM 5-822-14/AFJMAN 32-1019

may be exaggerated when the soil-lime is remixedover a long period of time, especially at moisturecontents less than optimum moisture. The fluffaction is usually minimized if adequate water isprovided and mixing is accomplished shortly afterlime is added. For soils that tend to fluff withlime, the subgrade elevation should be loweredslightly or the excess material trimmed. Trimmingcan usually be accomplished by blading the mate-rial onto the shoulder of embankment slopes. Theblading operation is desirable to remove the top0.25 inch because this material is not often wellcemented due to lime loss experienced duringconstruction. Excess rain and construction watermay wash lime from the surface, and carbonationof lime may occur in the exposed surface. If drylime is used, ripping or scarifying to the desireddepth of stabilization can be accomplished eitherbefore or after lime is added (fig 4-19). If the limeis to be applied in a slurry form, it is desirable toscarify prior to the addition of lime.

(2) Lime application.(a) Dry hydrated lime. Dry lime can be

applied either in bulk or by bag. The use of baggedlime is generally the simplest but also the mostcostly method of lime application. Bags of 50pounds are delivered in dump or flatbed trucksand placed by hand to give the required distribu-tion (fig 4-24). After the bags are placed they areslit and the lime is dumped into piles or trans-verse windrows across the roadway. The lime isthen levelled either by hand raking or by means ofa spike-tooth harrow or drag pulled by a tractor ortruck. Immediately after, the lime is sprinkled toreduce dusting. The major disadvantages of thebag method are the higher costs of lime because ofbagging costs, greater labor costs, and sloweroperations. Nevertheless, bagged lime is often themost practical method for small projects or forprojects in which it is difficult to utilize largeequipment. For large stabilization projects, partic-ularly where dusting is no problem, the use ofbulk lime has become common practice. Lime isdelivered to the job in self-unloading transporttrucks (fig 4-25). These trucks are large andefficient, capable of hauling 15 to 24 tons. Onetype is equipped with one or more integral screwconveyors that discharge at the rear. In recentyears pneumatic trucks have increased in popular-ity and are preferred over the older auger-typetransports. With the pneumatic units the lime isblown from the tanker compartments through apipe or hose to a cyclone spreader to a pipespreader bar-mounted at the rear (fig 4-26).Bottom-dump hopper trucks have also been tried,but they are undesirable because of difficulty in

unloading and obtaining a uniform rate of dis-charge. With the auger trucks, spreading is han-dled by means of a portable, mechanical-typespreader attached to the rear (fig 4-27) or throughmetal downspout chutes or flexible rubber bootsextending from the screw conveyors. The mechani-cal spreaders incorporate belt, screw, rotary vane,or drag-chain conveyors to distribute the limeuniformly across the spreader width. When bootsor spouts are used instead, the lime is deposited inwindrows; but because of lime’s lightness andflowability, the lime becomes distributed ratheruniformly across the spreading lane. Whether me-chanical spreaders, downspouts, or boots are used,the rate of lime application can be regulated byvarying the spreader opening, spreader drivespeed, or truck speed so that the required amountof lime can be applied in one or more passes. Withthe pneumatic trucks, spreading is generally han-dled with a cyclone spreader mounted at the rear,which distributes the lime through a split chute orwith a spreader bar equipped with several largedownspout pipes. Finger-tip controls in the truckcab permit the driver to vary the spreading widthby adjusting the air pressure. Experienced driverscan adjust the pressure and truck speed so thataccurate distribution can be obtained in one or twopasses. When bulk lime is delivered by rail, avariety of conveyors can be used for transferringthe lime to transport trucks; these include screw,belt, or drag-chain conveyors, bucket elevators,and screw elevators. The screw-type conveyors aremost commonly used, with large diameter units of10- to 12-inches being recommended for high-speedunloading. To minimize dusting, all types of con-veyors should be enclosed. Rail-car unloading isgenerally facilitated by means of poles and me-chanical or air-type vibrators. Lime has also beenhandled through permanent or portable batchingplants, in which case the lime is weigh-batchedbefore loading. Generally, a batch plant setupwould only be practical on exceptionally large jobs.Obviously, the self-unloading tank truck is theleast costly method of spreading lime, becausethere is no rehandling of material and largepayloads can be carried and spread quickly.

(b) Dry quicklime. Quicklime may be ap-plied in bags or bulk. Because of higher cost,bagged lime is only used for drying of isolated wetspots or on small jobs. The distribution of baggedquicklime is similar to that of bagged hydrate,except that greater safety emphasis is needed.First, the bags are spaced accurately on the areato be stabilized, and, after spreading, water isapplied and mixing operations started immedi-ately. The fast watering and mixing operation

4-13

TM 5-822-14/AFJMAN 32-1019

Figure 4-27. Distribution of quicklimefrom mechanical spreader on city street.

Figure 4-24. Application of lime by the bagfor a small maintenance project.

Figure 4-25. Application of lime by a bulk pneumatic truck.

Figure 4-26. Bulk pneumatic truck spreading limefrom bar spreader.

helps minimize the danger of burns. Quicklimemay be applied in the form of pebbles of approxi-mately 3/8 inch, granular, or pulverized. The firsttwo are more desirable because less dust is gener-ated during spreading. Bulk quicklime may bespread by self-unloading auger or pneumatic trans-port trucks, similar to those used for dry hydrate.However, because of its coarser size and higherdensity, quicklime may also be tailgated from aregular dump truck with tailgate opening controlsto ensure accurate distribution (fig 4-28). Becausequicklime is anhydrous and generates heat oncontact with water, special care should be takenduring stabilization to avoid lime burns. Wherequicklime is specified, the contractor should pro-vide the engineer with a detailed safety programcovering precautions and emergency treatmentavailable on the jobsite. The program should in-clude protective equipment for eyes, mouth, nose,and skin, as well as a first-aid kit containing aneyeball wash. This protective equipment should beavailable on the jobsite during spreading andmixing operations. The contractor should activelyenforce this program for the protection of theworkers and others in the construction area.

(c) Slurry method. In this method eitherhydrated lime or quicklime and water are mixedinto a slurry. With quicklime, the lime is firstslaked and excess water added to produce theslurry.

(d) Slurry made with hydrated lime. Thismethod was first used in the 1950s and is cur-rently very popular, especially where dust fromusing dry lime is a problem. The hydrated lime-water slurry is mixed either in a central mixingtank (fig 4-29), jet mixer (fig 4-30), or in a tanktruck. The slurry is spread over the scarifiedroadbed by a tank truck equipped with spray bars(fig 4-31 and fig 4-32). One or more passes may be

4-14

TM 5-822-14/AFJMAN 32-1019

Figure 4-28. Spreading of granular quicklime.

required over a measured area to achieve thespecified percentage based on lime solids content.To prevent runoff and consequent nonuniformity oflime distribution that may occur under certainconditions, it may be necessary to mix the slurryand soil immediately after each spreading pass (fig4-33). A typical slurry mix proportion is 1 ton oflime and 500 gallons of water, which yields about600 gallons of slurry containing 31 percent limesolids. At higher concentrations there is difficultyin pumping and spraying the slurry. Forty percentsolids is a maximum pumpable slurry. The actualproportion used depends on the percentage of limespecified, type of soil, and its moisture condition.When small lime percentages are required, theslurry proportions may be reduced to 1 ton of limeper 700 to 800 gallons of water. Where the soilmoisture content is near optimum, a stronger limeconcentration would normally be required. Inplants employing central mixing, agitation is usu-ally accomplished by using compressed air andrecirculating pump, although pugmills have alsobeen used. The most typical slurry plant incorpo-rates slurry tanks large enough to handle wholetank truck loads of hydrated lime of approximately20 tons. For example, on one job two 15,000 gallontanks, 10 feet in diameter by 26 feet in length,were used, each fitted with an 8-inch perforatedair line mounted along the bottom. The air linewas stopped 18 inches short of the end wall,thereby providing maximum agitation in the lime-feeding zone. A typical batch consisted of 10,000gallons of water (charged first) and 20 tons of lime,producing about 12,000 gallons of slurry in lessthan 25 minutes. Loading of the tank trucks washandled by a standard water pump, with oneslurry tank being unloaded while the slurry wasbeing mixed in the other tank. On another job thecontractor used a similar tank and air line, but, inaddition, a 4-inch recirculating pump was used for

mixing; the same pump loaded the tank trucks. Tokeep the lime from settling, the contractor deviseda hand-operated scraper fitted with air jets. Thenewest and most efficient method of slurry produc-tion, which eliminates batching tanks, involvesthe use of a compact jet slurry mixer. Water at 70pounds per square inch and hydrated lime arecharged continuously in a 65:35 (weight) ratio intothe jet mixing bowl where slurry is producedinstantaneously. The mixer and auxiliary equip-ment can be mounted on a small trailer andtransported to the job readily, giving great flexibil-ity to the operation. In the third type of slurrysetup, measured amounts of water and lime arecharged separately to the tank truck, with theslurry being mixed in the tank either by com-pressed air or by a recirculating pump mounted atthe rear. The water is metered and the limeproportioned volumetrically or by means of weightbatchers. Both portable and permanent batchingplants are used. Mixing with air is accomplishedat the plant. The air jets are turned on during theloading operation, and remain on until the slurryis thoroughly mixed which takes about 10 to 15minutes. The use of a recirculating pump, how-ever, permits mixing to occur during transit to thejob. Usually, 2-, 3-, or 4-inch pumps are used inthis operation, with the slurry being recirculatedthrough the tank by means of a perforated longitu-dinal pipe extending the length of the tank andcapped at one end. Spreading from the slurrydistributors is effected by gravity or by pressurespray bars, the latter being preferred because ofbetter distribution. The use of spray deflectors isalso recommended for good distribution. The gen-eral practice in spreading is to make either one ortwo passes per load. However, several loads maybe needed in order to distribute the requiredamount of lime. The total number of passes willdepend on the lime requirement, optimum mois-ture of the soil, and type of mixing employed.Windrow mixing with the grader generally re-quires several passes.

(e) Double application of lime. In some areaswhere extremely plastic, gumbo clay (PI 50+)abounds, it may prove advantageous to add therequisite amount of lime in two increments tofacilitate adequate pulverization and obtain com-plete stabilization. For example, 2 or 3 percentlime is added first, partially mixed, then the layeris sealed and allowed to cure for up to a week. Theremaining lime is then added preparatory to finalmixing. The first application mellows the clay andhelps in achieving final pulverization, and thesecond application completes the lime-treatmentprocess.

4-15

TM 5-822-14/AFJMAN 32-1019

Figure 4-29. Slurry mixing tank using recirculating pumpfor mixing hydrate and water.

Figure 4-32. Recirculation pump on top of a6,000-gallon wagon agitates the slurry.

Figure 4-30. Jet slurry mixing plant.

Figure 4-31. Spreading of lime slurry.

(f) Slurry made with quicklime. A recentunit developed for making lime slurry from quick-lime is the Portabatch Slaker (fig 4-34). This unitconsists of a lo-foot diameter by 40-foot tank thatincorporates a 5-foot diameter single shaft agitatorturned by a 100-horse power diesel engine. Thebatch slaker can handle 20 to 25 tons of quicklimeand about 25,000 gallons of water, producingthe slurry in about 1 to 1.5 hours. Because of the

4-16

Figure 4-33. Grader-scarifier cutting slurry into stone base.

Figure 4-34. Portabatch lime slaker.

exothermic action of quicklime in water, the slurryis produced at a temperature of about 185 degreesF.

(g) Some of the advantages and disadvan-tages of dry hydrated lime are as follows:

1 Advantages:Dry lime can be applied two or three

times faster than a slurry.Dry lime is very effective in drying out

soil.2 Disadvantages:

Dry lime produces a dusting problemthat makes its use undesirable inurban areas.

TM 5-822-14/AFJMAN 32-1019

The fast drying action of the dry limerequires an excess amount of waterduring the dry, hot seasons.

(h) Some of the advantages and disadvan-tages of dry quicklime are as follows:

1. Advantages:More economical as it contains approxi-

mately 25 percent more availablelime.

Greater bulk density for smaller-sizessilos.

Faster drying action in wet soils.Faster reaction with soils.Construction season can be extended, in

both spring and fall, because of fasterdrying.

2. Disadvantages:Field hydration less effective than com-

mercial hydrators, producing acoarser material with poorer distribu-tion in soil mass.

Quicklime requires more water thanhydrate for stabilization, which maypresent a problem in dry areas.

Greater susceptibility to skin and eyeburns.

(i) Some of the advantages and disadvan-tages of slurry lime are as follows:

1. Advantages:Dust-free application is more desirable

from an environmental standpoint.Better distribution is achieved with the

slurry.In the lime slurry method, the lime

spreading and sprinkling operationsare combined, thereby reducing jobcosts.

During summer months slurry applica-tion prewets the soil and minimizesdrying action.

The added heat when slurry is madefrom quicklime speeds drying action,which is especially desirable in coolerweather.

2. Disadvantages:Application rates are slower. High ca-

pacity pumps are required to achieveacceptable application rates.

Extra equipment is required, therefore,costs are higher.

Extra manipulation may be required fordrying purposes during cool, wet, hu-mid weather, which could occur dur-ing the fall, winter, and spring con-struction season.

Not practical for use with very wetsoils.

(3) Pulverization and mixing. To obtain satis-factory soil-lime mixtures adequate pulverizationand mixing must be achieved. For heavy clay soilstwo-stage pulverization and mixing may be re-quired, but for other soils one-stage mixing andpulverization may be satisfactory. This differenceis primarily due to the fact that the heavy claysare more difficult to break down.

(a) Two-stage mixing. Construction steps intwo-stage mixing consist of preliminary mixing,moist curing for 24 to 48 hours (or more), and finalmixing or remixing. The first mixing step distrib-utes the lime throughout the soil, thereby facilitat-ing the mellowing action. For maximum chemicalaction during the mellowing period, the clay clodsshould be less than 2 inches in diameter. Beforemellowing the soil should be sprinkled liberally tobring it up to at least two percentage points aboveoptimum moisture in order to aid the disintegra-tion of clay clods The exception to excess wateringwould be in cool, damp weather when evaporationis at a minimum. In hot weather, however, it maybe difficult to add too much water. After prelimi-nary mixing, the roadway should be sealed lightlywith a pneumatic roller as a precaution againstheavy rain, because the compacted subgrade willshed water, thereby preventing moisture increasesthat might delay construction. Generally, in 24 to48 hours the clay becomes friable enough so thatdesired pulverization can be easily attained duringfinal mixing. Additional sprinkling may be neces-sary during final mixing to bring the soils tooptimum moisture or slightly above (fig 4-35). Inhot weather more than optimum moisture isneeded to compensate for the loss through evapora-tion. Although disc harrows (fig 4-36) and graderscarifiers are suitable for preliminary mixing,high-speed rotary mixers (fig 4-37 to fig 4-39) orone-pass travel plant mixers (fig 4-15) are re-quired for final mixing. Motor graders are gener-ally unsatisfactory for mixing lime with heavyclays.

(b) One-stage mixing. Both blade and rotarymixing, or a combination, have been used success-fully in projects involving granular base materials.However, rotary mixers are preferred for moreuniform mixing, finer pulverization, and fasteroperation. They are generally required for highlyplastic soils that do not pulverize readily and forreconstructing worn-out roads in order to pulverizethe old asphalt.

(c) Blade mixing. When blade mixing isused in conjunction with dry lime, the material isgenerally bladed into two windrows, one on each

4 -17

TM 5-822-14/AFJMAN 32-1019

Figure 4-35. Watering of lime-treated clay on airport project.

Figure 4-36. Mixing with a disc harrow.

Figure 4-37. Rotary mixer.

Figure 4-38. Train of rotary mixers.

4-18

Figure 4-39. Rotary mixer on primary road project.

side of the roadway. Lime is then spread on theinside of each windrow or down the center line ofthe road. The soil is then bladed to cover the lime.After the lime is covered, the soil is mixed dry byblading across the roadway. After dry mixing iscompleted, water is added to slightly above theoptimum moisture content and additional mixingis performed. To ensure thorough mixing by thismethod, the material should be handled on themold board at least three times. When blademixing is used with the slurry method, the mixingis done in thin lifts that are bladed to windrows.One practice is to start with the material in acenter windrow, then blade aside a thin layer afterthe addition of each increment of slurry, therebyforming side windrows. The windrowed material isthen bladed back across the roadway and com-pacted, provided that its moisture content is atoptimum. A second practice is to start with a sidewindrow, then blade in a thin 2-inch layer acrossthe roadway, add an increment of lime, and bladethis layer to a windrow on the opposite side of theroad. On one job this procedure was repeatedseveral times until all the material was mixed andbladed to the new windrow. Because only one-halfof the lime had been added at this time, theprocess was repeated, moving the material back tothe other side. This procedure is admittedly slow,but it provides excellent uniformity.

(d) Central mixing. Premixing lime withgranular base materials is becoming popular onnew construction projects, particularly where sub-marginal gravels are used. Because the gravel hasto be processed anyway to meet gradation specifi-cations, it is a relatively simple matter for thecontractor to install a lime bin, feeder, and pug-mill at the screening plant. On one project a smallpugmill was installed at the head pulley of thecollecting belt conveyor (fig 4-20) and at anotheroperation a larger pugmill plant was utilized (fig4-21). The general practice is to add the optimum

TM 5-822-14/AFJMAN 32-1019

moisture at the pugmill, thereby permitting imme-diate compaction after laydown. Figure 4-22shows a crushed-stone plant where lime was addedto upgrade a clay bearing crushed stone.

(e) Pulverization and mixing requirements.Pulverization and mixing requirements are gener-ally specified in terms of percentages passing the1½-inch or 1-inch screen and the No. 4 sieve. Typi-cal requirements are 100 percent passing the 1inch, and 60 percent passing the No. 4 sieve,exclusive of nonslaking fractions. However, insome applications the requirements are relaxed.For example, the South Dakota Highway Depart-ment only requires 100 percent passing the 1.5inch screen with no requirement for the No. 4sieve. Other specifications may only require 40 to50 percent passing the No. 4 sieve. In certainexpedient construction operations, formal require-ments are eliminated and the “pulverization andmixing to the satisfaction of the engineer” clauseis employed.

(4) Compaction. For maximum development ofstrength and durability, lime-soil mixtures shouldbe properly compacted. Many agencies require atleast 95 percent of ASTM D 698 density forsubbase and 90 percent for bases. Some agencieshave required 95 percent ASTM D 1557 maximumdensity. Although such densities can be achievedfor more granular soil-lime mixtures, it is difficultto achieve this degree of compaction for lime-treated, fine-grained soils. If a thick soil-lime lift isto be compacted in one lift, many specificationsrequire 95 percent of ASTM D 698 maximumdensity in the upper 6 to 9 inches, and lowerdensities are accepted in the bottom portion of thelift. To achieve high densities, compacting atapproximately optimum moisture content with ap-propriate compactors is necessary. Granular soil-lime mixtures are generally compacted as soon aspossible after mixing, although delays of up to 2days are not detrimental, especially if the soil isnot allowed to dry out and lime is not allowed tocarbonate. Fine-grained soils can also be com-pacted soon after final mixing, although delays ofup to 4 days are not detrimental. When longerdelays (2 weeks or more) cannot be avoided, it maybe necessary to incorporate a small amount ofadditional lime into the mixture (0.5 percent) tocompensate for losses due to carbonation anderosion. Various rollers and layer thicknesses havebeen used in lime stabilization. The most commonpractice is to compact in one lift by first using thesheeps-foot roller (fig 4-40 and fig 4-41) until it“walks out,” and then using a multiple-wheelpneumatic roller (fig 4-42). In some cases, a flatwheel roller is used in finishing. Single lift com-

paction can also be accomplished with vibratingimpact rollers (fig 4-43) or heavy pneumatic roll-ers, and light pneumatic or steel rollers used forfinishing. When light pneumatic rollers are usedalone, compaction is generally done in thin liftsusually less than 6 inches. Slush rolling of granu-lar soil-lime mixtures with steel rollers is notrecommended. During compaction, light sprinklingmay be required, particularly during hot, dryweather, to compensate for evaporation losses.

(5) Curing. Maximum development ofstrength and durability also depends on propercuring. Favorable temperature and moisture condi-tions and the passage of time are required forcuring. Temperatures higher than 40 degrees F to50 degrees F and moisture contents around opti-mum are conducive to curing. Although somespecifications require a 3- to 7-day undisturbedcuring period, other agencies permit the immedi-ate placement of overlaying paving layers if thecompacted soil-lime layer is not rutted or distortedby the equipment. This overlying course maintains

Figure 4-40. Self-propelled sheepsfoot roller.

Figure 4-41. Dougle sheepsfoot roller.

4 -19

TM 5-822-14/AFJMAN 32-1019

Figure 4-42. Pneumatic roller completes compactionof LCF base.

Figure 4-43. Vibrating roller completes compaction of subgrade.

the moisture content of the compacted layer and isan adequate medium for curing. Two types ofcuring can be employed: moist and asphalticmembrance. In the first, the surface is kept dampby sprinkling with light rollers being used to keepthe surface knitted together. In membrane curing,the stabilized soil is either sealed with one shot ofcutback asphalt at a rate of about 0.10 to 0.25gallons per square yard within 1 day after finalrolling, or primed with increments of asphaltemulsion applied several times during the curingperiod. A common practice is to apply two shotsthe first day and one each day thereafter for 4days at a total rate of 0.10 to 0.25 gallons persquare yard. The type of membrane used, amount,and number of shots vary considerably. Usually, itis difficult to apply more than 0.2 gallons ofasphalt prime because the lime-stabilized layer isrelatively impervious after compaction.

4-3. Construction with Lime-Fly Ash (LF) andLime-Cement-Fly Ash (LCF). Construction proce-dures for LC and LCF are similar to those used forlime stabilization. Although both field in place andcentral plant mixing may be used with LF andLCF, the latter procedure is recommended to

4 - 2 0

obtain adequate proportioning and mixing. WithLCF, it also should be noted that the presence ofcement requires that the stabilized mixture becompacted as soon as possible.

4-4. Construction with Bitumen. Bituminousstabilization can involve either hot-mix or cold-mixmaterials. Bitumen and aggregate or soil can beblended in place or in a central plant. Construc-tion procedures presented in this manual are forcold-mix materials mixed in place or in a centralplant. Construction procedures for hot-mix hot-laidmaterials are similar to those used for asphaltconcrete and applicable standard construction pro-cedures should be followed when these materialsare involved.

a. Equipment for Mixed-in-Place Materials. Somepieces of equipment used for mixed-in-place bitu-minous stabilization are similar to those used instandard construction and will not be describedhere. These include water distributors, compactionequipment, and windrow sizers. Only equipmentespecially associated with or having special fea-tures applicable to bituminous stabilization will bediscussed.

(1) Mixing equipment.(a) Travel plants. Travel plants are self-

propelled pugmill plants that proportion and mixaggregates and asphalt as they move along theroad. There are two general types of travel plants:one that moves through a prepared aggregatewindrow on the roadbed, adds and mixes theasphalt as it goes and discharges to the rear amixed windrow ready for aeration and spreading(fig 4-44) and one that receives aggregate into itshopper from haul trucks, adds and mixes asphalt,and spreads the mix to the rear as it moves alongthe roadbed (fig 4-45). Certain features and perfor-mance capabilities are common to all travelplants, enabling them to operate effectively and toproduce a mix meeting design and specificationcriteria. To begin, the tracks or wheels on whichthe machine moves must be so sized, designed, andpositioned that they do not damage or rut thesurface on which it operates when the plant isfully loaded. The basic purpose of the travel plantis to mix asphalt and aggregate. Some machinesare equipped with devices that maintain theproper proportions automatically. Others, however,require that a uniform speed be maintained toensure uniform proportioning. Regardless of thetype, the manufacturer’s recommended proceduresfor calibrating and operating the travel plantshould be followed carefully. Finally, the efficienttravel plant should be capable of thoroughly mix-ing the asphalt and aggregates, uniformly dispers-

TM 5-822-14/AFJMAN 32-1019

Figure 4-44. Windrowtype pugmill travel plant.

Figure 4-45. Hopper-type pugmill travel plant.

ing the asphalt and adequately coating the aggre-gate particles, thus producing a mixture that isuniform in color. Hopper travel plants, and insome cases, windrow plants, require devices forensuring accurate controls of the flow of aggre-gates from the hopper to the pugmill so thatcorrect mix proportions are maintained. Feed ofasphalt to the pugmill similarly requires accuratecalibration. Typically, a positive displacementpump is utilized to deliver asphalt to the mixingchamber via a spray bar.

(b) Rotary-type mixers. Rotary or mechanicalon-site mixing is accomplished by what is essen-tially a mobile mixing chamber mounted on aself-propelled machine. Within the chamber, usu-ally about 7 feet wide and open at the bottom, areone or several shafts transverse to the roadbed, onwhich are mounted tines or cutting blades thatrevolve at relatively high speed. As the machinemoves ahead, it strikes off behind it a uniformcourse of asphalt-aggregate mixture. Some rotarymixers have up to four shafts or rotors (fig 4-46

and fig 4-47), but most have only one. Some singleshaft mixers are equipped with a system that addsasphalt by spraying it into the mixing chamber asthe machine moves ahead, with the amount ofspray being synchronized with the travel speed (fig4-48). Other machines, however, must be used inconjunction with an asphalt distributor that spraysasphalt on to aggregates immediately ahead of themobile mixer (fig 4-49). Both types of machinehave the common capability of effecting a smoothbottom cut and then blending the material withasphalt into the mixture specified. But each typeindividually is marked by certain devices andfeatures that enable it to perform. Machines withbuilt-in asphalt feeding must have the capabilityfor accurate metering and blending of asphalt intothe in-place materials in synchronization with acontinuous forward movement. Furthermore, theymust have spray bars that will distribute theliquid uniformly across the mixer’s width. Theymust be equipped with controls for both depth ofcutting and processing and for spreading themixed material being laid out behind. Rotarymixers without asphalt spraying equipment gener-ally feature controls that permit adjustment ofcutting depth to at least a lo-inch adjustment oftail board and adjustment of the hood itself foraeration purposes.

Figure 4-46. Multiple rotary mixer.

Figure 4-47. A processing chamber of a multiple rotary mixer.

4-21

TM 5-822-14/AFJMAN 32-1019

Figure 4-48. Single-shaft rotary mixer withasphalt supply tank.

Figure 4-50. Mixing with motor grader.

Figure 4-49. Single-shaft rotary mixer without asphalt.

(c) Motor graders. Blade mixing is the on-site mixing of asphalt and in-place materials onthe roadbed by a motor grader (fig 4-50). Theasphalt is applied directly ahead of the motorgrader by an asphalt distributor. For most effec-tive blade mixing, the motor grader should have ablade at least 10 feet long, and should have awheelbase of at least 15 feet. Motor graders usedfor final layout and finishing of the surface shouldbe equipped with smooth, rather than treaded,pneumatic tires. Scarifier or plow attachmentsmay be mounted before, behind, or both before andbehind the blade.

(d) Asphalt distributor. The asphalt distrib-utor is a key piece of equipment in cold mixconstruction, particularly when rotary pulverizermixers without built-in asphalt feed are used, orwhen blade mixing is utilized. The asphalt distrib-utor, either truck, or trailer-mounted, consists ofan insulated tank, self-contained heating system, apump, and a spray bar and nozzles through whichthe liquid asphalt is applied under pressure ontothe prepared aggregate materials (fig 4-51). As-phalt distributors range in performance and capa-bility, with some capable of spreading up to 15 feet

4-22

Figure 4-51. Distributor applying asphalt.

at controlled rates to as high as 3 gallons persquare yard. It is important to keep an adequatesupply of asphalt at or near the jobsite to avoiddelays. In rural areas, it may be advisable to havean asphalt supply truck at the project.

(2) Spreading equipment. Some cold mixesmay be spread to the required depth withoutaeration. Generally, these are open-graded mixes,placed under climatic conditions that will allowevaporation of moisture or volatiles within a rea-sonable time. They may be spread by a travelplant, from windrows by motor grader or by largemultipurpose equipment, such as a cutter-trimmer-spreader. On the latter machine, guidance andgrade are electronically controlled by sensors thattake reference from wires stretched along one orboth sides of the roadway.

b. Mixed-in-Place Construction.(1) Windrows. Several types of cold-mix con-

struction require that the aggregates be placed in

TM 5-822-14/AFJMAN 32-1019

windrows prior to mixing and spreading. If wind-rows are to be used, the roadway must be clearedof all vegetation to a width sufficient to accommo-date both windrow and traffic while the mixturecures. Because the thickness of the new pavementis directly proportional to the amount of aggregatein the windrow(s), accurate control and measure-ment of the volume of the windrowed material isnecessary. Usually, there is not enough loose mate-rial on the road surface to use in the road mix. Inthis case, it is best to blade the loose material ontothe shoulder rather than perform the severaloperations that are necessary to blend it with thematerial brought in from other sources. Some-times, however, incorporating the existing mate-rial on the roadbed into the mixture is consideredpractical, if it is uniform and enough is available.When this is done, the loose aggregate must firstbe bladed into a windrow and measured. Next, itmust be made to meet grading specifications byadding other aggregates as necessary. Finally, thewindrow is built up to the required volume withimplanted material that meets the specifications.If two or more materials are to be combined on theroad to be surfaced, each should be placed in itsown windrow. These windrows are then mixedtogether thoroughly before asphalt is added.

(2) Determining asphalt application rate. Be-fore mixing operations begin, the correct asphaltapplication rate and forward speed of the spraybar equipped mixer or asphalt distributor must bedetermined for the quantity of aggregate in thewindrow. Also, when using emulsified asphalt, itis frequently necessary to moisten the aggregatebefore applying the asphalt and the water applica-tion rate and forward speed of the water distribu-tor must be determined.

(3) Control of asphalt. Asphalt is added to theaggregate from an asphalt distributor or by atravel mixer. Whichever method is used, closecontrol of quantity and viscosity is required toensure a proper mixture. Maintaining the correctviscosity is critical because the asphaltic materialmust be fluid enough to move easily through thespray nozzles and to coat adequately the aggregateparticles: Cutback asphalts, and occasionally emul-sified asphalts, even though already fluid, requiresome heating in order to bring them to a viscositysuitable for spraying. If the proper grade of as-phalt has been used, and the mixing is donecorrectly, the cutback or emulsified asphalt willremain fluid until the completion of mixing. Asthe actual temperature of the mixture is controlledby that of the aggregate, care must be taken to seethat mixing is not attempted at aggregate temper-atures below 50 degrees F.

(4) Mixing.(a) Travel plant mixing. Travel-plant mixing

offers the advantage of closer control of the mixingoperation than is possible with blade mixing. Withthe windrow-type travel plant, the machine movesalong the windrow, picking up the aggregate,mixing it with asphalt in the pugmill, and deposit-ing the mixture in a windrow, ready for aeratingor spreading. For this type of plant, the asphaltapplication rate must be matched accurately withthe width and thickness of the course, forwardspeed of the mixer, and the density of the in-placeaggregate. As the thickness is specified, the den-sity is fixed, and the asphalt application rate isset; the variable is the forward speed. If theaggregate windrow is so large that all of theasphalt cannot be incorporated in one mixing pass,it should be split into two or more windrows andthe proper amount of asphalt added to each wind-row as it is mixed. Sometimes, further mixing ofthe windrowed material may be necessary afterthe addition of the asphalt. Unless the travelmixer can be used as a multiple pass mixer, thisaddition mixing usually is done with a motorgrader. This ensures that all of the windrowedmaterial is incorporated into the mix. It alsoaerates the mixture for the removal of diluents.The number of passes with the motor graderrequired for this purpose varies with different jobconditions. After the mixing and aeration proce-dure is completed, the windrow should be moved toone side of the area to be surfaced in preparationfor spreading. The hopper-type travel plant oper-ates by mixing, in its pugmill, the proper amountof asphalt with aggregate that is deposited by haultrucks, directly into the plant’s hopper; then itspreads the mixture. Except when using open-graded mixtures, care must be taken to ensuresufficient evaporation of diluents from the mixprior to compaction.

(b) Rotary mixing. As with windrow travelplants, rotary mixers equipped with built-in spray-ing systems require that the asphalt applicationrates be matched accurately with the width andthickness of the course, forward speed of the mix-er, and the density of the in-place aggregate. How-ever, when utilizing a rotary mixer not equippedwith spraybars, an asphalt distributor, operatingahead of the mixer, applies asphalt to the aggre-gate. Incremental applications of asphalt andpasses of the mixer are usually necessary toachieve the specified mixture. Most rotary mixersare now equipped with a spray system. Whenusing this type of mixer the following steps arerecommended:

4-23

TM 5-822-14/AFJMAN 32-1019

Step 1. Spread the aggregate to uniformgrade and cross section with motor graders.

Step 2. Thoroughly mix the aggregate byone or more passes of the mixer. When ready forthe asphalt the moisture content of the aggregateshould not exceed 3 percent, unless laboratorytests indicate that a higher moisture content willnot be harmful when the asphalt is added.

Step 3. Add asphalt in increments of about0.50 gallons per square yard until the total re-quired amount of asphalt is applied and mixed in.A total of 0.4 to 0.7 gallons per square yard perinch of compacted thickness of the course is usu-ally necessary. If the mixer is not equipped withspraybars the asphalt usually is applied with anasphalt distributor.

Step 4. Make one or more passes of themixer between applications of asphalt, as neces-sary to thoroughly mix it in.

Step 5. Maintain the surface true to gradeand cross-section by using a motor grader duringthe mixing operations.

Step 6. Aerate the mixture by additionalmanipulation, if needed.

(c) Blade mixing. With blade mixing, theimported or in-place material is shaped into ameasured windrow, either through a spreader boxor by running through a windrow shaper. Thewindrow is then flattened with the blade to aboutthe width of the distributor spraybar. The asphaltis applied by successive passes of the asphaltdistributor over the flattened windrow, each appli-cation not exceeding 0.75 gallons per square yard.After each pass of the distributor the mixture isworked back and forth across the roadbed with theblade, sometimes added by auxiliary mixing equip-ment. Prior to each succeeding application ofasphalt, the mixture is reformed into a flattenedwindrow. The material in the windrow is subjectedto as many mixings, spreading, shapings, andflattenings as are needed to disperse the asphaltthoroughly throughout the mixture, and to coateffectively the aggregate particles. During mixing,the vertical angle of the mold board may requireadjustment from time to time in order to achieve acomplete rolling action of the windrow as it isworked. As large a roll as possible should becarried ahead of the blade, since pressure from theweight of the aggregate facilitates mixing. Addi-tionally, during mixing, care must be taken to seethat neither extra material be taken from themixing table and incorporated into the windrownor any of the windrow be lost over the edge of themixing table or left on the mixing table withoutbeing treated. Sometimes, when cutback asphalt isused, the formation of “oil balls,” i.e., concentrated

4 -24

clusters of fine aggregate saturated and coatedwith excessive amounts of asphalt can make a mixdifficult to spread and compact. This condition canbe corrected by windowing the mixture into a tightwindrow and allowing it to cure for a few days.After mixing and aeration have been completed,the windrow is moved to one side of the roadbed inreadiness for subsequent spreading. If it is left forany length of time, periodic breaks in the windrowshould be cut to ensure drainage of rainwater fromthe roadbed.

(5) Aeration. Before compaction, most of thediluents that have made the asphalt cold mixworkable must be allowed to evaporate. In mostcases, this occurs during mixing and spreadingand very little additional aeration is required, butextra manipulation on the roadbed is needed occa-sionally to help speed the process and dissipate theexcess diluents. Until the mix is sufficiently aer-ated, it usually will not support rollers withoutexcessive pushing under the rolls. Generally, themixture is sufficiently aerated when it becomestacky and appears to “crawl.” Many factors affectthe rate and the required amount of aeration.Fine-g-rained and well-graded mixtures will re-quire longer aeration than open-graded and coarse-grained mixtures, all other things being equal.Also, if an asphalt cold-mix base course is to besurfaced within a short length of time, aerationbefore compaction should be more complete than ifthe course is not to be surfaced for some time; thesurface acts as a seal, greatly retarding the re-moval of diluents.

(a) Emulsified asphalt mixes. Experiencehas shown that break-down rolling of emulsifiedasphalt mixes should begin immediately before, orat the same time as, the emulsion starts to break(indicated by a marked color change from brown toblack). About this time, the moisture content ofthe mixture is sufficient to act as a lubricantbetween the aggregate particles, but is reduced tothe point where it does not fill the void spaces,thus allowing their reduction under compactiveforces. Also, by this time, the mixture should beable to support the roller without undue displace-ment.

(b) Cutback asphalt mixes. When using cut-back asphalt, correct aeration will be achievedwhen volatile content is reduced to about 50percent of that contained in the original asphalticmaterial, and the moisture content does not exceed2 percent by weight of the total mixture.

(6) Spreading and compacting. With mixingand aeration completed, spreading and compactingthe cold mix follows. Achieving a finished sectionand smooth riding surface conforming to the plans

TM 5-822-14/AFJMAN 32-1019

is the objective of these final two constructionsteps. The mixture should always be spread to auniform thickness (whether in a single pass or inseveral thinner layers) so that no thin spots existin the final mat. Mixtures that do not requireaeration may be spread to the required thicknessimmediately after mixing and then compactedwith pneumatic-tired vibratory or steel-tired roll-ers. Mixtures that require aeration, however, aregenerally deposited upon the roadbed in windrowsand then are spread from these windrows. Thewindrow may be placed along the centerline of theroad, or along one side if the mixture is to bespread by blade. Because there is a tendency toleave a hump in the road when blade spreadingfrom a center-line windrow, it is considered betterpractice to place the windrow to the side forspreading. Blade spreading should be accomplishedin successive layers, with no layer thinner thanabout 1.5 times the diameter of the maximumparticle size. As each layer is spread, compactionshould follow almost immediately with a pneu-matic-tired roller. Because the tires of the motorgrader compact the freshly spread mix, their trackswill appear as ridges in the finished mat unlessthere is adequate rolling between the spreading ofeach successive layer. The roller should followdirectly behind the motor grader in order toeliminate these ridge marks (fig 4-52). If, at anytime during compaction, the asphalt mixture ex-hibits undue rutting or shoving, rolling should bestopped. Compaction should not be attempted untilthere is a reduction diluent content, occurringeither naturally or by mechanical aeration. Afterone course is thoroughly compacted and cured,other courses may be placed on it. This operationshould be repeated as many times as necessary tobring the road to proper grade and crown. For asmooth riding surface the motor grader should beused to trim and level as the rollers completecompaction of the upper layer. After the mat hasbeen shaped to its final required cross section, itmust then be finish rolled, preferably with asteel-tired roller, until all roller marks are elimi-nated. Sometimes, a completed course may have tobe opened temporarily to traffic. In this event, toprevent tire pickup, it may be advisable to seal thesurface by applying a dilution of slow-settingemulsified asphalt and potable water (in equalparts) at a rate of approximately 0.10 gallons persquare yard. This should be allowed to cure untilno pickup occurs. For immediate passage of traffic,sanding may be desirable to avoid pickup.

c. Equipment for Plant Mixing.(1) Mixing equipment.

Figure 4-52. Spreading and compacting train.

(a) Stationary plants. Generally, stationaryplant mixing is accomplished at a location awayfrom the road site, frequently at the aggregatesource. A stationary plant consists of a mixer andequipment for heating the asphalt (if necessary)and for feeding the asphalt, aggregate, and addi-tives (if needed) to the mixer. It is similar in manyrespects to the hot-mix plant, except that it has nodryer or screens other than a scalping screen. Likethe bigger hot-mix plant, a stationary cold-mixplant may be either a batch or continuous type,although the latter is most prevalently used forcold-mix construction (figs 4-53 and 4-54). Anytype of plant that can produce an asphalt mixtureconforming to the specifications can be used. But,as a minimum, it should be equipped with temper-ature and metering devices to control accuratelythe asphalt material being applied to the aggre-gate and controlled feeders for proportioning ag-gregates and additives. Although not always aplant component, a storage silo allows a morecontinuous mixing operation, resulting in bettermix uniformity.

(b) Haul trucks. Several types of haul trucksmay be used for cold mix produced in stationaryplants; the type selected depends on the spreadingequipment. The traditional raised-bed end-dumptruck can be used with windrowers or pavers withhoppers. Bottom dumps produce windrows and arenot used with pavers with hoppers unless a low-liftloader is used to transfer the mix to the hopper.Horizontal discharge trucks deposit the mix di-rectly into the paver’s hopper without raising thebed. These trucks may also be used with windrowspreader boxes. A sufficient number of haul truckswith smooth, clean beds should be available toensure uniform operation of the mixing plant andpaver.

(2) Spreading equipment.(a) Paver. If climatic conditions and aggre-

gate gradation permit evaporation of moisture or

4-25

TM 5-822-14/AFJMAN 32-1019

Figure 4-55. Spreading cold mix with conventional paver.

Figure 4-53. Stationary cold-mix plant.

Figure 4-54. Flow diagram of a typicalcold-mix continuous plant.

volatiles without aeration by manipulation, a con-ventional self-propelled asphalt paver may be usedto place asphalt cold mixture (fig 4-55). A full-width paver may be used if the plant can produceenough mixture to keep the paver moving withoutstart-stop operation (fig 4-56).

(b) Spreaders. Spreading equipment such asthe Jersey Spreader and towed spreaders arecommonly used. The Jersey Spreader is a hopper,with front wheels, that is attached to the front endof a crawler or rubber-tired tractor, into which theasphalt mixture is dumped. The mixture fallsdirectly to the road and is struck off and spread tocontrolled thickness (fig 4-57). To begin spreadingthe mixture at the specified depth, the tractorshould be driven onto blocks or boards of a heightequal to the depth of spread and placed so that thetractor will ride directly onto the newly-placedmaterial. Once spreading has begun, a continuous

Figure 4-56. Spreading cold mix with full-width cutter-trimmermodified for paving.

flow of mixture from the haul truck to thespreader must be maintained. Towed-type spread-ers are attached to the rear of haul trucks (fig4-58). The asphalt cold mix is deposited into thehopper and falls directly to the surface beingpaved. As the truck moves forward, the mixture isstruck off by a cutter bar, a blade, or by the screedand is ironed out by the screed or by rollers. Manytowed-type spreaders have floating screeds. Inorder for the spreader to start out spreading to fulldepth, blocking should be placed under the screenbefore any mixture is dumped into the hopper. Thehopper should be kept full of material duringpaving operations to ensure a full, even spread.The spreader should be towed at a uniform speedfor any given setting of the screed or strike-offgate. Variations in towing speed will vary spreadthickness.

d. Central Plant Mix Construction.(1) Preparation of mixture. In batch-type

plants, mixing is usually accomplished by a twin-shafted pugmill having a capacity of not less than2,000 pounds. The correct amounts of asphalt andaggregate, generally determined by weight, are fedinto the pug-mill. The batch is then mixed anddischarged into a haul truck before another batchis mixed. In the continuous-mixing plant, thedevices feeding asphalt, aggregate, and water, ifneeded, are interlocked to maintain automaticallythe correct proportions. Typically, automatic feed-

4-26

TM 5-822-14/AFJMAN 32-1019

Figure 4-57. Jersey spreader.

Figure 4-58. Towed-type spreader.

ers measure and govern the flow of aggregates inrelation to the output of a positive displacement

asphalt metering pump. A spray nozzle arrange-ment at the mixer distributes the asphalt over theaggregate. As the proportioned materials movethrough the pugmill, completely mixed material,ready for spreading, is discharged for subsequenthauling to the road site.

(2) Aerating plant mix. Mixtures that requireaerating are generally deposited upon the roadbedin windrows and then are spread from thesewindrows. The cold mix is spread with a motorgrader and aerated by blading it back and forth, orit is aerated by rotary tiller mixing equipment.

(3) Spreading and compacting plant mix. Ifaeration is not required-as is generally the casewith plant-mixed emulsified asphalt mixes-themixture is most effectively spread with asphaltpavers having automatic controls. For deep lifts,however, other equipment such as the JerseySpreader type, towed spreaders, large cutter-trimmer-spreaders, or motor graders may be used.Similar to mixed-in-place, central plant cold mixesgain stability as the diluents (that have made themix workable) evaporate. It is important not tohinder this process. Therefore, lift thicknesses arelimited by the rate that the mixture loses itsdiluents. The most important factors affecting thisloss are the type of asphalt, diluent content,gradation, and temperature of the aggregate, windvelocity, ambient temperature, and humidity. Be-cause of these variables, local experience is likelyto be the best guide in determining allowableplacement thicknesses. The mixture should bespread uniformly on the roadbed, beginning at thepoint farthest from the mixing plant. Hauling overfreshly placed material should not be permittedexcept when required for completion of the work.

4 -27

TM 5-822-14/AFJMAN 32-1019

CHAPTER 5

QUALITY CONTROL

5-1. General Purpose. Quality control is essen-tial to ensure that the final product will beadequate for its intended use. It must also ensurethat the contractor has performed in accordancewith the plans and specification, as this is a basisfor payment. This section identifies those controlfactors which are most important in soil stabiliza-tion construction with cement, lime, lime-fly ash,and asphalt.

5-2. Cement Stabilization. Those factors whichare most important for a quality control stand-point in cement stabilization are: pulverization,cement content, moisture content, uniformity ofmixing, time sequence of operations, compaction,and curing. These are described in detail below.

a. Pulverization. Pulverization is generally not aproblem in cement construction unless clayey orsilty soils are being stabilized. A sieve analysis isperformed on the soil during the pulverizationprocess with the No. 4 sieve used as a control. Thepercent pulverization can then be determined bycalculation. Proper moisture control is also essen-tial in achieving the required pulverization.

b. Cement content. Cement content is normallyexpressed on a volume or dry weight basis. Fieldpersonnel should be aware of quantities of cementrequired per linear foot or per square yard ofpavement. Spot check can be used to assure thatthe proper quantity of cement is being applied, byusing a canvas of known area or, as an overallcheck, the area over which a known tonnage hasbeen spread.

c. Moisture content. The optimum moisture con-tent determined in the laboratory is used as aninitial guide when construction begins. Allowancemust be made for the in situ moisture content ofthe soil when construction starts. The optimummoisture content and maximum density can thenbe established for field control purposes. Mixingwater requirements can be determined on the rawsoil or on the soil-cement mix before addition ofthe mixing water. Nuclear methods can be used todetermine moisture content at the time construc-tion starts and during processing.

d. Uniformity of mixing. A visual inspection ismade to assure the uniformity of the mixturethroughout the treated depth. Uniformity must bechecked across the width of the pavement and tothe desired depth of treatment. Trenches can bedug and then visually inspected. A satisfactory

mix will exhibit a uniform color throughout;whereas, a streaked appearance indicates a nonu-niform mix. Special attention should be given tothe edges of the pavement.

e. Compaction. Equipment used for compactionis the same that would be used if no cement werepresent in the soil, and is therefore dependentupon soil type. Several methods can be used todetermine compacted density: sand-cone, balloon,oil, and nuclear method. It is important to deter-mine the depth of compaction and special attentionshould be given to compaction at the edges.

f. Curing. To assure proper curing a bituminousmembrane is frequently applied over large areas.The surface of the soil cement should be free of dryloose material and in a moist condition. It isimportant that the soil-cement mixture be keptcontinuously moist until the membrane is applied.The recommended application rate is 0.15 to 0.30gallons per square yard.

5-3. lime Stabilization. The most important fac-tors to control during soil-lime construction arepulverization and scarification, lime content, uni-formity of mixing, time sequence of operations,compaction and curing.

a. Pulverization and scarification. Before appli-cation of lime, the soil is scarified and pulverized.To assure the adequacy of this phase of construc-tion, a sieve analysis is performed. Most specifica-tions are based upon a designated amount ofmaterial passing the 1 inch and No. 4 sieves. Thedepth of scarification or pulverization is also ofimportance as it relates to the specified depth oflime treatment. For heavy clays, adequate pulveri-zation can best be achieved by pretreatment withlime, but if this method is used, agglomeratedsoil-lime fractions may appear. These fractions canbe easily broken down with a simple kneadingaction and are not necessarily indicative of im-proper pulverization.

b. Lime content. When lime is applied to thepulverized soil, the rate at which it is being spreadcan be determined by placing a canvas of knownarea on the ground and, after the lime has beenspread, weighing the lime on the canvas. Chartscan be made available to field personnel to deter-mine if this rate of application is satisfactory forthe lime content specified. To accurately determinethe quantity of lime slurry required to provide thedesired amount of lime solids, it is necessary to

5-1

TM 5-822-14/AFJMAN 32-1019

know the slurry composition. This can be done bychecking the specific gravity of the slurry, eitherby a hydrometer or volumetric-weight procedure.

c. Uniformity of mixing. The major concern is toobtain a uniform lime content throughout thedepth of treated soil. This presents one of the mostdifficult factors to control in the field. It has beenreported that mixed soil and lime has more or lessthe same outward appearance as mixed soil with-out lime. The use of phenolphthalein indicatorsolution for control in the field has been recom-mended. This method, while not sophisticatedenough to provide an exact measure of lime con-tent for depth of treatment, will give an indicationof the presence of the minimum lime contentrequired for soil treatment. The soil will turn areddishpink color when sprayed with the indicatorsolution, indicating that free lime is available inthe soil (pH = 12.4).

d. Compaction. Primarily important is theproper control of moisture-density. Conventionalprocedures such as sand cone, rubber balloon, andnuclear methods have been used for determiningthe density of compacted soil lime mixtures. Mois-ture content can be determined by either oven-drymethods or nuclear methods. The influence of timebetween mixing and compacting has been demon-strated to have a pronounced effect on the proper-ties of treated soil. Compaction should begin assoon as possible after final mixing has been com-pleted. The National Lime Association recom-mends an absolute maximum delay of one week.The use of phenolphthalein indicator solution hasalso been recommended for lime content controltesting. The solution can be used to distinguishbetween areas that have been properly treated andthose that have received only a slight surfacedusting by the action of wind. This will aid inidentifying areas where density test samplesshould be taken.

e. Curing. Curing is essential to assure that thesoil lime mixture will achieve the final propertiesdesired. Curing is accomplished by one of twomethods: moist curing, involving a light sprinklingof water and rolling; or membrane curing, whichinvolves sealing the compacted layer with a bitu-minous seal coat. Regardless of the method used,the entire compacted layer must be properly pro-tected to assure that the lime will not becomenonreactive through carbonation. Inadequatesprinkling which allows the stabilized soil surfaceto dry will promote carbonation.

5-4. Lime-Fly Ash (LF) and Lime-Cement-FlyAsh (LCF). The nature of lime-fly ash and lime-cement-fly ash stabilization is similar to that for

5 -2

lime only. Consequently, the same factors involvedfor quality control are suggested.

5-5. Bituminous Stabilization. The factors thatseem most important to control during construc-tion with bituminous stabilization are surfacemoisture content, viscosity of the asphalt, asphaltcontent, uniformity of mixing, aeration, compac-tion, and curing.

a. Surface moisture content. The surface mois-ture of the soil to be stabilized is of concern.Surface moisture can be determined by conven-tional methods, such as oven-drying, or by nuclearmethods. The Asphalt Institute recommends asurface moisture of up to three percent or more foruse with emulsified asphalt and a moisture con-tent of less than three percent for cutback asphalt.The gradation of the aggregate has proved to be ofsignificance as regards moisture content. Withdensely graded mixes, more water is needed formixing than compaction. Generally, a surfacemoisture content that is too high will delay com-paction of the mixture. Higher plasticity indexsoils require higher moisture contents.

b. Viscosity of the asphalt. The Asphalt Instituterecommends that cold-mix construction should notbe performed at temperatures below 50 degrees F.The asphalt will rapidly reach the temperature ofthe aggregate to which it is applied and at lowertemperature difficulty in mixing will be encoun-tered. On occasion, some heating is necessary withcutback asphalts to assure that the soil aggregateparticles are thoroughly coated.

c. Asphalt content. Information can be providedto field personnel which will enable them todetermine a satisfactory application rate. The as-phalt content should be maintained at optimum orslightly below for the specified mix. Excessivequantities of asphalt may cause difficulty in com-paction and result in plastic deformation in serviceduring hot weather.

d. Uniformity of mixing. Visual inspection canbe used to determine the uniformity of the mix-ture. With emulsified asphalts, a color changefrom brown to black indicates that the emulsionhas broken. The Asphalt Institute recommendscontrol of three variables to assure uniformity formixed-in-place construction: travel speed of appli-cation equipment; volume of aggregate beingtreated; and flow rate (volume per unit time) ofemulsified asphalt being applied. In many cases,an asphalt content above design is necessary toassure uniform mixing.

e. Aeration. Prior to compaction, the diluentsthat facilitated the cold-mix operation must beallowed to evaporate. If the mix is not sufficient-

TM 5-822-14/AFJMAN 32-1019

ly aerated, it cannot be compacted to accept-able limits. The Asphalt Institute has deter-mined that the mixture has sufficiently aeratedwhen it becomes tacky and appears to “crawl.”Most aerating occurs during the mixing andspreading stage, but occasionally additional work-ing on the roadbed is necessary. The AsphaltInstitute has reported that overmixing in centralplant mixes can cause emulsified asphalts to breakearly, resulting in a mix that is difficult to workin the field.

f. Compaction. Compaction should begin whenthe aeration of the mix is completed. The AsphaltInstitute recommends that rolling begin when anemulsified asphalt mixture begins to break (colorchange from brown to black). Early compactioncan cause undue rutting or shoving of the mixturedue to overstressing under the roller. The densityof emulsion stabilized bases has often been foundto be higher than that obtained on unstabilizedbases for the same compaction effort.

g. Curing. Curing presents the greatest problemin asphalt soil stabilization. The Asphalt Institutehas determined that the rate of curing is depen-dent upon many variables: quantity of asphaltapplied, prevailing humidity and wind, theamount of rain, and the ambient temperature.Initial curing must be allowed in order to supportcompaction equipment. This initial curing, theevaporation of diluents, occurs during the aerationstage. If compaction is started too early, thepavement will be sealed, delaying dehydration,which lengthens the time before design strength isreached. The heat of the day may cause themixture to soften, which prohibits equipment fromplacing successive lifts until the following day.This emphasizes the need to allow sufficient cur-ing time when lift construction is employed. TheAsphalt Institute recommends a 2- to 5-day cur-ing period under good conditions when emulsifiedbases are being constructed. Cement has been usedto accelerate curing.

5 - 3

TM 5-822-14/AFJMAN 32-1019

APPENDIX A

REFERENCES

Government Publications.Department of Defense

MIL-STD 619B

MIL-STD 620A

MIL-STD 621A

Unified Soil Classification System forRoads, Airfields, Embankments, andFoundations

Test Methods for Bituminous Paving ma-terials

Test Methods for Pavement Subgrade,Subbase, and Base Course Materials

Departments of the Army and Air Force

TM 5-822-5/AFM 88-7 Chap. 3

TM 5-822-8/AFM 88-6 Chap. 9

TM 5-825-2/AFM 88-6 Chap. 2

TM 5-825-3/AFM 88-6 Chap. 3

Pavement Design for Roads, Streets,Walks, and Open-Storage Areas

Bituminous Pavements-Standard Practice

Flexible Pavements Design for Airfields

Rigid Pavements for Airfields

Nongovernment PublicationsAmerican Society for Testing and Materials (ASTM): 1961Race Street, Philadelphia, PA 19103

Soil Stabilization with AdmixturesC 51-90 Terminology Relating to Lime and Lime-

stone (as Used by the Industry)C 150-89 Specification for Portland CementC 593-89 Fly Ash and Other Pozzolans for Use with

LimeC 977-89 Specification for Quicklime and Hydrated

Lime for Soil StabilizationD 98-87 Specification for Calcium ChlorideD 422-63 Particle-Size Analysis of SoilsD 423-66 Test for Liquid Limit of SoilsD 424-59 Test for Plastic Limit and Plasticity Index

of SoilsD 558-82 Test Methods for Moisture-Density Rela-

tions of Soil-Cement MixturesD 559-89 Test Methods for Wetting and Drying

Compacted Soil-Cement MixturesD 560-89 Test Methods for Freezing and Thawing

Compacted Soil-Cement MixturesD 698-78 Test methods for Moisture-Density Rela-

tions of Soils and Soil Aggregate Mix-tures Using 5.5-lb (2.49-kg) Rammer and12-in. (305-mm) Drop

D 806-89 Test Method for Cement Content of Soil-Cement Mixtures

D 1411-82 Test Methods for Water-Soluble ChloridesPresent as Admixes in Graded Aggre-gate Road Mixes

A - 1

TM 5-822-14/AFJMAN 32-1019

D 1557-78

D 1632-87

D 1633-84

D 1634-87

D 1635-87

D 1883-84

D 2487-85

D 2901-82 (1986)

D 3155-83

D 3551-83

D 3668-78 (1985)

D 3877-80 (1985)

D 4223-83

D 4318-84

D 4609-86

D 4832-88

Test Methods for Moisture-Density Rela-tions of Soils and Soil-Aggregate Mix-tures Using 10-lb (4.54-kg) Rammer and18-in. (457-mm) Drop

Practice for Making and Curing Soil-Cement Compression and Flexure TestSpecimens in the Laboratory

Test Method for Compressive Strength ofMolded Soil-Cement Cylinders

Test Method for Compressive Strength ofSoil-Cement Using Portions of BeamsBroken in Flexure (Modified CubeMethod)

Test Method for Flexural Strength of Soil-Cement Using Simple Beam with Third-Point Loading

Bearing Ratio of Laboratory CompactedSoils

Test Methods for Classification of Soils forEngineering Purposes

Test method for Cement Content ofFreshly Mixed Soil-Cement

Test Method for Lime Content of UncuredSoil-Lime Mixtures

Method for Laboratory Preparation of Soil-Lime Mixtures Using a MechanicalMixer

Test Method for Bearing Ratio of Labora-tory Compacted Soil-Lime Mixtures

Test Methods for One-Dimensional Expan-sion, Shrinkage, and Uplift Pressure ofSoil-Lime Mixtures

Practice for Preparation of Test Specimensof Asphalt-Stabilized Soils

Test Method for Liquid Limit, PlasticLimit, and Plasticity Index of Soils

Guide for Screening Chemicals for SoilStabilization

Test Method for Preparation and Testingof Soil-Cement Slurry Test Cylinders

A - 2

TM 5-822-14/AFJMAN 32-1019

APPENDIX B

pH TEST ON SOIL-CEMENT MIXTURES

B-1. Materials. Portland cement to be used for soil stabilization.

B-2. Apparatus. Apparatuses used are the pH meter (the pH meter mustbe equipped with an electrode having a pH range of 14), 150-millilitreplastic bottles with screw-top lids, 500-millilitre plastic beakers, distilledwater, balance, oven and moisture cans.

B-3. Procedure.a. Standardization. Standardize the pH meter with a buffer solution

having a pH of 12.00.b. Representative samples. Weight to the nearest 0.01 grams, representa-

tive samples of air-dried soil, passing the No. 40 sieve and equal to 25.0grams of oven-dried soil.

c. Soil samples. Pour the soil samples into 150-millilitre plastic bottleswith screw-top lids.

d. Portland cement. Add 2.5 grams of the portland cement.e. Mixture. Thoroughly mix soil and portland cement.f. Distilled water. Add sufficient distilled water to make a thick paste.

(Caution: Too much water will reduce the pH and produce an incorrectresult.)

g. Blending. Stir the soil-cement and water until thorough blending isachieved.

h. Transferal After 15 minutes, transfer part of the paste to a plasticbeaker and measure the pH.

i. Interference. If the pH is 12.1 or greater, the soil organic mattercontent should not interfere with the cement stabilizing mechanism.

B-1

TM 5-822-14/AFJMAN 32-1019

APPENDIX C

DETERMINATION OF SULFATE IN SOILSGRAVIMETRIC METHOD

C-1. Gravimetric Method.a. Scope. Applicable to all soil types with the possible exception of soils

containing certain organic compounds. This method should permit thedetection of as little as 0.05 percent sulfate as SO,.

b. Reagents. Reagents include barium chloride, 10 percent solution ofBaCl2 l 2H2O (Add 1 milliliter 2 percent HCl to each 100 milliliter ofsolution to prevent formation of carbonate.); hydrochloric acid, 2 percentsolution (0.55 N); magnesium chloride, 10 percent solution of MgCl2 l 6H2O;demineralized water; and silver nitrate, 0.1 N solution.

c. Apparatus. Apparatus used are a beaker, 100 milliliter; burner andring stand; filtering flask, 500 milliliter; Buchner funnel, 90 milliliter; filterpaper, Whatman No. 40, 90 millimeter; filter paper, Whatman No. 42, 90millimeter; Saran Wrap; crucible, ignition, or aluminum foil, heavy grade;analytical balance; and aspirator or other vacuum source.

d. Procedure.(1) Select a representative sample of air-dried soil weighing approxi-

mately 10 grams. Weigh to the nearest 0.01 gram. (Note: When sulfatecontent is anticipated to be less than 0.1 percent, a sample weighing 20gram or more may be used.) (The moisture content of the air-dried soil mustbe known for later determination of dry weight of the soil.)

(2) Boil for 1-1/2 hours in beaker with mixture of 300-milliliter waterand 15-milliliter HCl.

(3) Filter through Whatman No. 40 paper, wash with hot water, dilutecombined filtrate and washings to 50 milliliter.

(4) Take 100 milliliter of this solution and add MgCl2 solution until nomore precipitate is formed.

(5) Filter through Whatman No. 42 paper, wash with hot water, dilutecombined filtrates and washings to 200 milliliter.

(6) Heat 100 milliliter of this solution to boiling and add BaCl2

solution very slowly until no more precipitate is formed. Continue boilingfor about 5 minutes and let stand overnight in warm place, covering beakerwith Saran Wrap.

(7) Filter through Whatman No. 42 paper. Wash with hot water untilfree from chlorides (filtrate should show no precipitate when a drop ofAgNO3 solution is added).

(8) Dry filter paper in crucible or on sheet of aluminum foil. Ignitepaper. Weight residue on analytical balance as BaSO4.

e. Calculation.

Percent SO, =Weight of residue

Oven-dry weight of initial samplex 411.6

where

Oven-dry weight of initial sample

Note: If precipitated from cold solution, barium sulfate is so finely dispersed that it cannot beretained when filtering by the above method. Precipitation from a warm, dilute solution willincrease crystal size. Due to the absorption (occlusion) of soluble salts during the precipitationby BaSO4, a small error is introduced. This error can be minimized by permitting theprecipitate to digest in a warm, dilute solution for a number of hours. This allows the moresoluble small crystals of BaSO4 to dissolve and recrystallize on the larger crystals.

C-1

TM 5-822-14/AFJMAN 32-1019

C-2. Turbidimetric Methoda. Reagents. Reagents include barium chloride crystals (Grind analytical

reagent grade barium chloride to pass a 1-millimeter sieve.); ammoniumacetate solution (0.5 N) (Add dilute hydrochloric acid until the solution hasa pH of 4.2); and distilled water.

b. Apparatus. Apparatus used are a moisture can; oven, 200-milliliterbeaker; burner and ring stand; filtering flask; Buchner funnel, 90 millime-ter; filter paper, Whatman No. 40, 90 millimeter; vacuum source; spectro-photometer and standard tubes (Bausch and Lombe Spectronic 20 orequivalent) and pH meter.

c. Procedure.(1) Take a representative sample of air-dried soil weighing approxi-

mately 10 grams, and weight to the nearest 0.01 grams. (The moisturecontent of the air-dried soil must be known for later determination of dryweight of the soil.)

(2) Add the ammonium acetate solution to the soil. (The ratio of soil tosolution should be approximately 1:5 by weight.)

(3) Boil for about 5 minutes.(4) Filter through Whatman No. 40 filter paper. If the extracting

solution is not clear, filter again.(5) Take 10 milliliter of extracting solution (this may vary, depending

on the concentration of sulfate in the solution) and dilute with distilledwater to about 40 milliliter. Add about 0.2 gram of barium chloride crystalsand dilute to make the volume exactly equal to 50 milliliter. Stir for 1minute.

(6) Immediately after the stirring period has ended, pour a portion ofthe solution into the standard tube and insert the tube into the cell of thespectrophotometer. Measure the turbidity at 30-second intervals for 4minutes. Maximum turbidity is usually obtained within 2 minutes and thereadings remain constant thereafter for 3-10 minutes. Consider the turbidityto be the maximum reading obtained in the 4-minute interval.

(7) Compare the turbidity reading with a standard curve and computethe sulfate concentration (as SO4) in the original extracting solution. (Thestandard curve is secured by carrying out the procedure with standardpotassium sulfate solutions.)

(8) Correction should be made for the apparent turbidity of thesamples by running blanks in which no barium chloride is added.

d. Sample calculation.Given: Weight of air-dried sample = 10.12 grams

Water content = 9.36 percentWeight of dry soil = 9.27 grams

Total volume of extracting solution = 39.1 milliliters10 milliliters of extracting solution was diluted to 50 milliliters afteraddition of barium chloride (see step 5). The solution gave a transmissionreading of 81. From the standard curve, a transmission reading of 81corresponds to 16.0 parts per million. (See fig C-l)

Concentration of original extracting solution = 16.0 x 5 = 80.0 parts permillion.

Percent SO480.0 x 39.1 x 100

= =1,000 x 1,000 x 9.27

0.0338 percent

e. Determination of standard curve.(1) Prepare sulfate solutions of 0, 4, 8, 12, 16, 20, 25, 30, 35, 40, 45,

and 50 parts per million in separate test tubes. The sulfate solution is madefrom potassium sulfate salt dissolved in 0.5 N ammonium acetate (with pHadjusted to 4.2).

C-2

TM 5-822-14/AFJMAN 32-1019

(2) Continue steps 5 and 6 in the procedure as described in Determina-tion of Sulfate in Soil by Turbidimetric Method.

(3) Draw standard curve as shown in figure C-l by plotting transmis-sion readings for known concentrations of sulfate solutions.

Figure C-1. Example standard curve for spectrophotometer.

C-3

TM 5-822-14/AFJMAN 32-1019

APPENDIX D

pH TEST TO DETERMINE LIME REQUIREMENTS FORLIME STABILIZATION

D-1. Materials. Lime to be used for soil stabilization.

D-2. Apparatus. Apparatus include pH meter (the pH meter must beequipped with an electrode having a pH range of 14), 150-milliliter (orlarger) plastic bottles with screw-top lids, 50-milliliter plastic beakers,distilled water that is free of CO,, balance, oven, and moisture cans.

D-3. Procedure.a. Standardize pH meter. Standardize the pH meter with a buffer

solution having a pH of 12.45.b. Weight samples. Weigh to the nearest 0.01 gram representative

samples of air-dried soil, passing the No. 40 sieve and equal to 20.0 grams ofoven-dried soil.

c. Pour samples. Pour the soil samples into 150-milliliter plastic bottleswith screw-top lids.

d. Add lime. Add varying percentages of lime, weighed to the nearest0.01 gram, to the soils. (Lime percentages of 0, 2, 3, 4, 5, 6, 8, and 10, basedon the dry soil weight, may be used.)

e. Mix. Thoroughly mix soil and dry lime.f. Add distilled water. Add 100 milliliters of distilled water that is

CO,-free to the soil-lime mixtures.g. Snake soil-lime and water. Shake the soil-lime and water for a

minimum of 30 seconds or until there is no evidence of dry material on thebottom of the bottle.

h. Shake bottles. Shake the bottles for 30 seconds every 10 minutes.i. Transfer slurry. After 1 hour transfer part of the slurry to a plastic

beaker and measure the pH.j. Record pH. Record the pH for each of the soil-lime mixtures. The

lowest percent of lime giving a pH of 12.40 is the percent required tostabilize the soil. If the pH does not reach 123.40, the minimum limecontent giving the highest pH is required to stabilize the soil.

D-1

TM 5-822-14/AFJMAN 32-1019

The proponent agency of this publication is the office of theChief of Engineers, United States Army. Users are invited tosend comments and suggested improvements on DA Form 2028(Recommended Changes to Publications and Blank Forms) toHQUSACE (CEMP-ET), WASH DC 20314-1000.

By Order of the Secretaries of the Army and Air Force:

Official:

GORDON R. SULLIVANGeneral, United States Army

Chief of Staff

MILTON H. HAMILTONAdministrative Assistant to the

Secretary of the Army

OFFICIAL JAMES E. MCCARTHY, Maj General, USAFThe Civil Engineer

DISTRIBUTION:

Army: To be distributed in accordance with DA Form 12-34-E, block0773, requirements for TM 5-822-14.

Air Force: F

* U.S. G.P.O.:1994-300-723:58