NATIONAL BUREAU OF STANDARDS REPORT

INTERIM REPORT ON PROJECT 4847

STANDARDS FOR BUILT-UP ROOFS

by

W e C. CullenL. R. Kleinschmidt

H. R. Snoke

U. $. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

5422

THE NATIONAL BUREAU OF STANDARDS

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NATIONAL BUREAU OF STANDARDS REPORTNBS PROJECT NBS REPORT

1004-40-4847 August 1957 5422

INTERIM REPORT ON PROJECT 4847

STANDARDS FOR BUILT-UP ROOFS

by

W. C. CullenL. R. Kleinschmidt

H. R. Snoke

Floor, Roof and Wall Coverings SectionBuilding Technology Division

IMPORTANT NOTICE

NATIONAL BUREAU OF ST

intended for use within the

to additional evaluation and 1

listing of this Report, either

the Office of the Director, N;

however, by the Government

to reproduce additional copii

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST)

on October 9, 2015.

progress accounting documents

rmally published it is subjected

reproduction, or open-literature

sion is obtained in writing from

Such permission is not needed,

prepared if that agency wishes

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

INTERIM REPORT ON PROJECT 4847

STANDARDS FDR BUILT-UP ROOFS

INDEX

Page

I. INTRODUCTION 1

II. SUMMARY AND CONCLUSIONS 1

A. Field Studies 1

B„ Laboratory Studies 2

III. PROPOSED SPECIFICATION FOR ASPHALT FOR LOW-SLOPEROOFS 5

IV. ACKNOWLEDGMENT 6

APPENDIX 1. FIELD STUDIES OF BUILT-UP ROOFS 7

1. Introduction 72. Selection of Roofs for Inspection 8

3. Areas Included in the Studies 94. Methods of Inspecting and Rating Roofs 95. Results of Field Studies 12

APPENDIX 2. LABORATORY STUDIES 13

1. Introduction 132. Physical and Chemical Characteristics 143o Component Distribution 154. Susceptibility to Heat 165. Accelerated Durability Exposures 176. Outdoor Exposures 217 o Water Absorption Tests 22

APPENDIX 3. DISCUSSION OF REQUIREMENTS IN THE PROPOSEDSPECIFICATION FOR ASPHALTS FOR LOW-SLOPEROOFS 24

lo Conventional Requirements 242. New Requirements 25

.

*

INTERIM REPORT ON PROJECT 4847

STANDARDS FOR BUILT-UP ROOFS

by

W. C. CullenL. R. Kleinschmidt

H. R. Snoke

I. INTRODUCTION

This report gives the results of field studies of 101 low-pitched, mineral-surfaced, asphalt and coal-tar pitch, built-up roofs in the Western, Mid-Western and Eastern States, andof laboratory studies of 14 asphalts furnished by roofing manu-facturers as representative of materials sold by them for theconstruction of dead-level, mineral-surfaced, built-up roofs.Three samples of coal-tar pitch, furnished by two producers asrepresenting eastern and western production of one and easternproduction of the other, were included in some of the laboratorystudies.

While this was primarily a study of asphalts intended foruse in the construction of low-pitched, mineral-surfaced, built-up roofs, it was considered essential for proper evaluation tocompare the behavior of asphalt and coal-tar-pitch roofs in thefield and to compare the results of laboratory tests on repre-sentative samples of asphalt and coal-tar pitch where suchtests were applicable to both materials.

Complete details of the field studies are described inAppendix 1 of this report and of the laboratory studies inAppendix 2. Appendix 3 contains a discussion of the require-ments in the proposed specification for asphalts for low-sloperoof s

.

II. SUMMARY AND CONCLUSIONS

A, Field Studies

Figure 1 shows graphically the results of the field studies.In this and subsequent graphs, length of service is plottedagainst 100 minus the numerical rating; consequently, the lowerthb slope of the curve, the better the performance rating.Figures 2 to 7 and Table 2, Appendix 1, show details of thefield studies in the various areas. No data are shown forcoal-tar-pitch roofs on the West Coast because coal-tar pitchhas become generally available there only recently 0

.

opr

<GZOQZkJh-kJQ

0 10 20 30 40

EXPOSURE, YEARS

FIGURE 1. RESULTS OF FIELD STUDY.

2

Conclusions drawn from the field studies were:

1. Numerous low-pitched, mineral-surfaced, asphalt and coal-tar pitch, built-up roofs were observed in good, service-able condition in all areas after more than twenty yearsof exposure. Roofs of both types thirty years old werenot uncommon.

2. Coal-tar-pitch roofs were rated slightly higher, generally,than asphalt roofs, in the Eastern and Mid-Western States,This was most apparent in roofs exposed more than twentyyears.

3. Asphalt roofs in the Eastern and Mid -We stern States wererated significantly higher than those in the Western States,Asphalt roofs in the Mid-Western States were rated slightlyhigher than those in the Eastern States.

4. It is our strong opinion that good service from any con-ventional, bituminous, built-up roof depends more oninitial workmanship and subsequent maintenance than onthe materials that are used. This conclusion is not en-tirely a product of this investigation, but is based,rather, on considerable field experience.

B„ Laboratory Studies

In any appraisal of the results of these laboratorystudies, it should be borne in mind that specifications forasphalt and coal-tar pitch have always been based largely onphysical characteristics. Through the years specificationshave evolved which insure materials that can be handled well,will stay in place on a roof, etc.

,

but which give noassurance of the "quality" of the product, if one defines"quality" as service on a roof. That there is no generalagreement, even as regards physical characteristics, isshown by the wide variations in the properties of the mate-rials submitted for these tests.

We have made the standard tests to determine propertiesthat are usually listed in purchase specifications. Inaddition, we have made other tests, many of which show

.

.

- 3 -

differences among the materials tested. Some of these testsare reported here for the first time. We would expect thatdifferent bituminous technologists would interpret the re-sults of some of these tests differently.

Conclusions drawn from the laboratory studies are;

1. Types of Asphalt : Two types of asphalt are being furnishedby roofing manufacturers for low-slope, mineral-surfaced,built-up roofs. Type I is largely characteristic ofasphalt produced for many years for this use. Type IIasphalt is characterized chiefly by high ductility at77°F, embrittlement at 40°F, and a higher susceptibilityfactor than Type I asphalt. Eleven samples of Type I

and three samples of Type II asphalt were furnished bymanufacturers for this study.

2. Compliance with current specifications ; All specimens ofType I asphalt submitted complied with the requirementsof Federal Specification SS-A-666, Type 1, Class A, forsurfaced, built-up roofs, except in minor respects, andall complied with American Society for Testing MaterialsSpecification D312, "Mineral-Surfaced Flat".

The three Type II asphalts complied with Federal Speci-fication SS-A-666, Type 1, Class A, except for penetra-tion at 32°F and 77°F. They complied with A.S.T.M.Specification D312, "Mineral-Surfaced Flat", exceptthat for two of them the penetration at 77°F was lowerthan the minimum specified.

The three samples of coal-tar pitch complied with FederalSpecif ication' R-P-381

,Type I, for built-up roofing.

3. Component distribution in asphalts : The component dis-tribution in asphalts cannot be used alone as a criterionof quality.

4. Deterioration tests :

4.1 Accelerated weathering tests (Exposure to heat,light and water):

4.1.1 Hardening: Both asphalts and coal-tar pitchesshowed marked hardening as evidenced by increases insoftening point.

,* •

.

- 4 -

4 . 1.2 Shrinkage: The asphalts showed varying amounts ofshrinkage on long exposure. The two that shrank mostgave positive "spot" tests and contained the largest per-centage of matter insoluble in n-pentane. The coal-tarpitches showed no detectable shrinkage on long exposure.

4.1.3 Matter insoluble in n-pentane: All asphaltsshowed marked increases in matter insoluble in n-pentaneon long exposure.

4.1.4 Photochemical reactions: Water-soluble acidiccompounds formed from the asphalts were markedly greaterthan those from the pitches. The relatively large amountsof acidic materials formed when asphalts are exposed tolight and moisture emphasize the very important role ofmineral-surfacing materials in built-up roofs.

4.1.5 Self-healing characteristics: Both asphalts andcoal-tar pitches exhibited self-healing properties after4500 hours of accelerated weathering. The coal-tar-pitchspecimens healed more rapidly than the asphalt specimensin all cases. Variations in the rate of self-healingamong the asphalts could not be attributed to the typeof asphalt.

4.2 Outdoor weathering tests:

4.2.1 Hardening: Both asphalts and coal-tar pitcheshardened during outdoor exposures as evidenced by in-creases in softening point.

4.2.2 Self-healing: Both asphalt and coal-tar pitchexhibited self-healing properties during summer exposures;neither showed self-healing properties during winterexposure s

.

4.3 Heat susceptibility tests (Exposure to heat along):

4.3.1 Component distribution: Changes in the componentdistribution of the asphalts when exposed to heat alonewere essentially the same as those found by exposure toaccelerated weathering.

,* .

- 5 -

4.4 Water absorption tests:

4.4.1 Long-time immersion: The amounts of water absorbedby the asphalts in long-time immersion tests varied widely,but were not indicative of the type or source of asphalt.The water absorption of the coal-tar pitches fell withinthe range of the asphalts that absorbed the least.

From 0.05 to 0.1 ml of o.Ol N alkali solution was re-quired to neutralize material leached from each of theasphalts and the coal-tar pitch. This is in marked con-trast to the results of the accelerated weathering test(Exposure 3) where from 20 to 80 ml of 0.01 N alkaliwere required to neutralize the material formed fromdifferent asphalt specimens during 900 hours of exposure.Only 1.6 ml of 0.01 N alkali were required to neutralizematerial formed from the different coal-tar pitches ex-posed similarly.

5. Specification : Laboratory examination of the asphaltsfurnished indicates the desirability of a specifica-tion covering two types of asphalt, with requirementsthat are more restrictive than those of the Federaland A.S.T.M. specifications. A study of specificationsfurnished by manufacturers lends weight to this con-clusion.

III. PROPOSED SPECIFICATION FOR ASPHALTFOR LOW-SLOPE ROOFS

Table 1 lists chemical and physical requirements of twotypes of asphalt for use in the construction of mineral-surfaced, built-up roofs on slopes up to one inch per foot.Type I asphalts are characteristic of low-slope asphaltscovered by Federal and A.S.T.M. specifications, but therequirements in the proposed specification are more restric-tive than in either of those specifications. Type IIasphalts are processed to approximate, initially, some ofthe physical characteristics of coal-tar pitch, notably,high ductility at 77°F.

TABLE 1. PROPOSED SPECIFICATION FOR ASPHALTFOR LOW-SLOPE ROOFS.

Type I II

Min. Max. Min, Max.

Softening point (R & B),—^ °F

Ductility at 77° F-i/, 5 cm/135 1^5 135 145

min.,

cm. 15 100

Ductility at 40°F, 0.25 cm/3min.

,cm. —

Pene tr at ion-2/ at32°F, 200 g, 60 sec. 10 577°F, 100 g, 5 sec. 25 60 15 25

115°F, 50 g, 5 sec.

Weight loss, 5 hrs. at 325°F—

%

100ir\

oO

90

0.5Penetration of residue at 77°F,

percent of originalBitumen soluble in CC11+

, %

85 75

99

30

99

30Bitumen insoluble in

n-pentaneL^ J0

Flow test at l40°F,5 hrs .2^ cm. 2 9 2 9

Spot test.8/

Susceptibility factor^/ 2

Negative

5

Negative

Flash point, C.O.C.—^ °F 375 375

(Methods of Tests)1 /

2/

Vb/

1/

—^N.B.S . RF-2577.

A.S.T,,M. D36.

A.S.T,»M. D113. 8/A.S.T,,M. D5o

A.S.T,,M. D6. 1/

A.S.T,,M. D4.

(Modified ) .

A. A.S.H. 0. T102(“Naphtha)

.

10/A.S . T .M. D92.

Pen, at 115°F - Pen, at 32°F

Pen. at 77°F

- 6 -

The proposed specification contains some requirementsthat are not normally included in specifications for asphaltfor use in the construction of built-up roofs, namely,matter insoluble in n-pentane

,spot test, susceptibility

factor, and flow test, applicable to both types. In addi-tion, a minimum requirement for ductility at 40°F is in-cluded for Type I asphalt. The significance of the speci-fication requirements is discussed in Appendix 3- under"Discussion of Requirements in the Proposed Specificationfor Asphalts for Low-Slope Roofs".

Type I asphalt should be readily available in allareas. Type II asphalts have been available nationallyfor a relatively short time. Consequently, most of thelong-service roofs reported in the field study were ofType I asphalt.

IV. ACKNOWLEDGMENT

The authors acknowledge the assistance of the AsphaltRoofing Industry Bureau in furnishing the list of olderasphalt roofs of known history, and of manufacturers ofasphalt and coal-tar-pitch roofings for the locations ofroofs, assistance in making inspections, and the samplesof asphalt and coal-tar pitch that they furnished. Theassistance of Dr. William S. Connor of the Applied Mathe-matics Division, N.B.S., in the statistical aspects ofthe field survey is also acknowledged.

I

I

1

I

- 7 -

APPENDIX 1. FIELD STUDIES OF BUILT-UP ROOFS

1. Introduction

In planning the field studies of built-up roofs, thefollowing criteria were established as of primary importance:

a) The inspection areas should represent the widelydifferent climatic conditions in the United States,

b) The asphalt roofs should represent the principalsources of asphalt used in this country,

c) Only roofs of known history should be examined,

d) The system for selecting roofs for inspectionshould be entirely unbiased,

e) The system of rating the condition of a roofshould be on a numerical basis.

It was realized of course that many factors other thanthe quality of the bitumen must be considered in evaluatingthe performance of built-up roofs and that serious defectsmay occur that are in no sense related to the quality orkind of bitumen used. For example, it is our opinion thatmore premature roof failures are caused by faulty workman-ship than by faulty materials. Proper maintenance is alsoof great importance in determining the service of any built-up roof.

While the principal purpose of this field study was toevaluate the performance of mineral-surfaced, built-uproofs on low slopes, other roofs of particular interestwere inspected where available. Among these were: smooth-surfaced, built-up roofs; built-up roofs in which glass matreplaced the conventional felts; double-surfaced, built-uproofs; and one application of an elastomeric sheet (Neoprene)on a concrete deck. This report is confined to conventionalmineral-surfaced, built-up roofs.

»

*

mm

- 8 -

2. Selection of Roofs for Inspection

In order to obtain roofs of known history for inspec-tion, it was necessary to rely upon the roofing industry,, TheAsphalt Roofing Industry Bureau furnished a list of 86 mineral-surfaced, asphalt, built-up roofs known to be 10 years old orolder. Individual manufacturers of asphalt roofings whosubmitted asphalt specimens furnished lists of more than400 such roofs applied with the asphalts they are sellingcurrently, all less than two years old. Manufacturers ofcoal-tar pitch furnished the locations of coal-tar pitchroofs in the inspection areas. Frequently the local repre-sentatives of the roofing manufacturers and roofing con-tractors were able to point to older roofs of known history.

As it was obviously impracticable to inspect all ofthe roofs suggested, the initial list of older roofs wasdivided into three geographical areas, East Coast, Mid-West,and West Coast, and each of these groups were broken downinto seven sub-groups, by age, as follows: Less than 10years, 10 to 12, 13 to 15, 16 to 18, 19 to 21, 22 to 24, and25 years and older. Actual rodfs to be inspected wereselected by lot from each sub-group. Where it was foundthat a roof selected had been destroyed or reroofed, anattempt was made to find a replacement. One-hundred-onemineral- surfaced

,built-up roofs were inspected in this

study, distributed as shown in Table 2.

TABLE 2. DISTRIBUTION OF ROOFS INSPECTED

ASPHALT ROOFS

Location: East Coast Mid-We st West Coast

Age, Yrs. No. No. No.

10 or less 2 3 510 to 20 11 10 420 to 30 5 9 8+30 1

COAL-TAR-PITCH ROOFS

Age, Yrs. No. No.

10 or less 610 to 20 1020 to 30 6+30 1

7

5

71

No.

'

- 9 -

3o Areas Included in the Studies

Inspections were made in 23 cities in 16 States and the

District of Columbia, as follows:

1, Seattle and Tacoma, Washington,2 0 San Francisco and Los Angeles, California.3. Albuquerque, New Mexico.4 0 El Paso, Texas.5. Kansas City, Missouri.6. Kansas City and Wichita, Kansas.7. New Orleans, Louisiana.8. Oklahoma City, Oklahoma.9. Jacksonville, Florida.

10. Atlanta and Macon, Georgia.11. Columbia, South Carolina.12. Gastonia and Red Springs, North Carolina.13. Washington, D. C.14. Baltimore, Maryland.15. Marion and Columbus, Ohio.16. Philadelphia, Pennsylvania.17. New York, New York.

b. Methods of Inspecting and Rating Roofs

Practically all roofs were inspected in company with arepresentative of the manufacturer of the roofing materialsand, frequently, with the owner or manager of the building.

In order to secure the greatest possible uniformity inthe inspections a form was developed which included the his-tory of the roof and a check list of the elements that areimportant in a built-up roof. Each element was rated numerically in accordance with its importance as a factor in determining the condition of the roof. A copy of the inspectionform with the ratings assigned to the various elementsfollows

:

10

1 .

3 .

5 .

8 .

9 .

11 .

12 .

13.

14.

15 .

16 .

17.

18 .

1 .

2 .

3 .

4 .

ROOF INSPECTION FORM

Historical

Date

Rating

Building 2. Location

Used for 4. Year Applied

Slone 6. Sunshine

Roofing Contractor

Index 7. Rainfall Index

Manufacturer ©oi

—

1

1 Spec. No.

Bonded: Yes No 10 15 20

Deck: Wood Concrete Metal Gypsum Other

Type of Felt Flys 2 3 4 5

Insulation: Yes No Type Thickness

Character of Bitumen: Asphalt Coal Tar Other

Source ______ Soft. Pt. Pen. _____ Duct. Other

Wt. of Bitumen per square: Between plies Top pouring

History of Repairs

Observations

Water Tightness: No leaks (8) Leaks with long-continued

rain (4) Leaks every rain (0) Cause:

Repaired Areas: None (10) Few (5) Many (0)

Nature:

Blistering: None (12) Moderate (6) Serious (0)

Between plies Between deck & membrane

Remarks:

Cracking of

Remarks

:

Felts: None (12)_ Few (6) Many ( 0

)

Surfacing:

Poor (0)

Adhesion to Bitumen:

Remarks

:

Good (4) Fair (2)5 .

11

ROOF INSPECTION FORM (Continued)

6 0 Bare Areas: None (6) Few (I ) Many (0)_

7<, Felts: Good (8) Fair (4) Poor (0)

Condition:

8 0 Bitumen: Areas water standing or likely to stand:

a) Condition: Good (4) Fair (2) _____ Poor (0)

b) Hardness: Soft (2) Medium (1) Hard (0)

c) Blisters, Pits, etc: None (2) Few (1) Many (0)

d) Alligatored: None (6) Moderately (3) Severely (0)

e) Cracking, Flaking, etc: None (6) Moderate (3)

Severe (0) Other Observations:

9o Bitumen: Areas water unlikely to stand:

a) Condition: Good (4) Fair (2) Poor (0)

b) Hardness: Soft (2) Medium (1) Hard (0)

c) Blisters, Pits, etc: None (2) Few (1) _____

Many (0)

d) Alligatored: None (6) Moderately (3)

Severely (0)

e) Cracking, Flaking, etc: None (6) Moderate (3)

Severe (0) Other Observations:

.

'

12

Under this system of rating, the various elements areweighted in accordance with the degree of deterioration. A

roof with no defects would be rated 100 and the final ratingof a roof is the sum of the ratings of the elements. Thissystem was adopted as the method most likely to insure uni-form procedures in the inspections. It is certain that thenumerical ratings are more readily evaluated than meredescriptive terms.

This rating system might be used as a basis for deter-mining the treatment necessary in long-time maintenance ofbuilt-up roofs, though, obviously, it would not apply univer-sally. The following is a suggested application;

Deterioration Action Indicated

o - 5 Yearly inspection and preventive main-tenance »

5 - 15 Yearly inspection and minor mainten-ance .

15 - 30 Extensive maintenance and minor repair

30 - 50

Above 50

Major repair.

Reroofing probably indicated.

5. Results of Field Studies

The results of the field studies are shown graphicallyin Figures 2 to 6 inclusive. The age and deterioration ofeach roof inspected are shown by the points in Figures 2 to6. The positions of the graphs were determined by the methodof least squares and are presented as a means for comparingthe general ratings of asphalt and coal-tar-pitch roofs inthe different areas.

.

DETERIORATION

,

(IOO

-

RATING)

EXPOSURE, YEARS

FIGURE 2. ASPHALT ROOFS EASTERN STATES.

DETERIORATION

*

(IOO

-

RATING!

EXPOSURE, YEARS

FIGURE 3. ASPHALT ROOFS - MID-WESTERN STATES.

DETERIORATION,

(IOO

-RATING)

EXPOSURE, YEARS

FIGURE 4. ASPHALT ROOFS WEST COAST STATES.

DETERIORATION

,

(IOO

-

RATING!

EXPOSURE ,YEARS

FIGURE COAL-TAR PITCH ROOFS - EASTERNSTATES.

DETERIORATION

,

(IOO

-

RATING)

50

EXPOSURE ,YEARS

FIGURE'

6 . COAL-TAR PITCH ROOFS - MID-WESTERNSTATES.

- 13 -

APPENDIX 2. LABORATORY STUDIES

lo Introduction

The 14 samples of asphalt and 3 samples of coal-tarpitch were examined in the laboratory by chemical and physicaltests that are normally used to define the characteristics ofasphalts and pitches used in built-up roofs. While limitingvalues under these tests may be used in specifications tocontrol the physical characteristics of asphalts and pitchesto insure materials that can be handled satisfactorily andwill remain in place on a roof, they give no assurance of thequality of the product, when quality is considered in termsof long-time service on a roof.

Additional laboratory tests were made to determinedifferences among the asphalts and, wherever possible, betweenthe asphalts and coal-tar pitches. In devising these ’tests,consideration was given to the conditions to which the bitumensin low-slope, mineral-surfaced, built-up roofs are subjected.Among these were exposure to elevated temperatures, alternatewetting and drying accompanied by sunlight, where water runsoff quickly and where it evaporates in place. That a membranemay be cracked in cold weather by movements in the roof deckand subjected to long-continued exposure to water withoutsunlight were also considered.

Asphalts, when stored in closed containers at room tem-perature, are hardened and become more brittle, as evidencedby increases in softening point and in the amount of materialinsoluble in n-pentane

,and decreases in the penetration

values. These reactions are accelerated by elevated tempera-tures and will therefore apply in service to the moppingsbetween felts as well as to the surface coatings.

Exposure of asphalt to the sun induces a photochemicalreaction at the exposed surface, resulting in a thin surfacefilm of light-degraded material which is largely soluble inwater. When the slope of a roof is such that water runs offreadily, this light-degraded material is largely removed, thecoating loses weight and weathers to a dull, matt surface.On roofs where standing water evaporates in place, the light-degraded material is first dissolved and then deposited as afilm when the water evaporates. On further drying, this filmcauses a shrinkage of the surface of the coating. So-called"alligatoring" may result from surface shrinking, with crack-ing the eventual result.

>• '

>

- 14 -

Cracked coating and mopping layers of bitumen may not betoo important if the bitumen has the ability to "self-heal"in a reasonable time. Inability to self-heal could result inearly failure of a membrane 0 The flow test and the specialself-healing test are measures of the ability of a bitumento self-heal.

Knowledge concerning the importance of the initialdistribution of components or groups of compounds in anasphalt is insufficient for use in purchase specifications,but changes in the distribution of components, as in theincrease of n- pentane insoluble matter, give an indicationof the extent of degradation that has occurred

„

The spot test usually appears in specifications forroad asphalts as a control of quality

2. Physical and Chemical Characteristics

In Table 3 are reported the source of the crudes fromwhich the 14 asphalts included in this study were producedand the conventional physical and chemical characteristicsnormally used in purchase specif ications . These data showthat although the asphalts as a group fall within a narrowsoftening point range, other physical characteristics aremarkedly different. The ductilities and penetrations at77°F and 32°F of samples 7 9

12 and 13 indicate the desira-bility of including two types of material in a purchasespecification. Consequently, asphalts 1, 2, 3 9 4, 5, 6, 8,

9, 10, 11 and 14 will be referred to hereafter as Type I

asphalts, and Nos. 7, 12 and 13 as Type II asphalts.

All Type I asphalts complied with the requirements ofFederal Specification SS-A-666, Type I, Class A, for surfacedbuilt-up roofs, except in minor respects, and all compliedwith American Society for Testing Materials SpecificationD312, "Mineral-Surfaced Flat".

The three Type II asphalts complied with Federal Speci-fication SS-A-666, Type I, Class A, except for penetrationat 32°F and 77°F. They complied with A.S.T.M, SpecificationD312, "Mineral-Surfaced Flat", except that for two of them,the penetration at 77°F was lower than the minimum specified.

TABLE 3 . PHYSICAL AND CHEMICAL

Ductility—/ Pene trationi/

SampleNo,

Sourceof

Crude

Sof t .—

/

Point(R & B)

At 77°F5 cm/min.

At 40°F0.25 cm/min.

77°F100 g

5 sec

32°F. 200 g

.

. 60 sec.

115°F50 g.

5 sec

.

1

OJP cm. cm.

1 Wyo. 145 9 3.3 42 22 117

2 M 148 13 3.5 26 9 90

3ft 146 23 4.0 29 11 108

4 Texas 158 7 4 .

6

30 17 73

5 Calif

.

144 21 5.4 42 19 132

6 Mid, Con. l4l 38 6.0 31 13 113

7 Calif. 143 150+ 1.512/ 16 5 95

8 Mid, Con. 149 14 4.2 31 12 89

9 Mid. Con. 142 11 3.6 46 22 122

10 Calif

o

146 26 5.7 36 18 130I

11 Ven. 148 23 4. 6 28 15 98 1

12 Calif. 143 110 Li.O^/ 16 5 99|

13 l40 150+ Ll.oW 20 7 120

14 Mid. Con. 148 8 3 .

6

4l 21 105 1

1/ A.S.T.M. D-36. 4/ Pen. at 115°F minus Pen. at 32°F I

2/1/

A.S.T.M. D-A.S.T.M. D—

113.5. 1/

Pen. at 77°F

F. S. SS-S-164 (Modified).

1

CHARACTERISTICS OF ASPHALTS 0

f3uscep-ftibilityyactor^t/

Flow at120°F1/5 Hr s =

Heat Test, 5 Hrs.^^at 325°F

SolubilityCarbonJZ/Disulfide N-PentanelASoluble Insoluble

Spot Test^/

LossPenetration of

Residue Naphtha

jcm. X % %

1 2 0 26 2,0 L0.1 40 99.7 30.0 Negative

13o11 io 7

m 25 99.7 29.8 n

3.39 2» 2 it 27 99.8 28.5 ti

|! 1 0 86 Oc 7ii 28 34.4 ii

2 ° 69 1.9 ii 38 — 35.9 Positive

*' 3.23 3 o 6 it 29 — 24.2 Negative

j!5-62 3 * 6

ii 13 99.8 29 o 7it

2.48 lc 2 n 30 99.8 30.6 ii

|2.18 IcO it 43 99.9 27.4 it

I

3 ° 12 1.4 it 36 99.9 41.5 Positive

' 2.96 1.4 it 28 99.9 31.5 Negative

15.87 2.4 ii 14 99.7 29.7 it

5.65 4.4 ii 15 — 24.8 n

12 -° 5 1.0 it 39 — 27.2 n

6/ A. S . T .M„ D-6 0 %/ AcAcScHoOc T-102 (Naphtha).7/ AcScToMo D-4. 10/ FractureSc8/ NcBcSc RP2577.

- 15 -

The three samples of coal-tar pitch complied withFederal Specification R-P-381, Type I, for built-up roofing.

The examination of these materials also indicated thatthe softening point and penetration ranges contained in boththe Federal and A,S.T»M„ specifications for asphalt can bereduced to insure a better defined material. Although a

"susceptibility factor" and flow test are not included ineither the Federal or A,S,T„M 0 specifications

9these give

a numerical evaluation of the "relatively susceptibleasphalts" and "self-healing" properties, which the A.S.T.M.specification states are desirable.

3, Component Distribution

In Table 4 are reported the source of the crudes fromwhich the asphalts were produced, their softening points,and components distributions. The component distributionswere determined according to the procedures described inResearch Paper 2 577 ?

NBS J, Res, Vol, 54, No, 3, March 1955°Asphalt samples I to 6, 8 to 11

,and l4 were produced by

vacuum reduction or vacuum reduction accompanied by airblowing. Samples 7, 12 and 13 were produced by specialprocesses. Component analysis did not distinguish betweenthese two types of asphalt.

As reported in a subsequent section of this report,component analysis can be used to determine changes inasphalts occurring during accelerated durability exposures.The asphaltene content as determined by this componentanalysis may give some indication of the quality of theasphalt. Asphalts of the same softening points having thelower asphaltene content would normally be preferred. Whenused in conjunction with the spot test, it could eliminatematerials prepared from cracked residuums.

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4„ Susceptibility to Heat

Five grams of the asphalts contained in 250 ml beakerswere heated for 10 days at 200°F in an enclosed oven c Thesource of the crudes from which the asphalts were producedand their component distribution before and after exposureare reported in Table 5° All the asphalts showed markedsusceptibility to heat when evaluated by the increases intheir asphaltene content

„

After exposure at 200°F for ten days, asphalt samples

6, 8, 9 and 14, which had been produced from Mid-Continentcrudes, contained less n-pentane insoluble material(asphaltenes) than samples 1, 2, 3, 4, 5? 10 and 11, whichhad been produced from Wyoming, Texas, Venezuelan andCalifornia crudes 0 These samples would be classified underType I material of the suggested specificationo The twoasphalt samples 7 and 12, which were produced from Californiacrudes and which would be classified as Type II materialsunder the suggested specification, showed essentially thesame asphaltene content as samples 5 and 10, Type I materialswhich were also produced from California crude oils 0 Theasphaltene content of sample 13, a Type II material, wasslightly higher after exposure than that of asphalts producedfrom the Mid-Continent crude oils 0 No detectable weightlosses occurred during the heat exposure . Weight gains inthe order of 0 e 4 percent occurred during these heat exposures

These data indicate the changes that will occur inthe asphalt moppings between the plies of felts as well asin the top coatings of asphalt built-up roofs, because oftheir susceptibility to heat 0

TABLE

5„

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ASPHALTS

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17 -

5. Accelerated Durability Exposures

5c 1 Exposure 1

To simulate roof conditions where there are no run-offsand standing water evaporates in place

.

The specimens were prepared by depositing a uniform filmof the melted bitumens over the bottom of 3-1/2- X 1-in.petri dishes. The asphalt specimens were prepared at a

spreading rate qf 60 lbs/100 ft 2;

the coal-tar-pitch speci-mens at a spreading rate of 70 lbs/100 ft 2 .

The coatings were exposed in a horizontal position ina low- intensity

,enclosed carbon arc durability machine (see

Figure 7). They were exposed for 21 hours to light only.The petri dishes were then filled three-quarters full withdistilled water and re-exposed to the radiation of the arc,allowing the water to evaporate in place, which requiredfrom 6 to 8 hours. The temperature of the dry specimensduring their exposure was from 125°-130°F.

Shrinkage of coatings during exposure ; The shrinkageof the coatings from the sides of the dishes after 2500

,

3000, 3500, 4000 and 4500 hours of exposure is reportedin Table 6. Included in this table are the weight changeswhich occurred during 4500 hours of exposure.

The coal-tar-pitch coatings showed no shrinkage fromthe sides uf the petri dishes after 4500 hours of exposure.

Type I asphalts, samples 6, 8, 9 ? 11 and 14, showedless shrinkage from the sides of the dishes than samples1, 2, 3 , 4, 7 and 10, The shrinkages of samples 3 ? 5 and10 were essentially the same, approximately 0.6 inch, andwere the most pronounced of any of the Type I asphalts.Samples 7 and 12, Type II, produced from California crudes,showed much less shrinkage than Type I asphalt, samples 5and 10, also produced from California crude. Sample 13,Type II, showed less shrinkage than the averages shown byType I asphalts produced from Mid-Continent crudes. Figure8 shows the shrinkage which occurred after 4500 hours ofexposure in coal-tar-pitch sample 40 and asphalt samples 4,5 and 11

.

#

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FIGURE ACCELERATED DURABILITY TEST APPARATUS

TABLE

6.

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18 -

Water-soluble, photochemical. degradation products : After1000

,3000 , 3500

,4000 and 4500 hours of exposure to light

,

the petri dishes were filled with distilled water, allowed tostand for 18 hours, and the extracted material titrated with0.01N alkali solution. These data are reported in Table 7 .

This titratable material was a photochemical degradationproduct. The relative amounts were markedly greater forthe asphalts than for the coal-tar pitches. See Exposure 3for the amounts of titratable materials formed when they areremoved after each 21-hour exposure to light.

Changes in physical characteristics ; In Table 8 arereported the softening points and penetrations of theasphalts before and after exposure. All asphalts showedmarked hardening and embrittlement, as evidenced by theincreases in the softening points and decreases in penetra-tions ,

Changes in distribution of components ; In Table 9 arereported the component distribution of the asphalts beforeand after ^OO-hours exposure (Exposure 1), As in the expo-sures of the asphalts to heat alone, there were marked in-creases in the n-pentane insoluble components. Althoughthese exposures were made at temperatures of 125°-130°F,which were appreciably lower than maximum roof temperatures,heat degradation still occurred.

The percentage of n-pentane insoluble material insamples 6, 8, 9 and 14 after exposure was appreciably lowerthan that found in samples 1, 2, 3? 4, 5? 10 and 11. Allof these samples would be classified as Type I materialsunder the suggested specification. Samples 7 and 12, TypeII, produced from California crude oils, contained lessn-pentane insoluble material than samples 5 and 10, Type I,also produced from California crudes. The n-pentaneinsoluble content of sample 13, Type II, after exposure,was slightly less than the average of that formed in samples6, 8, 9 and 14, produced from Mid -Continent crudes. Theseincreases in n-pentane insoluble material, which were formedat the expense of the water-white oils and dark oils, re-sulted in a hardening of the asphalts as discussed under"Change in physical characteristics". Asphalts containingthe lesser amounts of n-pentane insoluble material afterexposure would be preferred. For example, if a choice had

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80

SOFTENING

POINTS

OF

ASPHALTS

AND

COAL-TAR

PITCHES

AND

PENETRATIONS

OF

ASPHALTS

BEFORE

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Exposure

„

B

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After

Exposure

»

'

.

*

TABLE

90

DISTRIBUTION

OF

COMPONENTS

IN

ASPHALTS

BEFORE

AND

AFTER

4500

HOURS

OF

EXPOSURE

TO

AOCFLERATED

DURABILITY

TEST

(EXPOSURE

1).

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1

1

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B=

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'

19 -

to be made among samples 5, 7, 10 and 12, all produced fromCalifornia crude oils, samples 7 and 12, Type II materials,would be preferred* By the same reasoning, sample 13 wouldbe preferred to sample 11*

5.2 Exposure 2

Exposures made to simulate conditions to which a crackedmembrane may be subjected.

The specimens were prepared and exposed as describedunder Exposure 1„ At fixed intervals, a groove 1/16 in,wide was cut through the coatings along a diameter. Thespecimens were then exposed dry to the radiation of the arcuntil the groove had healed. The temperature of the specimensduring their dry exposures was 125°-135°F. In Table 10 arereported the extent of self-healing in specimens which hadbeen exposed for 4500 hours before being grooved. Theself-healing in the coal-tar-pitch coatings was much morerapid than' in the asphalt specimens. Asphalt samples 2,

3 , 5, 7, 8, 9 ? 10, 11, 13 and l4 showed satisfactory self-healing within 96 hours of exposure. The percentages re-ported represent the approximate closure of the groovesat the times indicated. Asphalt samples 1, 4, 6 and 12were not included because of lack of space in the testequipment.

5.3 Exposure 3

Exposures made to simulate roof conditions where water-soluble, light-degraded products were partially removed asby dew or rain.

Specimens were prepared for this exposure as for Expo-sure 1, except that the coatings were applied in petridishes at a spreading rate of 18 lb/100 ft^, to acceleratedegradation.

The dry specimens were exposed horizontally to radia-tion from the carbon arc (Figure 7)» After 21 hours ofexposure the petri dishes were filled with water andallowed to stand, without light, for one hour, and thewater poured off. This process was repeated until thecoatings had been exposed to light for 900 hours. The

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20

coatings were dried and weighed after 200, 400, 600 and 900hours of exposure, and the accumulated washings to theseperiods titrated with 0.01N alkali. The coatings were alsoexamined for shrinkage. In Table 11 are reported the shrink-age, weight loss and amount of alkali required to neutralizethe water-soluble degradation products after 900 hours ofexposure. The latter is reported as grams of sodium hydroxiderequired to neutralize products formed on 100 sq. ft. ofexposed surface.

Marked differences were noted between the results ofExposure 1, where light-degraded products were partiallydissolved and redeposited on the coatings, and of Exposure

3, where these products were partially removed daily. InExposure 1, the alkali required to neutralize the light-degraded material formed from the asphalts during 1000 hoursof exposure varied from 3 to 9 grams per 100 ft^; in Expo-sure 3 ,

18 to 66 grams were required after 900 hours ofexposure. A number of the asphalts showed slight weightgains after 4500 hours under Exposure 1; all showedprogressively greater weight losses at the 200, 400, 600and 900 hour weighing periods of Exposure 3° The relation-ship of the weight losses in Exposure 3 to the amounts ofalkali required to neutralize the water-soluble degradationproducts indicates strongly that the weight losses were duelargely to the removal of water-soluble products.

In another investigation here it has been shown thatasphalts exposed to radiation from the carbon arc andwashed daily continued to lose weight during an exposureof 4500 hours duration. Similarly, specimens exposedoutdoors and weighed at intervals of 6 months, continuedto lose weight during a 3-year exposure. Since theformation of water-soluble degradation products is alight-induced reaction, the value of opaque mineralsurfacing for any asphalt roof is obvious.

Practically no shrinkage occurred in any of theasphalts during Exposure 3 <» This is in marked contrastto their behavior in Exposure 1, indicating that the re-deposited, water-soluble, degradation products caused theshrinkage. In Exposure 3 the asphalts weathered to adull, matt surface; in Exposure 1, the surfaces were dulland wrinkled.

*

> '

21

As in Exposure 1, the coal-tar pitches in Exposure 3showed markedly less light-degraded materials formed thanthe asphalts. The daily removal of the light-degraded mate-rials from the pitches did not increase appreciably theamounts of these materials that were formed. Weight lossesof the coal-tar-pitch specimens were confined to the first200 hours of Exposure 3

°

Changes in the component distribution of the asphaltsduring 900 hours of Exposure 3 are shown in Table 12. Thesechanges paralleled those in Exposure 1, with asphalts 5 and10, produced from California crudes, showing the largestamounts of matter insoluble in n-pentane at the end of thetest. Again, Type I asphalts 6, 8, 9 and l4, produced fromMid-Continent crudes, contained less matter insoluble inn-pentane than the other Type I asphalts. Of all of theasphalts, No. 13, Type II, contained the smallest amount ofmatter insoluble in n-pentane. The other Type II asphalts,7 and 12, produced from California crudes, contained lessthan Type I asphalts 5 and 10, also produced from Californiacrudes.

6. Outdoor Exposures

Changes in Physical Characteristics : In Table 13 arereported the softening points and penetrations of the asphaltsbefore and after 10 months of exposure outdoors.

For the outdoor exposure the specimens were prepared asfor Exposure 1. They were exposed in a horizontal positionon the roof of the Industrial Building, National Bureau ofStandards, during May 1956. The length of the exposure was10 months.

At the end" of the 10-month, outdoor exposure all asphaltsshowed a marked increase in softening point and a correspond-ing decrease in penetration values. The increases in soften-ing point ranged from 13 ° to 21°F , and were apparently notrelated to the initial softening points of the asphalts or tothe source of the crudes from which the asphalts were producedThese data indicate that asphalts having softening points nearthe minimum specification requirement would be preferred tothose whose softening points were near the maximum requirementThe coal-tar-pitch specimens also showed an increase in softening point after the 10-month exposure. The maximum increasewas 7°F.

TABLE

11.

SHRINKAGE,

WEIGHT

LOSS,

AND

MATERIALS

TITRATABLE

WITH

ALKALI

FORMED

AFTER

900

HOURS

EXPOSURE

TO

THE

ACCELERATED

DURABILITY

TEST

(EXPOSURE

3).

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TABLE

12

„

COMPONENT

DISTRIBUTION

OF

ASPHALTS

BEFORE

AND

AFTER

900

HOURS

OF

EXPOSURE

TO

ACCELERATED

DURABILITY

TEST

(EXPO-

SURE

3).

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After

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>

•

TABLE

13.

SOFTENING

POINTS

OF

ASPHALTS

AND

COAL-TAR

PITCHES

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„

B-

After

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„

22

Shrinkage : Since these exposures were of such shortduration, only traces of shrinkage of the asphalt coatingsfrom the sides of the petri dishes occurred,. No shrinkagewas detected in the coal-tar-pitch specimens.

Self-healing characteristics ; To determine self-healingability the specimens were grooved, as for Exposure 2, beforeexposure on May 22, 1956. Both asphalt and coal-tar specimenshealed within 24 hours. Specimens were grooved again on July12, 1956, and again all specimens healed within 24 hours.Specimens were grooved again November 8, 1956, and when in-spected on December 31, 1956, no self-healing was detectedin either the asphalt or coal-tar pitch specimens. Inspec-tion on February 27, 1957, showed evidence of incomplete self-healing in sample 7

»

On March 18, 1957, when the exposure was terminated, theasphalt specimens were essentially the same as in the pre-vious inspection. The coal-tar-pitch specimens showed someself-healing. These data indicate that little or no self-healing can be expected from either asphalt or coal-tarpitch during cold weather.

7. Water Absorption Tests

The water absorption tests were made on the asphaltsand coal-tar pitches to determine the amount of water ab-sorbed during long-time immersion in distilled water, Afurther objective was to determine the amount of alkali re-quired to neutralize material leached from the specimensduring immersion.

Approximately 25 grams of asphalt and 30 grams of coal-tar pitch werq melted, poured into molds, forming disks witha surface area of approximately 0.11 ft 2 , Each disk wasweighed, placed in a separate petri dish, and covered withdistilled water. The disks were removed from the water atintervals, blotted dry, and reweighed. Any gain in weightwas taken as the quantity of water absorbed during the period.The total amount of water absorbed per 100 ft 2 of exposedsurface in one year is shown in Table 14.

TABLE

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RESULTS

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After immersion for one year, the water in which eachspecimen was immersed was titrated with 0.01N sodiumhydroxide solution,, The results are reported in Table 14as grams of sodium hydroxide required to neutralize materialleached per 100 ft2 during one year of immersion.

All specimens were glossy black after one year ofimmersion.

24 -

APPENDIX 3. DISCUSSION OF REQUIREMENTS IN THE PROPOSEDSPECIFICATION FOR ASPHALTS FOR LOW-SLOPEROOFS

1. Conventional Requirements

Softening point ; All of the asphalts submitted in thisprogram had softening points within the range of l40°F tol65°F specified in Federal Specification SS-A-666, Type I,

Class A, for surfaced built-up roofs, and all but sample 4(158°F) within the range of 135°F to 150°F specified byA.S.T.M. Specification D312, "Mineral-Surfaced Flat". Webelieve that a softening point range of 135°F to l45°F willinsure, in large measure, asphalts of desirable qualities forlow-slope roofs.

Ductility at 77°F ; Federal Specification SS-A-666, TypeI, Class A, requires a minimum ductility at 77°F of 5 cm. andA.S.T.M. Specification D312, "Mineral-Surfaced Flat", a min-imum ductility of 10 cm. While five of the Type I asphaltshad a ductility lower than 17 cm. at 77°F, as suggested inthe proposed specification, four of these showed softeningpoints higher than the maximum specified. We believe thatthese asphalts would have met the higher ductility requirementif they had been processed to meet the softening point re-quirement in the proposed specification.

The high ductility at 77°F of asphalts 7, 12 and 13indicates that these asphalts have been processed to simulatesome of the physical characteristics of coal-tar pitch usedin low-slope roofs. The relatively high ductility of asphaltsof this type makes mandatory the inclusion of two types ofasphalt in the specification.

Penetration tests :

At 32°F: The Federal and A.S.T.M. Specification require-ments of 10 and 5 ?

respectively, can be raised safely to 15for Type I asphalts. This higher value is more likely toinsure desirable self-healing qualities. Examination of thethree Type II asphalts indicated a minimum penetration re-quirement at 32°F of 5.

- 25 -

At 77°F: The penetration limits of 25 to 60 suggestedare in line with the softening point and the penetrationvalues of the Type I asphalts tested . These limits alsoprovide a means for differentiating between Type I and TypeII asphalts. Limits of 15 to 25 are indicated for Type IIasphalts from the samples tested.

At H5°Fs Federal Specification SS-A-666, Type I, con-tains no requirement for penetration at 115°F„ Since aself-healing material is desired, a minimum requirement of100, for Type I asphalt, as specified in A.S.T.M. Specifica-tion D312, "Mineral-Surfaced Flat", is considered desirable.Tests indicate a minimum of 90 for Type II asphalts.

Weight loss. 5 hrs. at 32°F ; Tests of numerous asphaltshave indicated that the maximum requirement of 1.5% in theFederal and A.S.T.M. Specifications for this test is entirelyunrealistic. The loss on heating of each of the Type I andType II samples tested in this series was less than 0.1%.Consequently, the proposed maximum was placed at 0.5%«

Penetration at 77°F after heating : Here again the re-quire melrt^of

-I^T~ofthe^ 77°F before heating,

in both Federal and A.S.T.M. Specifications, is known to beunrealistic. Minimums of 85% and 75% for Types I and IIasphalts, respectively, are more realistic.

Bitumen soluble in CC14: The requirement of 99% bitumensoluble m caroon tetrachloride is standard for unfilledpetroleum asphalts.

2. New Requirements

Matter insoluble in n-pentane : The percentage of matterinsoluble in n-pentane is known to increase as the blowingoperation is continued; consequently, a minimum requirementfor the amount of material insoluble in n-pentane could con-trol the extent of blowing. Large percentages of matterinsoluble in pentane are characteristic of "cracked residuums",generally regarded as having poor resistance to weathering.

26 -

The two asphalts in the series tested that initiallycontained the largest percentage of matter insoluble inn-pentane a^so gave positive spot tests, showed the greatestshrinkage under Exposure 1, and were included in the threethat required the most alkali to neutralize water-solubledegradation products formed in Exposure 3 „ It is significantalso that the percentage of matter insoluble in n-pentaneincreased in all asphalts during the accelerated and outdoorweathering tests and the heat tests.

Spot test : The spot test has been used largely inspecifications for road asphalts to eliminate cracked resid-uums. It is believed that it can serve the same purposefor roofing asphalts. Note the reference to the two asphaltsthat gave positive spot tests, under "Matter insoluble inn-pentane "

.

Susceptibility factor : The susceptibility factor requiresno extra laboratory work since it is calculated from the pene-tration determinations. Inclusion of minimum requirements fora susceptibility factor serves to distinguish between Type I

and Type II asphalts and places numerical values on the"relatively susceptible" and "self-healing" properties de-scribed in A.S.T.M. specifications.

Flow test : The flow test, adapted from Federal Speci-fic ation~SS^S^l 64, "Sealer; Hot-Poured Type, for Joints inConcrete", was included in an attempt to insure asphaltswith good self-healing qualities.

Ductility at 40°F. 0.25 cm/min, : The principal purposeserved by this requirement is to distinguish between Type I

and Type II asphalts. All samples of Type II asphalt and allof the samples of coal-tar pitch tested fractured rather thanstretched in this test; all samples of Type I asphalt met therequirement for the test.

'*

U. S. DEPARTMENT OF COMMERCESinclair Weeks, Secretury

NATIONAL BUREAU OF STANDARDSA. V. Astin, Director

THE NATIONAL BUREAU OF STANDARDS

The scope of activities of the National Bureau of Standards at its headquarters in Washington,D. C., and its major field laboratories in Boulder, Colorado, is suggested in the following listing of

the divisions and sections engaged in technical work. In general, each section carries out spe-

cialized research, development, and engineering in the field indicated by its title. A brief

description of the activities, and of the resultant reports and publications, appears on the

inside front cover of this report,

WASHINGTON, D. C.

Electricity and Electronics. Resistance and Reactance. Electron Tubes. Electrical Instruments.

Magnetic Measurements. Dielectrics. Engineering Electronics. Electronic InstrumentationElectrochemistry.

Optics and Metrology. Photometry and Colorimetry. Optical Instruments. PhotographicTechnology. Length Engineering Metrology.

Heat and Power. Temperature Physics. Thermodynamics. Cryogenic Physics. Rheologyand Lubrication. Engine Fuels.

Atomic and Radiation Physics. Spectroscopy. Radiometry. Mass Spectrometry. Solid State

Physics. Electron Physics. Atomic Physics. Nuclear Physics. Radioactivity, X-rays. Betatron

Nucleonic Instrumentation, Radiological Equipment. AEC Radiation Instruments.

Chemistry. Organic Coatings. Surface Chemistry. Organic Chemistry. Analytical Chemistry.

Inorganic Chemistry. Elect rodeposition. Gas Chemistry. Physical Chemistry. Thermo-chemistry. Spectrochemistry Pure Substances.

Mechanics. Sound. Mechanical Instruments. Fluid Mechanics. Engineering Mechanics.

Mass and Scale. Capacity. Density, and Fluid Meters. Combustion Controls,

Organic and Fibrous Materials. Rubber. Textiles. Paper. Leather. Testing and Specifica-

tions. Polymer Structure Organic Plastics. Dental Research.

Metallurgy. Thermal Metallurgy. Chemical Metallurgy. Mechanical Metallurgy Corrosion

Metal Physics

Mineral Products. Engineering Ceramics. (Mass. Refractories. Enameled Metals. Concreting

Materials. Constitution and Microstructure

Building Technology. Structural Engineering. Fire Protection. Heating and Air (modi

tinning. Floor, Roof, and Wall Coverings, Codes and Specifications.

Applied Mathematics. Numerical Analysis. Computation. Statistical Engineering. Mathe-

matical Physics

Data Processing Systems. SEAC Engineering Group. Components and Techniques. Digital

Circuitry, Digital Systems Analogue Systems. Application Engineering.

• Office of Basic Instrumentation • Office of Weights and Measure-

BOULDER, COLORADOCryogenir Engineering. Cryogenic Equipment. Cryogenic Processes, properties of Materials

Gas Liquefaction

Radio Propagation Physics. Upper Atmosphere Research. Ionospheric Research. Regular

Propagation Services Sun-Earth Relationships.

Radio Propagation Engineering. Data Reduction Instrumentation. Modulation systems.

Navigation Systems. Radio Noise Tropospheric Measurements. 1 ropospherir Analysis Radio

Systems Application Engineering.

Radio Standards. Radio Frequencies Microwave Frequencies. High Frequency Fleet ricai

Standards. Radio Broadcast Service High Frequency Impedance Standards. Calibration

C . riter Microwave Physics. Microwave Circuit 'standards.