10
148 selected. The process of altering compaction moisture contents beneath the pavement can result in pavement damage in the form of longitudinal cracks, which in turn can result in the need for immediate pavement rehabilitation. For design engineers working in areas of expansive soils, six options are identified (2): 1. Alter the route–alignment to avoid the expansive soil. 2. Remove the expansive soil, and replace it with nonexpansive material. 3. Design for the low strength, and allow for maintenance to repair heave deformations. 4. Provide nonexpansive material as a cover or surcharge layer. 5. Control moisture movement. 6. Improve the expansive soil by stabilization. The last method is often used in different parts of the world, includ- ing the United States, India, South Africa, and several other countries where expansive soils are stabilized. Stabilization results in smaller volume changes that do not induce damage to pavements. Though chemical stabilization is not always a common practice in Saudi Ara- bia, an attempt is made in this research to study the effectiveness of such stabilization to improve the properties of expansive soils. This study focused on one type of expansive, clayey soil sampled from the Al-Qatif area of Saudi Arabia. Two chemical additives were considered and studied to try to determine their ability to mitigate the volume change potentials in this soil. BACKGROUND Bubshait (3) provided a comprehensive summary of the quality of pavement construction in Saudi Arabia. A majority of the pave- ments in this region are asphalt, and several factors contribute to both rutting and other types of distress. Silt is a commonly occurring soil, and it is often stabilized with cement to enhance its strength before construction of LVR-related asphalt pavements. Expansive soils are those that expand when hydrated and shrink when they are subjected to drying (4). This heave-and-shrink process has caused major problems to structures, including roads, buildings, steel structures, pipelines, culverts, and other infrastructure. Costs of maintenance or repairs are estimated to be millions of dollars annu- ally. Figure 1 is a map of Saudi Arabia showing various regions of known expansive soils. Many locations in Saudi Arabia possess expansive soils, includ- ing these: Al-Qatif, Al-Ghatt, Tabuk, Hofuf, Tayma, Sharorah, and Al-Madinah (6, 7 ). Pavements, in particular those with low-volume traffic conditions, often get distressed by movements of expan- sive soils. Figure 2 shows heave distress photographs of some of Evaluation of Chemical Stabilization of a Highly Expansive Clayey Soil E. Mutaz, Mosleh A. Shamrani, Anand J. Puppala, and Muawia A. Dafalla Lime and cement are widely used in stabilization and improvement of the expansive subsoils that support pavement infrastructure. In this research, an attempt is made to stabilize a highly expansive soil rich with smectite minerals with an aim to understand the mechanisms that result in soil property improvements. Influences of both the type of stabilizer and their dosages were studied for modifying expansive clay from the north-central region of Saudi Arabia. Al-Qatif soil is known for its highly expansive nature, and it is known to induce major damage to low- volume roads built on untreated to unbound sandy bases. This research was performed by first characterizing and classifying Al-Qatif clayey soil by means of routine index properties, X-ray diffraction studies, and swell and shrinkage tests. Next, lime and cement were used to stabilize control clayey soils, and the treated soils were then subjected to the same soil tests. Effects of lime and cement treatments on Atterberg limits, swell, and linear shrinkage strain properties are addressed. Major conclusions and findings from experimental investigations are presented. A low-volume road (LVR) is defined as one that has relatively low use (an average daily traffic of less than 400 vehicles), has low design speeds (typically less than 50 mph), and is composed of a system with few layers (1). Most of the pavements in the rural areas in Saudi Arabia are classified as LVRs. For community develop- ment, it is essential to construct and maintain a well planned and designed LVR system. It is also important to construct the roads on stable ground. To construct an LVR on a problematic soil such as expansive soil, it is essential to classify and understand the severe nature of the soil by using basic soil tests such as gradation, hydrometer, Atterberg lim- its, and compaction. All basic tests give evidence about the swelling tendency of the soil, and thus measuring the expected heave can be done afterwards by performing odometer-based, one-dimensional free-swell test or three-dimensional volumetric-swell test. In the case of designing roads in expansive soil, design engineers should consider the influence of expansive soils in mitigation of lon- gitudinal and transverse cracks on the pavements caused by heaving and cracking. It is necessary to identify the causes of heaving or shrinkage cracking before an optimum stabilizer and dosages are E. Mutaz, M. A. Shamrani, and M. A. Dafalla, Department of Civil Engineering, King Saud University, Riyadh, Saudi Arabia. A. J. Puppala, Department of Civil Engineer- ing, King Saud University, Riyadh, Saudi Arabia, and Department of Civil Engineering, Box 19308 University of Texas at Arlington, Arlington, TX 76019. Corresponding Author: M. A. Dafalla, [email protected]. Transportation Research Record: Journal of the Transportation Research Board, No. 2204, Transportation Research Board of the National Academies, Washington, D.C., 2011, pp. 148–157. DOI: 10.3141/2204-19

Evaluation of Chemical Stabilization of a Highly Expansive Clayey Soil

  • Upload
    muawia

  • View
    216

  • Download
    4

Embed Size (px)

Citation preview

Page 1: Evaluation of Chemical Stabilization of a Highly Expansive Clayey Soil

148

selected. The process of altering compaction moisture contentsbeneath the pavement can result in pavement damage in the form oflongitudinal cracks, which in turn can result in the need for immediatepavement rehabilitation.

For design engineers working in areas of expansive soils, sixoptions are identified (2):

1. Alter the route–alignment to avoid the expansive soil.2. Remove the expansive soil, and replace it with nonexpansive

material.3. Design for the low strength, and allow for maintenance to

repair heave deformations.4. Provide nonexpansive material as a cover or surcharge layer.5. Control moisture movement.6. Improve the expansive soil by stabilization.

The last method is often used in different parts of the world, includ-ing the United States, India, South Africa, and several other countrieswhere expansive soils are stabilized. Stabilization results in smallervolume changes that do not induce damage to pavements. Thoughchemical stabilization is not always a common practice in Saudi Ara-bia, an attempt is made in this research to study the effectiveness ofsuch stabilization to improve the properties of expansive soils.This study focused on one type of expansive, clayey soil sampledfrom the Al-Qatif area of Saudi Arabia. Two chemical additiveswere considered and studied to try to determine their ability tomitigate the volume change potentials in this soil.

BACKGROUND

Bubshait (3) provided a comprehensive summary of the quality ofpavement construction in Saudi Arabia. A majority of the pave-ments in this region are asphalt, and several factors contribute toboth rutting and other types of distress. Silt is a commonly occurringsoil, and it is often stabilized with cement to enhance its strengthbefore construction of LVR-related asphalt pavements.

Expansive soils are those that expand when hydrated and shrinkwhen they are subjected to drying (4). This heave-and-shrink processhas caused major problems to structures, including roads, buildings,steel structures, pipelines, culverts, and other infrastructure. Costs ofmaintenance or repairs are estimated to be millions of dollars annu-ally. Figure 1 is a map of Saudi Arabia showing various regions ofknown expansive soils.

Many locations in Saudi Arabia possess expansive soils, includ-ing these: Al-Qatif, Al-Ghatt, Tabuk, Hofuf, Tayma, Sharorah, andAl-Madinah (6, 7 ). Pavements, in particular those with low-volumetraffic conditions, often get distressed by movements of expan-sive soils. Figure 2 shows heave distress photographs of some of

Evaluation of Chemical Stabilization of a Highly Expansive Clayey Soil

E. Mutaz, Mosleh A. Shamrani, Anand J. Puppala, and Muawia A. Dafalla

Lime and cement are widely used in stabilization and improvement ofthe expansive subsoils that support pavement infrastructure. In thisresearch, an attempt is made to stabilize a highly expansive soil rich withsmectite minerals with an aim to understand the mechanisms that resultin soil property improvements. Influences of both the type of stabilizerand their dosages were studied for modifying expansive clay from thenorth-central region of Saudi Arabia. Al-Qatif soil is known for itshighly expansive nature, and it is known to induce major damage to low-volume roads built on untreated to unbound sandy bases. This researchwas performed by first characterizing and classifying Al-Qatif clayeysoil by means of routine index properties, X-ray diffraction studies, andswell and shrinkage tests. Next, lime and cement were used to stabilizecontrol clayey soils, and the treated soils were then subjected to the samesoil tests. Effects of lime and cement treatments on Atterberg limits, swell,and linear shrinkage strain properties are addressed. Major conclusionsand findings from experimental investigations are presented.

A low-volume road (LVR) is defined as one that has relatively lowuse (an average daily traffic of less than 400 vehicles), has lowdesign speeds (typically less than 50 mph), and is composed of asystem with few layers (1). Most of the pavements in the rural areasin Saudi Arabia are classified as LVRs. For community develop-ment, it is essential to construct and maintain a well planned anddesigned LVR system. It is also important to construct the roads onstable ground.

To construct an LVR on a problematic soil such as expansive soil,it is essential to classify and understand the severe nature of the soilby using basic soil tests such as gradation, hydrometer, Atterberg lim-its, and compaction. All basic tests give evidence about the swellingtendency of the soil, and thus measuring the expected heave can bedone afterwards by performing odometer-based, one-dimensionalfree-swell test or three-dimensional volumetric-swell test.

In the case of designing roads in expansive soil, design engineersshould consider the influence of expansive soils in mitigation of lon-gitudinal and transverse cracks on the pavements caused by heavingand cracking. It is necessary to identify the causes of heaving orshrinkage cracking before an optimum stabilizer and dosages are

E. Mutaz, M. A. Shamrani, and M. A. Dafalla, Department of Civil Engineering, KingSaud University, Riyadh, Saudi Arabia. A. J. Puppala, Department of Civil Engineer-ing, King Saud University, Riyadh, Saudi Arabia, and Department of Civil Engineering,Box 19308 University of Texas at Arlington, Arlington, TX 76019. CorrespondingAuthor: M. A. Dafalla, [email protected].

Transportation Research Record: Journal of the Transportation Research Board,No. 2204, Transportation Research Board of the National Academies, Washington,D.C., 2011, pp. 148–157.DOI: 10.3141/2204-19

Page 2: Evaluation of Chemical Stabilization of a Highly Expansive Clayey Soil

those pavements. Several types of clay minerals are present in thesoils: the kaolin group (kaolinite, dickite, halloysite and nacrite);the smectite group, which includes dioctahedral smectites, such asmontmorillonite and nontronite, and trioctahedral smectites, suchas saponite; and the illite group, which includes the clay–micas. Thepresence of the smectite group in the soil has a significance effecton swelling behavior. The process of swelling is caused mainly bythe intercalation of water molecules entering the interplane space ofsmectitic clay minerals (8–10). A schematic diagram of this heaveprocess is shown in Figure 3 (11).

STABILIZATION METHODS

To reduce the negative effects of the expansion behavior of the soilon the structures, various stabilization methods are used. These arechemical stabilization (use of cement, lime, and other additives),soil replacement, recompacting, prewetting, and preloading of thestructures. Lime stabilization on a reactive soil will generate long-term strength gain through pozzolanic reactions, and the benefitsof soil stabilization by lime include increased resilient modulus,improvements in shear strength, continued strength gain with time,and long-term durability over decades of service, even under severeenvironmental conditions.

The most notable effect of lime on soil is to improve workabilityand compactibility and reduce swelling and shrinkage potential bysaturating the clay particles with calcium ions (12). Several investi-gations were performed on stabilization of the soil by using lime atdifferent dosages. The best lime stabilization was at 3.5% to 5% bydry weight to stabilize clayey soil properties (13). During the appli-cation of lime in soil stabilization, an increase in the concentrationof hydroxide (OH−) ions will increase the pH level and lead to dis-solved alumina and silica in the clay fraction (14). These released

Mutaz, Shamrani, Puppala, and Dafalla 149

Al-Qatif

FIGURE 1 Distribution of expansive soils in Saudi Arabia (5).

(a)

(b)

FIGURE 2 Heave distress problems on LVRs in different regionsof Saudi Arabia: (a) distortion and cracks aggravated by seepingwater (Al-Zulfi District) and (b) pavement subjected to heavedamage and cracks in Tabuk City.

Page 3: Evaluation of Chemical Stabilization of a Highly Expansive Clayey Soil

silica and alumina interact with calcium ions to produce twocementing agents of pozzolanic reaction, calcium–silicate–hydrate[C-S-H (3CaO-2SiO2-3H2O)] and calcium–aluminate–hydrate[C-A-H (3CaO-Al2O3-Ca(OH)2-12H2O)], respectively, whichcause cohesive soils to become more workable and less plastic (15).

Another chemical stabilizer often used is portland cement, whichproduces cementing compounds such as C-S-H and C-A-H, as wellas excess calcium hydroxide. These compounds result in stabiliza-tion of soils by cementing the soil particles closely. The permeabil-ity of cement-stabilized material is greatly reduced, and the result isa moisture-resistant material that is highly durable and resistant toleaching over a long period (16).

The main objective of this research is to study the potential ofboth lime and cement additives to successfully stabilize expan-sive clay, which is characterized as a highly expansive in nature.This soil collected from Al-Qatif area was characterized firstwithout any stabilization and was later treated with cement andlime additives at different dosages. Both untreated and treatedsoils were subjected to various geotechnical tests, including phys-ical property tests, volume change–related swell and shrinkagetests as well as mineralogical studies using X-ray diffraction (XRD)techniques. Descriptions of these studies appear in the followingsections.

STABILIZATION DESIGN

Chemical stabilization is not often used for treating subgrades andbases supporting pavements for low-volume traffic conditions.Pavement conditions often deteriorate when the subsoils containlarge amounts of expansive clay minerals. Several cities, includ-ing Al-Qatif and Tabuk, are affected by these pavement distressproblems. In the present study, a laboratory design was developedto stabilize soils from the Al-Qatif area. Focus was mostly on thevolume change properties, as any reductions in these will help in pro-ducing uniform treated subgrades for the support of pavements.Researchers currently anticipate building a few test sections todemonstrate the performance of chemical stabilization in enhanc-ing the pavement structure performance in this region. This paperpresents the laboratory test results and a few mineralogical studieson how the chemical treatment has provided effective stabilizationof Al-Qatif expansive clay formation.

150 Transportation Research Record 2204

SITE DESCRIPTION

This research study was conducted at King Saud University inRiyadh, Saudi Arabia, by first collecting soil samples from Al-Qatifarea, which includes a formation of expansive soil. Al-Qatif is a his-toric coastal oasis region on the western shore of the Persian Gulf inthe Eastern Province of Saudi Arabia (26°56′0″ N, 50°1′0″ E). Itextends from Ras Tanura and Jubail in the north to Dammam in thesouth and from the Persian Gulf in the east to King Fahd InternationalAirport in the west. This region includes the town of Al-Qatif as wellmany nearby smaller towns and villages (4). Figure 4 depicts thecutting process used for sample collection from Al-Qatif area withthe help of the local municipality.

EXPERIMENTAL PROGRAM AND TEST RESULTS

Untreated-Soil Tests

Once soil samples were collected from Al-Qatif, several basic soiltests were conducted. These tests include gradation, Atterberg lim-its, specific gravity, and standard Proctor compaction tests. To pre-dict the heaving, a three-dimensional volumetric-swell test was

Si

Si

H2O

H2O

H2O

H2O

H2O H2O H2O H2O

H2O H2O H2O H2O

5 − 10 Å

Al

Si

Si

Al

FIGURE 3 Schematic diagram of intrusion of water molecules in interplane spaceof clay smectites (11).

FIGURE 4 Sample collection from Al-Qatif.

Page 4: Evaluation of Chemical Stabilization of a Highly Expansive Clayey Soil

conducted to measure the vertical- and volumetric-swell strains ofthe untreated soil.

The gradation test results that include sieve and hydrometer testresults depicted in Figure 5. The selected soil from Al-Qatif is a fine-grained soil with the majority of the soil (>90%) passing the No. 200(<0.075-mm) sieve. Atterberg limits (liquid limit, plastic limit, andshrinkage limit), linear shrinkage, specific gravity data, and the per-centage of fine grained materials in the selected soil were determined;these results are presented in Table 1. Figure 6 shows a standard Proc-tor compaction curve of the same soil. The optimum moisture con-tent (OMC) of this soil is 32%, and the maximum dry unit weight(MDUW) is 11.9 kN/m3.

Volumetric-Swell Tests on Untreated Soil

A volumetric-swell test was conducted by using a three-dimensional(3-D) swell test setup at a low confining seating pressure of 1 kPa. The3-D swell setup contains a compaction mold that is 70 mm in dia-meter and 140 mm in height. The sample was prepared and compactedat OMC and MDUW conditions, and then it was subjected to hydra-tion. The sample compacted in the mold was then subjected to watersaturation from both top and bottom porous stones. The sample wasallowed to swell freely in both vertical and horizontal directions. Ver-tical swelling of the sample was measured by using a dial gauge, andthe lateral swelling was measured by using a pie tape as shown in Fig-ure 7 (4). Both vertical and lateral swelling strains were measuredfor several hours until the readings stabilized.

The results of both the vertical- and volumetric-swell strains areplotted in Figure 8. The maximum vertical strain was about 20%,

Mutaz, Shamrani, Puppala, and Dafalla 151

and the maximum volumetric strain was found to be 50%. Thesevalues are considered extremely high and indicate the highlyexpansive nature of this soil.

XRD Studies

The swelling and volume change behaviors are dependent on the clayminerals in a soil. Addition of cement or lime will certainly affect thechemical balance and may lead to some changes in the structure of amineral or sometimes a slight change in the mineral. Evidence of thischange can be detected by the use of the XRD technique. As part ofthis research, XRD was performed by using a Shimadzu XRD-7000setup at a 40-kV copper K alpha (CuKα) radiation source and a scan-ning speed of 2°/min. The aim of chemical saturations is to character-ize different clay minerals including smectite, illite, and kaolinite. Thed-spacing of smectite is around 14 or 15 Å with the magnesiumchloride (MgCl) saturation, and 18 Å with ethylene glycol saturationto 11 to 13 Å with potassium chloride (KCl) saturation to 10 to 11 Åwith heating. The d-spacing for illite is around 9.9 to 10.1 Å, and itremains constant with MgCl, ethylene glycol, and KCl saturations.The d-spacing of kaolinite is 7.15 Å with MgCl, ethylene glycol, andKCl saturations, and the kaolinite disappears when heated at 550°C(Figure 9a).

The smectite group indicates the expansive nature of the presentclayey soil, and its presence is identified in the range of 12 to 15 Å atair drying condition. After treatment with ethylene glycol or glycerol,the smectite group expands to its high value and the d-spacingincreases to 17 to 18 Å (Figures 9b and 9c); with oven drying andheating, this value drops to about 10 to 11 Å due to removal of theinterlayer water (17). As Figure 9 shows, for the smectite group, inthe case of saturation with MgCl, the value of d-spacing is 12.96 Å(Figure 9d), and it increases to 17.89 Å with ethylene glycol (Fig-ure 9b) and decreases to about 10 Å with KCl (Figure 9c). Allthese values confirm the strong presence of the smectite group inAl-Qatif clay.

The illite group is characterized by d-spacing of 9.9 to 10.1 Å withall chemical treatments and heating. Figure 9 also presents d-spacingof 9.78 to 10.65 Å with all treatments, which is within the range of9.9 to 10.1 Å. These results also provide evidence of the illite groupin Al-Qatif clay.

The kaolinite group is characterized (a) by d-spacing of about7.15 Å with all chemical treatments and (b) by disappearing withheating. Figure 9 again shows that the d-spacing is about 7.07 to7.13 Å with all treatments. These readings also show evidence forthe presence of the kaolinite group in Al-Qatif clay. Overall, XRDtest results on Al-Qatif clay show the abundant presence of the

FIGURE 5 Grain size distribution details of Al-Qatif soil.

TABLE 1 Physical Properties ofAl-Qatif Soil

Soil Property Magnitude

Liquid limit (%) 136

Plastic limit (%) 60

Shrinkage limit (%) 12

Linear shrinkage (%) 28

Plasticity index (%) 76

Specific gravity 2.70

% finer than 200 μm 99.1

USCS classification CH

NOTE: CH = clay of high plasticity.

Page 5: Evaluation of Chemical Stabilization of a Highly Expansive Clayey Soil

152 Transportation Research Record 2204

smectite group, which is primarily responsible for the high swellingphenomenon recorded on the present soil.

Chemical Stabilization Studies

To stabilize the present soil, both quick lime and Type I portlandcement were considered and used with different dosage percentages.These were 4% and 8% for lime by dry weight of soil and 3% and 6%of cement by dry weight of soil. Table 2 summarizes the test resultsof the control and lime as well as cement-stabilized Al-Qatif clays.Both Atterberg limits and linear shrinkage strains were measured andincluded in this table.

Figures 10 and 11 present the decrease in the liquid limit from136% for an untreated sample to about 110% by using 8% of the limeadditive and to about 113% by using 6% of cement. The liquid limitof the control (untreated) soil decreased with an increase in stabilizerdosage for both lime and cement treatments. Figures 10 and 11 alsodepict the increase in the plastic limit from 60% for the untreatedsample to about 90% by using 8% of lime and about to 85% by using6% of cement. Furthermore, a decrease in the plasticity index from

FIGURE 6 Standard Proctor compaction curve of Al-Qatif soil.

Collar

Dial gauge

Height(5.6 in.)

Membrane

Mold forwater bath

Diameter(2.8 in.)

Pie tape

FIGURE 7 Volumetric-swell test setup.

FIGURE 8 Volumetric- and vertical-swell strain for Al-Qatif soil at OMC.

Page 6: Evaluation of Chemical Stabilization of a Highly Expansive Clayey Soil

Mutaz, Shamrani, Puppala, and Dafalla 153

17.89A°

9.98A°

7.13A°4.98A°

6000

5000

4000

3000

Inte

nsi

ty

2000

1000

02 7 12 17 22

2 θθ Degrees27 32 37

10.35A°

7.10A°4.97A°

4.25A°

3.35A°

3.24A°2.49A°

6000

5000

4000

3000

Inte

nsi

ty

2000

1000

02 7 12 17 22

2 θ Degrees27 32 37

(a)

(b)

(c)

(d)

9.78A°

4.92A°

6000

5000

4000

3000

Inte

nsi

ty

2000

1000

02 7 12 17 22

2 θ Degrees27 32 37

12.96A°

6000

5000

4000

3000

Inte

nsi

ty

2000

1000

02 7 12 17 22

2 θ Degrees27 32 37

10.65A°

7.07A°4.98A° 4.25A°

3.35A°

2.48A°

FIGURE 9 Identification of clay minerals for Al-Qatif soil.

Page 7: Evaluation of Chemical Stabilization of a Highly Expansive Clayey Soil

154 Transportation Research Record 2204

TABLE 2 Effects of Cement and Lime Treatment on Physical Properties of Al-Qatif Soil

Property Untreated Soil 4% Lime 8% Lime 3% Cement 6% Cement

Liquid limit (%) 136 119 110 118 113

Plastic limit (%) 60 83 91 82 85

Plasticity index (PI) 76 36 19 36 28

Shrinkage limit (%) 12 17 18 19 31

Linear shrinkage (%) 28 25 19 23 17

FIGURE 10 Effect of lime on liquid limit, plastic limit, and plasticity index of treated soil.

FIGURE 11 Effect of cement on liquid limit, plastic limit, and plasticity indexof treated soil.

76% for the untreated sample to about 19% by using 8% of lime andto about 28% by using 6% of cement was recorded. Figure 12 pre-sents the linear shrinkage strain trends. The linear shrinkage strainof the untreated Al-Qatif soil sample is about 28%, and it is reducedto 25% when treated with 4% of lime and further reduced to 19%when treated with 8% of lime. For cement treatments, the strain isreduced close to 23% when treated with 3% of cement and to 17%when treated with 6% of cement.

Cement treatment has a profound and significant influence inreducing the linear shrinkage strains when compared with lime treat-ment. This difference is attributed to an increase in strength with

cement rather than with lime. During shrinkage, tensile strength isimportant, as it provides resistance to the tensile stresses generated dur-ing the drying process. The tensile strength of the cement-treated soilis expected to be much higher than that of lime-treated soil, and hencecement-treated soil experiences low shrinkage strains.

Volumetric-Swell Tests on Stabilized Soil

A volumetric-swell test was conducted on stabilized soil speci-mens with different percentages of lime and cement additives.

Page 8: Evaluation of Chemical Stabilization of a Highly Expansive Clayey Soil

Mutaz, Shamrani, Puppala, and Dafalla 155

FIGURE 12 Effect of stabilizer dosage on linear shrinkage strain.

Untreated sampleTreated sample with 4% LimeTreated sample with 8% LimeTreated sample with 3% CementTreated sample with 6% Cement

25

20

15

VE

RT

ICA

L S

TR

AIN

(%

)

10

5

00 1000 2000 3000 4000

TIME (min)5000 6000 7000 8000

FIGURE 13 Vertical-swell strain versus elapsed time for untreated and treated soils.

Soil specimens were prepared at OMC and MDUW conditions.The soil specimen in the compaction mold was subjected to waterinundation and allowed to swell freely in both vertical and hori-zontal directions. Soil specimens were also stabilized with limeand cement additives and then cured for 7 days. Cured specimenswere then subjected to swell tests. Both vertical- and volumetric-

swell strains were measured and plotted against the elapsed time, as shown in Figures 13 and 14. Table 3 presents vertical and volumetric-swell strains for both treated and untreated soils.Table 4 illustrates effects of chemical treatments on the percent-age decrease in both vertical and volumetric strains of control andtreated soils.

FIGURE 14 Volumetric-swell strain versus elapsed time for untreated and treated soils.

Page 9: Evaluation of Chemical Stabilization of a Highly Expansive Clayey Soil

A comparison was made between the vertical- and volumetric-swell strain test results of treated and untreated soil samples to mea-sure the degree of improvement achieved by using cement and limeadditives at different percentages. The vertical-swell strain wasreduced from 21% for an untreated soil specimen to about 15% and17% for treated soils with 4% and 8% of lime, respectively, and thesame swell strains were also reduced to about 15% and 8% with 3%and 6% of cement, respectively.

Overall, the volumetric-swell strain was reduced from about 50%for the untreated sample to about 48% and 38% by using 4% and 8%of the lime additive, respectively. For cement treatments, the volu-metric-swell strains were reduced to 40% and 26% under the cementtreatments of 3% and 6%, respectively. Both lime and cement treat-ments again show significant influence in the stabilization processby reducing both vertical and volumetric-swell strains, with cementproviding greater improvements.

SUMMARY AND CONCLUSIONS

From the test results reported in this research, the followingconclusions can be drawn:

1. Al-Qatif area has an expansive soil formation, and the sam-ples in this research have shown a high percentage of clayey soils.This high percentage of clay particles—in particular smectite—has resulted in highly expansive nature of this soil. In XRD testson untreated soils, it can be concluded that there is an abundantamount of smectite group clay minerals, which are responsible forthe high swelling and shrinkage phenomena observed in the swelland shrinkage tests.

2. The present clay has exhibited a plasticity index of 76% and aliquid limit value of 136%. This clay also exhibited a high tendencyto shrink in drying because this soil has a shrinkage limit of 12% andan extremely high linear shrinkage strain of 28%. From volumetric-swell tests, the vertical strain of Al-Qatif clay was about 20% andthe volumetric strain was close to 50%. Both numbers represent aquite highly expansive clayey soil.

3. Both lime and cement were used effectively in stabilizing thesoil; the cement showed a slightly better ability to stabilize this soil

156 Transportation Research Record 2204

than the lime. Effects of lime and cement additives on the physicalproperties of the clay can be summarized as follows:

– Increase in the plastic limit and shrinkage limit of the controlsoil,

– Decrease in the liquid limit and linear shrinkage strains of thecontrol soil, and

– Decrease in the vertical and volumetric strains.

Overall, on the basis of the stabilization studies with lime andcement, though both stabilizers showed some improvements, theoverall enhancements achieved were slightly higher when this soilwas stabilized with cement at a dosage of 6%. Hence, cement treat-ment at a dosage of 6% by dry weight of soil is recommended forstabilizing the clayey soil, which can be used to support low-volumepavements. Strength and stiffness property tests, which were notconsidered in this research, should be investigated for treated soils.Typically, expansive soils from this region are relatively stiffer, andhence strength-related issues are not a major concern. However,strength and stiffness measurements using unconfined compressivestrength and resilient moduli will provide further insights into thechemical treatments. Field validation studies are still needed for fur-ther evaluation of the cement treatment for effectively stabilizingthis highly expansive clayey soil.

REFERENCES

1. Keller, G., and J. Sherar. Low-Volume Roads Engineering: Best Manage-ment Practices Field Guide. Final report. U.S. Agency for InternationalDevelopment, USDA Forest Service, and Virginia Polytechnic Instituteand State University, Blacksburg, 2003. http://ntl.bts.gov/lib/24000/24600/24650/Index_BMP_Field_Guide.htm.

2. Gourley, C. S., D. Newill, and H. D. Schreiner. Expansive Soils: TRL’sResearch Strategy. Proc., 1st International Symposium on EngineeringCharacteristics of Arid Soils, City University, London, July 1993.

3. Bubshait, A. A. Quality of Pavement Construction in Saudi Arabia. Prac-tice Periodical on Structural Design and Construction, Vol. 6, No. 3,Aug. 2001, pp. 129–136.

4. Shamrani, M. A., E. Mutaz, A. J. Puppala, and M. A. Dafalla. Charac-terization of Problematic Expansive Soils from Mineralogical and SwellCharacterization Studies. In Proc., Geoflorida, American Society ofCivil Engineers, West Palm Beach, Fla., 2010.

5. Abduljauwad, S. N., G. J. Al-Sulaimani, I. A. Basunbul, and I. Al-Buraim. Laboratory and Field Studies of Response of Structures

TABLE 3 Vertical and Volumetric Strains for Treated and Untreated Samples

% Stabilizer 0% 4% Lime 8% Lime 3% Cement 6% Cement

Vertical strain (%) 20.7 14.8 17 15 8.6

Volumetric strain (%) 49.8 48 38 40 26

NOTE: All tests were conducted at corresponding optimum moisture contents.

TABLE 4 Reduction in the Vertical- and Volumetric-Swell Strains of PresentChemically Treated Soils

4% Lime 8% Lime 3% Cement 6% Cement

Reduction in vertical strain (%) 5.9 3.7 5.7 12.1

Reduction in volumetric strain (%) 1.8 11.8 9.8 23.8

Page 10: Evaluation of Chemical Stabilization of a Highly Expansive Clayey Soil

to Heave of Expansive Clay. Geotechnique, Vol. 48, No. 1, 1998, pp. 103–121.

6. Dhowian, A., I. Ruwiah, and A. Erol. The Distribution and Evaluation ofthe Expansive Soils in Saudi Arabia. Proc., 2nd Saudi Engineering Con-ference, Volume 4, King Fahd University of Petroleum and Minerals,Dhahran, Saudi Arabia, 1985, pp. 1969–1990.

7. Abduljauwad, S. N. Study on the Performance of Calcareous ExpansiveClays. Engineering Geology, Vol. 30, No. 4, 1993, pp. 481–498.

8. Low, P. F., and J. F. Margheim. The Swelling of Clay: I. Basic Conceptsand Empirical Equations. Soil Science Society of America Journal, Vol. 43,1979, pp. 473–481.

9. Schafer, W. M., and M. J. Singer. Influence of Physical and Mineralog-ical Properties on Swelling of Soils in Yolo County, California. SoilScience Society of America Journal, Vol. 40, 1976, pp. 557–562.

10. Parker, J. C., D. F. Amos, and L. W. Zelazny. Water Adsorption andSwelling of Clay Minerals in Soil Systems. Soil Science Society ofAmerica Journal, Vol. 46, 1982, pp. 450–456.

11. Taboada, M. A. Soil Shrinkage Characteristics in Swelling Soils. Pre-sented at College on Soil Physics, Abdas Salam International Centre forTheoretical Physics, Trieste, Italy, March 2003.

Mutaz, Shamrani, Puppala, and Dafalla 157

12. Arabani, M., and M. V. Karami. Geomechanical Properties of Lime-Stabilized Clayey Sands. Arabian Journal for Science and Engineering,Vol. 32, No. 1B, Nov. 2006.

13. Akawwi, E., and A. Al-Kharabsheh. Lime Stabilization Effects onGeotechnical Properties of Expansive Soils in Amman. ElectronicJournal of Geotechnical Engineering, Paper 2002-020, 2002.

14. Ouhadi, V. R., and R. N. Yong. The Role of Clay Fraction of MarlySoils on Their Post Stabilization Failure. Engineering Geology, Vol. 70,No. 3, Nov. 2003, pp. 365–375.

15. Yong, R. N., and V. R. Ouhadi. Experimental Study on Instability ofBases on Natural and Lime–Cement Stabilized Clayey Soils. AppliedClay Science, Vol. 35, No. 3–4, 2006, pp. 238–249.

16. Little, D. N., E. H. Males, J. R. Prusinski, and B. Stewart. CementitiousStabilization. Transportation in the New Millennium, 2000. http://onlinepubs.trb.org/onlinepubs/millennium/00016.pdf.

17. Mitchell, J. K., and K. Soga. Fundamentals of Soil Behavior, 3rd ed.John Wiley and Sons, New York, 2005.

The Committee for the 10th International Conference on Low-Volume Roadspeer-reviewed this paper.