Eﬀect of cement type on the mechanical behavior of a …asatid.tabrizu.ac.ir/PDF/727_7f003fd3-d370-45ea-9c10-21...The complete process of sample preparation with Portland cement

Effect of cement type on the mechanical behavior

of a gravely sand

S. M. HAERI1, A. HAMIDI1,w, S. M. HOSSEINI1, E. ASGHARI2

and D. G. TOLL3

1Civil Engineering Department, Sharif University of Technology, Tehran, Iran2Group of Engineering Geology, Tabriz University, Tabriz, Iran3School of Engineering, University of Durham, Durham, UK

(Received 13 July 2004; accepted 14 December 2004)

Abstract. The behavior of a cemented gravely sand was studied using triaxial compressiontests. Gypsum, Portland cement and lime were used as the cementing agents in sample prep-

aration. The samples with different cement types were compared in equal cement contents.Three cement contents of 1.5%, 3.0% and 4.5% were selected for sample preparation. Drainedand undrained triaxial compression tests were conducted in a range of confining pressures from

25 kPa to 500 kPa. Failure modes, shear strength, stress–strain behavior, volume and porepressure changes were considered. The gypsum cement induced the highest brittleness in soilamong three cement types while the Portland cement was found to be the most ductile

cementing agent. In lower cement contents and lower confining pressures the soil cemented withPortland cement showed the highest shear strength. However, in the same range of cementcontent, the soil cemented with gypsum showed highest shear strength for highest tested con-

fining stress. For higher cement contents the shear strength of soil cemented with Portlandcement is higher than that for the two other cement types for the range of confining pressurestested in the present study. The samples cemented with lime had the least peak and ultimateshear strength and the highest pore pressure generation in undrained tests. Contrary to the soil

cemented with lime, the brittleness of soil cemented with gypsum and Portland cement reducesin undrained condition. Finally it was found that the effect of cement type on the shear strengthof cemented soils is more profound in drained condition compared to undrained state.

Key words. brittleness, cementation, cement type, dilation, gravely sand, gypsum, lime, porepressure, portland cement.

1. Introduction

Cemented soils are usually formed due to the chemical effects of materials that exist in

ground water. Cementation causes formation of weak to strong bonds between soil

particles. Carbonates, silicates, iron oxides and gypsum are usual natural cementing

agents. The bonds strongly affect the mechanical behavior of cemented soil. Cemen-

tation increases the soil stiffness and brittleness. The effect of cementation on the

mechanical behavior of fine sandy soils has been considered by several researchers.

wCorresponding author: Amir Hamidi, Department of Civil Engineering, Sharif University of

Technology, P.O.Box 11365-9313, Tehran, Iran. tel.: 98-21-6164270; fax: 98-21-6013201; e-mail:

[email protected] or [email protected]

Geotechnical and Geological Engineering (2006) 24: 335–360 � Springer 2006DOI 10.1007/s10706-004-7793-1

Saxena and Lastrico (1978), Dupas and Pecker (1979), Clough et al. (1981), O’Rourke

and Crespo (1988), Lade and Overton (1989), Leroueil and Vaughan (1990), Chang

andWoods (1992), Coop andAtkinson (1993), Airey (1993), Huang andAirey (1998),

Malandraki and Toll (2001), Schnaid et al. (2001), Ismail et al. (2002) and Rotta et al.

(2003) presented useful contributions in this field. Study of the effect of cementation

on the mechanical behavior of cemented gravely sands started in late 20th century

(1998) when the mechanical behavior of coarse-grained alluvium of the city of Tehran

was investigated. A study conducted to define a representative gradation for the

Tehran alluvium using several gradation tests. Haeri et al. (2002), Haeri and Hosseini

(2003), Asghari et al. (2003), Haeri et al. (2004) and Hamidi et al. (2004) studied the

mechanical properties of the mentioned soil. Haeri et al. (2002) carried out some large

direct shear tests on uncemented and artificially cemented gravely sands using lime as

the cementing agent. The results showed a curved failure envelope for the cemented

soil. Asghari et al. (2003) conducted some drained and undrained triaxial tests on the

same soil that was artificially cemented with lime. Contrary to the uncemented soil, the

maximum rate of dilation in drained tests and maximum rate of excess pore water

pressure in undrained tests occur after the maximum stress ratio. Haeri and Hosseini

(2003) and Haeri et al. (2004) conducted a parallel study using Portland cement as the

cementing agent. According to the test results, the uncemented samples and lightly

cemented samples at high confining pressure showed contractive behavior accompa-

nied with positive excess pore water pressure and barreling failure mode. However,

cemented samples and uncemented samples at low confining pressure showed dilative

behavior accompanied with negative pore water pressure. Hamidi et al. (2004) showed

that increase of the cement content from a certain value reduces the stiffness, dilation

and negative pore pressure of the cemented soil. Also they showed that the failure

envelopes of a cemented soil in drained and undrained conditions are not the same.

The effect of cement type on the mechanical behavior of fine sandy soil has been

studied by some researchers. Ismail et al. (2002) studied the effect of cement type on

the mechanical behavior of cemented fine sandy soil. They introduced the unconfined

compressive strength as a measure of the cementing bonds. According to the results

the cement type strongly affects the shear behavior of cemented soil. The Portland

cement was known as the most ductile cementing agent. Also Portland cement in-

duced the maximum shear strength in the soil. Clough et al. (1981) stated that the

gradation has a very important role in the mechanical behavior of cemented soil. It is

expected that the mechanical behavior of cemented gravely sand to be different in

some aspects from cemented fine sand. In order to investigate the effect of cement type

on the mechanical behavior of gravely sands a comparative study is conducted among

the aforementioned researches, and the results are presented in this paper.

2. Soil and cementing agent

Table 1 shows the physical properties of the studied soil. The maximum grain size is

limited to 12.5 mm for triaxial testing of 100 mm diameter specimens. The soil

S. M. HAERI ET AL.336

contains 45% gravel, 49% sand and 6% fine and can be named as SW–SM in unified

system of soil classification and sandy gravel in BS standard. Coarse-grained par-

ticles consist mainly of tuff, shale and volcanic rocks. Particle shapes are usually sub-

angular. The degree of cementation is highly variable in different parts of Tehran

alluvium and is mainly formed from carbonates like calcite. However, in order to

study the behavior of Tehran alluvium, in addition to some tests on natural ce-

mented soil and a number of in situ tests, a set of tests is conducted on artificially

cemented soils using hydrated lime, Portland cement and gypsum as the cementing

agents.

3. Sample preparation

The method used for sample preparation with Portland cement and gypsum is nearly

the same. However, the method of sample preparation with lime is different to some

extent. So the subject is presented here in two individual parts.

3.1. SAMPLES CEMENTED WITH PORTLAND CEMENT AND GYPSUM

The complete process of sample preparation with Portland cement and gypsum are

presented in Haeri et al. (2004) and Hamidi et al. (2004), respectively. Different

particle sizes were mixed to obtain the representative gradation curve of Figure 1.

0

10

20

30

40

50

60

70

80

90

100

0.01 0.1 1 10 100

Particle size (mm)

Pas

sing

per

cent

# 4# 200

GravelSandFines

Figure 1. The gradation of tested soil.

Table 1. Physical properties of tested soil

Soil Gs

D50

(mm)

D10

(mm) Fine (%) Sand (%) Gravel (%)

cmin

(kN/m3)

cmax

(kN/m3)

SW–SM 2.58 4.0 0.2 6 49 45 16.00 18.74

EFFECT OF CEMENT TYPE ON THE MECHANICAL BEHAVIOR 337

The gradation has been determined using several gradation tests on the soil

gathered from different parts of the North section of city and limiting the maxi-

mum grain size to 12.5 mm (Haeri et al., 2002). The grain size distributions of the

tested soils are also shown in Figure 1. In order to prepare the specimen for

triaxial testing, a mould of 200 mm high and 100 mm diameter was used. Soil–

cement mixture was mixed with 8.5% water and then placed in to the mould. Each

sample was prepared in eight layers. Each layer was compacted using a metal

hammer to a dry unit weight of about 1.8 g/cm3. This is the average value of dry

unit weights of undisturbed samples obtained from the field (Haeri et al., 2002).

After opening the moulds the samples cemented with gypsum were oven cured in a

constant temperature of 50 �C. Since water reduces the gypsum stiffness and

strength extremely, these samples were completely dried in order to reach to the

maximum strength. Samples cemented with Portland cement were cured for a

period of 28 days in a humid room.

3.2. SAMPLES CEMENTED WITH LIME

The complete process of sample preparation with hydrated lime is presented in

Asghari et al. (2003). After preparation of appropriate amount of the base soil for

each sample, it was mixed with the appropriate amount of hydrated lime and 8.5%

of distilled water. Sections of high strength P.V.C perforated pipes, 200 mm high and

100 mm diameter, were used as moulds for sample preparation. The prepared soil–

lime mixture was then placed in the mould in eight layers and each layer was

compacted to achieve the required height. The dry unit weight of the samples was set

to be 1.8 g/cm3. The soil was cured for 6 weeks before testing in order to produce the

pozzolanic cementation compounds formed by reaction between lime and soil silica.

The samples were kept in the perforated moulds during the curing period. The

temperature of the curing water tank was kept constant at 25 �C. The samples were

kept in a plastic bag containing distilled water to avoid the water from the tank

leaching into the sample.

4. Criteria for evaluation of the cementation degree

Many researchers have proposed different methods to illustrate the degree of

cementation in cemented soils. Ismail et al. (2002) introduced unconfined com-

pressive strength of the cemented soil as a direct measurement of the soil degree of

cementation. They performed triaxial compression tests on samples cemented with

different cementing agents. The cement content was controlled in a manner to

reach identical unconfined compressive strengths for different cement agents. Hu-

ang and Airey (1993) also emphasized that the mechanical parameters like

unconfined compressive strength can be used as a measurement of the cementation

degree. In order to investigate the ability of different parameters as an indicator of

the cementation degree, different criteria are examined to determine a suitable


representative of the degree of cementation. For this purpose cement content,

unconfined compressive strength, Brazilian tensile strength and triaxial compressive

strength under low confining stress are considered. Several tests were performed on

cemented samples with different cement contents and different cementing agents.

The samples were tested in a condition like that they previously cured to obtain the

maximum strength of the cementing bonds. For example the strength of gypsum

cemented soil reduces when it is saturated with water, lime cemented soil has the

maximum strength when it is hydrated with water and the Portland cement agent

reaches its maximum strength when it is cured in humid condition for a period of

4 weeks. So quite dry soil samples cemented with gypsum, saturated samples ce-

mented with lime and humid samples cemented with Portland cement were used in

the tests.

4.1. BRAZILIAN TENSILE TESTS

Brazilian tensile tests were carried out on cylindrical samples with a diameter and

height of 100 mm. The samples were loaded vertically on the side until a diagonal

crack showed a tensile mode of failure. The tests were conducted on samples ce-

mented with gypsum, lime and Portland cement. Figure 2 shows the variation of

tensile strength with cement content for different cementing agents. Samples ce-

mented with Portland cement showed the highest tensile strength. Also the gypsum

cemented samples showed higher tensile strength compared to the lime cemented

samples. For a given tensile strength, the lowest required cement content belongs to

the Portland cement.

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10

Cement Content (%)

Ten

sile

Str

engt

h(kP

a)

gypsum

Lime

Portland cement

Figure 2. Variation of tensile strength with cement content for different cement types. The hashed lines are

the linear approximation.


4.2. UNCONFINED COMPRESSION TESTS

Unconfined compression tests were conducted on cylindrical samples with a diam-

eter of 100 mm and height of 200 mm. All the samples were loaded vertically with a

loading velocity of 0.84 mm/min until failure was appeared. The tests were con-

ducted on samples cemented with different cement types. Figure 3 shows the vari-

ation of unconfined compressive strength with cement content. According to this

figure the soil cemented with Portland cement shows the highest unconfined com-

pressive strength. However, the soil cemented with lime shows the lowest unconfined

compressive strength.

4.3. TRIAXIAL COMPRESSION TESTS

Due to the errors involved in simple tests such as Brazilian and unconfined com-

pressive strength tests, consolidated drained triaxial tests were carried out under very

low confining pressure of 25 kPa to determine the triaxial compressive strength

variation with cement content. Figure 4 shows the triaxial compressive strength

variations with cement content for soil cemented with different cementing agents.

The triaxial compressive strength of soil cemented with Portland cement is still

higher than that of soils cemented with two other cementing agents.

4.4. DISCUSSION

Table 2 shows a comparison of different criteria used to indicate the degree of

cementation. The strength of cemented soil with 4.5% Portland cement is calculated

0

500

1000

1500

2000

2500

3000

0 2 4 6 8 10Cement Content (%)

Unc

onfin

ed C

ompr

essi

ve S

tren

gth

( kP

a ) Gypsum

Lime

Portland cement

Figure 3. Variation of unconfined compressive strength with cement content for different cement types.

The hashed lines are the linear approximation.


for Brazilian, unconfined compression and triaxial compression test under low

confining pressure. Using one of the cementing agents and a linear interpolation, the

equivalent cement content for an identical strength is determined for the other ce-

ment types. Table 2 shows that there is a large difference between cement contents of

different cementing agents for an identical strength. This results in some differences

among the gradation of different types of cemented soils having the same strength

criteria. The only criterion in which the gradation of the soil is held relatively con-

stant for different cement types is the equal cement content. In the present study the

effect of cement type is studied using samples with equal cement contents. In this

manner the effect of the cement content and cement type on the behavior of

cemented soils can be investigated.

5. Main triaxial tests

Consolidated undrained and drained triaxial tests were performed on a soil cemented

with different cement types. The specimens were made in three main groups with

0

500

1000

1500

2000

2500

3000

3500

4000

0 2 4 6 8 10Cement Content (%)

Tria

xial

Com

pres

sive

Str

engt

h (k

Pa)

Gypsum

Lime

Portland cement

Figure 4. Variation of triaxial compressive strength with cement content for different cement types under

confining stress of 25 kPa. The hashed lines are the linear approximation.

Table 2. Cement contents for an identical mechanical strength

Criteria Lime content Gypsum content Portland cement content

Cement content 4.5 4.5 4.5

Brazilian tensile strength 33 12 4.5

Unconfined compressive strength 12 8 4.5

Triaxial compressive strength under

low confining pressure

9 8 4.5


lime, Portland cement and gypsum. Triaxial tests were conducted under different

confining pressures. The tests on lime cemented soil were conducted on samples with

1.5%, 3% and 4.5% cement contents. The confining pressures varied between

25 kPa and 1000 kPa. Details of this study are presented in Asghari et al. (2003).

The tests on Portland cement and gypsum cemented soil were conducted using 1.5%,

3%, 4.5%, 6% and 9% cement. The confining pressures varied between 25 kPa and

500 kPa. Details of these tests can be found in Haeri and Hosseini (2003), Haeri

et al. (2004) and Hamidi et al. (2004), respectively.

A total of 42 triaxial tests consist of 33 consolidated drained and 9 consolidated

undrained triaxial tests were selected from the mentioned tests. Consolidated drained

and undrained triaxial tests on soil cemented with lime were carried out on saturated

soil. Triaxial drained tests on soil cemented with Portland cement were carried out

on wet and saturated samples. The samples cemented with Portland cement had a

water content of approximately 12–16% with an average of 14% after curing in

humid room for 28 days. Haeri and Hosseini (2003) made a comparison between

failure envelopes of wet and saturated samples under consolidated drained triaxial

tests. They showed that the wet cemented samples having about 14% water content

tested in triaxial compression apparatus give the same shear strength and show

stress–strain behavior as those of saturated samples, due to the small values of

suction in unsaturated samples. The consolidated undrained triaxial tests on soil

cemented with Portland cement were performed on saturated samples. Haeri et al.

(2004) reported the results of triaxial tests on cemented samples having the same

gradation and cement content to examine the repeatability of the tests or to inves-

tigate other factors that might have effect on the behavior of the cemented soils.

They showed that there is some differences in stress–strain and other mechanical

behavior of cemented soils and the reason could be the different fabric and structure

of different samples. The samples, however, were prepared using the same procedure.

The only difference between the tests on pure uniform sand and the used material is

the gradation and the variety of the material involved. Therefore in sample prepa-

ration, one can not prepare identical samples with this material even if one takes

special care about the sample preparation. However, in order to evaluate the effect of

cement type on the behavior of cemented soils, the effect of fabric is not considered

herein and a set of tests with the best consistency is selected in this way. Consolidated

undrained triaxial tests on soil cemented with gypsum were conducted on saturated

samples saturated with silicon oil. Due to the extreme reduction of gypsum stiffness

and strength with water as the pore fluid, gypsum cemented samples were saturated

using light silicon oil with a very low viscosity. As several researchers like Lambe and

Whitman (1979) observed, the stress–strain behaviors of dry and saturated granular

soils are analogous provided that pore fluid can flow freely into or out of pores and

no excess pore pressure can develop. Therefore consolidated drained triaxial tests on

gypsum cemented soil were performed on completely dry samples.

After sample preparation and before test, the surface of the sample is covered with

a thin film of mixed clay and fine sand to minimize membrane penetration effects.


The samples are set up on triaxial apparatus and saturated in three stages. The

sample and drainage lines were flushed for about 1 h with CO2 under a pressure of

10 kPa and a cell pressure of 20 kPa as the first step of saturation. The saturation of

the samples are continued with flushing water for Portland cement and lime cements

and light silicon oil for gypsum cement from bottom of the sample under a very low

pressure difference of 10 kPa. To complete the saturation process both cell and back

pressures were ramped simultaneously to values of 215 kPa and 200 kPa. The sat-

uration process finished when a B value of 0.95 or greater was achieved. The axial

loading applied with a strain rate of 0.325% per minute for drained tests on com-

pletely dry samples and 0.1% per minute for undrained tests on saturated and wet

samples. A data acquisition system with electronic sensors recorded cell pressure,

volume change, pore pressure, displacement and load continuously in triaxial tests.

The volume changes of dry and wet samples were measured on cell pressure line. In

this method the volume change of the sample is determined according to the volume

changes of the water in the triaxial cell. The factors affecting the water percolation

into or out of the cell were taken into account as stated by Head (1986).

6. Analysis of test results

The results are analyzed using parameters such as r¢1, r¢3, e, ev, Du, q, p¢. The effectivemajor and minor principal stresses are named as r¢1 and r¢3, e and ev are the axial

and volumetric strains, e is the void ratio and Du is the excess pore pressure, q and p¢are deviatoric and mean effective stresses defined as:

q ¼ r01 � r03 ð1Þ

p0 ¼ ðr01 þ 2r03Þ=3 ð2Þ

7. Mode of failure

It is apparent that the cementation causes increase in brittleness and dilative

behavior of the soil. The cemented soil brittleness depends on the cement content

and cement type. Samples cemented with the lowest gypsum cement content showed

dilative failure behavior and an apparent shear zone even under the highest tested

confining pressure. This case was not seen for the other cement types. For example,

samples cemented with 1.5% Portland cement and 3% lime showed a barreling mode

of failure when they were sheared under 500 kPa and 1000 kPa confining stresses

respectively in drained triaxial tests. The samples cemented with 3% lime showed a

shear zone during undrained shearing with a 500 kPa confining stress contrary to the

drained ones.

Consoli et al. (1998) defined the brittleness index using the following equation:

IB ¼ ðqmax=qultÞ � 1 ð3Þ


Table

3.Shearstrength

parametersforthecementedsand

1.5%

(Drained

condition)

3%

(Drained

condition)

4.5%

(Drained

condition)

3%

(Undrained

condition)

Variable

0%

Gypsum

Lim

e

Portland

cement

Gypsum

Lim

e

Portland

cement

Gypsum

Lim

e

Portland

cement

Gypsum

Lim

e

Portland

cement

C(kPa)

25.0

157.0

121.7

342.3

197.2

169.6

383.1

288.1

247.7

435.0

91.3

52.3

516.6

/(degrees)

36.0

43.8

40.3

31.1

43.9

37.2

31.2

45.9

40.8

47.9

43.7

42.7

43.3


In equation 3 IB is the brittleness index, qmax is the shear strength and qult is the

ultimate strength. Figure 5 shows the brittleness index calculated for the tests.

According to this figure the gypsum cement causes more brittleness than two other

cementing agents in drained and undrained condition up to 3% cement. For 4.5%

cement, the brittleness of Portland cement increases and overrides the gypsum ce-

ment in a range of confining pressures. The figure shows an increase in the brittleness

of soil cemented by Portland cement when the cement content increases to 4.5% or

more in tested soils.

It is also evident that the soil brittleness is lower in undrained condition. Ma-

landraki and Toll (2001) showed that this difference can be attributed to the volu-

metric strains occur in drained testing of the cemented soils. These volumetric strains

contribute to the brittle failure of cementing bonds and a more brittle behavior in

drained condition.

8. Stress–strain behavior

Figures 6–8 show the deviatoric stress (q) plotted against axial shear strain (e) forconsolidated drained tests on cemented soil with different cementing agents, con-

fining pressures and cement percents of 1.5, 3.0 and 4.5. Also Figure 9 shows the

similar results obtained from consolidated undrained triaxial tests on the same soil

with 3% cement. All the stress–strain curves show an apparent peak point. For equal

cement contents and equal confining pressures the shear strains at peak stresses are

nearly equal for three cement types. After the peak shear stress, the stress decreases

Figure 5. Variation of the brittleness index in drained and undrained condition for different cement types.


1.5% CementConfining Stress=100 kPa

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 5 10 15 20Strain (%)

Dev

iato

ric S

tres

s (k

Pa)

GypsumLimePortland Cement

(a)


0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 5 10 15 20

Strain (%)

Dev

iato

ric S

tres

s (k

Pa)


(b)


0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 5 10 15 20

Strain (%)

Dev

iato

ric S

tres

s (k

Pa)


(c)

Figure 6. Stress–strain curve for cemented soils with 1.5% cement in drained condition.


and finally reaches to a constant value in large strains of more than 20%. These

figures show that the shear strength of the cemented gravely sand is a function of

three important parameters i.e. cement content, confining stress and cement type. In

3% CementConfining Stress=25 kPa

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 5 10 15 20

Strain (%)

Dev

iato

ric S

tres

s (k

Pa)

Gypsum

Lime

Portland Cement

(a)3% Cement

Confining Stress=100 kPa

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 5 10 15 20Strain (%)

Dev

iato

ric S

tres

s (k

Pa)

Gypsum

Lime

Portland Cement

(b)


0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 5 10 15 20Strain (%)

Dev

iato

ric S

tres

s (k

Pa)


(c)3% Cement


0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 5 10 15 20

Strain (%)

Dev

iato

ric S

tres

s (k

Pa)

Gypsum

Lime

Portland Cement

(d)

Figure 7. Stress–strain curve for cemented soils with 3% cement in drained condition.

4.5% CementConfinng Stress=25 KPa

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 5 10 15 20

Strain (%)

Dev

iato

ric

Str

ess

(kP

a)

Gypsum

Lime

Portland Cement

(a)4.5% Cement

Confining stress=100 kPa

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 5 10 15 20

Strain (%)

Dev

iato

ric S

tres

s (k

Pa)

Gypsum

Lime

Portland Cement

(b)


0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 5 10 15 20Strain (%)

Dev

iato

ric S

tres

s (k

Pa)

Gypsum

Lime

Portland Cement

(c)4.5% Cement


0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 5 10 15 20Strain (%)

Dev

iato

ric S

tres

s (k

Pa)

Gypsum

Lime

Portland Cement

(d)

Figure 8. Stress–strain curve for cemented soils with 4.5% cement in drained condition.


3% CementConfining Stress =100 kPa

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 5 10 15 20Strain (%)

Dev

iato

ric S

tres

s (k

Pa)


3% CementConfining Stress = 300 kPa

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 5 10 15 20Strain (%)

Dev

iato

ric S

tres

s (k

Pa)



0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 5 10 15 20Strain (%)

Dev

iato

ric S

tres

s (k

Pa)


Figure 9. Stress–strain curve for cemented soils with 3% cement in undrained condition.


low cement contents like 1.5% and 3.0%, the highest shear strength belongs to the

Portland cemented soil for low confining pressures like 25 kPa and 100 kPa.

Increasing the confining stress to 300 kPa, the shear strength of soil cemented with

Portland cement drops lower than the shear strength of soils cemented with gypsum.

However, the shear strength of Portland cemented soil is still higher than the shear

strength of soils cemented with lime. For the higher confining stress of 500 kPa the

shear strength of soil cemented with Portland cement will be the same as the shear

strength of soil cemented with lime. So it can be concluded that the rate of increase in

the shear strength of soil cemented with Portland cement reduces with increase in

confining pressure. In higher cement contents like 4.5% the Portland cement bonds

are so strong that they keep their stiffness even in high confining pressures. The shear

strength of soil cemented with 4.5% of Portland cement is always higher than the

shear strength of soil cemented with two other cementing agents and does not reduce

with increase in confining stresses. This type of behavior shows that the Portland

cement is a ductile cementing agent and its behavior is dependent on the amount of

cement content and the applied confining stresses. When the amount of cement in the

soil is small, its stiffness reduces with increase in confining pressure. However, when

the cement content increases in the soil, the cemented soil keeps the acquired strength

up to the higher confining stresses.

These figures also show that the soil cemented with gypsum presents higher shear

strength compared to that of the soil cemented with lime even in high confining

pressures. For the undrained tests the shear strength of the soil cemented with lime is

higher than that of the soil cemented with gypsum for a confining stress of 500 kPa.

According to the Figure 6 the brittleness of lime cement increases slightly with

confining pressure in undrained condition. But the brittleness of gypsum cemented

soil decreases with increase in confining pressure in undrained condition.

Figure 10 (a)–(c) shows the variation of peak shear strength of cemented soil with

confining stress for different cement agents. Also Figure 10 (d) presents the same

data for consolidated undrained triaxial test. Comparison of these figures show that

the effect of the cement type on the stress–strain response of the soil increases with

increase in cement content. As the cement content increases, the difference between

curves associated with different cement types increases in each figure. Also com-

parison of Figure 10 (d) with other figures show that the difference between shear

strengths of soils cemented with different cement types is very smaller for undrained

tests. It can be concluded that the effect of cement type reduces in undrained con-

dition. This can be attributed to the reduction in the brittleness of cemented bonds

due to the prevention of volumetric strains in undrained condition.

9. Volume changes

Figures 11–13 show the variation of volumetric strain with axial strain for cemented

samples under consolidated drained triaxial tests. According to these figures the

ultimate dilation induced in samples cemented with gypsum is more than the dilation


of samples cemented with two other types of cement. This is observed for all cement

contents and all confining stresses tested in this study. It can be concluded that

gypsum is the most dilative cementing agent between three tested cement types.

There is no reduction in dilation of gypsum cemented soil with increase in confining

stress.

For low cement contents and low confining stresses, the final dilation induced with

Portland cement is nearly equal or more than the dilation induced in the tests on soil

cemented with lime.

As the confining stress increases, the dilation induced in the soils cemented with

Portland cement reduces and becomes less than the dilation associated with the tests

on soils cemented with the lime. This confirms the reduction in the brittleness of

Portland cement with increase in confining stress as stated before.

Figure 13 shows that when the cement content increases to 4.5% the final dilation

associated with Portland cement is more than the dilation of soil cemented with lime

for all confining pressures. But it is still less than the dilation induced in the soils

cemented with gypsum. This is also in agreement with the foregoing discussion about

reduction of Portland cement brittleness. In low Portland cement contents the

cementing bonds are weak and compressible. There is a little dilation in high con-

fining pressures. As the Portland cement content increases the bonds behave stiffer

and results in more dilation during the shear. For the tested soils, the highest rate of

increase in peak shear strength belongs to the increase of cement content from 3% to

4.5%. It can be concluded that for this soil the most effective cementing bonds forms

1.5% CementDrained Test

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3.0% CementUndrained Test

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Portland Cement

Figure 10. Variation of peak deviatoric stress with cement content.


1.5% CementConfining Stress =100 kPa

-5

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1.5% CementConfining Stress = 300 kPa

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Figure 11. Variation of volumetric strain with axial strain for 1.5% cement content.


when the cement content is about 4.5%. At this amount of cement, the Portland

cement bonds are stiffer than the lime cemented bonds and a higher dilation occurs

during the shear in the Portland cemented soil.


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Portland Cement


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Portland Cement



10. Pore water pressure changes

Figure 14 shows the variation of pore pressure vs. mean effective stress for a cement

content of 3% and different confining pressures. According to this figure the max-

imum positive pore pressure induced is lower for the soil cemented with gypsum. But

the ultimate suction generated using this cement type is more than that of two other

cementing agents. As indicated in Figure 14 the final suction in soil with lime

cementation is more than that of gypsum cementation for a confining stress of

500 kPa. This confirms the more reduction in brittleness of gypsum cement in un-

drained condition. Figure 15 shows the variation of pore pressure with mean

effective stress for 1.5% and 4.5% cement contents. For both of these cement con-

tents the maximum positive pore pressure induced in the soil cemented with gypsum

is less than that of soils cemented with two other cementing agents. Also the max-

imum suction induced in the soils cemented with gypsum is more than the corre-

sponding values induced in the soils cemented with two other cementing agents.

As indicated earlier in Figure 13 the ultimate dilation is more in Portland ce-

mented soil compared to that of the lime cemented soil in drained tests. Contrary to

the drained tests the maximum negative pore pressure induced in undrained shearing

of the soils cemented with 4.5% Portland cement is not more than that of the soils

cemented with lime. This may be in agreement with the higher reduction in brittle-

ness of Portland cement when is compared to that of lime in undrained condition.

11. Stress paths

Figure 16 shows the stress path for undrained tests conducted on samples cemented

with 1.5%, 3.0% and 4.5% cement content in triaxial compression test under a

confining pressure of 100 kPa. For 1.5% and 3.0% cement contents the increase in

deviatoric stress with the mean effective stress is approximately the same for different

cement types. So the stress paths are nearly coincided for different cement types. This

trend continues until the stress condition approaches close to the yield point of the

soil. After that the stress paths diverge. According to this figure the maximum mean

effective stress occurs for the soil cemented with gypsum. This can be attributed to the

high pore pressure induced at the failure of the soil cemented with gypsum. When the

cement content increases to 4.5%, the rate of increase in deviatoric stress with mean

effective stress is more for Portland cement compared to the two other cement types.

The stress path of soil cemented with Portland cement moves sharper and steeper than

the stress paths for two other cement types. The maximum value of mean effective

stress for Portland cement is higher than two other cement types. This confirms that

the effect of cement type changes when the cement content varies in the soil.

12. Failure envelope and shear strength parameters

The previous studies showed that the failure envelope for the cemented gravely

sand is curved (Haeri et al., 2002, 2004; Asghari et al., 2003). The study on



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Portland Cement

Figure 14. Variation of pore pressure with mean effective stress for 3.0% cement content.


cemented soil with gypsum confirms this finding. However in order to compare

the failure envelopes and the shear strength parameters for three different cement

types, in the present study the failure envelope and the shear strength parameters

are determined using a linear interpolation. Figure 17 shows the failure envelopes

determined from drained and undrained triaxial tests on uncemented and ce-

mented soils with different cement types. The difference between failure envelopes

is more in drained condition. This confirms that the effect of cement type is more

profound in drained condition when is compared to that of undrained state. This

may be attributed to volumetric strains occur in drained condition. As a result

the influence of stiffness and brittleness of cementing agent is more in drained

condition.


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Figure 15. Variation of pore pressure with mean effective stress for 1.5% and 4.5% cement content.



0

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Figure 16. Stress paths for triaxial undrained tests.


For the undrained condition the failure envelope for the soil cemented with

Portland cement is above the failure envelopes of the soil cemented with two other

cementing agents. The slopes of the failure envelopes for the soils cemented with

different cement types are approximately identical for undrained condition. Parallel

and adjacent failure envelopes (Figure 17) are indication of lower participation of

the effect of cement type on the friction angle and cohesion of the cemented soils in

undrained condition. Assuming linear failure envelope Table 3 shows the values of

friction angle and cohesion intercept for the soil cemented with different cement

types in drained and undrained condition. According to this table the cohesion

intercept of the soil cemented with all cement types increases with cement content.

For equal cement content the cohesion induced in soil with Portland cement is more

than two other cement types. Also the cohesion intercept of the soil cemented with

gypsum is more than that introduced with lime.

For the undrained condition the cohesion intercept of the soil cemented with

Portland cement is higher than those of the two other cementing agents. It can be

concluded that Portland cement is the most suitable cement type for coarse-grained

soil in undrained condition. Table 3 shows that Portland cement produces cohesion

intercept of about 5.5 times of that produced by gypsum and 10 times of that

produced by lime for an equal cement content of 3%. Thus to prevent phenomena

like liquefaction that occurs in undrained condition the most suitable cement type is

Portland cement as stated by Dupas and Pecker (1979).

Table 3 indicates that the friction angle of soil cemented with gypsum slightly

increases with cement content. But the friction angle of the soil cemented with lime

Undrained Condition3% Cement

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Portland cement

Drained Condition1.5% Cement

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Drained Condition4.5% Cement

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Lime

Portland cement

Figure 17. Failure envelope for drained and undrained condition and different cement contents.


decreases when the cement content increases from 1.5% to 3% and then increases

with cement content. There is a large increase in friction angle of the soil cemented

with Portland cement when its cement content reaches to 4.5%. This might be an

effective threshold for the amount of Portland cement to be added to the soil for

gravely sand and sandy gravel stabilization. The friction angle of the soil cemented

with gypsum is nearly equal in drained and undrained conditions. But the friction

angles of the soil cemented with lime and Portland cement in undrained condition

are higher than those in drained state. This increase is higher in the soil cemented

with the Portland cement. This fact confirms the effectiveness of the Portland cement

in undrained condition as the cementing agent.

13. Conclusion

The mechanical behavior of a gravely sand was studied using different cement types.

According to the test results the following conclusions can be stated:

1. Equal cement content can be used as a useful indicator of the degree of cemen-

tation to investigate the effect of cement type on the behavior of cemented soils.

This is true where the cement acts as a bonding agent and not as a filler of voids

between soil grains. The above said criterion is not valid while the cement acts as a

filler of the voids.

2. Gypsum cement produces the most brittle condition for cemented soil in com-

parison to the two other cement types considered in this research. The gypsum

cemented soils tested in this research, dry and saturated with silicon oil, fail with

shear zone even in high confining pressures.

3. In low cement contents and low confining pressures the highest shear strength of

cemented soils belongs to the soil cemented with Portland cement. Increasing the

confining stress, the shear strength of soil cemented with Portland cement drops

lower than the shear strength of the soil cemented with gypsum. However, it is still

higher than the shear strength of the soil cemented with lime. For higher confining

pressures like 500 kPa the shear strength of the soil cemented with Portland ce-

ment also drops lower than the shear strength of the soil cemented with lime. So

one can conclude that the rate of increase in shear strength of soils cemented with

Portland cement reduces with increase in confining stress when the amount of

cementation is low. When the cement content increases to 4.5% the shear strength

of the soil cemented with Portland cement is always higher than the shear strength

of the soil cemented with two other cementing agents.

4. The Portland cement is a ductile cementing agent and the behavior of the soil

cemented with Portland cement depends on the amount of cement content and the

applied confining stress. When the cement content is small in the soil, the soil

stiffness reduces with increase in confining pressure. However, when the cement

content increases in the soil, the soil keeps its stiffness and strength up to high

confining pressures.


5. The final dilation induced in samples cemented with gypsum is more than the

dilation of samples cemented with two other cement types.

6. The brittleness of the soil cemented with Portland cement decreases in undrained

condition for confining pressures between 300 kPa and 500 kPa as drained tests.

However, contrary to the drained tests there is an increase in the brittleness of the

gypsum and limy cemented soil in the same range of confining pressure in un-

drained condition.

7. The effects of the cement type on the behavior of cemented soil increases with

increase in cement content. Also the effect of cement type is clearer in drained

condition compared to the undrained state.

8. The failure envelope is curved for the cemented gravely sand. If a linear approxi-

mation is considered for a simpler comparison, the shear strength parameters can

be determined. As a consequence the results of this study indicate that the cohe-

sion intercept of the soil cemented with Portland cement is the highest in drained

and undrained conditions. A detailed information about the shear strength

parameters of soils cemented with different cement types under different condi-

tions are presented in Table 3. In general, the Portland cement is the most effective

cementing agent in undrained condition compared to the two other cement types

tested in this research to mitigate phenomenon like liquefaction.

References

Airey, D.W. (1993) Triaxial testing of naturally cemented carbonate soil, ASCE J. Geotech.Eng. Div., 119(11), 1379–1398.

Asghari, E., Toll, D.G. and Haeri, S.M. (2003) Triaxial behavior of a cemented gravelly sand,

tehran alluvium, J. Geotech. Geol. Eng., 21(1), 1–28.Chang, T. and Woods, R.D. (1992) Effect of particle contact bond on shear modulus, ASCE J.

Geotech. Eng. Div., 118(8), 1216–1233.Clough, G.W., Sitar, N., Bachus, R.C. and Rad, N.S. (1981) Cemented sands under static

loading, ASCE J. Geotech. Eng., 107(6), 799–817.Coop, M.R. and Atkinson, J.H. (1993) The mechanics of cemented carbonate sands, Geo-

technique, 43(1), 53–67.

Consoli, N.C., Prietto, D.M. and U1brich, L.A. (1998) Influence of fiber and cement additionon behavior of sandy soil, ASCE J. Geotech. Geoenviron. Eng., 124(12), 1211–1214.

Dupas, J. and Pecker, A. (1979) Static and dynamic properties of sand cement, ASCE J.

Geotech. Eng. Div., 105(3), 419–436.Haeri, S.M., Yasrebi, S. and Asghari, E. (2002) Effects of cementation on the shear strength

parameters of tehran alluvium using large direct shear test In: Proc., 9th IAEG Cong.,Durban, South Africa, pp. 519–525.

Haeri, S.M. and Hosseini, S.M. (2003) A comparison of drained tests on wet and saturatedcemented sandy gravel, Research Report, Sharif University of Technology, Tehran, Iran.

Haeri, S.M., Hosseini, S.M., Toll, D.G. and Yasrebi, S.S. (2004) Experimental study of the

behavior of a cemented gravely sand, J. Geotech. Geol. Eng. (In Press).Hamidi, A., Haeri, S.M. and Tabatabaee, N. (2004) Influence of gypsum cementation on the

shear behavior of cemented sands, In: Proc. 1st Nat. Cong. Civil Eng., Sharif University of

Technology, Tehran, Iran, Paper No. 56.


Head, K. H. (1986) Manual of Soil Laboratory Testing, Vol. 3, Pentech Press, London, UK.

Huang, J.T. and Airey, D.W. (1998) Properties of artificially cemented carbonate sand, ASCEJ. Geotech. Geoenviron. Eng., 124(6), 482–499.

Ismail, M.A., Joer, H.A., Sim, W.H. and Randolph, M.F. (2002) Effect of cement type onshear behavior of cemented calcareous soil, ASCE J. Geotech. Geoenviron. Eng., 128(6),

520–529.Lade, P.V. and Overton, D.D. (1989) Cementation effects in frictional materials, ASCE J.

Geotech. Eng., 115(10), 1373–1387.

Malandraki, V. and Toll, D.G. (2001) Triaxial tests on a weakly bonded soil with changes instress path, ASCE J. Geotech. Geoenviron. Eng., 127(3), 282–291.

O’Rourke, T.D. and Crespo, E. (1988) Geotechnical properties of cemented volcanic soil,

ASCE J. Geotech. Eng. Div., 114(10), 1126–1147.Rotta, G.V., Consoli, N.C., Prietto, P.D.M., Coop, M.R. and Graham, J. (2003) Isotropic

yielding in an artificially cemented soil cured under stress, Geotechnique, 53(5), 493–501.Saxena, S.K. and Lastrico, R.M. (1978) Static properties of lightly cemented sand, ASCE J.

Geotech. Eng., 104(12), 1449–1465.Schnaid, F., Prietto, P.D.M. and Consoil, M.H.T. (2001) Characterization of cemented sand

in triaxial compression, ASCE J. Geotech. Geoenviron. Eng., 127(10), 857–867.


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