Cement effects on the physical properties of …...European International Journal of Science and Technology ISSN: 2304-9693 74 Cement effects on the physical properties of expansive

European International Journal of Science and Technology ISSN: 2304-9693 www.eijst.org.uk

74

Cement effects on the physical properties of expansive clay soil and

the compressive strength of compressed interlocking clay blocks

Ronoh, Victor1*

, Jonah Kiptanui Too2 and James Wambua Kaluli

3

1*

(Graduate Student, Civil engineering Department, Pan African University (PAUISTI)

2(Civil engineering Department, JKUAT)

3(Department of Biomechanical & Environmental Engineering, JKUAT)

Corresponding Author:

*Mr Ronoh Victor

Pan African University Institute of Basic Science,

Technology and Innovation, Nairobi, Box 62000-00200,

Nairobi, Kenya

Email: [email protected]

Abstract

Building with earth is an ancient technology which is still being practiced today. The resources used in the

production of concrete blocks and fired clay bricks tend to be unsustainable. Therefore, there is need to

identify sustainable material and technologies. This study investigated the compressive strength of

compressed earth block which have been stabilized with cement. This study investigated how stabilizing soft

clays with cement affects the compressive strength of interlocking blocks. Particle size distribution,

Atterberg limits, standard proctor compaction and compressive strength tests were carried out according to

British standard procedures (BS 1377-1990: Part 2 & 4). The soil used was classified as A-7-5 in the

AASHTO classification system. Its liquid limit, plasticity index and linear shrinkage decreased while the

plastic limit, maximum dry density (MDD), and optimum moisture content (OMC) increased with increasing

cement content. The cement stabilized clay blocks had average compressive strength ranging from 0.3 MPa

to 1.1 MPa at 7 days of curing and 0.8 to 3.1MPa at 28 days of curing. This study established that to achieve

minimum strength of soil blocks (2.5 MPa); the soil should be stabilized with at least 8% cement.

Key words: Stabilize, Soil, Sustainable, Compressed earth block, Compressive strength, Cement

European International Journal of Science and Technology Vol. 3 No. 8 October, 2014

75

1 Introduction

Clay soil is an earth material and it’s highly and readily available for construction purposes but due to its

weakness, it requires great improvement of its properties before use. In the construction industry, clay soils

are proving to be an Engineer’s nightmare. They have high swelling and shrinkage and are very much

sensitive to changes in environment (Narasihma et al, 2014). Walls made from mud swell and crack when

exposed to alternate wet and dry weather. These are some of the factors that have made clay soil to be

classified among the least suitable soils for construction.

Large quantities of clay are generated from construction sites and dumped as waste. There is need to identify

ways of utilizing this material to enable utilization of heavy clay soils stabilization to reduce swelling and

shrinkage would be necessary. Ordinary Portland cement, one of the substances that can be used for soil

stabilization, is readily available. Compressed stabilized blocks require less cement compared to the quantity

used in the hollow concrete blocks. The amount of additives necessary to stabilize these expansive soils

depends on the mineralogical composition of the soils (Venkaramuthyalu et al 2012). Cement contents

below 2 or 3% will not actually enhance the wet compressive strength or improve stabilization (Rigassi,

1985). The minimum amount required for stabilizing soils for the production of building blocks, has been

identified as 5% by weight (Rigassi, 1985).

Stabilized earth blocks do not require kiln-firing. Therefore, production of soil blocks with stabilized soils

reduces air emission pollution and the consumption of non renewable resources. The commercial

exploitation of these resources often leads to various environmental problems such as improperly filled up

clay mines which can collect water and allow mosquitoes to breed. Extensive sand mining can lower the

river- beds and allow salt-water intrusion inland. Therefore, the development of many alternative walling

materials as possible will be of immense benefit to minimize the impact on the environment. Earth is a

cheap, environmentally friendly and abundantly available building material and has been used extensively

for wall construction around the world, particularly in developing countries (Hanifi et al, 2005) However,

there are few undesirable properties such as loss of strength when saturated with water, erosion due to wind

or driving rain and poor dimensional stability (Narasihma et al, 2014). These draw backs can be eliminated

significantly by stabilizing the soil with a chemical agent such as cement. Cement stabilized soil is generally

used as individual blocks compacted either with manual hydraulically operated machines. Significant

research data are available for these applications either as block strength or wall strength (Perera and

Jayasingh, 2003; Reddy and Jagadish, 1989).

Stabilized earth blocks are environmentally sustainable because they have low embodied energy as they use

locally available soil, low labour cost and lower quantity of cement compared to concrete blocks (Mbumbia

et al., 2000). They are environmental friendly compared to clay fired bricks as they require no burning to

acquire strength thus no cutting down of trees. Environmentally unsustainable practices such as burning

firewood and dredging river sand are also sometimes used in the production of clay fired bricks and concrete

blocks, (Agevi, 1999; Mbumbia, et al., 2000).

Therefore, concrete blocks and clay fired bricks use unsustainable materials during their local production.

River sand used for hollow concrete blocks (Shan & Meegoda, 1998) and firewood used as fuel for the

burning of clay fired bricks (Mbumbia et al., 2000) are environmentally unacceptable, and in any case likely

to face rising prices driven by increasing scarcity. Consequently the only small-scale method of block

manufacture left deals entirely with the stabilization of locally available un-graded soil. Thus this study

considers the use of cement to stabilize clay soil dumped as waste from the construction sites to produce

sustainable, low cost and environmentally friendly stabilized clay blocks for low cost housing. This is a case

study carried out in Kenya considering the excavated soils from a construction site in Juja, Kiambu County.


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2 Methodology

2.1 Materials

The raw materials used in this research include clay soil, Ordinary Portland cement (Grade 32.5) and tap

water. Black Cotton Soil was sourced from a construction site in Juja. One soil sample was taken from the

homogenous layers below 200 mm from the top of soil. This was done to limit the amount of organic matter

in the sample. The sample was left to dry and the lumps formed were crushed into small pieces and sieved

through 5mm mesh sieve in accordance with BS 1377-1 (1990).

2.2 Laboratory tests

2.2.1 Particle size distribution and Atterberg limits tests

The Particle Size Distribution and Atterberg limits for the soil sample were determined in accordance with

the British Standard procedures as outlined in BS 1377-1990: Part 2. For Atterberg limits, the soil was

sieved through 425µm sieve and the soil passing this sieve was oven dried before conducting the test. The

tests were carried out on the soil alone and soils with different proportion of cement.

A combination of sieve analysis and hydrometer test was used to determine the particle size distribution

(Figure 1). The soil was classified as A-7-5 in the AASHTO classification system and as CH (Inorganic

clays of high plasticity, fat clays) according to Unified Soil Classification System (USCS).

2.2.2 Compaction tests

Standard Proctor compaction test, according to BS 1377–1990: Part 4 was applied to determine the

maximum dry density (MDD) and the optimum moisture content (OMC) of the soils. The soil mixtures, with

and without additives, were thoroughly mixed with various moisture contents before compaction. The first

series of compaction tests were aimed at determining the compaction properties of the unstabilized soils.

Secondly, tests were carried out to determine the proctor compaction properties of the clay upon

stabilization with varying amounts of cement.

2.2.3 Unconfined compressive strength test

Fifteen specimens for unconfined compressive tests were prepared. They were molded in a cylindrical

mould of 50 mm diameter by 100 mm height, at the OMC and MDD of each mix. The test was conducted

according to BS 1924: Part 2 – Section 4. Specimens were, after molded, cured in plastic bag for 7 days to

prevent the moisture due to change. Three specimens per mix composition were tested for unconfined

compressive strength, in accordance with BS 1924-2; 1990 Section 4, using a compression machine.

2.2.4 Block production and Compressive strength test

Batching of materials was done by weight and cement percentages were 0%, 6%, 8%, 10% and 12%. Dry

materials (clay soil and cement) were mixed first until uniform mixture was produced, then water was added

and mixing continued until a homogeneous mix was obtained. The mixed sample was then placed in the

CINVA-Ram press machine and manually pressed to produce the blocks which were extruded immediately.

They were cured in a shade while covered with polythene bag. Nine replicates of the blocks were produced

for each mix where three blocks were tested on 7, 14 and 28 days respectively. The average compressive

strength of three blocks was determined in accordance to BS EN 772-1 (2003). The results were then

analyzed to determine the minimum percentage of cement necessary for stabilizing black cotton soils and

achieves the minimum required standard of 2.5MPa as specified by Kenyan Standard, KS 02-1070:1993,

Specification for stabilized soil blocks.

3 Results and discussion

3.1 Determination of soil classification

The soil consisted of 12.82% gravel, 7.92% sand and 79.26% fines (Figure 1). According to Rigassi (1985),

the range of particle distribution suitable for building of earth block is: 0 – 40% gravel, 25 - 80% sand and


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18 - 55% fines (silts and clays). This implies that the Juja soil used in the study does not meet the minimum

requirements for earth block production. In other word, the soil considered requires an improvement or

stabilization for it to be utilized in block production. Furthermore the results of the natural soil are

summarily tabulated in Table 1.

3.2 Effect of cement content on Atterberg limits

There was a reduction in plasticity index from 57.81% to 27.57% is due to liquid limit decrease from

90.25% to 75.32% and plastic limit increase from 47.75% to 32.44% with the increase of cement content

from 0% to 12% in the soil. Linear shrinkage had a constant decrease from 16.14% to 9.68% for 0% to 12%

cement content respectively (Figure 2). This fact means that floccules numbers do not have significant

change when cement content is more than 10% because the liquid limit, plastic limit and plasticity index are

nearly becoming constant. The unstabilized soil sample had 90.25% liquid limit, 32.44% plastic limit,

57.81% plasticity index and 16.14% linear shrinkage.

The reduction in the plasticity index values resulted from the decrease in liquid limit and plastic limit. With

the decrease in the plasticity index and liquid limit, the engineering properties of soil are improved as the

shear strength of the admixed soil improves and become more workable.

3.3 Effect of cement content on soil compaction

The relation between the optimum moisture content (OMC) and maximum dry density (MDD) for the

cement stabilized soil mixture using standard proctor are shown in Figure 3.

It was observed that MDD increased with the increase in cement content and the OMC decreased with

increase in cement content (Figure 4). MDD increased from 1382kg/m3 for the unstabilized/natural soil to

1439kg/m3 for the stabilized soil with 12% cement content. The cement dosage was from 6% to 12% by

weight of dry soil. According to Otoko & Precious (2014), the increase in MDD with cement content may be

attributed to the relative higher specific gravity of cement to that of the soil (2.55). The increase in dry

density is a designate an improvement in the soil sample.

The OMC of the black cotton soil also increases with the increase of cement content (Figure 5) and this

might be as a result of water needed for the hydration of cement as it reacts and binds the soil particles

together, Behmanesh, J., & Mehrmousavi, Z. (2014) also reported the same. It might also be due to the

additional water held with the flocculant soil structure resulting from cement interaction. The OMC

increased from 15.8% for unstabilized soil to 21.6% for the 12% cement content in the stabilized soil.

The increase in dry density is an indicator of improvement of soil properties and that the compaction energy

is more than that of the soil in a natural state while the increase in optimum moisture content indicates that

the increasing desire for water is somewhat commensurate to the increasing amount of cement, as more

water is required for the dissociation of cement into Ca2+

and OH- ions to supply more Ca

2+ for the cation

exchange reaction.

3.4 Unconfined compressive strength (UCS)

There was a tremendous improvement in the UCS observed after 7 days of curing period where the UCS

increased from 268KPa

at 0%, 734KPa

at 6%, 849KPa at 8%, 1087KPa at 10% and 1188KPa at 12% cement

content (Figure 6). The increase in cement content in the stabilized soil results in deposition of interlocking

cement gel between the soil particles binding the soil particles together and creates high strength thus the

increase in UCS with the increase in cement content.

According to Oriola, & Saminu. (2012), the increase in UCS values could be attributed to ion exchange at

the surface of clay particles. The chlorides in the cement additive reacted with the lower valence metallic

ions in the clay microstructure which resulted in agglomeration and flocculation of the clay particles. The

increase in UCS after the 7 days curing was due to the long-term hydration reaction that resulted in the

formation of newer compounds due to the presence of chlorides which are known to be stabilizing agents.


78

The increase in unconfined compressive strength is due to the soil-cement reaction which is the

improvement of the engineering properties of the natural soil. When water reacts with cement in the

specimens, it bonds the components together; hence robust stone-like specimens are created resulting in high

unconfined compressive strength than for natural soil.

3.5 Blocks compressive strength

It was observed that compressive strength of unstabilized interlocking blocks (the control) varies from 0.280

N/mm2

to 0.811 N/mm2

as the curing age increases from 7 to 28 days (Figure 7). For cement stabilized

interlocking blocks it varies from 0.529 N/mm2

to 2.434 N/mm2, 0.670 N/mm

2 to 2.575 N/mm

2, 0.776

N/mm2

to 2.646 N/mm2

and 1.093 N/mm2

to 3.104 N/mm2

for 6%, 8%, 10% and 12% stabilization,

respectively, during the same period of curing(Figure 7).

The unstabilized blocks showed some strength but it didn’t achieve the required standard strength and

developed some cracks immediately after demoulding and kept to cure. This might be due to the chemical

nature of soil where the soil hardens and the bonds start weakening.

Compressive strength increased with increase in cement content from 0% to 12% cement content. Cement is

mainly composed of Lime (CaO) and Silica (SiO2) which react with each other and the other components in

the mix when water is added. This reaction forms combinations of Tri-calcium silicate and Di-calcium

silicate referred to as C3S and C2S in the cement literature, (Neville, 1995).

It was determined that the mixture with 8%, 10% and 12% cement content achieved the minimum required

standard compressive strength of 2.5MPa as per the Kenyan Standard, KS 02-1070:1993, Specification for

stabilized soil blocks. This implies that the blocks can be recommended for utilization in single storey

constructions and interior non load bearing walls for other construction purposes.

The chemical reaction eventually generates a matrix of interlocking crystals that cover any inert filler and

provide a high compressive strength explaining why as the cement content increases the compressive

strength also increases.

4 Conclusions

� Introduction of cement in expansive clay soil resulted in reduced plasticity which is an indication of

improved soil engineering properties.

� With the addition of 12% cement to black cotton soil, the maximum dry density (MDD) increased

from 1382kg/m3 for the unstabilized/natural soil to 1439kg/m

3 for the stabilized soil, indicating an

improvement in the soil sample.

� Addition of 12% cement to black cotton soil increased OMC from15.8% for unstabilized soil to

21.6% for the stabilized soil, indicating desire for more water with increase in cement content.

� Addition of 12% cement to black cotton soil increased the unconfined compressive strength of the

soil from 268KPa

for the natural soil to 1188KPa.

� This study established that the minimum amount of cement required to stabilize black cotton soil and

achieve the minimum required compressive strength of 2.5MPa for a stabilized building block, was

8% by weight.


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5 References

1. Agevi, E. (1999). Technology Dissemination in Kenya. Development Alternatives Newsletter,

Vol: 9 (11), 7-9.

2. Behmanesh, J., & Mehrmousavi, Z. (2014). Effect of Hydraulic Binders on the Geotechnical

Properties of Stabilized Clayey Soil, Journal of Basic and Applied Scientific Research. 4(3),

261–269.

3. British Standards Institution. (1990). Method of test for soils for civil engineering purposes. Part

1. General requirements and sample preparation. BSI 1377: Part 1: 1990. BSI. England.


2. Classification tests. BS 1377: Part 2: 1990. BSI. England.


4. Compaction-related tests. BS 1377: Part 4: 1990. BSI. England.

6. British Standards Institution. (1990). Stabilized materials for civil engineering purposes. Part 1.

General requirements, sampling, sample preparation and tests on materials before stabilization.

BS 1924: Part 1: 1990. BSI. England.

7. British Standards Institution. (1990). Stabilized materials for civil engineering purposes. Part 2:

Methods of test for cement-stabilized and lime-stabilized materials. BS 1924: Part 2: 1990. BSI.

England.

8. British Standard Institution. BS EN 772-1 (2003). Specification for masonary units.

9. Kenya Standard, KS 02-1070:1993: Specification for Stabilized Soil Blocks.

10. Mbumbia, L., Mertens de Wilmars, A., & Tirlocq, J. (2000). Performance characteristics of

lateritic soil bricks fired at low temperatures: a case study of Cameroon. Journal of Construction

and Building Materials, Vol: 14 121-131.

11. Narasihma, A. V, Penchalaiah, B., Chittranjan, M., & Ramesh, P. (2014). Compressibility

Behaviour of Black Cotton Soil Admixed with Lime and Rice-Husk Ash, International Journal of

Innovative Research in Science, Engineering and Technology. 3(4), 11473–11480.

12. Neville, A. M. (1995). Properties of Concrete, Longman.

13. Oriola, F. O. P., & Saminu, A. (2012). Influence of Textile Effluent Waste Water on Compacted

Lateritic Soil. The Electronic Journal of Geotechnical Engineering. Vol. 17. 167–177.

14. Otoko, G. R., & Precious, K. (2014). Stabilization of Nigerian deltaic clay (Chikoko) with

groundnut shell. International Journal of Engineering and Technology Research. 2(6), 1–11.

15. Perera A. and Jayasinghe C. (2003). Strength characteristic and structural design methods for

construction earth walls. Masonry International. 16(1): 34-38.

16. Reddy B.V. and Jagadish J.S. (1989). Properties of soil – blocks masonry. International Masonry

Society. 3(2): 80-84.

17. Rigassi, Vincent. (1985). Compressed earth blocks - Volume 1: Manual of production. A

publication of the Deutsches Zentrum fur Entwicklungtechnologien-Gate.

18. Shan, H.-Y., & Meegoda, J. N. (1998). Construction use of abandoned soils, Journal of

Hazardous Materials. Vol: 58 133-145.

19. Venkaramuthyalu, P., Ramu, K., & Raju, G. V. R. P. (2012). Study on performance of

chemically stabilized expansive soil. International Journal of Advances in Engineering &

Technology, 2(1), 139–148.

20. Hanifi, B., Orhan, A., & Kaplan, H. (2005). Utilization of alternative materials in manufacturing

of mud brick. Journal of Engineering Sciences, 309–316.

European International Journal of Scien

6 Tables and Figures

Figure 1: Particle size distribution of t

Table 1: Physical properties of the soil

S. No. Description

1 Specific gravity

2 Liquid limit (%)

3 Plastic limit (%)

4 Shrinkage limit (%)

5 Plasticity Index (%)

6 Maximum Dry density (Kg/m

7 Optimum Moisture content (%

8 Colour

Figure 2: Effect of cement content on

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

90.00

100.00

0.001 0.01 0.1

Per

cen

tag

e P

ass

ing

(%

)

Gr

0

10

20

30

40

50

60

70

80

90

100

0 2 4 6

Att

erb

erg

lim

its

(%)

Cement Cont

ence and Technology ISSN: 2304-9693

f the soil sample

oil

Measured Values

2.55

90.25

32.44

16.14

57.81

/m3) 1382

t (%) 15.8

Dark Grey

n Atterberg limits

0.1 1 10Grain Size (mm)

Sieve analysis

8 10 12 14ntent (%)

LIQUID LIMIT

PLASTIC

LIMIT

PLASTICITY

INDEX

LINEAR

SHRINKAGE

www.eijst.org.uk

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Figure 3: Variation of Dry Density with Moisture content

Figure 4: Effects of cement content on the Dry Density Figure 5: Effects of cement on the moisture

content

Figure 5: Effect of cement content on unconfined compressive strength

1200

1250

1300

1350

1400

1450

10.0 15.0 20.0 25.0 30.0

Dry

Den

sity

(K

g/m

3)

Moisture content (%)

0% Cement

6% Cement

8% Cement

10% Cement

12% Cement

1350

1370

1390

1410

1430

1450

0 5 10 15

Ma

xim

um

Dry

De

nsi

ty (

Kg

/m3

)

Cement Content (%)

MDD

14

15

16

17

18

19

20

21

22

0 5 10 15

Op

tim

um

Mo

istu

re C

on

ten

t (%

)

Cement Content (%)

OMC

0

200

400

600

800

1000

1200

1400

0 5 10 15

UC

S (

Kp

a)

Cement Content (%)


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Figure 6: Effects of cement content on the compressive strength of interlocking blocks

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

0 5 10 15

Co

mp

ress

ive

Str

eng

th (

MP

a)

Cement Content (%)

7 Days

14 Days

28 Days

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Cement effects on the physical properties of …...European International Journal of Science and Technology ISSN: 2304-9693 74 Cement effects on the physical properties of expansive