SOIL STABILIZATION WITH CEMENT AND LIME
Engineering Project Report
Arslan Ahmad 2015-CIV-127
Meesum Tanveer 2015-CIV-128
Umar Farooq 2015-CIV-129
Umar Nazir 2015-CIV-132
Miss Hina Samar
Civil Engineering Department
University of Engineering & Technology, Lahore
We hereby declare that the semester project entitled “Soil Stabilization with Cement and
Lime.” The project is done under the supervision of Dr. Sardar Baber Khan, Professor, Department of Civil Engineering, UET Lahore. This project is submitted as an assignment of technical report writing to Miss Hina Samar.
All group members
All praises and thanks for Al-mighty ALLAH who is the entire source of all knowledge and wisdom to mankind, Lord of the universe, for availing us opportunities to carry out this research work.
We are pleased to express our gratitude to Dr. Sardar Baber Khan, our supervisor in this research, in whom we found an eminent scholar, sincere and hardworking person. He has patiently gone through our manuscript and enlightened us on every aspect of research. We acknowledge his care, guidance and patience with due respect.
With pleasant feelings of gratitude, we acknowledge the guidance of Head of Geotechnical Division, Civil Engineering Department, UET Lahore, Dr. Khalid Farooq. Also, Chairman Civil Engineering Department, UET Lahore, Dr. Muhammad Ilyas for his kind attitude.
We dedicate our research work to Dr. Sardar Baber Khan, Professor, Civil Engineering, University of Engineering & Technology, Lahore, who is going to retire at the end of this year from his duties.
We dedicate our research work to our families and friends who supported us a lot.
TABLE OF CONTENTS
TITLE PAGE ………………………………………………………………….…………. i
ACKNOWLEDGEMENTS Error! Bookmark not defined.
TABLE OF CONTENT iv
LIST OF FIGURES……. ………………………………………………………………… vi
LIST OF TABLES vi
1. INTRODUCTION 1
2. LITERATURE REVIE 2
2.1 Methods of Soil Stabilization 2
2.1.1 Cement Stabilization 3
2.1.2 Lime Stabilization 4
18.104.22.168 Chemistry of Lime Stabilization 5
3. METHODOLOGY 7
4. RESULTS AND DISCUSSION 8
5. CONCLUSION 11
LIST OF FIGURES
Figure 1 Relationship between unconfined compressive strength and cement content 12
Figure 2 Effect of curing time on unconfined compressive strength of soil 12
Figure 3 Soil stabilization with lime 13
Figure 4 Atterberg Limits 14
Figure 5 Change is consistency state of soil due to lime mixing 14
Figure 6 Relationship between Atterberg limits with lime content 14
Figure 7 Soil loaded in compression 15
Figure 8.2 Moulds for preparing samples
Compression testing machine
Figure 9 Comparison of strength vs % of admixture of stabilized soil 18
LIST OF TABLES
Table 1 Description of test specimens 16
Table 2 Basic engineering properties of soil 17
Table 3 Compressive strength of soil with different percentage of cement admixture 17
Table 4 Compressive strength of soil with different percentage of lime admixture 18
PI = Plasticity Index
FM = Fineness Modulus
SDD = Surface Dry Density
Wn = Moisture Content
fc = Compressive Strength
UCS = Unconfined Compressive Strength
B.C = Bearing Capacity
Psi = Pound per Square Inch
Civil engineering structures are constructed on soil deposits. Thus, for safe design this soil bed needs to be stabilized before the start of construction work. Many techniques have been developed for the improvement of soil. The popular technique to improve such soil condition is the use of cement and lime as admixtures in the soil. The properties of soil are improved by the addition of these materials in the soil. For this reason, a comprehensive study of the behaviours of the cement stabilized soil and lime stabilized soil became necessary. In this research work, a detailed testing has been carried out to study the behaviour of stabilized and non-stabilized soil with respect to its compressive strength. The soil used in this research is taken from Shahdara, near the Ravi Bridge. This research studies three aspects, such as the effect of admixtures, the effect of %age of admixtures and the effect of curing time. Compressive strength of soil samples is determined by using compression testing machine. The test results show that the compressive strength of soil increases with increase of content of admixture. Also, the strength of soil enhances when curing period is increased.
The basic load transfer mechanism of any civil engineering structure is as follows:
Consider frame structure for example. The live loads by activities and movements of humans and all dead loads of non-living things are being transferred to the slab of the frame structure, then from slab to the beams, then from beams to the columns, then from columns to the foundation, and in the end from foundation to the soil. Because the foundation is on the soil, no matter which type of building it is, of whichever materials it is made up, whatever foundation type has been provided, ultimately all the loads are transferred to the soil underneath. So, soil cannot be ignored in civil engineering. Rather it is the most important thing to work on before any construction activities. The soil should be strong enough to bear the loads of the structure. Luckily, if the construction is going to start on some type of rock, its B.C is not needed to be considered. Generally, rocks will give enough bearing capacity to the structure. But mostly, civil engineers encounter the weak soil strata like loose sand, loose silt or close clay, on which the construction of a structure like roads, dams, slopes or buildings is planned. So, what things come to our minds if weak soil is encountered: –
a) Shift the location of structure to other site where soil strata have enough B.C
b) Change the design of the structure so that the maximum load is borne by the soil underneath the structure
c) Improve the condition of loose soil underneath
The best solution to the problem is the third one i.e., to improve the soil’s condition.
“In a broad sense, improvement or stabilization of soil involves the different methods used for modifying the soil properties to improve its engineering performance 1, p. 13.” “Stabilization of soil means improving of soil strength under load applied to the soil. The properties of soil will be improved reasonably with or without adding the admixtures so that base or sub-base soil is able of supporting the load 1, p. 17.” “In the recent years, the improvement of soil with appropriate admixture such as lime, cement, chlorides of calcium, fly ash, bituminous material etc. is effectively used on collective scale for the construction of road foundation in Bangladesh, India, United Kingdom, and U.S.A etc 2, p. 365.” Cement and lime as admixtures are considered in this research work. Some admixtures improve poor soils and make the soil capable of supporting greater loads but they are not economical. The quantity of stabilizer is usually determined by means of arbitrary tests, which simulate field conditions of weathering and other durability processes.
In this research work, improvement of soil is carried out to attain the following objectives:
1. To increase the strength or stability of soil and to reduce the construction cost by making best use of the locally available materials
2. To modifying or increase the properties of soil by using locally available admixtures
3. To devise the methods of adding the missing property through the economical method
4. To modify the chemical properties of soil which is to be stabilized
5. To determine the physical properties like density, expansion, shrinkage, stability etc. of soil samples
2. LITERATURE REVIEW
2.1 Methods of Soil Stabilization
Methods of soil stabilization may be classified under two main types:
a) Modification or improvement of soil property of the existing soil without any admixture.
b) Modification of soil with the use of admixtures.
The examples of the first type are compaction and drainage which improve the inherent shear strength of soil. Examples of second type are
1. Mechanical stabilization
2. Fly ash stabilization
3. Bitumen stabilization
4. Cement stabilization
5. Lime stabilization
Cement and lime stabilization methods are discussed here: –
2.1.1 Cement Stabilization
Stabilization of soil by the addition of cement in it is known as cement stabilization. Soil-cement is a mixture of crushed soil and measured quantity of cement and water added in the soil, then compacted to the required density and finally cured. The part of cement is to enhance the engineering properties of soil such as its compressive strength, permeability, swelling potential and sensitivity to variations in moisture content. Cement can be applied to stabilize any type of soil, except soils with organic content greater than 2% or having pH lower than 5.3. The maximum dry density of sand and highly plastic clays enhance by adding cement to the soil but the SDD of silt is however reduced. The other main effects of cement-soil stabilization are decrease in shrinkage and swell potential, increase in strength, modulus of elasticity and resistance against the effect of moisture and freeze-thaw action.
The effect of cement quantity and curing time on UCS are shown in Figures 1 and 2. Figure 1 shows that unconfined compressive strength of fine and coarse soils increases with the increase of cement content. The 28-day unconfined compressive strength is proportional to the content of cement; it changes from 40% of cement content for the fine-grained soils to 150 % of cement content for the coarse-grained soils
Figure 1. Relationship between unconfined compressive strength and cement content
Figure 2. Effect of curing time on unconfined compressive strength of soil
2.1.2 Lime Stabilization
When stabilization of soil is achieved by adding lime in appropriate proportion, this process is called as soil lime stabilization. “Lime can improve almost all fine-grained soil types but the most affected improvement achieves in clayey soils of moderate to high plasticity 1.” Commonly, fine-grained clayey soils (minimum 25% passing through #200 sieve (75micron) and a PI greater than 10 are considered to be suitable for lime stabilization. Soils which contain significant quantities of organic matter (more than about 1 %) or sulfates (more than 0.3 %) may need extra quantity of lime.
22.214.171.124 Chemistry of Lime Stabilization
Drying of the Soil
If quicklime (CaO) is mixed, it immediately hydrates (i.e., chemically reacts with water) and evolves heat. Soil is dried, because water present in the soil contributes in this hydration reaction, and as the heat produced in this reaction can evolve additional moisture from soil.
The hydrated lime produced by these initial reactions will subsequently react with clay particles (discussed in the following paragraphs). These successive reactions will gradually yield additional drying because they decrease the soil’s moisture holding capacity.
If hydrated-lime or hydrated-lime slurry is used rather than quick lime, drying happens only due to the chemical changes in the soil that reduce its capacity of water carrying and increase the stability. Figure 4 is showing the Atterberg Limits at different moisture contents. In Figure 5, if the initial moisture content of soil is Wn and after the lime has mixed, its final moisture content is reduced to Wn’. So, it is observed that the consistency of soil has been changed from liquid range to the solid range.
Figure 3. Soil stabilization with lime 3
Figure 4. Atterberg Limits
After initial mixing of lime, the calcium ions (Ca++) from hydrated lime move towards the surface of the clay particles and displace water and other ions. The soil gets converted into friable and granular state thus making it easier for working and compaction. At this stage, the PI of the soil as shown in Figure 5 decreases significantly, so its tendency of swelling and shrinking also gets decreased. What happens to the Liquid limit, Plastic Limit and eventually Plasticity Index, it is well shown in the Figure 6.
Figure 5 Change is consistency state of soil due to lime mixing
Figure 6. Relationship between Atterberg limits with lime content
The soils for research work were collected from Shahdara near the Ravi Bridge. The soils were collected from this area because the soils are of very low bearing capacity. The basic properties of soils were determined without adding admixtures. Different tests were conducted to determine different engineering properties of soil as shown in Table 2.
“To perform the research work 60 cubes of size 2//x 2// x2// having same proportion of the mix are prepared 4.” The detail of the test specimens is given in Table 1 as given below. The curing period of 30 cubes is 3 days and curing period of remaining 30 cubes is 7 days. The cubes are tested for compressive strength by using compression testing machine. The reason for performing the compression test is that the soil is mostly loaded in compression and it fails in shear. (Figure 15). So, the determination of compressive strength is an indirect measure of soil’s shear strength.
“Of each %age of cement, 1 group of 3 cubes is cured for 3 days and other group of 3 cubes is cured for 7 days 5.” Similarly of each %age of lime, 1 group of 3 cubes is cured for 3 days and other group of 3 cubes is cured for 7 days.
Figure 7. Soil loaded in compression
Table 1 Description of test specimens
Total no. of cubes = 60
Total no. of cement treated cubes = 30
Total no. of lime treated cubes = 30
No. of cubes with 1% cement = 3+3
No. of cubes with 3% cement = 3+3
No. of cubes with 5% cement = 3+3
No. of cubes with 7% cement = 3+3
No. of cubes with 9% cement = 3+3
No. of cubes with 1% lime = 3+3
No. of cubes with 3% lime = 3+3
No. of cubes with 5% lime = 3+3
No. of cubes with 7% lime = 3+3
No. of cubes with 9% lime = 3+3
4. RESULTS AND DISCUSSION
Table 2 shows different engineering properties of soil used in the compressive test. The sample cubes were tested in compression testing machine and the compressive strength of cubes is determined by the relation fc = P/A, where fc is compressive strength, P is applied load and A is cross-sectional area. Compressive strength of soil-cement stabilized soils and soil without any admixture with different percentages is shown in Table 3.
Table 2 Basic engineering properties of soil
Basic properties Tested value
Diameter corresponding to 30 % finer, D30
Diameter corresponding to 60 % finer, D60
Uniformity co-efficient, Cu
Co-efficient of curvature, Cc
Fineness Modulus, FM 0.15 0.21
Water content (%) 12.35
Liquid limit (%) 30.00
Plastic limit (%) 18.86
Shrinkage limit (%) 14.98
Optimum moisture content (%) 16.20
Maximum dry density (gm/cm3) 1.78
Table 3 Compressive strength of soil with different percentage of cement admixture
Admixture % of
admixture Curing period (days) Size of
3 2//x 2// x2//
2//x 2// x2//
2//x 2// x2//
2//x 2// x2//
2//x 2// x2// 50.41
1 7 2//x 2// x2// 60.41
3 7 2//x 2// x2// 89.58
5 7 2//x 2// x2// 147.91
7 7 2//x 2// x2// 209.16
9 7 2//x 2// x2// 259.58
Without — — 2//x 2// x2// 23.33
For 3 days curing period, the compressive strength of cement stabilized soil has been increased from 50.41 psi with 1% cement to 202.91 psi with 9% cement. For 7 days curing period, the compressive strength varies from 60.41 psi to 259.58 psi with increase in %age of cement from 1% to 9%. Whereas, the fc of non-stabilized soil sample is 23.33 psi.
Similarly, compressive strength of soil-lime stabilized soils and soil without any admixture with different percentages is shown in Table 4.
Table 4 Compressive strength of soil with different percentage of lime admixture
Admixture % of
admixture Curing period (days) Size of specimen Compressive
7 2//x 2// x2//
2//x 2// x2//
2//x 2// x2//
2//x 2// x2//
2//x 2// x2//
2//x 2// x2// 24.98
3 7 2//x 2// x2// 42.08
5 7 2//x 2// x2// 62.08
7 7 2//x 2// x2// 82.91
9 7 2//x 2// x2// 95.83
Without — — 2//x 2// x2// 23.33
For 3 days curing period, the compressive strength of lime stabilized soil has been increased from 24.98 psi with 1% lime to 70.87 psi with 9% lime. For 7 days curing period, the compressive strength varies from 27.91 psi to 95.83 with increase in %age of lime from 1% to 9%. Whereas, the fc of non-stabilized soil sample is 23.33 psi.
A comparison between cement-stabilized and lime-stabilized soil strengths is given in Figure 20. It can be seen that the strength of cement-stabilized soil is greater than that of lime-stabilized for both 3 days and 7 days curing period. The binding properties of cement are more than those of lime for the soil used in the research.
Figure 9. Comparison of strength vs % of admixture of stabilized soil
In this research, five different mix proportions (1%, 3%, 5%. 7% and 9%) of cement-soil and lime-soil were investigated. From this study, the following conclusions can be drawn:
1. Strength of soil is increased by the addition of admixtures and hence stability increases.
2. Strength and stability is increased with the increase in amount of admixtures used.
3. Strength and stability is increased with the increase of curing period of sample.
4. Strength and stability improved by cement is much higher than lime for the soil used in research
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