A PROJECT REPORT ON
“SUBGRADE SOIL STABILIZATION BY USING FLYASH AND LIME” Submitted to Vikash College of Engineering for Women, Bargarh In Partial Fulfillment of the requirements
For the degree of Bachelor of Technology In Civil Engineering By
SUMAN PATEL (1121337003)
DEPARTMENT OF CIVIL ENGINEERING VIKASH COLLEGE OF ENGINEERING FOR WOMEN BARGARH VIKASH COLLEGE OF ENGINEERING FOR WOMEN BARGARH ODISHA SESSION: 2010-2014
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CERTIFICATE This is to certify that the project on the subject “ SUBGRADE SOIL STABILIZATION STABILIZATION
BY USING FLYASH AND LIME ” has been successfully completed and delivered by th
SUMAN PATEL (1121337003) belonging to 7 semester, Civil Engineering. This project
development and presentation was accomplished under my supervision.
Mr. NABEEN BAGE Project supervisor
VIKASH COLLEGE OF ENGINEERING FOR WOMEN BARGARH- 768028, ODISHA SESSION: 2010-2014
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CERTIFICATE OF APPROVAL
This project report entitled
“
SUBGRADE SOIL STABILIZATION
BY USING
FLYASH AND LIME ” submitted by SUMAN PATEL (1121337003) of 7th semester Civil Engineering to VCEW, Bargarh has been examined by us. The project report is found fit and approved for the award of the degree of BACHELOR OF TECHNOLOGY in Civil Engineering
EXTERNAL EXAMINER
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ACKNOWLEDGEMENT
This is to acknowledge the help and encouragement that we received from various persons and sources during our project work. In this connection we would like to the name of our project guide Mr. NABEEN BAGE , who was a constant source of valuable instruction and constant encouragement. We are indebted to our guide for providing his valuable time, constant guidance, co-operation and scrupulous supervision to complete this project report. His untiring effort, availability in spite of his preoccupations and friendly behavior needs special mention .We are extremely grateful to all the faculty members of civil engineering department who shared not only their vast knowledge with us, but also lent their valuable time. Finally, we are saluting to all those websites those need worth mentioning for sufficing us with some hard found materials.
SUMAN PATEL (1121337003)
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CONTENTS CERTIFICATE ACKNOWLEDGEMENT ……………………………………………………………………..Page no ABSTRACT…………………………………………………………………………………………… 1 CHAPTER 1
2-3
INTRODUCTION……………………………………………………………………………………. .2 GENERAL……………………………………………………………………………………………….2 SCOPE OF THE OBJECT…………………………………………………………………………. 3 OBJECTIVES OF THE PROJECT………………………………………………………………..3
CHAPTER 2:
4-10
LITERATURE REVIEW 2.1:RECENT RESEARCHES……………………………………………………………………… 4 2.2:GENERAL……………………………………………………………………………………….’. 6 2.3:SOIL STRUCTURE…………………………………………………………………………… .6 2.5:QUALITY IMPROVEMENT………………………………………………………………. 7 2.6:STABILIZATION TECHNIQUES………………………………………………………… 7 2.7.1 STABILIZATION WITH LIME…………………………………………………………………………… 7 2.7.2 STABILIZATION WITH FLY ASH……………………………………………………………… 10
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CHAPTER 3:
11-14
EXPERIMENTAL PROGRAMME 3.1: INTRODUCTION………………………………………………………………………………….11 3.2: MATERIALS USED …………………………………………………………………………………………. 11 3.3: LAB TESTING ……………………………………………………………………………………………….. ..12 3.4: SOIL PREPARATION ……………………………………………………………………………………… ..12 3.5: STANDARD PROCTOR TEST ………………………………………………………………………….… 13 3.6: CBR TEST
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…………………………………………………………………………………………………………………………..
3.7: SPECIFIC GRAVITY
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3.8: LIQUID LIMIT
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……………………………………………………………………………………………………………..
………………………………………………………………………………………………………………………
CHAPTER 4:
15-18
RESULT AND DICUSSION ………………………………………………………………………….15 CHAPTER 5:
19-20
SUMMARY AND CONCLUSION………………………………………………………………..19 REFERNCES ……………………………………………………………………………………………..20 LIST OF TABLES:
Table 1-PROPERTIES OF SOIL USED IN THE STUDY Table 2-VARIATION OF MDD & OMC & CBR VALUE WITH FLYASH CONTENT
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Table 3-VARIATION OF MDD & OMC & CBR VALUE WITH LIME CONTENT
ABSTRACT Subgrade is basic foundation for any civil engineering structures. It is required to bear the loads without failure. In some places, soil may be weak which cannot resist the upcoming loads. In such cases, subgrade soil stabilization is needed. Numerous methods are available in the literature for subgrade soil stabilization. But sometimes, some of the methods like chemical stabilization, lime stabilization etc. Adversely affects the chemical composition of the subgrade soil. In the study, flyash and lime were mixed with subgrade soil to compaction. The effect of flyash and lime on the geotechnical characteristics subgrade-flyash and subgrade-lime mixtures was investigated by conducting standard proctor compaction tests. The test were performed as per Indian standard specifications. The following materials were used for preparing the samples:
Subgrade soil
Flyash
Lime
The subgrade soil used for these experiments was brought from a site, near Bargarh. The physical property of the subgrade were determined as per IS specifications. In this test programmed, without additive subgrade was tested to find the optimum moisture content, bearing strength. Flyash and lime were added 7
in varying percentages and that fraction for which maximum strength is obtained was found out.
CHAPTER 1 INTRODUCTION: GENERAL Transport in the Republic of India is an important part of the nation’s economy. Roads are the vital lifelines of the economy making possible trade and commerce. They are the most preffered modes of transportation and considered as one of the cost effective modes. An efficient and well-estabilished network of roads is desired for promoting trade and commerce in any country and also fulfils the needs of a sound transportation system for sustained economic development. To provide mobility and accessibility, all weather roads should connect every nook and corner of the country. To sustain both static and dynamic load, the pavement should be designed and constructed with utmost care. The performance of the pavement depends on the quality of materials used in road construction. Subgrade is in situ material upon which the pavement structure is placed. Although there is a tendency to look at pavement performance in terms of pavement structures and mix design alone, the subgrade soil can often be the overriding factor in pavement performance. The construction cost of pavements will be considerably decreased if locally available low cost materials are used for construction of lower layer of pavements such as subgrade, sub base etc. If the stability of local soils is 8
not adequate for supporting for the loads, suitable methods to enhance the properties of soil need to adopt. Soil stabilization is one such method. This report contains a summary of the performance of lime and flyash used with subgrade. Flyash are finely divided residue resulting from aluminium plant. Lime is another additive used, which is locally available, to improve subgrade characteristics. It is obtained by heating limestone at elevated temperatures.
SCOPE OF THE PROJECT The soil used in the study is subgrade soil brought from a site, near Bargarh. Pavement subgrade over there is composed of natural soil whose bearing capacity is sufficient. This proves to be economic for road construction. Soil stabilization can be done using different additives, but use of flyash which is a waste material from aluminium plant at the same time difficult to dispose material will be much significant.
OBJECTIVE OF THE PROJECT The major objectives of the project are: 1. To explore the possibility of using flyash in road construction program. 2. To study the effect of lime and flyash on proctor’s density and OMC of subgrade soil. 9
3. To study the effect of lime and flyash on the liquid limit of subgrade soil. 4. To stu 5. dy the changes in bearing strength of soil by addition of lime and flyash.
CHAPTER 2 LITERATURAL REVIEW The losses due to extensive damage to highways running over expansive soil subgrades are estimated to be in billions of dollars all over the world (Jones and Holtz, 1973; Steinberg, 1992). Various remedial measures like soil replacement (Snethen et al, 1979; Chen, 1988), prewetting (Bara, 1969; Rao and Satyadas, 1980), moisture control (Mohan and Rao, 1965; Marienfeld and Bakeras 1999), lime stabilization (Holtz and Gibbs, 1956; Thompson and Robnett, 1976; Bansal et al, 1996) have been practiced with varied degree of success. However, these technique suffer from certain limitations respect to their adaptability like longer time periods required for prewettting the highly plastic clays, (Felt,1953; Steinberg,1977), difficulty in constructing the ideal moisture barriers (Snethen et al,1979; Chen,1988), pulverization and mixing problems in case of lime stabilization (Holtz,1969; Ramana Murty,1998) and high cost for hauling suitable refill material for soil replacement (Snethen et al,1979; Chen,1988)etc. In India there are about 82 thermal power plants, which are currently producing about 100 million tons of flyash per annum (Dhar, 2001). In order to utilize fly ash in bulk quantities, ways and means are being explored all over the world to use it for construction of embankments and roads (Hausmann, 1990; Veerendra Singh et al, 1996; Boominathan 10
and Ratna Kumar, 1996; Murthy, 1998). According to the latest MORHT specifications, several types of gravel are found to be unsuitable for road construction in view of higher finer fraction and excessive plasticity properties. Krupavaram had made attempt to use lime stabilized flyash subbase course in model field pavement stretches. Standard proctor test and CBR tests were conducted on flyash subbase and lime stabilized fly ash subbase stretches constructed on different subgrades(i.e expansive soils & sand) and observed that lime stabilized flyash stretch showed better performance in load carrying capacity and reduction of heave laid on expansive soil subgrade. In another investigation an attempt was made to use cement stabilized flyash subbase course in field pavement stretches and compared performance with flyash subbase. Standard proctor test and CBR test were conducted in flyash subbase and cement stabilized flyash subbase stretches constructed on different subgrades (i.e sand &expansive soil)and found that cement stabilised flyash stretch had shown better performance in load carrying capacity and reduction of heave compared to conventional stretch, laid on expansive soil subgrade. Kumar et al had conducted on experimental program to study the effect of lime stabilization of geotechnical characterstics of flyash soil-mixture. From results it was observed that the expansive soil can be successfully stabilized by the combined action of lime and flyash. Zha et al studied the potential use and the effectiveness of stabilization of expansive soil using flyash and flyash-lime admixture.The test results showed that the plasticity index, activity, free, swell, potential, swelling pressure and axial shrinkage percent decreased with an increased flyash or flyash – lime content.
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Rao et al carried out a study on the performance of lime stabilized flyash cushion and found that it was quite effective in arresting volume changes in expansive soils.
GENERAL Stabilization is the process of blending and mixing materials with asoil to improve certain properties of the soil. The process may include the blending of soils to achieve a desired gradation or the mixing of commercially available additives that may alter the gradation, texture or plasticity, or act as a binder for cementation of the soil. The process of reducing plasticity and improving the texture of a soil is called modification. Monovalent cations such as sodium and potassium are commonly found in sugrade soil and these cations can be exchanged with cations of higher valencies such as calcium which are found in lime and flyash. This ion exchange process takes place almost rapidly, within a few hours. The calciumcations replace the sodium cations around the clay particles, decreasing the size of bound water layer, and enable the clay particle to flocculate. The flocculation creates a reduction in plasticity, an increase in shear strength of subgrade soil and improvement in texture from a cohesive material to more granular, sand-like soil. The change in structure causes a decrease in the moisture sensitivity and increase the workability and constructability of soil. Soil stabilization includes the effect from modification with a significant additional strength.
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SOIL STRUCTURE Soil structure refers to the gross arrangement of the soil particles into aggregates. A soil may have either a simple or a compound structure. Sands and gravels, examples of soils with a simple structure, have very little cohesion, plasticity, and consistency, the resistance of the particles in the soil to separation. Simple-structured soils are usually composed of materials that are relatively resistant to weathering, such as quartz sand. They, are also said to have a single-grain structure. As the liquid limit greater than 35 and less than 50 with medium compressibility the soil can classified as fine grained soil, which is under inorganic clay (CI).
USES OF STABILIZATION Pavement design is based on the premise that minimum specified structural quality will be achieved for each layer of material in the pavement system. Each layer must resist shearing, avoid excessive deflections that cause fatigue cracking within the layer or in overlying layers, and prevent excessive permanent through densification. As the quality of a soil layer is increased, the ability of that layer to distribute the load over a greater area is generally increased so that a reduction in the required thickness of the soil and surface layers may be permitted.
QUALITY IMPROVEMENT The most common improvements achieved through stabilization include better soil gradation, reduction of plasticity index or swelling potential, and increases in durability and strength. In wet weather, stabilization may also be used to provide a working platform for construction operations. These types of soil quality improvement are referred to as soil modification.
STABLIZATION WITH LIME 13
Lime stabilization is done by adding lime to soil. This is useful for the stabilization of subgrade soil. When lime reacts with soil there is exchange of cations in the adsorbed water layer and a decrease in the plasticity of the soil occurs. The resultant material is more friable than the original natural soil, and is more suitable as subgrade. Lime is produced by burning of limestone in kiln. The quality of lime obtained depends on the parent material and the production process. And ther e are basically 5 types of limes. 1. High calcium, quick lime (CaO) 2. Hydrated high calcium lime [Ca(OH)2] 3. Dolomitic lime [CaO+MgO] 4. Normal, hydrated Dolomitic lime [Ca(OH)2+MgO] 5. Pressure, hydrated Dolomitic lime [Ca(OH)2+MgO2] The two primary types of lime used in construction today are quick lime (calcium oxide) and hydrated lime (calcium hydroxide). Heating lime stone at elevated temperatures produce quick lime and addition of water to quick lime produces hydrated lime. Equation shows the relation that occurs when limestone is heated to produce quick lime with carbon dioxide as by-product. CaCO3 + heat → CaO + CO2 Addition of water to quick lime produces hydrated lime along with heat as product: CaO + H2O → Ca(OH)2 + heat For stabilization with lime, soil conditions and mineralogical properties have a significant effect on the long term strength gain.
MECHANISM 14
For soil stabilization with lime, soil conditions and mineralogical properties have a significant effect on the long-term strength gain. A pozzolanic reaction between silica and alumina is the soil particles and calcium from the lime can form a cemented structure that increases the strength of the stabilized soil. Residual calcium must remain in the system to combine with the available silica or alumina to keep the pH high enough to maintain the pozzolanic reaction. Soil that should be consider for lime treatment include soil with a PI that exceeds 10 and have more than 25 percent passing the #200 sieve. In lime stabilization the liquid limit of soil generally decrease but the plastic limit increases. Thus the plasticity index of the soil decreases. The strength of lime stabilized soil is generally improved. It is partly due to the formation of cementing material. Increase in the unconfined compressive strength is as high as 60 times. The modulus of elasticity of the soil also increases substantially. Addition of lime causes a high concentration of calcium ions in double layer. It causes a decrease in the tendency of attraction of water. Consequently, the resistance of soil to water absorption, capillary rise and volume changes on wetting or drying is substantially increased. The lime-stabilized bases or subbases form a water resistant barrier which stops penetration of rain water. There is an increase in optimum moisture content and a reduction in maximum density. In swampy areas where the water content is above the optimum, application of lime to soil helps in drying of soil. Cyclic freezing and thawing can causes a temporary loss of strength, but because of subsequent healing action, there is no loss of strength in long run. Construction method used in lime stabilization are similar to those used in cement stabilization.
However, the following points are to be noted. 1. As the reaction in the case of lime is low, there is no maximum time limit between the addition of lime to the soil and the 15
completion of compaction. However, care should be taken to avoid carbonation of lime in the process. 2. Lime may be added in form of slurry instead of dry powder. 3. A rest period of 1 to 4 days is generally required for spreading lime mixing of lime and soil. 4. The soil lime is compacted to the required maximum dry density. After compaction, the surface is kept moist for 7 days and then covered with a suitable wearing coat. Sometimes, the wearing coat is applied soon after the compaction to help hold the moisture. STABILIZATION WITH FLYASH Class C flyash is an industrial by product generated at coal field electricity generating power plants that contains silica, alumina and calcium based minerals.Upon exposure to water, these calcium compounds hydrate and produce cementious products similar to the formed during the hydration of Portland cement. It is therefore more desirable to mix and compact flyash as quickly as practical.
The hydration property depends on coal source ,boiler design and the type of ash collection system. The coal source governs the amount and type of organic matter present in it.Eastern coal source contain small amount of calcium. This class F flyash does not exhibit self-cementing characteristics. Western coal contain higher amount of calcium(about 20%-35%)and are classified as class C flyash. The amount of calcium oxide in flyash is lower than that of lime and much of it is combined with silicate and aluminates,soflyash has less effect on plasticity than lime. Boiler design and operations depends on the rate at which the hydration occurs .During combustion the inorganic matter is fused consequently rapid cooling of fused particles occur. So the flyash particles are noncrystalline in nature. Compaction time after mixing is crticalto achieve maximum density and strength. When compaction delayed hydration products begin to bond 16
with loose particles and disruption of these aggregations is required to density the material. So a portion of compactive energy is utilized in overcoming cementation and maximum densities are reduced. In flyash the high loss in ignition is due to the presence of unburnt carbon. The combined amount of silica alumina and iron oxide(84.6%)indicate its suitability as a pozzolanic material .Flyash is no-plastic in nature. Its moisture condition does not predominantly affect the dry density. The flyash has high angle of internal friction. From the grain size distribution on flyash, it is found that it is a fine grained material and about 86% of the sample passes through 75 micron sieve indicating that flyash is essentially a silt size material.
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CHAPTER 3 EXPERIMENTAL PROGRAMME INTRODUCTION In this chapter , a brief review of experiments conducted using natural soil and the stabilized with lime and flyash is explained.
MATERIALS USED 1. Natural soil Soil is brought from near a construction side of Bargarh. Soil over there is less plastic soil. Therefore the strength of pavement sub grade needs to be ascertained to withstand the compressive load
Table 1-Properties of soil used in the study: Sl No 1 2 3 4 5
Properties Max. dry density Optimum moisture Liquid limit Plasticity limit Plasticity index
Values 1517 kg/m3 23.15 40.1% 14.67% 25.43
2. Additives The additives used for stabilization and modification include lime and flyash. The soils were mixed with each of these additives for which there were reasonable expectations of improved engineering 18
properties. The amount of additive used was determined based on testing the strength for addition of varying percentages and selecting the one with greatest strength. The lime percentage was fixed at 8% and flyash 12%.
Physical properties and chemical composition of flyash
Physical properties Specific gravity
2.36
Chemical composition Silica (SiO2) Aluminium (Al2O3)+Iron oxide (Fe2O3) Calcium oxide (CaO) Magnesium oxide (MgO)
58.3% 26.3% 2.2% 0.3%
LAB TESTING The various tests conducted on the sample are the following: 1. 2. 3. 4.
Atterberg limits Specific gravity Proctor compaction test CBR Test
Firstly the above tests were conducted on plane soil sample to determine its properties. Thereafter, certain percentages of lime and flyash are added to the soil sample to stabilize it. And the percentages of the above additives which produce the optimum strength to the soil.
Soil preparation 19
The soil was collected from site in large sacks. It is brought to the lab and is dried in oven for 24 hours in large pans. This soil due to loss of water formedbig lumps which is broken to smaller pieces or even fine powder and is sieved according to the needs of different experiments.
Compaction test Compaction is the densification of soil by reduction of air voids. The purpose of a laboratory compaction test is to determine, the quantity of water to be added for field compaction of soil and resultant density expected. When water is added to dry fine grained soil, the soil absorbs water. Addition of more of water helps in sliding of particles over each other. This assists the process of compaction. Up to a certain point, additional water helps in reduction of air voids, but after a relatively high degree of saturation is reached, the water occupies the space, which could be filled with soil particles, and the amount of entrapped air remains essentially constant. Therefore, there is optimum amount of water for a given soil and compaction process, which gives rise to maximum dry density. Compaction of soil, soil-lime and soil-flyash mixtures were carried out using standard proctor test with three layers on each 25 blows. Samples for conducting compaction tests were prepared using moulds of dimensions 10 cm diameter and 15 cm height. In study, lime is added for about 4-20% and flyash also . The values of optimum moisture content and maximum dry density are obtained in a plot of dry density versus moisture content.
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dry density 2.5 2 1.5 dry density
1 0.5 0 0
10
20
30
Specific gravity The specific gravity of solid particles is defined as the ratio of the mass of a given volume of solids to the mass of an equal volume of water at 4degree centigrade. Specific gravity of normal soils is between 2.6 to 2.80.Specific gravity of soil mass indicates the average value of all the solid particles present in the soil mass. Also it is an important parameter used for the determination of void ratio and particle size. The specific gravity of the supplied soil was 2.6.
Consistency limits The consistency of fine grained soil is the physical state in which it exists. It is used to denote the degree of firmness of soil. The water content at which soil changes from one state to another is known as consistency limits. A soil containing high water in the liquid state. It has no resistance and can flow like liquid. As the water content is reduced, the soil becomes stiffer and starts developing resistance to shear deformation. The water content at which soil changes from liquid state to plastic state is known as liquid limit. The liquid limit is finding out by Casagrande’s liquid limit devices. The number of blows of this device is finding out at 21
different water content. Flow curve is plot with number of blows on Xaxis and water content on Y-axis. The water content corresponding to 25 blows is the liquid limit. Plastic limit is the water content below which the soil stops behaving as plastic material. It begins to crumble when rolled into a thread of soil of 3mm diameter. At this water content, the soil loses its plasticity and passes to the semi-solid state. The liquid limit, plastic limit and plasticity index of the soil sample was found to be 36%, 21%, and 15% respectively.
CHAPTER 4 RESULTS AND DICUSSION
Table 2 Variation of MDD and optimum moisture content and CBR value with flyash content.
Sl no.
1 2 3 4 5
Flyash content (%) 4 8 12 16 20
MDD (gm/cc) 1.96 1.94 1.92 1.89 1.85
OMC (%) 17.5 20.22 23.89 25 28.34
Max.CBR (%) 2.65 10.4 37.06 24.90 15.1
Table 3 Variation of MDD and optimum moisture content and CBR value with lime content.
Sl. no
Lime content
MDD (gm/cc)
OMC (%)
Max.CBR (%) 22
(%) 1 2 3 4 5
4 8 12 16 20
1.73 1.70 1.68 1.63 1.60
16.9 19.2 21.37 23.97 26.63
2.8 11.6 36.71 26.63 17.96
GRAPH 1- FLYASH CONTENT VS MDD
MDD 1.98 1.96 1.94 1.92 MDD
1.9 1.88 1.86 1.84 0
5
10
15
20
25
GRAPH 2- FLYASH CONTENT VS OMC
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OMC 30 25 20 15
OMC
10 5 0 0
5
10
15
20
25
GRAPH 3- FLYASH CONTENT VS CBR VALUE
CBR VALUE 40 35 30 25 20
CBR VALUE
15 10 5 0 0
5
10
15
20
25
GRAPH 4- LIME CONTENT VS MDD
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MDD 1.74 1.72 1.7 1.68 1.66
MDD
1.64 1.62 1.6 1.58 0
5
10
15
20
25
GRAPH 5- LIME CONTENT VS OMC
OMC 30 25 20 15
OMC
10 5 0 0
5
10
15
20
25
GRAPH 6- LIME CONTENT VS CBR VALUE 25
CBR 40 35 30 25 20
CBR
15 10 5 0 0
5
10
15
20
25
SUMMARY AND CONCUSION Based on laboratory tests, the following conclusion have been made: 1. As the locally available borrow soil has generally low plasticity, it was good to use for construction. The test carried out with difference proportion of flyash indicated that the workability is maximum with 12% flyash. Also the dry density observed is maximum for 12% flyash. 2. The natural soil used for construction shall be dried with moisture content below 4%. If soil has more moisture it is difficult to mix with flyash. Such soil shall spread on surface and allowed to dry before construction. 3. It was observed that the addition of lime and flyash greatly reduce the plasticity characteristics and plasticity index. 26
4. It was also found that the addition of lime and flyash increases the bearing capacity of the soil sample. 5. The maximum dry density of soil decreases with lime content may be due to light weight of lime and soil replaced by lime.
REFERENCES 1.Alhassan, M. (2008). “Potentials of fly Ash for Soil Stabilization”. AU J.T. 11(4): 246-250 2.Murty A V S R, utilization of fly ash for embankment construction, proc of experience sharing meet on use of fly ash in roads and embankment, CRRI New delhi, 1998, 15-20 3.Veerendrasingh, Narendrakumar & Devendramohan, Use of fly ash stabilization for roads, proc IGC-96,Madras 1996, 411-414 4.Bhoominathan, A. and Ratnakumar, j.(1996), “Lime treated fly ash as embankment material”, preceeding of Indian Geotechnical conference, [IGC-96, Madras, pp. 523-526] 27
5.Eades and Grim, “A quick test to determine lime requirement for lime stabilization”., Highway research record No-139, Highway research board, Washington D.C, 1969
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