Project Report on Soil Stabilization Using Lime and Fly Ash

ABSTRACT

Soil is the basic foundation for any civil engineering structures.It is required to  bear the loads without failure.In failure.In some places, soil may be weak which which cannot resist the oncoming loads.In such cases,soil stabilization is needeed.Numerous methods are availa available ble in the litera literatur turee for soil soil stabil stabiliza izatio tion.B n.But ut someti sometimes mes,so ,some me of the methods methods like chemical chemical stabilizat stabilization,l ion,lime ime stabiliza stabilization tion etc. adversly adversly affects affects the chemical composition of the soil. In this study,fly ash and lime were mied with clay soil to investigate the relative stre streng ngth th gain gain in term termss of unco unconf nfin ined ed comp compre ress ssio ion, n,be bear arin ing g capa capaci city ty and and compaction.!he effect of fly ash and lime on the geotechnical characteristics of  clay"f clay"fly ly ash and clay"l clay"lime ime mitur mitures es was invest investiga igated ted by conduc conductiu tiung ng standa standard rd #roctor compaction tests,unconfined compression tests,$B% tests and permeability test.!he tests were performed as per Indian Standard specifications. !he following materials were used for preparing the samples& 

$layey soil  'ly ash  (ime !he soft soft clay clay used used for these these eperi eperimen ments ts was brough broughtt from a site,n site,near  ear  )uma )umara rako kom. m.!h !hee phys physic ical al prop propert ertie iess of the the soil soil were were dete determ rmin ined ed as per per IS specifications. 'ly ash for the study was brought from *industan Newsprints,#iravam.it Newsprints,#iravam.it is finely divided divided residue resulting resulting from the combustion combustion of ground ground or powdered coal from electric generating plants. It has high water absorption capacity. (ime for the study is locally available.it imparts much strength to the soil by  pozzolanic reaction which which is eplained later later in the report.

In this test programme,without additives clay was tested to find the optimum mois moistu ture re cont conten entt ,$B% ,$B% valu valuee ,pla ,plast stic icit ity y inde inde  and and unco unconf nfin ined ed comp compre ressi ssion on strength.' strength.'ly ly ash and lime were added in varying varying percentages percentages and that fraction fraction for  which maimum strength is obtained was found out.!he miture is cured for +, and - days.

CHAPTER 1 INTRODUCTION

General

!ransport in the %epublic of India is an important part of the nation/s economy economy.. %oads are the vital lifelines of the economy making possible trade and commerce. !hey are the most preferred modes of transportation and considered as one of the cost effective modes. 0n efficient and well"established network of roads is desired for promoting trade and commerce in any country and also fulfills the needs of a sound sound transp transport ortati ation on system system for sustai sustained ned econom economic ic develo developme pment. nt. !o provid providee mobility and accessibility, all weather roads should connect every nook and corner  of the country. !o sustain both static and dynamic load, the pavement should be designed and constructed with utmost care. !he performance of the pavement depends on the quality of materials used in road construction . Sub grade is the in situ material upon which the pavement structure is placed. 0lth 0lthou ough gh there there is a tend tenden ency cy to look look at pave paveme ment nt perfo perform rman ance ce in terms terms of   pavement structures and mi design alone, the subgrade soils can often be the overriding factor in pavement performance. !he construction cost of the 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 not adequate for supporting the loads, suitable methods to enhance the properties of soil need to be adopted. Soil stabilization is one such method. Stabilizing the subgrade with an appropriate chemical stabilizer 1such as

2uicklime, #ortland cement, 'ly 0sh or$omposites3 increases subgrade stiffness and reduces epansion tendencies, it performs as a foundation 1able to support and

distribute loads under saturated conditions3. !his report contains a summary of the  performance of lime and fly ash used with clay.

'ly ashes are finely divided residue resulting from the combustion of ground or   powdered coal from electric generating plants. (ime 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

!he soil used in the study is natural clay brought from )umarakom.#avement subgrade over there is composed of clayey soil whose

bearing capacity is

etremely low.4ue to this reason ,the roads require periodic maintenance to take up repeated application of wheel loads.!his proves to be costly ,and at the same time, conditions of raods during monsoon seasons is etremely poor.!herefore, a thought on how to enhance the stability of roads by chaper means demands appraisal. Soil stabilization can be done using different additives ,but use of fly ash which is a waste material from thermal power plants,at the same time difficult"to"dispose material will be much significant.

OBJECTIVES OF THE PROJECT

!he ma5or ob5ectives of the pro5ect are&

-. !o eplore the possibility of using flyash in road construction programme. 6. !o study the effect of lime and flyash on proctor7s density and 89$ of  clayey soil. +. !o study the effect of lime and flyash on the consistency limits of clayey soil. . !o study the changes in $B% of soil by the addition of lime and fly ash :. !o study the effect of curing period on the properties of clayey soil.

CHAPTER 2 LITERATURE REVIEW General

Stabilization is the process ofblending and miing materials with a soil to improve certain properties of the soil. !he process may include the blending of  soils to achieve adesired gradation or the miing of commerciallyavailable additives that may alter the gradation, teture or plasticity, or act as a binder for  cementationof the soil.

!he process of reducing plasticity and improving the teture of a soil is called soil modification. 9onovalent cations such as sodium and potassium are commonly found in epansive clay soil and these cations can be echanged with cations of  higher valenciessuch as calcium which are found in lime and flyash. !his ion echange process takes place almost rapidly, within a few hours. !he calcium cations replace the sodium cations around the clay particles, decreasing the size of   bound water layer, and enable the clay particle to flocculate. !he flocculation creates a reduction in plasticity, an increase in shear strength of clayey soil and improvement in teture from a cohesive material to a more granular, sand"like soil. !he change in the structure causes a decrease in the moisture sensitivity and increase the workability and constructability of soil. Soil stabilization includes the effects from modification with a significant additional strength.

Soil sr!"!re

!he clay particles in the soil structure are arranged in sheet like structures composed of silica tetrahedral and alumina octahedra. !he sheets form many different combinations, but there are three main types of formations .the first is kaolinite,which consists of alternating silica and alumina sheets bonded together. !his form of clay structure is very stable and does not swell appreciably when wetted .the net form is montmorillonite, which is composed of two layers of silica and one alumina sheet creating aweak bond between the layers. !his weak bonding

 between the layers allows water and other cations to enter between the layers,resulting in swelling in the clay particle. !he last type is illite, which is very similar to montmorillonite ,but has potassium ions between each layer which help  bond the layers together. Inter layer bonding illite is therefore stronger than for  montmorillonite,but weaker than kaolinite. $lay particles are small in size but have alarge to mass ratio,resulting in alarger  surface area available for interaction with water and cations.the clay particles have negatively charged surfaces that attract cations and polar molecules,including water forming a boundwater layer around the negatively charged clay particles. !he amount of water surrounding the clay particles is related to the amount of  water that is available for the clay particle to take in and release. !his moisture change around the clay particles causes epansion and swelling pressures within clays that are confined .

Uses o# sa$ili%aion

#avement design isbased on the premise that minimum specifiedstructural quality will be achieved for each layerof material in the pavement system. ;ach layermust resist shearing, avoid ecessive deflectionsthat cause fatigue cracking within the layer or inoverlying layers, and prevent ecessive permanentdeformation through densification. 0s the qualityof a soil layer is increased, the ability of that layerto distribute the load over a greater area isgenerally increased so that a reduction in therequired thickness of the soil and surface layersmay be permitted.

Quality improvement .

!he most common improvementsachieved through stabilization includebetter soil gradation, reduction of plasticity indeor swelling potential, and increases in durabilityand strength. In wet weather, stabilizationmay also be used to provide a working

platformfor

construction operations.

!hese

types

of soilquality

improvement are referred to as soil modification. Thickness reduction.

!he strength and stiffnessof a soil layer can be improved through theuse of  additives to permit a reduction in designthickness of the stabilized material compared withan unstabilized or unbound material.

STABILI&ATION TECHNI'UES

Sa$ii%aion (i) *orlan+ "e,en

#ortland cement can be used either to modify or improve the quality of the soil into a cemented mass with increased strength and durability. !he amount of cement used will depend upon whether the soil is to be modified or stabilized.

$ement stabilization is most commonly used for stabilizing silt, sandy soils with small quantities of silt or clayey fractions stabilization of soil with cement has been

etensively used in road construction. 9iing the pulverized soil and compact the mi to attain a strong material does this stabilization. !he material thus obtained by miing soil and cement is known as