College of Engineering, Pune Department of Civil Engineering

CHAPTER 1

INTRODUCTION

1.1 GENERAL

Soil is the basic construction material. It supports the substructure of any structure and in

case of pavement structures; subgrade soil is an essential component as it supports the

sub-base/base. However, in many situations, soils in natural state may not possess adequate

geotechnical properties so as to be used as foundation layers, pavement layer or as a construction

material. This may be due to the fact that the existing soil at a particular location exhibits poor

bearing capacity and higher compressibility. Also, soils with significant plasticity may shrink

and swell substantially with changes in moisture conditions. The repeated cycles of swelling or

shrinkage of soil, further cause deteriorations and distresses on the structures if these are

supported in these types of soils. This necessitates the improvement/stabilization of soil at a site

as an indispensable activity, due to rising cost of the land and a huge demand for infrastructure

development in developing countries like India.

Soil stabilization is a technique introduced with the main purpose to modify the

geotechnical properties of the soils making them capable of meeting the requirements of the

specific engineering projects. The most common improvements achieved through stabilization

include better soil gradation, reduction of plasticity index or swelling potential and increases

strength and durability. Various stabilizers such as lime, cement and calcium chloride are

traditionally used for the stabilization of expansive soils. However, the over dependency on the

utilization of such industrially manufactured soil stabilizing additives may significantly increase

the cost of construction.

In order to make poor soils useful and meet geotechnical engineering design

requirements, efforts are to be made to explore the potential of cost effective materials that are

locally available from industrial (e.g. fly ash) and agricultural waste (e.g., Rice Husk ash,

Sugarcane Bagasse Ash, Groundnut Shell Ash) which exhibit cementitious value, in stabilization

of such soils. Incidentally, the production of large quantity of such Industrial/Agricultural wastes

all over the world faces serious problems of handling and disposal. The disposal of these wastes

M. Tech (Geotechnical Engineering)

College of Engineering, Pune Department of Civil Engineering

creates a potential negative impact on the environment causing air pollution, water pollution

finally affecting the local ecosystems. Hence safe disposal of such wastes becomes challenging

task for the engineers. Thus, use of such waste products for improving the weak soil will give

dual benefits such as possible reduction in the cost of construction as well as reduction or

elimination of the environmental hazards caused by such waste.

1.2 MOTIVATION OF THE STUDY

In this context, investigations conducted by the earlier researchers related to application

of fly ash (FA) and rice husk ash (RHA) for improving the soil properties are worth mentioning.

Dhawan et al. (1994) explored the feasibility of fly ash, which is a non-crystalline pozzolanic

and slightly cementitious material, for utilization in road construction. They considered three

types of ashes as fly ash; bottom ash & pond ash admixed with different types of soil. The result

CBR values indicated that improvement of CBR values of the soil with the coal ash from thermal

power station and FA can be used as sub base materials, sub-grade & embankment.

Prabakar et al. (2004) studied influence of fly ash on soils and reported that the addition

of fly ash reduced the dry density of the soil due to the low specific gravity and unit weight of

soil and improved the shear strength.

Kumar et al. (2008) evaluated the strength parameters of four locally available materials

for their use in the sub base course of a pavement. Fly ash had the lowest CBR of 9%, but its

behavior under dynamic load is better than that of stone dust, which has shown the maximum

value of CBR.

Several studies have been carried out on the effectiveness of clay stabilization by Rice

Husk Ash (RHA) admixing. In this context, Basha, E.A. et al. (2005) studied the stabilization of

residual soils by chemically using cement and RHA. In general, 6-8% of cement and 10-15%

RHA show the optimum amount to reduce the plasticity of soil. CBR value determined

maximum at 4% cement and 5% RHA mixtures with soil. According to compressive strength

and PI, 6-8% of cement and 15-20% RHA showed the optimum amount to improve the

properties of soils.

M. Tech (Geotechnical Engineering)

College of Engineering, Pune Department of Civil Engineering

Jha and Gill (2006) evaluated the effectiveness of RHA to enhance the lime treatment of

soil.

A similar kind of agricultural waste product is Bagasse Ash which is a residue obtained

from the burning of bagasse in sugar producing factories. Bagasse is the cellular fibrous waste

product after the extraction of the sugar juice from cane mills. It is currently used as a bio fuel

and in the manufacture of pulp and paper products and building materials. For each 10 tons of

sugarcane crushed, a sugar factory produces nearly 3 tons of wet bagasse which is a by-product

of the sugar cane industry. When this bagasse is burnt the resultant ash is bagasse ash. Western

Maharashtra is having large number of sugar factories which face a disposal problem of large

quantity bagasse ash. Though some of the researchers (Cordeiro 2009, Gritsada and Natt 2013,

etc.) have studied the application of this bagasse ash in concrete, not many efforts are made till

date regarding the application of this ash in Geotechnical Engineering. As this material contains

amorphous silica which is indication of cementing properties and which can develop good

bonding between soil grains in case of weak soil, its potential in stabilizing the weak soils need

to be explored.

With this in view, efforts are made in the present study to understand the influence of

bagasse ash on some properties of the soil. For this purpose, initially physic-chemical properties

of this material were determined and then efforts were focused on its bulk utilization in view of

its huge production and increasing scarcity of disposal sites. As the utilization in geotechnical

applications such as land reclamation, subgrade/soil improvement, structural fills etc. has the

potential for bulk utilization, potential use of bagasse ash in one of these applications was

considered in this study.

1.3 ORGANIZATION OF THE THESIS

This thesis is organized in the following five chapters.

Chapter 1 presents an introduction of the topic and motivation for the present study.

Chapter 2 presents a comprehensive review of the existing literature related to application of

industrial and agricultural waste products such as fly ash, rice husk ash, bagasse ash in civil

engineering, followed by the critical appraisal of the literature and the scope of work.

M. Tech (Geotechnical Engineering)

College of Engineering, Pune Department of Civil Engineering

Chapter 3 presents details of the field and laboratory investigations conducted for determining

the influence of bagasse ash on some Geotechnical properties.

Chapter 4 presents results obtained from various experimental investigations, followed by their

interpretation and discussion.

Chapter 5 This chapter presents the conclusions drawn from the present work followed by the

scope for the future work and the references for the study.

M. Tech (Geotechnical Engineering)