THE EFFECT OF ELAPSE TIME ON THE GEOTECHNICAL PROPERTIES OF LIME-BAGASSE ASH STABILIZED BLACK COTTON SOIL
THE EFFECT OF ELAPSE TIME ON THE GEOTECHNICAL PROPERTIES OF LIME-BAGASSE ASH STABILIZED BLACK COTTON SOIL
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Date
2008-07
Authors
OCHEPO, JOSHUA
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Abstract
This research was carried out to investigate the effect of elapse time after mixing on the
geotechnical properties of soil-lime-bagasse ash mixture. Preliminary investigation on the black
cotton soil used showed that the soil belongs to A-7-6 and CH in the AASHTO and Unified Soil
Classification System (USCS), respectively.
Soils in these groups are unsuitable for engineering purposes. Evaluation of the effect of elapse
time on the Atterberg limit, moisture – density relationship, unconfined compressive strength,
durability and California bearing ratio (CBR) of the soil-lime-bagasse ash mixes showed that the
consistency, compaction and strength properties of the soil decreased with increase in elapse
time. The liquid limit, plastic limit and plasticity index of the soil reduced from 60 to 37 %, 22 to
11 % and 38 to 23 % at 8 % lime/6 %,
8 %lime/6 % bagasse ash and 8 % lime/4 % bagasse ash treatment respectively after 3 hours
elapse time.
The maximum dry density (MDD) of soil treated with 6 % lime/8 % bagasse ash reduced
from 1.42 to 1.31 Mg/m3, 1.55 to 1.29 Mg/m3 and from 1.83 to 1.42 Mg/m3 after 3 hours delays
for British Standard light (BSL), West African Standard (WAS) and British Standard heavy
(BSH) compactive efforts, respectively.
The unconfined compressive strength (UCS) values decreased for all compactive efforts
and curing periods with elapse time. At the peak curing period of 28 days considered in this
study, the UCS decreased from 540 to 380 kN/m2, 850 to 620 kN/m2, and 1330 kN/m2 reduced to
1020 kN/m2 for soil treated with 6% lime/ 8% bagasse ash at BSL, WAS and BSH energy levels.
Durability assessment of the soil-lime-bagasse ash mix showed a decrease in the
resistance to loss in strength of the mixes with elapse time for all compactive efforts. A peak
value of 50 kN/m2 was attained at 6 % lime/8 % bagasse ash for BSL, 120 kN/m2 for WAS and
200 kN/m2 for BSH compactive efforts. This decrease to 20, 58 and 60 kN/m2 after three hours
respectivly.
The CBR values also showed a decrease in value with elapse time. A decrease from 14
% to 5 %, 24 to 11 % and 34 to 20 % after three hours elapse time was observed at 6 % lime/8 %
bagasse ash treatment for BSL, WAS and BSH energy level.
The strength properties of the soil-lime-bagasse ash obtained in this work at no
compaction delay and at compaction delay of three hours established the maximum and
minimum that can be achieved. An optimal mix of 6 %lime/8 % bagasse ash is recommended at
the BSH compactive effort and elapse time not exceeding one hour.
Description
A THESIS SUBMITTED TO THE POSTGRADUATE SCHOOL,
AHMADU BELLO UNIVERSITY, ZARIA
IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE DEGREE
OF MASTER OF SCIENCE IN CIVIL ENGINEERING
DEPARTMENT OF CIVIL ENGINEERING
FACULTY OF ENGINEERING
AHMADU BELLO UNIVERSITY
ZARIA, NIGERIA
July, 2008
Keywords
EFFECT,, ELAPSE,, GEOTECHNICAL,, PROPERTIES,, LIME-BAGASSE,, ASH STABILIZED,, BLACK,, COTTON., SOIL.