Abstract:
The conventional techniques of soil stabilization are becoming
expensive day by day
due to the rising cost of the stabilizing agents like, cement, lime, etc. The cost of
stabilization and environmental hazards may be minimized by replacing a good
proportio
n of stabilizing agent using the supplementary cementitious mat
erials
.
Rice
husks are among the waste material that must be managed in rice production areas.
This study investigated t
he
structural performance
of
Rice Husk Ash (
RHA
)
as
partial
replacement of cement
to stabilize clay for the production of compressed ea
rth
blocks
.
Black cotton
soil
collected from a construction site
was used in this study.
Particle size distribution
of the soil
together with
its
Atterberg
limit
s
as well as its
compaction characteristics
were established
according to British standard
procedures
(
BS 1377
-
1990: Part 2 & 4)
.
Stabilized soil s
pecimens
were prepared
and
tested for
unconfined compressive strength, in accordance with BS 1924
-
2
:
1990 Section 4
.
The soil
sample
used was classified as A
-
7
-
5 in the AASHTO classification system.
While increasing cement content resulted in decreased
liquid limit, plasticity index
and linear shrinkage
;
the same resulted in increase
d plastic limit, maximum dry
density (MDD), and optimum moisture content (OMC). The cement stabilized clay
blocks had
an
average compressive strength ranging from 0.3 MPa
for 0% cement
to
1.1 MPa
for 12% cement
at 7 days of curing
;
and 0.8
for 0% cement
to 3.1MPa
for
12% cement
after
28 days of curing. This study established that to achieve
a
minimum strength
of
2.5 MPa
for
soil blocks
the
soil should be stabilized with at least
8% cement.
Replacement of cement
with RHA
led to
a decrease in MDD
, an
increase
vi
in OMC
and
a decrease in mean compressive strength of the blocks.
T
he 28 day
compressive strength for blocks stabilized
with 5
%
cement
and
7.5% RHA
was
2.
6
MPa
which was higher than the
Kenyan Bureau of Standard
s requirements (2.5
MPa). It was not possible to measure water absorp
tion of soil blocks after soaking for
24 hours. This is because b
locks
stabilized with 8% cement
alone
crumbled
after
12
hours while t
he blocks
stabilized
with
5
%
c
ement
and
7.5
%
RHA
crumbled
six
hours
after being immersed in water
.
These results suggest that stabilized earth blocks
should only be used in an environment which is not exposed to water
.