Abstract:
Cement is the conventional stabiliser used for Compressed Stabilised Earth Blocks
(CSEB), which has been in use as a building material over the ages. However, its
production causes environmental pollution. Hence, efforts have been directed at
finding partial replacements for it with domestic, industrial and agricultural wastes
such as Palm Kernel Shell Ash (PKSA). The PKSA has been used to partially replace
cement in concrete blocks but information on its use in CSEB is sparse. Therefore,
the potential of using PKSA as a supplementary cementitious material in CSEB was
investigated.
The physical properties (specific gravity, moisture content, liquid limit, plastic limit
and plasticity index) of lateritic soil used for the production of the CSEB were
determined, as well as the chemical composition of PKSA. The CSEB
(100x100x100mm) cubes were produced from lateritic soil, cement, PKSA and water
at 11.5% water to mixture of soil and binder. The cement-PKSA mixes were
stabilised at 8:2, 6:4, 4:6, 2:8, while the control mix was stabilised at 10.0% cement.
The mixes were compacted with a pressure of 6 MPa for the production of 66 Control
Mix Blocks (CMB) and 528 Cement-PKSA Blocks (CPB). The blocks were cured at
100% humidity followed by 28 days secondary curing. Wet and Dry Compressive
Strengths (WCS and DCS), Block Dry Density (BDD) and Total Water Absorption
(TWA) of the blocks were determined according to standards. Data were analysed
using a t-test at α0.05.
Specific gravity, moisture content, liquid limit, plastic limit and plasticity index values
were 3.3, 17.7, 53.4, 59.5 and 6.1%, respectively. The average chemical compositions
of PKSA were 46.6 SiO2, 13.5 Al2O3, 11.8 Fe2O3, 0.5 SO3, 1.0 MgO, 1.5 K2O, 1.4
Na2O and 9.8% CaO, while specific gravity was 2.0. The WCS for CMB was 8.99
MPa, while CPB were 9.84, 7.51, 5.29, 3.21 MPa for 8:2, 6:4, 4:6, 2:8 mix proportions,
respectively. The DCS for CMB was 9.84 MPa and at 8:2, 6:4, 4:6, 2:8 mix
proportions, CPB were 11.79, 9.66, 7.33, 4.61 MPa, respectively. These values fare
better than the 3.00 and 4.12 MPa recommended standards for WCS and DCS,
respectively. The BDD for CMB was 2128±0.33 kg/m3, while CPB ranged from 2102
to 2132 kg/m3 for 8:2, 6:4, 4:6, and 2:8 mix proportions, respectively, all within the
required minimum standard of 2000 kg/m3. The TWA for CMB was 7.5% and ranged
from 6.8 to 9.8% for CPB. These values were lower than the 12% maximum standard.
A 44% decrease in TWA with variation in cement content from 2 to 8% was attained;
with a 2.3% increase in density. An increase in BDD led to an increase in WCS for
both CMB and CPB (100% positive correlation). An increase in BDD led to a 44%
decrease in TWA for both CMB and CPB (strong negative correlation).
Palm kernel shell ash is a suitable partial cement replacement in the production of
compressed stabilised earth blocks, with the best performance obtained at 4% PKSA
and 6% Cement.
