Abstract:
Hollow Concrete Blocks (HCB) are one of the most widely used walling materials in the
construction industry. It is widely used in construction of residential buildings, factories
and multi-storied buildings. Because of its low cost and speed of installation, it has been
used all over the world [13].
The objective of this study is investigating the properties of Hollow concrete block using
rice husk ash (RHA) as a partial replacement of cement.
A laboratory experimental study was conducted by preparing two types of HCB test
samples. The first test samples of HCB was produced by using mix proportion 1:2:1:2 of
cement, sand, gravel 00 and crushed aggregate 01 respectively as a control group and
the second sample of HCBs are produced with the same mixing proportion but the partial
replacement of cement with RHA is in different percentage,5% increment of RHA in
volume. The properties of RHA, properties of HCB, optimum replacement of RHA and
economical effect of RHA were investigated.
The chemical composition of RHA satisfies the requirement of ASTM pozzolan standard.
The 28’s day mean compressive strength of 0% RHA hollow concrete block is 5.01 N/mm2
and 4.69 ,4.6 , 4.58 and 4.527 N/mm2
of compressive strength were achieved by 5%
,10%,15% and 20% rice husk ash replacement respectively. The compressive strength of
OPC and RHA concrete blocks increases with curing age and decreases as the
percentage of RHA content increases. The optimum replacement was obtained at 20%
replacement for the desired class B HCB. The higher replacement is slightly reducing the
performance of the hollow concrete block. The material cost of all HCBs with RHA was
found to be lower than the HCB without RHA. Replacing RHA with cement by 5% in
volume can decrease the production cost by 1.65 birr.
general replacing of cement with rice husk ash for the production of Hollow Concrete
Block can be applicable and the replacement can give us other comparable material
without compromising the desired strength but the replacement percentage should not be
greater than 20% in volume for class B HCB.
