Abstract:
Rice husk ash (RHA) and clay are well-known pozzolan materials that can be incorporated to tailor
the properties of commercial bricks in the construction industry. Clay brick waste (CBW) is a clay
product that is largely generated during mass-scale demolition activities. Although several works
reported the use of RHA for developing bricks with improved physical properties, no work
investigated how CBW influence the performance of RHA-based bricks. Accordingly, this work
investigated how brick waste can be incorporated into RHA-based cement brick and how its
properties such as compressive strength, water absorbency and morphology are influenced. For this,
untreated RHA (particle size: 63-500 μm), CBW, OPC cement and water were used, and several
bricks with dimensions 7×5×3 cm were developed by using different volume mixing ratios. The
optimum mixing ratio among constituents was determined based on the brick’s porosity, surface
finish and de-moulding capability. Results indicate that the optimum volume mixing ratio is 2:3:6:1
(cement: CBW: RHA: water). The RHA content should be less than 13% w/w to ensure de-moulding
Having BCBW content of more than 44% w/w is acceptable for a better product, but too high
contents around 64% w/w are not desirable as it discourages the removal of the brick for the mould.
The brick with the optimum mixing ratio shows a water absorbance of 51% w/w and compressive
strength of 3.61 MPa (28 days). Without RHA, the brick maintains the same compressive strength
while reducing the water absorbance down to 20%. Compared to bricks reported in the literature
using RHA/clay, RHA/lime/cement, RHA/aggregates, the proposed brick has significantly high
water absorbency, and the compressive strength is around the reported values. Considering its
properties, and the presence of heavy-metal-adsorptive RHA, the brick can be proposed for
construction areas where wastewater channels are involved.
Keywords: Rice husk ash; RHA; Clay brick waste; Compressive strength; Water absorbance;
Optimum mixing ratio
