Effect of rice husk ash on physical, mechanical, and hydric properties of clay-based geopolymer

This study explores the production of geopolymer using a mixture of rice husk ash (RHA), clay and a local alkaline activator. To emulate previous research, the bricks are formulated for thermal curing at 60°C for 24 hours. The formulation of geopolymers incorporates varying mass percentages (0%, 5%, 10% and 15%) of RHA. The results of physical, mechanical, and water spray resistance tests carried out on the developed geopolymer adobe bricks indicate that the formulation containing 5% RHA performs in accordance with civil construction requirements. In particular, it exhibits a maximum linear shrinkage of 8.33% and an apparent density of 1.72 g/cm 3 , in line with the limits recommended by standards such as ASTM D560 for shrinkage, and the guidelines of ASTM C62 or NBR 8492 (Brazil) for stabilized raw earth materials. The formulation in question has an apparent density of 1.72 g/cm 3 , a mass loss of 1.63% following water erosion tests, and a compressive strength of 32.28 MPa. These results reflect high mechanical performance and durability, in line with the requirements of standards applicable to geopolymer construction materials and stabilized earth elements, thereby reinforcing the potential of this composition for structural applications in aggressive environments. The incorporation of RHA into geopolymer concretes has been observed to enhance their mechanical strength. The RHA was observed to exert a filling effect within the clay matrix. The geopolymer reactions between the amorphous mixture (MK 0 + RHA) and the alkaline solution (c), obtained by leaching the fine sand with a 10 M sodium aqueous solution of local factory “Faso Chimie”, has been found to produce a hydrated sodium aluminosilicate gel (N-A-S-H).