Characterisation of prepared rice husk ash and its effects on strength development in recycled aggregate concrete

Waste and by-product materials have a negative impact on the environment due to the pollution associated with them. The conversion of these materials from useless or harmful to valuable substances by, for example, incorporating them into concrete, can thus be considered to be an issue worthy of consideration in the search to reduce this impact. This study aims to prepare and characterise the ash produced from rice husk wastes to discover the ash's effect when used as a cement replacement in recycled aggregate concrete in the presence of styrene butadiene rubber (SBR). The rice husks were burned in the oven at 550 to 650 °C for two hours. Afterward, the rice husk ash (RHA) was characterised using X-rays, FT-IR, and grain size analysis tests. Thereafter, four concrete mixes, 0% RHA + 0% SBR, 1% RHA + 1% SBR, 3% RHA + 1% SBR, and 0% RHA + 1% SBR were made. The RHA was used as cement replacement, while the SBR was used as mixing water replacement, with percentages measured by weight for both materials. Crushed clay bricks were employed as coarse aggregate for all mixes. Compressive strength tests were carried out at 7 and 28 days. The X-ray and FT-IR results demonstrate that an amorphous form of silica with good purity was produced from the prepared RHA. For concrete mixes, the results indicate an important enhancement in compressive strength obtained by using RHA.