Acid leached rice husk ash (ARHA) in concrete: A review

Abstract

The incorporation of Rice Husk Ash (RHA) is getting popular due to increasing awareness on the environmental impacts result by high production of ordinary Portland cement (OPC). RHA is reported to have high silica (SiO2) content. However, the application of RHA in concrete industry remains low due to its fluctuating quality as a result of high carbon content and portions of the SiO2 presence in crystalized (non-reactive) phase. This paper reviews the potentials of acid leaching treatment on the rice husk prior to the combustion stage and the performances of acid leached rice husk ash (ARHA) in concrete. Reported studies highlight the importance of removing the organic and metallic impurities, especially the deleterious alkalis such as Na2O and K2O in the rice husk by leaching with acids prior to the combustion. RHA that contains high amorphous silica, i.e. reactive can be synthesized with acid leaching treatment. Acid leaching parameters include types of acid, acid concentration, leaching duration and leaching temperature. Literatures reach to a common conclusion that variations on acid concentration has no significant impact. Hence, it is recommended that the future research should explore the prolong leaching duration at ambient temperature using the lowest concentration of acid and low combustion temperature.

Keywords

• Rich husk ash
• Acid leaching treatment
• Amorphous silica
• Crystalized phase
• Deleterious alkali