Optimized preparation of rice husk ash (RHA) as a supplementary cementitious material

For years, supplementary cementitious materials (SCM) has been extensively used as an integral component in the production of concrete. This has been motivated by sustainability efforts and reduced environmental impact. Correspondingly, this study intended to develop an appropriate method for the use of rice husk ash (RHA), a by-product of rice husk (RH) which exists abundantly in the Philippines, as a partial replacement to ordinary Portland cement (OPC). Different studies have suggested optimal percentage replacement values of RHA, from 10% to 20%, which demonstrated vast improvement in strength of the resulting blended concrete. These optimal values, however, immensely depends on the burning preparation of RHA which adversely affects the amorphous silica components, and therefore the pozzolanic activities of RHA in concrete. In this research, a potential approach to convert RH into optimized and highly reactive RHA by controlled burning and grinding is provided. The effect of RHA in the strength of cement mortar was investigated through the various proportions of 5, 10, 15, and 20% RHA by weight replacement of cement. Some of the findings are: (i) controlled combustion of RH with temperature ranging from 400 to 600 °C and a slow method of cooling for 6 to 8 hours were some of the critical factors needed to produce high silica content, (ii) concrete containing up to 10% RHA replacement is optimal in maximizing the strength of cement mortar, and (iii) the incorporation of RHA in concrete by 15% and 20% replacement by weight indicated a lower workability. © Int. J. of GEOMATE