Effect of agro waste ash on the mechanical properties of recycled coarse aggregate concrete

Abstract

The present research focuses on the study of the influence of agro waste ash on the mechanical strength properties of recycled coarse aggregate (RCA) concrete. The agro waste ashes employed in this study are obtained by burning rice straws and cotton stalks. To determine the optimal substitution levels of rice straw ash (RSA) and cotton stalk ash (CSA), preliminary experimental investigation is carried out on mortar mixes by replacing cement in the mortar in various percentages by weight. From the preliminary study the optimum replacement levels for RSA and CSA, individual mixes, are found as 5% and 10%, respectively. Then the mortar developed with 5% RSA, 10% CSA and 85% cement is shown the maximum strength over all the mixes. Keeping the cementitious content with 5% RSA, 10% CSA and 85% OPC cement, M30 grade concrete is developed using natural aggregates and is designated as Mix0. Different concrete mixes are then developed by replacing natural coarse aggregate with 10%, 20%, 30%, 40%, 50% and 60% by weight with RCA, and the mixes are designated as Mix1, Mix2, Mix3, Mix4, Mix5 and Mix6, respectively. The mechanical strength properties (compressive, tensile and flexural strengths) are evaluated and found that the concrete mix with 50% substitution of conventional coarse aggregates with RCA has maximum strength properties. From this research it is found that concrete with superior mechanical properties can be developed using RSA, CSA and RCA, over the conventional concrete.