Evaluating the combined effect of recycled aggregate and rice husk ash on concrete properties

This paper evaluates the synergistic influence of utilizing agricultural wastes i.e. rice husk ash (RHA) and coarse recycled concrete aggregates (CRCA) on the properties of recycled aggregate concrete (RAC). The RAC mixes were made with 0%, and 100% substitution of coarse natural aggregates by CRCA. Cement is further substituted by RHA at 0%, 5%, 10%, 15%, 20%, 25% and 30% to understand the influence of RHA on the fresh and hardened properties of RAC. The mechanical properties were investigated through com-pression, tension and flexure test at various ages such as 7, 28 and 56 days and other hardened properties like the water penetration resistance and the dry density were also studied. The various properties of the RAC were found to be improved as the RHA quantity is raised till 25% and further decreased when RHA content is increased to 30%. The use of RHA has proved to be very effective as the compressive strength improved by about 26% at 25% RHA. The correlation among the different strength parameters in the RAC mixes has also been established. The water permeability of the concrete mixes got reduced and the dry density increased with the increase in RHA content due to the reduced porosity. This was possible because of the pozzolanic reaction of amorphous silica present in RHA. Hence, the short comings of RAC can be overcome with the use of low end pozzolanic materials like RHA and can be used for retaining the performance of concrete containing 100% RCA. Copyright (c) 2022 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the F-EIR Conference 2021 on Environment Concerns and its Remediation: Materials Science