An experimental study on the use of Rice Husk Ash in Recycled Coarse Aggregate Concrete as a replacement for Cement and Fine Aggregate

This study aimed to produce higher-strength recycled aggregate concrete (RAC) by using rice husk ash (RHA) as a partial replacement material for cement and fine aggregate (sand), respectively. And aimed to introduce RHA in concrete as a cementitious component, which can be used as a percent replacement of sand as a strength enhancement admixture or as a percent replacement of cement for economical purposes. The test was conducted in two series. In both series, the mix ratio was 1:1.5:3 (cement: fine aggregate: coarse aggregate) for grade M20 with a different water-cement (w/c) ratio. Samples were tested for workability, water absorption, and compressive strength. In the first series, the water-cement ratio varied for different conditions of the concrete mixture to obtain the same workability condition. Rice husk ash was replaced by 10% of the cement and fine aggregate, by weight, sequentially. Both samples with 10% rice husk ash as a replacement for cement and sand showed nearly the same compressive strength compared to each other after 28 days. The strength was compared with normal aggregate concrete (NAC), and with the recycled aggregate concrete (RAC) without rice husk ash introducing shows relatively smaller strength. So, for an economic purpose, cement replacement was more suitable than sand replacement with rice husk ash. But, recycled aggregate concrete doesn’t gain strength by introducing RHA. So, RHA doesn’t improve the concrete quality, but it can be used as a partial replacement of cement for economical purposes. In the second series, the compressive strength was also measured for the same water-cement ratio to determine the effect of water-cement ratio on concrete strength. Then it exhibits that cement replacement with rice husk ash concrete results in more strength compared to sand replacement with rice husk ash concrete. But this time, RAC without RHA also shows better performance than with RHA. So, RHA doesn’t improve the concrete quality, but it can be used as a partial replacement of cement for economical purposes.