Optimizing fly ash and rice husk ash as cement replacements on the mechani-cal characteristics of pervious concrete

Abstract

Replacing cement with fillers while being environment-friendly con-tributes to the performance enhancement of conventional concrete. In the investi-gation, nine batches of concrete mix were prepared with different amounts of ce-ment, fly ash (FA) and rice husk ash (RHA). This experiment investigated the consequence of substituting cement with FA at various water-to-binder (W/B) pro-portions. The FA content was ranged from 5% to 20% of cement by weight, and the W/B ratio was adjusted to 0.3, 0.35, 0.4, and 0.45. Furthermore, for 10% ce-ment replacement, FA and RHA combination of 10:0, 7.5:2.5, 5:5, 2.5:7.5 and 0:10 by weight were used. When FA alone was used as cement replacement, the optimal mix achieved a 28-day compressive strength of 31.33 MPa at a W/B ratio 0.40 with 10% FA. Moreover, incorporating FA and RHA resulted in a cost re-duction of approximately 15% per cubic meter of concrete and a decrease in CO₂ emissions by 20% compared to conventional concrete production. The findings demonstrate that FA and RHA can be effectively combined to manufacture pervi-ous concrete that enhances performance, reduces costs, and minimizes environ-mental pollutants.