Investigating Fly Ash as a Sustainable SCM for Self-Compacting Concrete: Workability and Strength Analysis

Abstract

Self-compacting concrete (SCC) is modern concrete which can flow and compact naturally without requiring mechanical vibration. This attribute minimizes the labour and time spent on construction thus SCC is highly efficient. The use of supplementary cementitious materials or SCMs has gained momentum over the recent years to partially substitute cement in conventional concrete to maintain strength without increasing cost and environmental degradation. Nevertheless, the use of SCMs in self-compacting concrete is scarcely being researched, and thus individuals are not eager to apply it due to the uncertainty in its performance. The present work studies the behaviour of SCC on the addition of fly ash instead of some cement to bridge this gap. Cement was substituted with fly ash in weight percentages of 0%, 5%, 10%, 15%, 20%. Standard concrete cubes were made for every mix ratio. To assess the fresh SCC's workability and identify the ideal fly ash content, the slump flow test was performed. A Compressive Testing Machine (CTM) was used to evaluate the samples' compressive strength following 14 days and 28-days water curing period. The results showed that the maximum workability was achieved when fly ash was substituted for 15% of the cement. Furthermore, blends with 10% to 15% fly ash replacement had the highest compressive strength. These results show that fly ash, when used in the right amounts, improves flowability and strength in SCC and is a cost-effective partial substitute for cement.