PERFORMANCE OF FLY ASH-BLENDED CONCRETE FOR IMPROVED COMPRESSIVE STRENGTH AND DURABILITY: A REVIEW

Abstract

Fly ash, a coal combustion byproduct from thermal power plants, has emerged as a promising supplementary cementitious material (SCM) for enhancing concrete performance while reducing environmental impact. This review synthesizes current research on fly ash-blended concrete, examining effects on compressive strength development, durability properties, and microstructural characteristics. A comprehensive analysis of 60+ peer-reviewed studies reveals that fly ash incorporation leads to delayed early-age strength but significantly improves long-term compressive strength, with optimal replacement levels typically ranging from 15–30% by mass of cement. Durability enhancements are particularly pronounced, with fly ash-blended concretes demonstrating 40–80% reductions in chloride ion penetration, improved sulfate resistance, and enhanced resistance to freeze–thaw cycles. The pozzolanic reaction between fly ash silica and calcium hydroxide produces denser microstructures and refined pore networks, directly contributing to improved durability. However, performance varies considerably based on fly ash class (C or F), fineness, carbon content, and replacement level. This review establishes evidence-based guidelines for optimizing fly ash incorporation across diverse applications while addressing challenges related to early strength development. Environmental benefits include CO₂ emission reductions of 40–80% and lower energy consumption compared to conventional Portland cement concrete. Future research must focus on improving early-age performance through chemical activation, exploring high-volume fly ash systems (50–70%), and validating long-term field performance under diverse exposure conditions.