Optimization of Type C Fly Ash Utilization on the Mechanical Properties of Eco-Friendly Concrete

Abstract

This study investigates the use of Class C fly ash (FA-C) as a partial replacement for Ordinary Portland Cement (OPC) in concrete mixtures to enhance its mechanical properties and environmental sustainability. FA-C, a by-product of coal combustion with a high calcium oxide (CaO) content, is known for its self-cementing properties, which contribute to improved hydration products, such as calcium silicate hydrate (C-S-H). The experiment involves varying FA-C replacement levels 10%, 20%, and 30% in concrete mixtures while maintaining a constant water-to-cement (w/c) ratio of 0.5. The effects of FA-C substitution on workability, compressive strength, flexural strength, water absorption, and porosity were analyzed at 7, 14, and 28 days of curing. Results show that FA-C significantly improved workability, reduced water absorption, and enhanced concrete durability by reducing porosity. The optimal FA-C substitution of 20% led to the highest improvements in compressive and flexural strengths, particularly at 28 days. However, higher FA-C contents 30% slightly decreased early-age strength, highlighting the need for careful control of hydration and curing conditions. This study demonstrates that FA-C can be effectively utilized in eco-friendly concrete applications, contributing to reduced carbon emissions while maintaining desired structural performance.