Exploration of High Early Performance Concrete with Varying Accelerator and Coal Ash Doses

This experimental study investigates an innovative approach to producing high early performance concrete (HEPC) tailored for fast-track construction projects, where rapid strength gain is crucial for timely formwork removal and accelerated building schedules. The research centres on steel fibre reinforced concrete (SFR-C) mixtures incorporating coal ash—a sustainable cement replacement at levels of 20–50%—and calcium formate (Ca(HCOO)2) as a chemical accelerator at concentrations of 0.2–1%. All mixes consistently included 1% steel fibres by volume, aiming to boost crack resistance and overall toughness. Concrete specimens were water-cured and Compressive strength was evaluated at 1, 7, 14, and 28 days. Key findings demonstrate that a 20% coal ash substitution, paired with 0.45–1% calcium formate, significantly accelerates early strength development, achieving up to 20 MPa compressive strength within just 24 h of curing—an outcome highly applicable to the demands of rapid construction. The addition of steel fibres further enhances mechanical performance, imparting superior crack resistance. This synergy between coal ash, calcium formate, and steel fibres not only expedites construction timelines but also fosters sustainability by repurposing industrial byproducts, contributing to cost-effectiveness and environmental stewardship. The proposed concrete mixture thus offers a robust solution for modern infrastructure projects seeking both speed and sustainability.