Fly ash concrete-potential without misuse

This paper presents a comprehensive review of the engineering properties of fly ash concrete in its fresh and hardened form. It is shown that two major factors influence the properties of fly ash concrete—its intrinsic variation in composition, and the philosophy of mix proportioning adopted to produce the concrete. The effects of ash variability can be covered by three basic criteria of mix proportioning—namely, low water-cementitious ratio, inclusion of a water-reducing plasticizer, and an early and long curing period. It is then shown that these criteria can be utilized to produce concrete containing 50% ash replacement and having 40 to 60 MPa 28-day strength, with high workability, low water/cementitious ratios of 0.30 to 0.45, and one-day strengths of 10 to 20 MPa. Properties of strength, elasticity, shrinkage and creep are reported, and durability aspects briefly discussed. The paper unfolds the secret of utilizing the full pozzolanic potential of fly ash in practice.