Improvement of Early-Age Strength of High-Volume Siliceous Fly Ash Concrete with Nanosilica - A Review

High-volume fly ash concrete, which incorporates more than 50 % fly ash as a replacement of cement in concrete, is a breakthrough development in concrete technology. Many of its properties have been investigated through decades of research, and the results have been disseminated. However, the construction industry has never showed confidence in using high-volume fly ash concrete. This is primarily due to its slow rate of strength development at early ages, notwithstanding its promising engineering and environmental benefits. Attempts have been made earlier to improve the early strength of the high-volume fly ash concrete by mechanical grinding, chemical activation of fly ash, addition of supplementary cementitious materials like silica fume, blast furnace slag, and metakaolin, etc. Nanosilica is a recent entry to the family of supplementary cementitious materials and has exhibited a better performance in concrete than other supplementary cementitious materials. This review discusses the limitations of high-volume fly ash concrete, most widely attempted methods to improve its early-age strength, and progress made on the use of nanosilica in this regard. The article also underlines the need for further research on nanosilica-incorporated high-volume fly ash concrete for developing a structurally viable and practically possible high-volume fly ash concrete, which could be a sustainable solution for the construction industry in future.