Effect of artificial fly ash aggregate as a partial river sand replacement on bulk density and compressive strength of hardened concrete

Abstract

The purpose of this research concentrates on fabricating fine aggregate from fly ash (FAA) and investigating the effect of FAA as a partial replacement of river sand on slump of fresh concrete, bulk density, and compressive strength of hardened concrete. Through a pelletization process, FAA with a size ranging from 1.25 to 5 mm was made from 85% fly ash, 15% Portland cement, a water-to-binder of 0.21 and cured in 1-day air condition and 13-day water bath. Based on experimental results regarding particle size distribution of fine aggregate mixtures (including FAA and river sand), it was found that mixture A (30% FAA and 70% river sand) and mixture B (40% FAA and 60% river sand) were optimal because they were within the allowable limit of fine aggregate with coarse sizes as per TVCN 7570:2006. When using these fine aggregate mixtures, slump of fresh concrete increased when FAA content increased, while bulk density and compressive strength of hardened concrete changed negligibly. Consequently, FAA can be used to replace river sand up to 40% for the concrete production to eliminate the exploitation of river sand and utilize the most of fly ash released from the coal-fired power plants, towards sustainable development for concrete industry.