Properties of Cold-Bonded Lightweight Aggregate Based on High Calcium Fly Ash

The object of research is a cold-bonded fly ash aggregate based on high-calcium fly ash from Berezovskaya GRES (Russia). The study presents a developed lightweight aggregate for concrete, consisting of high-calcium fly ash, microsilica and MgCl2 and Ca(NO3)2 additives. The physical and mechanical properties of the filler were experimentally investigated. The average aggregate density is 1.42 g/cm3, true density is 2.65 g/cm3, bulk density is 800 kg/m3, water absorption is 23%, total porosity is 46% and frost resistance is not less than 15 cycles of freezing and thawing. Most of the aggregate pores are open (capillary) and account for 33% of the granule volume. This results in fast and efficient water uptake when saturated. For internal curing of concrete, the optimal water saturation time for the produced fly ash aggregate is 45 min. After this time, the weight gain of the aggregate does not occur. The obtained characteristics of the aggregate show the possibility of its use in high performance concrete, self-compacting concrete, lightweight concrete and geopolymer concretes.