Effect of curing time on the hydration and material properties of cold-bonded high-calcium fly ash–Portland cement lightweight aggregate

Abstract

Artificial aggregates, such as fly ash lightweight aggregates, can be used as eco-friendly alternatives to natural aggregates. This work aims to investigate the effect of curing time on the hydration and material properties (voids, shrinkage, crushing strength and pH) of cold-bonded high-calcium fly ash–Portland cement lightweight aggregate. Fly ash was used as a lightweight material (at 90% by mass), and Portland cement was used at 10% by mass. A 100% FA lightweight aggregate was also prepared for comparison. Thermogravimetry (TG) and derivative thermogravimetry (DTG) were performed at three different curing times (0, 3 and 28 days). Shrinkage test specimens were kept in sealed bags and exposed to air curing conditions and were measured at 3, 7, 14, 21 and 28 days. Calcium silicate hydrate, calcium hydroxide and calcium carbonate were observed in both mixes (100FA and 90FA10PC). The TG showed that the calcium silicate hydrate phase increased when 10% Portland cement was used compared to that of the 100FA mix. Furthermore, with increasing curing time, the calcium silicate hydrate phase increased while the calcium hydroxide phase decreased due to pozzolanic and hydration reactions. The shrinkage of fly ash lightweight aggregate with 10% Portland cement had a lower value than that of the 100FA mix for different curing conditions due to the effect of pore refinement.