Synthesis and characterization of geopolymer composites based on gasification coal fly ash and steel slag

Gasification coal fly ash is a solid residue produced from gasifier system in the petrochemical industry and is seldom reused. This study synthesizes a novel geopolymer composite from Shell coal gasification fly ash (SFA) and steel slag (SS). The geopolymer comprises 67% SFA, 30% SS, and 3% metakaolin activated at 8 mol/L NaOH, Na2SiO3, and liquid/solid ratio of 0.33. The products are characterized by mechanical properties, chemical composition, mineral composition, microstructure, and environmental impact. Results show that the geopolymer has an extraordinarily high physical strength owing to the amorphous content in SFA and the synthesized condensed microstructure. The binding energies of Si and Al in products induced the formation of zeolite precursor. Hydration and geopolymerization occurred synchronously during curing. The geopolymer product effectively immobilized heavy metals. Incorporating SFA into an alkali-activated material is one way of utilizing solid wastes as construction materials for civil engineering applications. (C) 2019 Elsevier Ltd. All rights reserved.