Study of Alite-Calcium Sulfoaluminate Cement Produced from a High-Alumina Fly Ash

Abstract

The purpose of this research was to produce an alite-calcium sulfoaluminate (A/CSA) cement using high-alumina coal fly ash as raw material in replacement for bauxite. This ash is different from bauxite in terms of mineralogy and would represent a less-expensive bauxite alternative in A/CSA clinkering. The hydration behavior, as well as the mechanical and physical properties including mechanical strength, carbonation, dimensional stability, and resistivity, were determined and compared to high-quality commercial ordinary portland cement (OPC) and CSA cements. The main conclusions include the successful production of A/CSA clinker from high-alumina fly ash, with high contents of alite (30 wt.%) and ye'elimite (51 wt.%) at a low firing temperature. The main hydration products include ettringite and AFm (or alumina, ferric oxide, monosulfate) phases. The A/CSA cement exhibits higher early compressive strength than commercial OPC and CSA cements after 1, 7, and 14 days, and presents similar mechanical properties to CSA cement after 90 days, with no visible carbonation.