The cementitious composites using calcium silicate slag as partial cement

Abstract Calcium silicate slag (CSS) is an industrial waste residue produced by the extraction of Al2O3 from high-alumina fly ash. CSS, along with cement, is used as a cementing material to reduce land pollution and to utilize industrial waste effectively. The effects of the replacement rate and age of CSS on the compressive strength and hydration degree of the cementitious composite system are examined, and a model for predicting compressive strength is constructed. Results show that the strength and hydration degree of the cementitious composites decrease slightly with the increase in the replacement rate of CSS. When the replacement rate did not exceed 50%, the strengths of the cementitious composites could still reach the 32.5 MPa standard. Microstructural analysis indicated that amorphous C-(A)-S-H, flaky CH, and a small amount of rod-like ettringite (e.g., AFt) made the sample structure compact. The compressive strengths of the cementitious composites were calculated using the response surface method (RSM), and the results show that RSM could predict the compressive strength of cementitious composites accurately. This study shows that CSS can be used as a substitute for cement, thereby providing an effective method for the large-scale utilization of CSS.