Preparation of low-carbon and environmentally friendly non-sintered ceramsite (NSC) employing steel slag, GGBS and fly ash: Experiment and performance regulation

Using solid waste to prepare lightweight aggregate non-sintered ceramsite (NSC) with excellent performance is a major breakthrough in the utilization of solid waste. In this study, low-carbon environment-friendly NSC was prepared by employing steel slag, ground granulated blast-furnace slag (GGBS) and fly ash as the main matrix materials for the preparation of NSC, using cement as binder, and adding water glass and dihydrate gypsum as alkali activator. Through the comparative analysis of single factor experiment and orthogonal experiment, the performance of NSC was explored and analyzed, and the best preparation scheme of NSC with excellent performance was obtained. The composition and structural mechanism of NSC were observed and analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) to explore and confirm the performance of NSC. Considering the cylinder compressive strength, bulk density, specific surface area and 1-hour water absorption, it was determined that when the water consumption is 35%, the cement dosage is 10%, and the steel slag: GGBS and fly ash: GGBS = 1:1, the prepared NSC has the best performance. The cylinder compressive strength of NSC could reach 4.2 MPa and 12.4 MPa respectively, and 1-hour water absorption was 13%. This indicates that the comprehensive performance of NSC prepared by fly ash + GGBS as matrix material was better. The steam curing method is more beneficial to the development of NSC strength. Considering the actual situation, it is more appropriate to control the steam curing time at 12 h. The optimum dosage of alkali activator in NSC was determined by orthogonal test analysis: water glass 3%, dihydrate gypsum 5%, and the optimum steam curing temperature was determined to be 60 °C. This work realized the utilization of steel slag with low activity and large doping, which was conducive to fully studying and understanding the recycling of solid waste, and solved the problem that steel slag was difficult to be used and treated for a long time to a certain extent.