Preparation of All Solid Waste Low-Carbon Cementitious Materials Using Response Surface Methodology

Abstract

To achieve the green and low-carbon transformation of the building materials industry and promote the resource utilisation of industrial solid waste, this study uses silicon-aluminium solid waste, such as fly ash and slag powder, as the main raw materials, and uses carbide slag and desulfurization gypsum as composite activators. The Box Behnken design in response surface methodology (RSM) is used to optimize the proportion of geopolymer cementitious materials for all solid waste. The system investigated the effects of fly ash content (10%~30%), carbide slag content (8%~20%), and desulfurization gypsum content (5%~10%) on the 3D and 28 day compressive strength of cementitious materials, and established a quadratic regression model with the 28-day compressive strength as the response value. The results showed that the model fitting effect was good (R ²=0.8847), and there were significant interactions between various factors. The theoretical optimal ratio obtained through model optimisation is 20% fly ash, 14% carbide slag, and 7.5% desulfurization gypsum (with the remainder being slag powder). The 28-day compressive strength of the cementitious material prepared under these conditions can reach 27.72 MPa. This all-solid-waste system not only avoids the high-temperature calcination process in traditional cement production, significantly reducing carbon emissions, but also achieves "waste treatment" by incorporating activators such as carbide slag and desulfurization gypsum into the category of solid waste utilization. It has the dual advantages of low cost and environmental friendliness, and has broad application prospects in the field of non-structural materials in civil engineering.