Research on the impact of carbide slag content on the strength and microstructure of solidified sludge during composite excitation

A composite material was developed using carbide slag, water glass, slag, and micron silicon to facilitate the use of industrial waste resources. The mechanical properties of dredge sludge (DS) were analyzed, considering different proportions of cement, organic debris, and carbide slag. The composition and microstructure of the hydration products were analyzed using the X-ray diffractometer (XRD), scanning electron microscopy (SEM), and thermogravimetric (TG) analysis. The results indicate that with a precursor content of 20%, a water glass content of 3%, and an increase in carbide slag content from 4% to 12%, the strength of the sample initially increases and subsequently drops at each age. With a carbide slag level of 8%, the combination of CaO in the slag and water glass stimulated the slag and micron silica, leading to the formation of gel substances such C-S-H and C-A-S-H. The soil particles exhibited increased density as a result of the cohesive properties of the gel products. Following a maintenance period of 28 days, the sample's compressive strength rose to 2280 kPa. When the carbide slag level exceeds 8%, the presence of Ca(OH)2 in the mixture leads to the formation of carbonates, such as calcite, during the carbonization process. The organic matter subsequently undergoes a reaction with the Ca(OH)2 produced during the hydration of the mixture, leading to the formation of a highly soluble complex. As a result, only a limited quantity of calcium ions in the pore solution participate in the pozzolanic reaction, hence reducing the formation of gel reaction products such C-S-H.