The reuse of waste glass to enhance strength during the introduction of municipal sewage sludge in shale brick manufacturing

The increasing depletion of natural clay resources and the indiscriminate dumping of solid waste has exerted unprecedented pressure on the environment. This study primarily aims to assess the efficacy of waste glass (WG) in enhancing the compressive strength of sludge-shale bricks. The mass loss (ML), apparent porosity (AP), bulk density (BD), water absorption (WA), and compressive strength (CS) of the sludge-shale bricks were evaluated in accordance with the relevant Chinese standards. The optimal parameters were determined to be a WG dosage of 30%, a molding pressure of 20 MPa, a sintering temperature of 1000 °C, and a holding time of 2 h. The performance of the products under optimum conditions was further evaluated through freeze–thaw tests, leaching tests, microstructural and mineralogical analysis. The results indicated that the AP, BD, WA, and CS of sludge-shale bricks prepared under optimum conditions were 35.31%, 1.69 g/cm³ and 15.29% 52.01 MPa, respectively. Leaching tests revealed that incorporating WG and elevation of sintering temperature enhance the efficacy of heavy metal immobilization. Following 25 freeze–thaw cycles, weight loss values for all sludge-shale bricks remained considerably below national limits. Elevated WG dosage and sintering temperature promote structure vitrification and densification, facilitating anorthite formation that enhances CS. This study provides robust data support for the synergistic preparation of sintered bricks using shale, municipal sewage sludge (MSS) and WG.

Graphical abstract