Resource recovery of waste glass and incinerated sewage sludge residues in self-foaming lightweight aggregate

Abstract

Waste glass powder (WGP) and incinerated sewage sludge residues (ISSR) were used as raw materials to produce self-foaming lightweight aggregate (LWA). WGP provided the glassy matrix and reduced the softening temperature, while ISSR acted as a self-foaming agent. The decomposition and evaporation of soluble salts, and the release of CO2 from the reaction between C and Fe3+ in ISSR caused foaming and volume expansion. The study aimed to investigate the influence of WGP: ISSR ratio (50:50 to 75:25) and foaming temperature (750 °C to 950 °C) on the amount of the liquid phase formed, matrix viscosity, pore structure and mechanical properties. Increasing WGP content resulted in a reduction in porosity but an increase in the proportion of closed pores, improving the mechanical strength. Higher foaming temperatures led to increased volume expansion, higher total porosity, and lower strength. It was found that LWA with 75:25 WGP: ISSR ration formed at a foaming temperature between 800 and 900 °C had optimal strength and uniform pore distribution, with diopside and wollastonite as the main crystalline phases present.