Production of glass-ceramic aggregates from solid wastes for high-strength and low-shrinkage lightweight mortars

To alleviate the shortage of traditional aggregates and reduce energy consumption, glass-ceramic aggregates were produced from incinerated sewage sludge ash (ISSA) and waste glass powder (WGP) through low-temperature sintering at 800 ℃ without fluxing or nucleation agents. Thermodynamic calculations were employed to predict phase equilibria and quantification of aggregates. The density, porosity, compressive strength, and crystalline phases in the aggregates were investigated as a function of WGP content (0–80 wt% with an interval of 20 wt%). The resulting glass-ceramic aggregates exhibited compressive strength of 1.9–47.0 MPa, density of 1526–2379 kg/cm³, and open porosity of 44.5% to 9.8%. Further application of glass-ceramic aggregates in mortars was assessed compared to manufactured sand (Ref-M) and expanded clay aggregate (Ref-C), including shrinkage, thermal conductivity, alkali-silica reaction, and microstructural characteristics. Results indicated that glass-ceramic aggregates reduced the 12.4–26.6% oven-dry density, 45.0–64.0% thermal conductivity, and 68.8–538.2 με 7-d autogenous shrinkage of lightweight mortars compared to Ref-M. Moreover, 3.0–35.5% drying shrinkage reduction and 5.7–139.0% 28-d compressive strength increase were achieved compared to Ref-C. The lightweight mortars containing glass-ceramic aggregates did not show any alkali-silica reaction risks. The synthesis of glass-ceramic aggregates at low temperatures and their successful application in lightweight products provided new insights and viable outlet for solid wastes.