Effect of Temperature and Humidity on the Synthesis of Alkali-Activated Binders Based on Bottom Ash from Municipal Waste Incineration

Weathered bottom ash (WBA) from municipal solid waste incineration is a calcium aluminosilicate-rich material mainly used in construction and civil engineering as a secondary aggregate. However, its use is also being considered as a precursor in the manufacture of alkali-activated binders (AA-WBA). This preliminary research aimed to deepen understanding of the potential use of WBA (>8 mm fraction) as the sole precursor of alkali-activated binders. To gain better knowledge of this material, the physicochemical, mechanical, and environmental properties of AA-WBA binders were evaluated. In addition, the effect of curing temperature (25 degrees C, 45 degrees C, 65 degrees C, and 85 degrees C) and humidity conditions (oven and climate chamber) were assessed. The results of this study revealed that temperature and humidity conditions play a fundamental role during the early formation stages of AA-WBA binders. Maximum compactness and compressive strength (29.8 MPa) were obtained in the sample cured at 65 degrees C in the oven and room humidity. At higher temperatures (85 degrees C), a substantial decrease in mechanical strength (21.2 MPa) was observed due to a lower cohesion of the binder phases. Curing in the climate chamber led to an increase in humidity, and therefore a decrease in compressive strength. Finally, lower porosity and longer curing time substantially decreased the heavy metals and metalloid leaching concentration of AA-WBA binders.

Automated summary

This study evaluated the potential use of weathered bottom ash (WBA) from municipal solid waste incineration as a precursor for alkali-activated binders. The results showed that temperature and humidity conditions play a crucial role in the formation of alkali-activated binders. Optimal compactness and compressive strength were achieved under specific curing conditions. Additionally, lower porosity and extended curing time helped reduce the leaching concentration of heavy metals and metalloids.