Macro-Properties and Microstructures of Foam Concrete Containing Porosity Sludge Gasification Particles

Aiming to enhance environmental sustainability and cost-effectiveness, a new foam concrete was created by utilizing sludge gasification particles (SGPs) as a partial replacement of cement. This study assessed the impact of SGPs content (0–30%) on the dry density, compressive and flexural strengths, drying shrinkage, thermal conductivity and pore structures of foam concrete. The results indicate that the designed foam concrete met the A07 density grade and FC3~FC2 strength grade as per the technical specification of foam concrete in China code JGJ/T 341, while the thermal conductivity was 33.3% lower than the standard requirement. The inclusion of SGPs led to a reduction in compressive strength by 35.2–52.6% and in flexural strength by 28.6–42.8%, while it resulted in a notable improvement in drying shrinkage with a reduction of 7.5–32.2%, and in thermal insulation performance with an increase of 17.3–23.4%. The foam concrete reached optimal performances with an SGPs content of 10%. Microscopic analysis revealed that SGPs increased the porosity and average pore diameter while altering the pore morphology towards large and more irregular shapes. These findings suggest that SGPs with optimal content can contribute to producing low-carbon, thermally efficient, and dimensionally stable foam concrete that is suitable for sustainable construction.