Lightweight properties and pore structure of foamed material made from sewage sludge ash

Pore structure significantly affects the lightweight characteristics and thermal performance of materials. Therefore, in this study, sewage sludge ash (SSA) was used to make lightweight materials. Physical and chemical properties, and how the mixing proportions affected the foaming behavior were investigated, including the lightweight characteristics and pore structure of the materials produced. The experiments showed that the minimum required cement amount was determined by the compressive strength of the sewage sludge ash foamed material (SSAFM), not its alkali content. The hydration of cement and SSA mainly generated pores with diameters of less than 0.1  μm, but cement added with metallic aluminum powder produced pores with diameters larger than 10  μm. The addition of SSA increased the volume of pores smaller than 10  μm. The thermal conductivity of SSAFM was between 0.084 and 0.102 W/m K. Therefore, SSA could be used as the lightweight filler and heat-insulating material.