Preparation of castable foam with regular micro-spherical pore structure as a substitute for diatomite brick

To replace the existing diatomite brick used in the field of medium and low temperature (below 1000 °C) thermal insulation and realize the comprehensive utilization of waste resources, a novel foamed insulation material was prepared with waste granite via a direct foaming method. In particular, the proportion of waste granite reached 88 wt%. The optimum parameter for the specimens were obtained at 1050 °C with 8 wt% foam and milling time of waste granite was 7 h. Meanwhile, the experimental results showed that the bulk density was 0.7 g/cm3, the linear shrinkage was 3.71%, the total porosity was 73.59%, the compressive strength was 8.0 MPa, the linear shrinkage of resintering at 900 °C for 8 h was 0.2%, and the thermal conductivity was 0.108 W/(m·K) at 300 °C. The effects of particle size of waste granite, content of foam on the macro and micro properties were systematically investigated, then the MIAPS software was used to obtain the pore structure parameters. Finally, the relationship between the pore structure and properties of specimens under different variables was analyzed based on image method and fractal geometry. The results show the potential use of waste granite as the main raw material to replace the use of natural diatomite brick.