Evaluation of porosity, mechanical and thermal properties of self-ignition coal gangue-based foams via fast microwave foaming

Recently, the large-scale stock and pollution of solid waste has become a serious environmental and economic problem. Upcycling the solid waste to produce porous materials is a value-added waste management method. Self-ignition coal gangue-based alkali-activated foams were suc-cessfully produced via a fast microwave foaming method within a few minutes. The effect of alkali concentration on pore structure, porosity, mechanical and thermal properties of alkali -activated foams was explored. Alkali-activated foams with low bulk density (0.41-0.81 g/cm3), high total porosity (65.6-83.5 vol%), acceptable compressive strength (0.92-4.42 MPa), and low thermal conductivity (0.11-0.14 W/mK) were obtained by a fast microwave foaming method. The foams showed excellent high temperature performance. The compressive strength showed an increasing trend after heat treatment from 500 to 1100 degrees C. Simultaneously, a low high -temperature volume shrinkage (4.0-4.1%) was achieved. The obtained foams can be used as high-performance proppant materials, thermal insulation building materials, and in fire-resistant applications.

Automated summary

Recently, the issue of large-scale accumulation and pollution of solid waste has become a significant environmental and economic problem. This study successfully produced self-ignition coal gangue-based alkali-activated foams using a fast microwave foaming method. The impact of alkali concentration on the foam's pore structure, porosity, mechanical, and thermal properties was investigated. The alkali-activated foams obtained through fast microwave foaming exhibited low bulk density, high total porosity, acceptable compressive strength, low thermal conductivity, and excellent high-temperature performance.