Experimental investigation on cement-based foam developed to prevent spontaneous combustion of coal by plugging air leakage

Cement-based foam material (CBFM) was prepared by mixing the cementitious system and foam system for preventing coal spontaneous combustion. Different types of surfactants and organic polymer (OP) material were selected to prepare a foam system with high stability and water-retention characteristics. The orthogonal experiment was designed to analyze the fluidity, expansion ratio and mechanical strength of CBFM under different ratios including fly ash content, foam system content and water-binder ratio. The result showed that the high stability foam system could be obtained by mixing the anionic surfactant and the zwitterionic surfactant in the mass ratio of 6:4 with 4 parts per thousand OP. Based on the orthogonal experiment, the optimized ratio of CBFM was obtained including 25% for the fly ash, 2 times the volume of the gelling slurry for the foam, and 0.5 for the waterbinder ratio. Microscopic test indicated that CBFM was composed of a porous uniform structure with closed cells, which would affect the airtightness and anti-impact force of material, implying that CBFM shows the potential to be utilized as airtight plugging material for preventing coal spontaneous combustion.