Enhanced toughness of ultra-fine sulphoaluminate cement-based hybrid grouting materials by incorporating in-situ polymerization of acrylamide

Deep coal mining requires grouting reinforcement materials with adjustable setting time, high early strength and toughness. Sulphoaluminate cement-based grouting materials (SCGM) have been widely used due to their low cost, but still suffer from poor deformation and toughness. To solve this problem, in-situ polymerization of acrylamide was developed to modify SCGM, and the effects of acrylamide addition on the fluidity, setting time, mechanical properties, and microstructure evolution of SCGM were systematically investigated. The results indicated that the addition of acrylamide significantly improved the toughness of SCGM. When the acrylamide content reached 35 wt%, the flexural strength of SCGM increased to 10 MPa and the compressive strength reached 35 MPa. In light of microstructural analysis, the exothermic heat of SCGM hydration promoted the free radical polymerization of acrylamide to form inorganic–organic hybrid grouting material with a three-dimensional interpenetrating network structure, which was responsible for the enhanced toughness of SCGM. Those results provided a new method to enhance the toughness of SCGM, making it more suitable for grouting reinforcement engineering.