Proportion optimization of grouting materials for roadways with soft surrounding mass

Severe deformation and failure frequently occur in roadways with soft or weak surrounding rock and have greatly influenced safe and efficient mining of coal in many coal mines. Using portland cement, emery and fly ash as main raw materials, through laboratory tests, effect of water/binder ratio, cement/sand ratio, water/sodium silicate ratio, water reducing agent, fly ash/cement ratio and various performance indexes of grout of fluidity, viscosity, setting time, bleeding rate, compressive strength, concretion rate and various performance indexes were systematically analyzed. An optimized mixture ratio of the main raw materials added in the grouting material proportion was determined through uniform design method, an optimal mixture ratio was determined by regression analysis. The results show that: 1) The flow performance is significantly affected by change of sodium silicate and water reducer, the compressive strength of grouting material increases significantly with increase in emery content, and decreases significantly with increase in water reducer. 2) An optimized mixture ratio among water cement ratio, cement sand ratio, water/sodium silicate ratio, water reducing agent, fly ash/cement ratio in the grouting material is 0.75, 1.2, 8%, 3% and 0.18, respectively. Field test demonstrated that the material has better performance in reinforcing weak and broken rock mass.