Development of a New Geopolymer Based Cementitious Material for Pumpable Roof Supports in Underground Mining

Ground falls are one of the significant hazards in underground mining which lead to severe fatalities and injuries. Effective roof support is critical to prevent ground falls and ground fall accidents. Several roof support techniques have been used in mining industry, including rock bolts, cribs, posts, long wall shields, cans, and pumpable roof supports. Among them, pumpable roof supports have advantages over other roof support systems and have been increasingly used in underground mines. The major constituent of a pumpable roof support system is the cementitious material such as calcium-sulfo-aluminate (CSA) cement and Portland cement currently used in practice. However, these conventional cementitious materials cannot achieve the normally conflicting responses such as high stiffness and large residual strength required for an effective roof support system. The present study investigates the feasibility of utilizing Class F fly ash and natural biopolymer to develop a hybrid geopolymer-biopolymer cementitious material having high load stiffness, high peak strength, and large residual strength. A series of laboratory tests, including setting time, viscosity, and unconfined compression tests, have been carried out. The results indicate that the new hybrid material is a promising pumpable cementitious material which can possess the normally conflicting properties of high load stiffness, high peak strength, and large residual strength.