Phosphate combined with refractory castables to produce rapid setting

     The rapid setting phenomenon mainly refers to the rapid and violent reaction of the cement with the powder and the coagulant, forming a thin wrap hard shell around the aggregate particles, which makes the casting material difficult to form and reduces the compressive strength or even no strength at all. Under normal circumstances, when the composition of the phosphate-bonded refractory castable, the amount of the coagulant and the binder are constant, and the concentration of the binder is too large, a rapid setting phenomenon occurs. Because the concentration of the binder is too large, the reaction speed with the powder, the coagulant and the aggregate is fast. In this case, a phosphoric acid solution or water is added to the mixture, the surface of the material is very wet, and the castable is still not solidified after molding. Since the coagulant has been rapidly reacted with the high concentration of phosphoric acid, the reaction product adheres to the particles, but there is no strong bond between the loose particles. In addition, when a coagulant is added in excess or a material such as MgO and CaO is mixed in the material, rapid setting may occur.

      Different types of cements have some effect on the properties of refractory castables. It should also be noted that the optimum value of the binder concentration and amount varies depending on the refractory aggregate and the powder and the variety and molding method. In addition, when the moisture content of the raw material is too high, the concentration of the cement should be appropriately increased or the amount of the cement should be reduced. Otherwise, the performance of the refractory castable may be lowered or the retardation or non-condensation may occur, so that the refractory castable cannot be used.