Effect of Phosphorus and Fluorine on Hydration Process of Tricalcium Silicate and Tricalcium Aluminate

By means of hydration heat, XRD and SEM, effect of phosphorus and fluorine (P2O5 and F-) in phosphorous slag on hydration process of tricalcium silicate (C3S) and tricalcium aluminate (C(3)A) was explored. The results indicated that the early hydration exothermic rate of C3S and C(3)A was obviously lowered by P2O5 and F- in phosphorous slag, the second peak occurring time of C(3)A was delayed by 0.9 h, the exothermal output of C3S was reduced by 25.04% and the time of accelerating stage was postponed by 0.86 h. The early hydration degree of C3S and C(3)A was also decreased. Due to the influence of P2O5 and F-, more pores and thinner crystals can be observed in the microstructure of hardened paste and the chance of cracks was reduced.