Effect of phosphorus and fluorine on hydration process of tricalcium silicate and tricalcium aluminate

Abstract

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 (C₃A) was explored. The results indicated that the early hydration exothermic rate of C₃S and C₃A was obviously lowered by P₂O₅ and F⁻ in phosphorous slag, the second peak occurring time of C₃A 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 C₃A was also decreased. Due to the infl uence 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.

Keywords

phosphorous slag / tricalcium silicate (C₃S) / tricalcium aluminate (C₃A) / hydration heat / hydration process

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