矿物外加剂与水泥石的膨胀行为

Mineral Additives and Expansion Behaviors of Hardened Cement Paste

通过实验测定了水泥的安定性和水泥石的膨胀率、膨胀应力，分析探讨了粉煤灰、矿渣、硅灰等矿物外加剂与游离氧化钙之间的相互作用机制及其对水泥石膨胀行为的影响机理．结果表明，粉煤灰等低活性矿物外加剂并不能从根本上有效地改善水泥的安定性，它们对水泥安定性的作用只是外加剂的一种稀释效应而已．只要水泥石内部的膨胀应力大于粘结应力，水泥石就会产生表观体积膨胀．高钙粉煤灰用作矿物外加剂时，必须严格控制其掺加量，以防止水泥安定性不良或混凝土产生膨胀破坏．

The soundness of cement, the expansion rate and expansion stress of hardened cement paste(HCP) were tested. The effects of various mineral additives such as fly ash, blast furnace slag and silica fume on the action of free lime in cement, and the mechanism of their effects on the cement soundness and expansion behaviors of HCP have been studied and discussed. The results show that the additives such as fly ash with lower hydration reactivity can not improve the soundness effectively, it has only a dilution effect of additives. When the expansion stress is larger than cohesive force, the apparent volume of HCP will expand. If the fly ash with high free lime is used as mineral additive, the use level must be strictly controlled.