缓凝剂对掺UNF-5高C3S水泥水化的调控

Controlling of retarder to the hydration of high C_3S Portland cement containing UNF-5

采用流动度、电阻率和水化热等实验方法,研究了缓凝剂对掺定量UNF-5高C3S水泥浆初始水化历程的调控,着重研究了3种缓凝剂与UNF-5的叠加效应在高C3S水泥浆初始水化历程中产生的主要现象,以及这些现象对改善UNF-5与高C3S水泥的相容性的影响.实验表明:在浆体流动性方面,葡萄糖酸钠和多聚磷酸钠与UNF-5叠加时存在一个最佳掺量,柠檬酸出现负效应.在一定的温度范围内,叠加前后水泥浆体的流动度均随温度的增加而增大.缓凝剂对早期C3A水化的作用效应显著影响含UNF-5水泥浆体的流动度与早期电阻率之间的关系.缓凝剂的参与延缓水泥浆体结构的形成,放热峰削弱且得以宽化,有效解决放热集中的问题.对水泥浆体结构形成的延缓能力,葡萄糖酸钠最强,多聚磷酸钠次之,而柠檬酸相对最弱.

The controlling of retarder to the early hydration process of high C3 S Portland cement containing UNF -5 was studied by means of hydration heat, electrical resistivity and so on. The phenomenons showed in the early hydration caused by the compound of retarder and UNF -5 and the influence of these phenomenons on the compatibility improvement of UNF -5 with high C3S Portland cement were investigated. The results show that critical amounts of sodium gluconate and sodium tripolyphosphate exist in improving the fluidity, while the fluidity is decreased when mixed with citric acid. The fluidity of cement paste with or without admix- tures is improved by the increase of temperature in a certain range. The relationship between fluidity and early resistivity is affected by the mechanism of retarders on the hydration of C3A. The early hydration is retarded and the second heat peak is weakened and widened by retarders, which are effective to solve the problem of heat concentration. The ability of retardation is showed as follows： sodium gluconate 〉 sodium tripolyphosphate 〉 citric acid.