不同羧基密度聚羧酸减水剂对水泥浆体性能的影响

摘要

通过自由基聚合法,合成了一系列不同羧基密度的聚羧酸减水剂(PCE).研究了不同羧基密度的聚羧酸减水剂对水泥浆体流动度的影响规律,并采用紫外分光光度计、水化量热仪以及X射线衍射仪(XRD),测定了不同羧基密度聚羧酸减水剂在水泥颗粒表面的吸附量,分析了不同羧基密度聚羧酸减水剂对水泥水化性能的影响.结果表明:聚羧酸减水剂分子中羧基密度越高,其在水泥颗粒表面的吸附量越大,对水泥浆体的分散性越好;聚羧酸减水剂分子中羧基密度的提高可促进水泥水化进程,表现为Ca(OH)2生成量增加,水化加速期最大水化放热速率增加,水化加速期早期水化放热速率的加速率(KAB)增加.%A series of polycarboxylate superplasticizers(PCEs) with different carboxylic density have been synthesized through radical copolymerization in aqueous phase.The dispersing capability and the adsorption behavior of the PCEs were analyzed via flow table test and ultraviolet spectrophotometer.The influence of different molecular structured PCEs on the hydration properties of cement paste was studied through isothermal conductive calorimeter and the X-ray diffracmeter (XRD).The results show that higher carboxylic density in PCE molecules leads to greater adsorption amount onto cement surface and a higher dispersing capability in fresh cement paste.Increase in carboxylic density results in enhancement in cement hydration process,which is due to increase in the formation of Ca(OH)2 product,increase in the maximum hydration evolution rate in acceleration period,and increase in the acceleration rate of hydration rate in the early stage of the acceleration period.