以乙二醇乙烯基聚氧乙烯醚、丙烯酸、丙烯酸羟乙酯为原材料,通过调整酸醚比、酯酸比(均为摩尔比),合成一系列不同微结构的缓释型聚羧酸减水剂.通过凝胶渗透色谱和颗粒电荷仪对其结构进行表征,后用总有机碳仪和微量热仪测试其在水泥中的吸附量和对水化热的影响.结果表明:从吸附角度来看,随着酸醚比的增大和酯酸比的减小,减水剂的吸附速率和电荷密度呈上升趋势;当酸醚比和酯酸比都呈上升趋势时,水泥颗粒表面的饱和吸附量也相应增加.减水剂在水泥颗粒表面的吸附行为符合Langmuir等温吸附模型和准二级动力学吸附模型.从水化角度来看,掺入减水剂会使水泥水化诱导期结束时间延缓约1 h,同时水化放热峰出现时间延迟约7 h.
Adsorption and hydration characteristics of slow-release polycarboxylate acid superplasticizer
Ethylene glycol vinyl polyoxyethylene ether,acrylic acid and hydroxyethyl acrylate were utilized as raw materials,and by adjusting the acid-ether and ester-acid ratios,a series of slow-release polycarboxylate superplasticizers with diverse microstructures were synthesized.The structure of the resulting PCE was characterized using gel permeation chromatography and a particle charge detector,and their adsorption on the cement system and impact on the hydration heat were measured by using a total organic carbon analyzer and a microcalorimeter.The results show that from an adsorption perspective,both the adsorption rate and charge density of the superplasticizers exhibit an increasing trend with the rise of the acid-ether ratio and a decrease of the ester-acid ratio.When both the acid-ether and ester-acid ratios increase,the saturated adsorption amount on the cement particle surface also shows a corresponding increase.The adsorption behavior of these superplasticizers on cement particles aligns well with the Langmuir isotherm adsorption model and the pseudo-second-order kinetic adsorption model.From a hydration standpoint,incorporating these superplasticizers results in a delay of approximately 1 h in the termination of the cement hydration induction period,and the appearance time of the hydration heat release peak is also delayed by about 7 hours.
slow-releasepolycarboxylic acidadsorptionhydrationacid-ether ratioester-acid ratio
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