小坍落度混凝土用聚羧酸保坍剂的合成与分析

Synthesis and mechanism analysis of polycarboxylic acid slump retaining agent for small slump concrete

梳型结构的聚羧酸分子具备自由度大、可设计性强等优点可以解决混凝土耐久性问题,基于自由基组合理论,以甲基丙烯聚氧乙烯醚(HPEG)、丙烯酸、丙烯酸羟乙酯、乙烯基膦酸为主要原材料,成功合成了小坍落度混凝土用聚羧酸保坍剂;通过正交试验考察了不同配合比对合成保坍剂的性能影响,当酸醚比为2.3、酯醚比为4、链转移剂用量0.4%、乙烯基膦酸用量5%(占单体总质量)时,合成的保坍剂具有极佳的水泥净浆流动度保持能力;通过红外光谱检测了合成保坍剂的分子结构;保坍剂在小坍落度混凝土中的应用效果表明,保坍剂能使混凝土在2 h内无坍落度损失,且混凝土24 h收缩率小,使用前景广阔。

In practical application,if the concrete slump is too large,cracks will occur in the setting and hardening process,which will lead to poor durability of concrete.Polycarboxylic acid with comb structure has the advantages of large degree of freedom and strong designability,which can solve the problem of concrete durability.Based on the theory of free radical combination,polycarboxylic acid slump retaining agent for small slump concrete was successfully synthesized by using methacrylate polyoxyethylene ether(HPEG),acrylic acid,hydroxyethyl acrylate and vinyl phosphonic acid as main raw materials The results show that the ratio of acid to ether is 2.3,the ratio of ester to ether is 4,the amount of chain transfer agent is 0.4%,and the amount of vinyl phosphonic acid is 5%.The results show that the synthesized slump retaining agent has excellent fluidity retention ability of cement paste.The molecular structure of the synthesized slump retaining agent is detected by infrared spectrum.The application effect of slump retaining agent in small slump concrete shows that the slump loss of concrete can be avoided within 2 hours,and the shrinkage rate of concrete in 24 hours is small,so the application prospect is broad.