氰基及酯基改性聚羧酸减水剂性能研究

Properties of Cyano and Ester Modified Polycarboxylate Superplasticizers

在异戊烯醇聚氧乙烯醚(TPEG)和丙烯酸(AA)二元共聚合成聚羧酸减水剂PCA1的基础上,分别以丙烯腈(AN)、丙烯酸羟乙酯(HA),以及马来酸二甲酯(DMM)为改性单体,实现了三元共聚进行聚羧酸减水剂(PCA)的改性合成PCA2、PCA3、PCA4,显著提高了PCA的减水率、保坍性。四种PCA的分散机理初步研究表明:氰基、酯基的水解对初始分散及分散保持能力影响显著;氰基改性PCA分散性最好,水泥浆体屈服应力最低,更接近牛顿流体;在掺量为0.20%时,马来酸二甲酯改性PCA的新拌混凝土减水率为34.80%,混凝土坍落度1 h坍落度增长2.22%,实现了高减水且具有一定缓释效应。

The polycarboxylate superplasticizer （PCA1） of methallyl polyoxyethylene ether （TPEG） with acroleic acid （AA） was obtained by solution free radical eopolymerization. PCA2, PCA3 and PCA4 were synthesized through terpolymerization by respectively exploiting acrylonitrile （AN）, using hydroxyethyl acrylate （HA） and dimethyl maleate （DMM） as modified monomers. Compared with PCA1, modified polycarboxylate superplasticizers remarkably enhanced the water reducing ratio and slump retaining ability. The preliminary studies on dispersion mechanism of four PCAs were implemented. It shows that the hydrolysis of cyanos and esters ensures a high initial fluidity and a long slump life. AN-modified PCA possesses the best dispersion property and the lowest yield stress, of which the premixed concrete is closer to Newtonian fluid. At the dose of 0.20% for DMM-modified PCA, the water reducing ratio was 34. 80% , and the concrete slump was increased by 2.22% after 1 h. Among the three modified PCAs, DMM-modified PCA possesses the highest ratio of water reducing as well as the best slow-released function.