聚羧酸减水剂支链密度对水泥水化行为的影响

以聚乙二醇单甲醚((-M)n=750)与丙烯酸为单体,通过酯化反应合成聚乙二醇单甲醚丙烯酸酯大分子单体.用此种大分子单体与烯丙基磺酸钠和不同摩尔比例的丙烯酸在引发剂过硫酸铵的作用下,制备了五种带有聚醚不同支链密度的聚羧酸减水剂.比较了不同支链密度的聚羧酸减水剂对水泥净浆、砂浆性能的影响,以及对水泥浆体水化的影响.结果表明:随着聚氧乙烯基支链密度的增大,水泥净浆流动度增大,分散效果增强,分散保持性增强,且当n(-COOH)∶ n(-OC_2H_4-)为1∶ 1时效果最好;减水率都较高(超过24%),且当n(-COOH)∶ n(-OC_2H_4-)为1∶ 1时高达28.5%.掺加此种比例的减水剂后水泥水化速度提高,水泥砂浆3 d、7 d、28 d抗折、抗压强度明显高于空白样(不掺减水剂的水泥).硬化浆体的SEM和XRD分析也显示聚羧酸减水剂的引入可以加速水泥水化速度,提高水泥砂浆强度.

Influence of Side Chain Density of Polycarboxylate Superplasticizer on Hydration of Cement

Polyethylene glycol monomethyl ether acrylate macromer was synthesized by esterification using polyethylene glycol monomethyl ether ((-M)n=750)and acrylic acid as monomers. Polycarboxylate superplasticizer with different side chain density (-OC_2H_4-) was synthesized by copolymerization with macromer, sodium allylsulfonate and acrylic acid at different molar ratio in the initiator of ammonium persulfate. The results shown that the fluidity, dispersivity was increased with -OC_2H_4- increased, especially at n(-COOH)∶ n(-OC_2H_4-)=1∶ 1. The water reduction ratio was over 24 % and reached maximum value 28.5% as n(-COOH)∶ n(-OC_2H_4-)=1∶ 1. The strength of cement mortar was enhanced with -OC_2H_4- increased comparing with blank cement. It can also be proved by SEM and XRD analysis.