超早强型聚羧酸减水剂的制备及性能研究

Preparation and properties of super early strength polycarboxylic acid superplasticizer

将环状二酸酐醇解制备端羟基接枝羧基的聚醚大单体CA-HPEG,再与氨基硅氧烷进行酰胺化反应制得改性聚醚LPEG,将LPEG与酰胺类单体引入共聚反应中,制备长侧链、短主链的超早强型聚羧酸减水剂SPE。对SPE进行工艺优化,并探讨SPE对水泥净浆流动度、砂浆早期强度及混凝土拌合物性能的影响,然后通过傅里叶红外光谱对LPEG及SPE的结构进行表征,X射线衍射仪对SPE的水泥水化产物进行分析。结果表明,改性聚醚CA-HPEG的最佳酯化条件为:n(1,2-环己二甲酸酐)∶n(HPEG5000)为2∶1,反应时间为2h,反应温度为60℃。SPE的最佳合成工艺参数为:n(LPEG)∶n(HPEG5000)=2∶3,n(AA)∶n(AM)=3∶1,n(AA+AM)∶n(LPEG+HPEG5000)=4.5,引发剂APS用量为聚醚单体质量的0.45%,链转移剂用量为聚醚单体质量的0.25%,反应温度为常温,滴加时间为3 h。最佳工艺合成的减水剂对混凝土的初凝及终凝时间均有较好的缩短效果,并且早期抗压强度增强效果明显。

Modified polyether CA-HPEG with hydroxyl end grafted carboxyl group was prepared by alcoholysis of cyclic diacid anhydride,and then modified polyether LPEG was prepared by amidation reaction with amino siloxane.The modified polyether LPEG was introduced into copolymerization reaction with amide monomer to prepare ultra-early strong polyether car-boxylic acid water reducing agent SPE with long side chain and short main chain.Optimize the process of SPE and explore its effects on the flowability of cement paste,early strength of mortar,and performance of concrete mixtures,the structures of modified polyether LPEG and SPE were characterized by infrared spectroscopy,and the cement hydration products of SPE was analyzed by X-ray diffractometer.The test results show that the optimum esterification conditions of modified polyether CA-HPEG are as fol-lows:molar ratio of cyclic dianhydride to HPEG5000 is 2∶1,reaction time is 2 h and reaction temperature is 60℃.The optimum synthesis parameters of SPE are:n(LPEG)∶n(HPEG5000)=2∶3,n(AA)∶n(AM)=3∶1,n(AA+AM)∶n(LPEG+HPEG5000)=4.5∶1,the amount of initiator APS was 0.45%of the mass of polyether monomer,the amount of chain transfer agent was 0.25%of the mass of polyether monomer,the reaction temperature was normal temperature,and the drop time is 3 h,SPE can shorten the initial and final setting time of concrete,and the early compressive strength increases obviously.