VPEG-保坍型聚羧酸减水剂的制备及其性能研究

Preparation and Properties of VPEG-slump-retention typepolycarboxylate superplasticizer

以4-羟丁基乙烯基聚氧乙烯醚(VPEG)为大单体,丙烯酸(AA)、丙烯酸羟乙酯(HEA)为共聚单体,巯基乙酸(TGA)为链转移剂,在H_(2)O_(2)/维生素C(V_(C))氧化-还原引发体系下,经自由基聚合合成VPEG-保坍型聚羧酸减水剂(PCE-ZZ)。将PCE-ZZ与普通减水剂复配制得减水剂(PCE-1),与市售复配减水剂(PCE-2)进行对比,分别考察其对表面张力、气泡高度、水泥净浆流动性、水泥试块抗压强度、水泥水化过程等的影响。结果表明,PCE-ZZ的最佳合成工艺为n(AA)∶n(HEA)∶n(VPEG)=1∶2.5∶1,链转移剂和H_(2)O_(2)用量均为VPEG的0.4%(质量分数),VPEG相对分子质量为3000,A、B料液滴加时间为60 min。PCE-1与PCE-2相比,PCE-1具有更优异的和易性与坍落度保持性。PCE-1对水泥水化过程的延缓作用强于PCE-2,能更好地促进水泥水化产物的紧密排列,进而提高水泥试块抗压强度。

A VPEG-slump-retention type polycarboxylate superplasticizer(PCE-ZZ)was synthesized by free radical polymerization using 4-hydroxybutyl vinyl polyoxyethylene ether(VPEG)as the macro-monomer,acrylic acid(AA)and hydroxyethyl acrylate(HEA)as the co-monomers and thioglycolic acid(TGA)as the chain transfer agent under the H_(2)O_(2)/Vitamin C(V_(C))oxidation-reductioninitiator system.The water-reducing admixture(PCE-1)was prepared by compound of PCE-ZZ and ordinary water reducer,and compared with the commercial water-reducing admixture(PCE-2).The influences of PCE-1 and PCE-2 on the surface tension,bubble height,fluidity of cement slurry,compressive strength of cement test blocks,and the hydration process of cement were investigated,respectively.The results showed that the optimal synthesis process of PCE-ZZ as follows:n(AA)∶n(HEA)∶n(VPEG)=1∶2.5∶1,the content of chain transfer agent and H_(2)O_(2) were 0.4 wt%of the mass of the VPEG,the molecular weight of VPEG was 3000,and the dropping time of A and B were 60 minutes.Compared with PCE-2,PCE-1 had better workability and slump-retention.Furthermore,the delayed effect of PCE-1 on the hydration process of cement was stronger than that of PCE-2,which can better promote the close arrangement of cement hydration products and further improve the compressive strength of cement test blocks.