减水保坍型聚羧酸减水剂的合成及性能研究OACSTPCD

The water-reducing and slump-protecting polycarboxylate superplasticizer(V-HEA)was prepared by free-radical polymerization with 4-hydroxybutyl vinyl polyoxyethylene ether(VPEG)macromonomer and acrylic acid(AA)as the main raw materials by adding the slump-preserving monomer hydroxyethyl acrylate(HEA),and mercapto-propionic acid(MPA)as chain transferr agent under the H2 O2/L-vitamin C(Vc)oxidation-reductioninitiator system.The synthesized V-HEA was characterized by infrared spectroscopy,gel chromatography testing,and it was subjected to hydration heat analysis and concrete performance comparison analysis with commercially available slump-preserving polycarboxylate superplasticizer(HPWR-S).The results show that the optimal synthesis process parameters of V-HEA are acid-ether ratio of 4.4,ester-ether ratio of 2.5,and the dosage of initiator,ferrous sulfate and chain transfer agent accounted for 0.76％,0.10％and 0.74％of the mass of the macromonomer,respectively.The incorporation of ferrous sulfate could improve the conversion rate of monomers,and the number average molecular weight of V-HEA is 17 650,the weight average molecular weight is 42 713,and the conversion rate of monomers is as high as 95.03％.The peak temperature of hydration reaches by the incorporation of V-HEA is delayed by 4 h 24 min compared with HPWR-S,and the occurrence time of the second hydration rate peak is delayed by about 4 h,which further delays the hydration of cement.In comparison test of concrete performance,the 2 h slump only decreases by 5.8％with the addition of V-HEA,and the strength of concrete is comparable to that of HPWR-S products,so V-HEA has good application prospects.