Experimental Study On The Use Of High Anti-Collapse And Viscosity-Reducing Polycarboxylate Superplasticizer For High Strength Concrete

With the rapid development of the construction industry,ordinary concrete admixture materials are difficult to meet the requirements of various modern engineering on the viscosity,slump loss,mechanical properties and durability of fresh mix high-strength concrete.In this paper,a new type of Polycarboxylic Water Reducer with high slump retention and viscosity reduction was developed.A new type of polycarboxylic acid water reducer BT-JN with excellent viscosity reduction performance was synthesized by free radical polymerization in aqueous solution using 2400 molecular weight Methylallyl polyoxyethylene ether macromonomer(TPEG2400),methacrylic acid(MAA),hydroxyethyl methacrylate(HEMA)and butyl acrylate(BA).Through orthogonal experiment,the optimum monomer ratio was determined.The optimum monomer ratio of BT-JN is TPEG2400 : MAA : HEMA : BA = 1?3.7?1.5?2.5.The optimum synthesis process of BT-JN was determined by single factor analysis test,and the effects of various factors on the properties of BT-JN were obtained.The results show that the initial dispersion,slump retention and viscosity reduction properties of the synthesized polycarboxylic acid water reducer are the best when the amount of chain transfer agent is0.4 %,the amount of initiator is 0.5 %,the holding time is 1.5 h and the dripping time is 1.5 h.The adsorption capacity,molecular weight and molecular weight distribution of polycarboxylate superplasticizer were analyzed by adsorption test and gel chromatography.Characterization shows that BT-JN has higher adsorption performance and better molecular weight and molecular weight distribution than the other two polycarboxylic acid water reducers sold in the market.Comparing with other commercial slump-retaining Polycarboxylic Water Reducers PC-1and PC-2,the compatibility of BT-JN with different kinds of cement and mineral admixturesand the sensitivity to temperature were tested.By comparison,BT-JN has better cement adaptability,mineral admixture adaptability and temperature adaptability than other slump-retaining polycarboxylic acid water reducers sold in the market,so it can be concluded that BT-JN has stronger stability.Through the mixed test of PC-C and BT-JN in high-strength concrete,when BT-JN: PC-C is 3 : 7,the slump of high-strength concrete prepared in one hour changes slightly,and its workability is better,and its viscosity is lower.Compared with two kinds of slump-retaining Polycarboxylic Water reducers,PC-1 and PC-2,they have better slump-retaining performance and excellent viscosity-reducing performance.