Study On The Synthesis And Properties Of Low Sensitive Ether-ester Copolymer Polycarboxylate Superplasticizer

With the large-scale development of infrastructure construction in China,the quality requirements of commercial concrete are becoming more and more strict,and polycarboxylic acid high performance water-reducing agent is widely used.The ester water reducing agent of polycarboxylic acid superplasticizer has good adaptability to cement,low sensitivity to content and material and other advantages,but the synthesis condition is harsh,the cost high,the production process is complex,and the quality control requirement of the product is higher.Ether superplasticizer has the advantages of high water reducing rate,low price,simple production process,but has different adaptability to different cement,and it's sensitive to content and material,easy to bleed out of concrete.In actual engineering,the use effect of polycarboxylic acid superplasticizer is directly affected by the shortcomings of esters or ether polycarboxylic acid superplasticizer.In this paper,based on the synthesis technology of polycarboxylic acid superplasticizer,the copolymerization of ester ether is carried out through the reasonable molecular structure design,aiming at the problems caused by ether and ester polycarboxylic acid superplasticizer.A low sensitive polycarboxylic acid water reducer with excellent performance was developed.The effects of ester ether ratio,acrylic acid,initiator,chain transfer agent,reaction time and reaction temperature on the properties of water reducer were investigated by free radical copolymerization in aqueous solution.The synthesis of low sensitivity ester ether polycarboxylate superplasticizer was optimized.The best synthesis conditions were: the ratio of ester to ether is 1:2,The dosage of initiator is 0.2%,the amount of chain transfer agent is0.25%,the amount of acrylic acid is 4.65%,the reaction temperature is 30?,and the reaction time is 3.5h.Through the test of pulp fluidity of polycarboxylate superplasticizer,the fluidity of slurry reaches 260 mm at 0.3% content and 0.4 Water-cement ratio.It is concluded that synthetic superplasticizer has high dispersibility of ethers.Through the concreteslump test,it is concluded that the synthetic polycarboxylic acid water reducing agent has low sensitivity to the dosage,temperature,water consumption and raw material,and the order is as follows: ether superplasticizer > ester ether copolymer superplasticizer > ester superplasticizer,the synthetic superplasticizer has good adaptability to cement as ester superplasticizer,which can solve the problem of sensitivity ether type superplasticizer.The molecular structure of poly-carboxylic acid superplasticizer was characterized by infrared spectroscopy,and the ideal molecular structure of polycarboxylic acid water reducer was obtained by combining with the raw materials used in the synthesis test.