Study On The Synthesis And Properties Of Polycarboxylic Acid Type High Performance Water-Reducer

Polycarboxylic acid type water-reducer which exhibit an excellent ability of water-reducing and prevention of slump loss,represent the trend of warer-reducers for concret in the future.In this thesis the research and application actualities of high performance water reducers both in an outside china were introduced in detail,the synthetic methods and debelopment trends of Polycarboxylic acid type high performance water-reducer was analyzed.Though the molecule design,beginning with the chemical structure and antion mechanisms of high performance water-reducers, polycarboxylic acid type water-reducer which contain,hydroxy carboxyl, sulfonic,polyoxyethylene groups and so on with comb-like molecular structure was synthesized.In this thesis, polycarboxylic acid type water-educer was synthesized by two steps .First, methoxy polyethylene glycol acrylate(mamonomer) was synthesized by direct esterification reaction with methoxy polyethylene glycol and methacrylic acid as the primary metieral。Second, polycarboxylate acid type water-reducers was synthesized by radical polymerization in aqueous system which mixed with methacrylic acid, sodium methallyl sulfonate, methoxy polyethyleneglycol acrylate. Maleic ,2-hydroxypropyl methacrylate,2-acrylamido-2-methyl propane sulfonic acid etc.The water-reducing ratio of the SPs in concrete was nearly at the solid dosage of 0.4%.The slump of concretes with SPs was maintained with little loss for 2 hours.The compatibility between SPs with cement is excellent.The properties of SPs were obviously superior to those of the conventional naphthalene-based water-reducers , and equal to those of the imported polycarboxylic acid type water-reducersThrough the studying of surface properties such as surface tension of water-reducer concentration, zeta potential and adsorption capacity of water–ruducer onto cement particles and IR analysis of synthetic product, the water-reducing mechanism was exploited.It was found that Space steric hindrance electrostatic repulsion of charged ion made the main contribution to water-reducing effect of SPs. the PEO chain length and the quantity of macromers influenced the average molecular weight and it's distribution of copolymers of SPs,and thus determined the capability of SPs to disperse cement particles and maintain the flowability of concrete. capability of water-recucer to maintain the flowability of concrete is stronger,when the water-reducer molecule contains active group. dispersibility and the flow retainability of SPs were increased, when some crylic acid were replaced by maleic acid.