| The research and development for comb-like polycarboxylic acid type superplasticizerswere attracted much attention because of their small dosage,excellent ability of water reducingand preventing the slump loss of concrete. In this dissertation,poly(ethylene oxide) methacrylate(MPEOMA) macromonomer,MPEOMA-AA-MAA-SAS and BPEOMA-AA-MAA-AMPS havebeen synthesized. Their structure,properties,dispersing performance and the mechanism wereinvestigated in detail.The methoxy poly(ethylene oxide) methacrylate (MPEOMA) macromonomer has beensynthesized with methyl methacrylate and methoxy poly(ethylene oxide) monoether (MPEO,n=23) by transesterification reaction and screening out suitable catalyst,inhibitor and synthesisconditions. Ideal transesterification rate about 98% can be obtained.Superplasticizers SP-1 and SP-2 were copolymerized from acrylic acid ( AA ),α-methylacrylic acid(MAA),Sodium allylsulfonate(SAS),2-acrylamido-2-methyl propanesulfonic (AMPS) with MPEOMA or buthoxy poly(ethylene oxide) methacrylate (BPEOMA).The structures of SP-1 and SP-2 were characterized through FTIR and their dispersing propertieson cement paste were investigated in detail. Results indicate that SP-2 exhibits excellentdispersing and flow retention ability. At the comb-like polymer usage of 0.3wt% andwater-cement ratio of 0.29,the fluidity of cement grout can attain 290mm and still there is noslump loss within 90 minutes. Compared with sulphonated naphthalene (SNF) basedsuperplasticizer,the polycarboxylic superplasticizer possess better propertities of lower dosage,higher fluidity and lower slump loss.The water-reducing mechanism of polycarboxylic superplasticizers was dicussed by the testof Zeta potential and surface tension. Results indicate that for naphthalene-type water-reducer,electrostatic repulsion plays an important part,but for polycarboxylic superplasticizer,with theaction of air-entraining and steric hindrance,steric hindrance results in high fluidity and highwater-reducing rate.
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