Study On Synthesis Of Polycarboxylate High Range Water Reducer By Copolymerization Of MA-AA-MAS

Polycarboxylate high range water ruducer was synthesized by copolymerization of maleic anhydride(MA),acrylic acid(AA)and methyl propylene sulfonic acid sodium(MAS)using potassium persulfate(KPS)as the initiator.To obtain the optimal synthesis process conditions,single factor variable method and orthogonal design were performed.The high range water reducer synthesized under the optimal conditions was characterized by FT-IR and TGA-DSC.Interfacial tension and performance of foaming of the high range water reducer solution were also analyzed.Lastly,performance of the high range water reducer was studied,including relationship among dosage of the high range water reducer,initial fluidity of cement paste and water reducing rate,relationship between dosage of high range water reducer and Zeta potential,and effect of dispersive station and hydration of cement paste containing high range water reducer.With single factor variable method,the influence order of various factors on the performance of high range water reducer was obtained.According to the effecting degree on performance of high range water reducer synthesized,from large to small,it is reaction temperature,dosage of MA,dosage of initiator,dosage of AA and dosage of MAS.Through orthogonal design,the optimal synthesis process conditions were determined:when AA and KPS are added by dropwise,and the reaction time is 5 h,the reaction temperature is 80 ℃,the dosage of intiator is 10%and dosage of MA,AA and MAS is 0.03 mol,0.14 mol and 0.06 mol,respectively.Initial fluidity of cement paste can reach to 296 mm,adding high range water reducer synthetized under the optimal conditions.Results of FT-IR and TGA-DSC indicated that MA,AA and MAS were copolymerized successfully,and there was-COO-,-COOH and-SO3-in the high range water reducer.Results of interfacial tension and performance of foaming of the high range water reducer solution indicated that this high range water reducer is not air-entraining,and it does not have the effect of air-entraining.Adding the high range water reducer,Zeta potential of the cement system decreases significantly,and initial fluidity of the cement paste improves obviously.Because cenment particles absorbes high range water reducer,which makes electrostatic repulsion stronger.Besides,the flocculation structure of the cement system is destroyed.Thus,water is released and the initial hydratyion is delayed.