Study On Polycarboxylate High Range Water-Reducing Agent Prepared By Copolymerization Of AAMPEG1500 And AA

Macromonomer(AAMPEG1500) has been synthesized by catalytic esterification with acrylic acid(AA) and monomethoxy poly(ethylene glycol)(MPEG1500) as the major raw materials, sulfuric acid as the catalyst, silica gel as the water-absorbent. The effects of catalyst dosage, water-absorbent dosage and reaction temperature on reaction conversion have been investigated and the best preparation conditions have been selected as follows: n(H2SO4):n(AA):n(MPEG)=0.2:1:1, w(absorbent)=14.0%, t=110℃, reaction time 96.The copolymerization of acrylic acid/macromonomer(AA/AAMPEG1500) has been carried out in the water solution with potassium persulphate/sodium hydrogen sulfite as the initiator. The effects of initiator concentration(cI), total monomer concentration(cM) and polymerization temperature(T) on copolymerization rate(r) and copolymer intrinsic viscosity([η]) have been investigated, the results are as follows: r∝cI0.60cM0.94e-7 258/T;[η]∝cI-1.53cM0.84e10 663/T.The chemical compsition of AA/AAMPEG1500 copolymer at the lower conversion(<10%) has been determined by acid-base titration method. The reactivity ratios of AA and AAMPEG1500 have been obtained by YBR method and K-T method, and the results are as follows: r1 = 0.327,r2 = 0.316 (YBR method);r1 = 0.298,r2 = 0.311 (K-T method).The polycarboxylate high-range water-reducing agent has been prepared by the solution copolymerization of monomethoxy acrylic acid/poly(ethylene glycol) acrylate/(AA/AAMPEG1500) with potassium persulphate/sodium hydrogen sulfite as the initiator. The effect rules of reaction conditions on the cement flowage have been investigated. And then, the copolymer’s water reducing ratio, cement adaptability and effects on the mechanical performances of cement paste, mortar and concrete have been investigated. The results show that the water-reducing agent possesses optimal water-reducing ratio and cement adaptability, and can greatly increase the mechanical performances of cement materials such as bending strength and compressing strength. Its performances are superior to those of the commercial naphthalene-based water-reducing agent.