Synthesis And Performances Of New Ether Type Polycarboxylic Acid Superplasticizers

Polycarboxylic acids superplasticizers,a kind of new chemical admixtures,can improve the concrete's workability obviously and reduce the dosage of water.The advantages of low admixing dosage,high water reducing rate,high performance in reinforcing and low slump loss cause them to hit the research area in 21st century.The work on synthesis and performances of ether type polycarboxylic acid superplasticizer was showed as follow.1.Different degree of polymerization macromonomers monomethoxy-poly(ethylene glycol) allyl ether(MAPEG,n=17,29,45) were obtained by Willianmson reaction, and the reacting conditions of preparing MAPEG were studied.2.New type of Polycarboxylic acid superplasticizers(PC) were designed and synthesized by using self-made macromonomers MAPEG(n=17,29,45),maleic anhydride(MA) and sodium allyl sulphonate(SAS) as copolymerization monomer, ammonium persulfate(APS) as the initiator.The effects of initiator and polyreaction time and temperature on dispersing capability of the superplasticizers were studied, and the length of side-chain on dispersing capability and dispersion stability of the superplasticizers were studied also.The optimum synthesis condition(88℃,7h) by orthogonal experiment was obtained.(1) Superplasticizer with the fluidity on cement slurry 235mm at the dosage of 0.3% and water to cement mass ratio of 0.29 was obtained at the optimum ratio of monomers of n_SAS:n_MA:n_MAPEG=2.0:4.0:2.5(mole ratio) and initiator 2%while using MAPEG(n=17);and that 248mm at the optimum ratio of monomers of n_SAS:n_MA: n_MAPEG=1.0:3.5:1.0(mole ratio) and initiator 5%while using MAPEG(n=29);and that 240mm at the optimum ratio of monomers of n_SAS:n_MA:n_MAPEG=1.5:3.0:0.5(mole ratio)and initiator 7%while using MAPEG(n=45).(2) Superplasticizer with different length side-chain using mixed MAPEG(n=17,n=45) as macromonomer and fluidity on cement slurry 250mm at the dosage of 0.3%and water to cement mass ratio of 0.29 was obtained at the optimum ratio of monomers of n_SAS:n_MA:n_MAPEG(n=17:45)=2.5:3.5:1.0(1:3) and initiator 5%.3.New type of polycarboxylic acid superplasticizer was synthesized under microwave irradiation,and effects of irradiation time and irradiation power on the molecular structure and performances of superplasticizer were studied.Under conditions of n_SAS:n_MA:n_MAPEG(n=29)=1.0:3.5:1.0 and initiator 5%,irradiation power 260W for 6min, or 130W for 8～10min,superplasticizer with the fluidity on cement slurry 230mm at the dosage of 0.3%and water to cement mass ratio of 0.29 was obtained.4.The structures of superplasticizers synthesized were characteristed by intrinsic viscosity and infrared spectrum analysis.The surface tensionin andζpotential in the system of cement-water of superplasticizers were tested,and water reducing rate, solid cement compressive strength after adding superplasticizers are tested also.The hardened cement and concrete morphology sclerosis are observed by SEM.The results showed that the intrinsic viscosities of superplasticizers with good capability may range from 2.431×10^-2dL·g^-1 to 3.042×10^-2dL·g^-1.At the same reacting condition,the vaules of intrinsic viscosity by microwave radiation are less than normal heating.The extent of increasingζabsolute value of superplasticizer with defferent length side-chain is higher than that of with homogeneous length side-chain. The superplasticizer with mixed side-chain(17:45=3:1) got the performances of water reducing ratio of 23.7%and compressive strength ratio of 163%(28d) at the dosage of 0.3%.