Synthesis And Properties Of Polycarboxylate Superplasticizer Based On EPEG Macromonomer

With the continuous development of economy,China’s infrastructure is also developing rapidly.As one of the important additives of concrete,the research of superplasticizer has been widely concerned.Polycarboxylate superplasticizer has the advantages of designable structure and high water reducing rate.However,the addition of montmorillonite leads to the poor dispersion of polycarboxylate superplasticizer,so it is urgent for us to improve the resistance of polycarboxylate superplasticizer to montmorillonite.In recent years,ethylene glycol monovinyl polyethylene glycol ether(EPEG),a six-carbon macromonomer,has entered people’s field of vision because of its high activity.Compared with traditional macromonomer,EPEG macromonomer needs lower reaction temperature and shorter reaction time,and the synthesized superplasticizer has good workability.If EPEG monomer is used to synthesize superplasticizer and modified to synthesize mud-resistant polycarboxylate superplasticizer,not only the production efficiency can be improved,but also the performance of concrete can be better improved.Therefore,on the basis of studying EPEG superplasticizer,this paper selects different functional monomers to introduce into the new superplasticizer,explores the compatibility between functional monomers and EPEG,and selects polycarboxylate superplasticizer with the best mud resistance.Firstly,three kinds of superplasticizer PCE-H,PCE-T and PCE-E with different macromonomers HPEG(Methyl allyl polyethylene glycol ether),TPEG(Isopentenyl polyethylene glycol ether)and EPEG were prepared with acrylic acid(AA).The optimum synthesis process of superplasticizer was determined by single factor experiment method.The dispersion properties of three superplasticizer were compared by cement paste fluidity test,cement paste rheological property test,adsorption film thickness test and adsorption capacity test.The experimental results show that the fluidity of PCE-E is 285 mm and the saturated adsorption capacity is 25.21 mg/g without montmorillonite,which are higher than PCE-H and PCE-T,indicating that the dispersion of superplasticizer synthesized by EPEG monomer is better.The spacing of montmorillonite treated with pure water is 1.24 nm,and the spacing of montmorillonite treated with three superplasticizer is more than 1.5 nm,which shows that all three superplasticizer can perform intercalation adsorption.Secondly,on the basis of PCE-E superplasticizer,the cationic group of methacryloyloxyethyl trimethyl ammonium chloride(DAC)and two sulfonate groups of sodium allyl sulfonate(SA)and sodium p-styrene sulfonate(SSS)were introduced to synthesize two kinds of amphoteric polycarboxylate superplasticizer PCE-ES1 and PCE-ES2.The fluidity test of cement paste shows that PCE-ES2 and PCE-ES1 improve the dispersibility of cement,both of which are above 290 mm..After adding 1%montmorillonite,both of them have certain mud resistance,and PCE-ES2 has better mud resistance than PCE-ES1.The spacing between montmorillonite layers is 1.44 nm and 1.41 nm,respectively,which is less than 1.63 nm of PCE-E,indicating that neither of these two superplasticizer has been intercalated.The thickness of the adsorption layer of PCE-ES1 and PCE-ES2 on cement is 4.61 nm and 5.35 nm,and the adsorption capacity is 30.27 mg/g and 34.58 mg/g,both of which are larger than PCE-E,and their dispersion performance is better than PCE-E.Finally,on the basis of PCE-E superplasticizer,2-hydroxy ethyl methacrylate phosphate(HEMAP)and capped amide phosphate(CAP)functional monomers were introduced to synthesize two kinds of phosphoric acid polycarboxylate superplasticizer PCE-EP1 and PCE-EP2.The experimental results show that the dispersion effect and anti-sludge effect of the two superplasticizer are improved.The spacing between montmorillonite layers is 1.43 nm and 1.39 nm,respectively,and there is no intercalation adsorption.PCE-EP2 has the best dispersibility and mud resistance among the seven superplasticizer.The fluidity of PCE-EP2 cement paste can reach 300 mm without adding montmorillonite,and the fluidity can still reach 275 mm initially after adding 2%montmorillonite.The Zeta potential of PCE-EP2 on cement and montmorillonite is-5.25 mV and-10.5 mV,respectively.The thickness of the adsorption film is 5.96 nm and 9.50 nm,and the adsorption capacity is 36.87 mg/g and 69.15 mg/g,respectively,which are higher than other superplasticizer.