Modification Research Of Polycarboxylate Superplasticizer For Enhancing Clay Tolerance

As the third generation of water reducing agent,polycarboxylate superplasticizer has a series of virtues such as high water reducing rate,environment friendly,adjustable molecular structure.It can improve the construction properties of concrete such as workability,pumpability,the durability,etc.But with polycarboxylate superplasticizer was widely used,applicators noticed that most PCE products exhibit a marked sensitivity for different clay qualities.With the increase of the clay content,the dispersibility and the slump loss resistance of PCE would rapidly decrease.With the good aggregate resources were deficient day by day,it became an urgent problem to improve the anti-clay performance of PCE.To resolve this problem,we selecting acrylamide(AM)?diallyldimethylammonium chloride(DMDACC)? acyclic acid(AA)? 2-(Dimethylamino)ethyl methacrylate(DMAEMA)as polymeric monomers,sodium methallyl sulfonate(SMAS)as the chain transfer agent,ammonium persulfate and ascorbic acid(Vc)as the initiators,was synthesized the anti-clay agent based on polycarboxylate superplasticizer by using aqueous solution polymerization.The fluidity of cement paste within doped bentonite was taken as indexes,the influencing factors such as n(AM),n(DMDACC),n(AA)n(SMAS),temperature were studied with orthogonal design and single factor experiment.The result show that n(AA),n(DMDACC)and temperature were identified as main variables that affect the fluidity of cement paste by orthogonal array design,relied on a 10% significance level.The single experiment show that when the n(AA),n(DMDACC)and temperature increasing,the fluidity of cement has a maximum.Optimized by single factor and orthogonal experiment to be n(AA):n(DMDACC):n(AM): n(SMAS)=3.6:1.4:2.5:0.5,65?,m(APS-Vc)are 6% of all monomers.Under the optimized conditions,adding 0.05% anti-clay agent,it can significantly improve the clay tolerance of polycarboxylate superplasticizer,The fluidity of cement paste mixing with 5% bentonite and0.15%PCE is 270 mm.Under the same condition without anti-clay agent,the fluidity of cement paste is just 205 mm.On the other hand,we selecting prenyl polyoxyethylene ether macromonomer(TPEG)and crylic acid(AA)as main raw materials,2-methacryloyloxyethyl-trimethyl ammonium chloride(DMC),acrylamide(AM),hydroxyethyl acrylate(HEA)as functional monomers,synthesized anti-clay polycarboxylate superplasticizer by mixture Design.The research result show the AM and DMC have significant influence to the properties of the PCE.The optimal combination scheme is m(TPEG): m(AA):m(AM):m(DMC)=100:13:4.876:3.124.Fluidity of cement paste test show the anti-clay polycarboxylate superplasticizer has good dispersion effect,the clay dosage is increasing,the anti-clay PCE is better than traditional PCE in dispersion effect.The methods of infrared absorption spectroscopy and gel permeation chromatography analysis were used to the characterization molecular structural.The results show that the the main functional groups of the molecular structure of the anticlay polycarboxylate superplasticizer include amino,hydroxyl,carboxylic acid,ester and poly vinyl groups,the main functional groups of the molecular structure of the anti-clay agent includeamino,hydroxyl,carboxylic acid,sulfonic acid group.The molecular weight of the anti-clay agent is 2700.