Research Of The Impact Claycontent On Property Of Polycarboxylate Superplasticizer And Synthesis Of An Anti-clay Agent

More and more poor quality gravel (with increasing clay content) was usedin the preparation of concrete, which have significant impact on superplasticizerand liquidity of concrete. In order to explore the effects of clay content exerts onfluidity of cement and superplasticizer performance. Montmorillonite, kaoliniteand illite were incorporated into concrete mixed with polycarboxylatesuperplasticizer. The results of grout flow experiments, mortar and concretecollapse flow experiments indicate that these three clays have different impactson concrete performances. Montmorillonite is most effective angent to changethe concrete performances, while the illite has limited impact.The main action mechanism among montmorillonite, kaolinite andpolycarboxylate were investigated by microstructure of the cement and clay,adsorption capacity and Zata potential. The results indicate that themontmorillonite and kaolinite have the same impact on the polycarboxylatesuperplasticizer, and different extents of affection are caused by differentscalability of their lamellar structures. Compared to kaolinite, montmorillonitehas remarkable intercalated water absorption effect and larger volume expansion,leading to a greater impact on work performance and post mechanical strength ofconcrete. It implies that these two clays affect the properties of the concrete areboth through the intercalation of the PC side chain and the adsorption to watermolecules. The intercalation of PEO to the clay and clay’s absorption to waterare mutually reinforced. Thus, the anti-clay studies of concrete mixedpolycarboxylate superplasticizer should focus on breaking down these mutualpromotion processes.Based on above results, structure of anti-clay agent was designed, a seriesof polymer with low molecule weight (Mw) were synthesized via free radical polymerization, in which hydroxypropylmethacrylate (HPMA) was used toreplace PEO side chain, a cationic monomer2-(3-carboxyacryloyloxy)-N-(carb-oxymethyl)-N,N-dimethyl ethanamnim (CAC) synthetized in our institute wasemployed and acrylic acid (AA) and sodium acrylate methacrylate acted asanionic adsorption monomers. Effects of synthesis conditions and pH of goalproducts on applied performances of the anti-clay agents were investigated indetails. It was found that the optimal synthesis conditions are monomer molarratio of CAC: AA: HPMA: SMAS=2.5:1:3:0.5, reaction temperature of70°C,initiator dosage of6%, reaction time of5hours and pH of7~9, in this conditions,the goal products have the best performances. Mechanical properties of cementsand testing found that, compared with no doping anti-clay polymer cementmortar, when the anti-clay polymer dosage is0.1%of the dosage of cement, thework performance has been greatly improved when the parameters of concretewith montmorillonite than no doping anti-clay agent. Porosity and SEM illustratethe concrete dopped anti-clay agent have a more homogeneous mixing cementand a more reasonable pore distribution. The porosity of concrete containedmontmorillonite in7d and28d were reduced by39.6%and34.7%, respectively.The28d compressive strength of the mortar which doping montmorillonite up to51.6MPa, improved by27.7%compared with mortar have no anti-clay agentcontaining. This new anti-clay agent has good prospect.