Synthesis And Performance Of Anti-Clay Polycarboxylate Superplasticizers

Polycarboxylate superplasticizer(PCE)has been widely used in concrete industry because of its high water-reducing rate and strong molecular structure regulation.However,the dispersibility of PCE can be affected by the clay content in aggregate,which will have a negative effect on the workability of concrete.In this paper,by the usage of ethylene glycol monovinyl polyethylene glycol ether(EPEG)and acrylic acid(AA)as main raw materials,three kinds of anti-clay polycarboxylate superplasticizer were synthesized via the addition of various functional monomers.In comparison with common polycarboxylate superplasticizer,the anti-clay effect of these polycarboxylate superplasticizers was explored,and the anti-clay mechanism of the polycarboxylate superplasticizer was proposed.(1)By using EPEG and AA as raw materials and optimizing the synthesis conditions,a common polycarboxylate superplasticizer with fine performance was obtained and denoted as O-PCE.By the introduction of three functional monomers(acrylamide(AM),methylacryloxyethyl trimethyl ammonium chloride(DMC)or N,Ndimethyl(methylacryloxyethyl)aminopropyl sulfonate(DMAPS),three kinds of anticlay polycarboxylate superplasticizers were prepared respectively.A-PCE series,DPCE series and S-PCE series,were synthesized by substituting AA with different molar ratios.Using the fluidity of cement paste as the evaluation index,the test results show that A2-PCE in A-PCE series,D2-PCE in D-PCE series and S1-PCE in S-PCE series have relatively ideal dispersion and mud resistance.(2)To investigate the mud resistance effects of different functional monomers,A2-PCE,D2-PCE and S2-PCE under the same molar ratio were selected for follow-up experiments.The structure of the polycarboxylate superplasticizer was characterized by gel permeation chromatography and infrared spectroscopy.The cement paste experiment and the cement slurry experiment with sodium-bentonite showed that A2-PCE,D2-PCE,and S2-PCE of anti-clay polycarboxylate superplasticizer had better dispersibility and mud inhibition than O-PCE.The results of the fluidity of mortar and the mortar with sodium-bentonite are consistent with the results of cement slurry.In the fluidity test of cement slurry and mortar,the anti-mud effect and dispersion effect of water reducing agent are successive: S2-PCE,D2-PCE,and A2-PCE;The experimental results show that the water reduction rate of the three anti-clay polycarboxylate superplasticizers is slightly higher than that of O-PCE.(3)The test results of cement mortar strength and concrete compressive strength showed that the strength of cement mortar and concrete decreased after adding 0.5%sodium bentonite.Adding A2-PCE,D2-PCE and S2-PCE water-reducing agents has no adverse effect on its strength,and the strength value is slightly higher than that of OPCE.The strength test results of the mortar containing 0.5% sodium bentonite show that the 28-day compressive strength of S2-PCE with the best performance is 13% higher than that of O-PCE.The test results of the compressive strength of concrete containing0.5% sodium bentonite show that the 28-day compressive strength of S2-PCE is 8.9%higher than that of O-PCE,and that of A2-PCE and D2-PCE is 3.6% and 7.6% higher than that of O-PCE.(4)The adsorption experiment results show that the adsorption capacity of water reducing agent on clay increases with the increase in concentration.The adsorption capacity of anti-clay polycarboxylate superplasticizer on clay is in the order of S2-PCE< D2-PCE < A2-PCE,and the adsorption capacity of O-PCE on clay is higher than that of the three anti-clay polycarboxylate superplasticizers.XRD results show that the distance between clay layers after water reducing agent treatment becomes larger.In combination with the results of TOC adsorption and XRD experiment,it indicates that there is adsorption between the anti-clay polycarboxylate superplasticizers and clay.This study not only provides a new approach for the design and synthesis of mudresistant polycarboxylate superplasticizers,but also offer a new platform for studying the relationship between structure and performance.In addition,a theoretical basis for the development and application of mud-resistant polycarboxylate superplasticizers can be established.