Synthesis And Performance Investigation Of Sustained Released Polycarboxylate Superplasticizers

Due to the excellent water-reducing effect and dispersing performance of the superplasticizers,it is recognized as an important chemical admixture in the field of modern concrete engineering.The main function of the superplasticizers is to reduce the water-cement ratio while making the concrete have good dispersibility and durability.The polycarboxylate acid-based superplasticizers has the advantages of high water-reducing rate,good dispersion performance,and design of molecular structure through the main chain adsorption and side chain dispersion.Based on the idea of molecular structure design of polycarboxylate superplasticizer,this paper introduces functional monomers with different functional groups,and studies the superplasticizers with different properties,and is committed to the wide application and promotion in the construction industry.Firstly,the paper successfully introduced a phosphate group and a quaternary ammonium salt to synthesize polycarboxylate superplasticizers PCE-P and PCE-N with different charge distributions.The charge density of the main chain was regulated by adjusting the proportion of monomers participating in the reaction.And side chain distribution.It was characterized by FT-IR,cement paste fluidity test,moisture retention performance test,zeta potential analysis and rheometer.The results show that PCE-P has strong electrostatic adsorption with the surface positive charge of cement particles under the same water-cement ratio and dosage.When the dosage is 0.3%,the fluidity can reach 300mm,and it can still be maintained within 120min.The fluidity is above 280mm,while the other two water reducing agents lose the fluidity to 180mm after 40min.When the addictives is added,the average particle diameter of the particles is reduced from 16.98 ?m to 11,88 ?m,and the surface potential of the particles is more negative.Application in concrete systems can improve the construction performance of concrete.The three polymers synthesized in this study can alleviate the problem of concrete bleeding in different degrees.The concrete material added with PCE-P is more full and stable,which is conducive to concrete construction and pumpingIn order to further design a polycarboxylic acid superplasticizers with more comprehensive performance,a high performance slow release polycarboxylic acid superplasticizers with three different monomer ratios was prepared in the same manner.The polymer was obtained by copolymerization of acrylic acid(AA),allyl polyoxyethylene ether(HPEG)and methoxy polyethylene glycol methacrylate(PEG400MA).Comparing the fluidity of the ether water reducing agent,it is found that the ester ether copolymer water reducing agent has a certain sustained release effect,and the replacement ratio is 30%of the polymer.The initial fluidity of the cement paste is only 253,120 min,and the fluidity reaches 303 mm;The water reducing agent was added to the cement paste to test the surface potential of the cement particles and the water and kinetic radius.The particle size is reduced,the surface potential is more negative,and the substitution ratio is 40%.When the dosage is 0.2%,the potential drops to-15.63 mv,which shows good dispersion performance.Through the total organic carbon adsorption test(TOC),when the amount of the water reducing agent is 0.2%,the adsorption amount is 0.521 mg/g,and when the dosage is 0.8%,the adsorption amount is increased to 4.05 mg/g.