Synthesis Of Polycarboxylic Superplasticizers And Its Application In Quick Flowing Mortar

In this work,polycarboxylate superplasticizers had been modified by adding the functional monomer which contains 2-acrylamide-2-methyl propane sulfonic acid(AMPS)and maleic acid methyl ester(MMM)monomer based on the binary copolymerization.The effects of modified functional groups on the properties and mechanisms of polycarboxylate superplasticizers had been investigated.According to the fast flow mortar system of two main indicators,fluidity and segregation resistance,a series of experiments of the fluidity of cement paste,mortar water-reducing rate,Marsh cone time,rheology test and so on,were tested for researching comprehensive performance of different water-reducing agent.And the compatibility of mortar with different super-plasticizers is quantitatively evaluated by combining the Marsh cone time with the bleeding rate,finally it is obtained a suitable high performance polycarboxylate superplasticizer for fast flow mortar system.In this paper,using acrylic acid(AA)and isoamyl alcohol polyoxyethylene ether(TPEG)as raw materials,the optimized basic polycarboxylate superplasticizers(P1)was prepared by single factor experiment in the oxidation–reduction initiator system.On this condition,the third modified monomer AMPS and MMM were synthesized through orthogonal optimization test and the synthesized polycarboxylate superplasticizer was prepared by the method of infrared and high performance liquid chromatography.The structure and reaction rate of the product were analyzed:(1)The best synthesis conditions of P1(binary-basic polycarboxylate superplasticizer): n(AA):n(TPEG)=4,n(TBHP):n(TGA)=3,the dosages of reducetant and thiolhistidine acid are 0.3 wt% and 0.7 wt% of total monomers,respectively,and reaction temperature 25?.(2)The best synthesis conditions of P2(AMPS-modified polycarboxylate superplasticizer): n(AMPS):n(TPEG)=1:2,n(AA):n(TPEG)=4,n(TBHP):n(TGA)=3,the dosages of Sodium formaldehyde sodium formaldehyde sulfoxylate(reductant)and thiolhistidine acid(chain transfer agent)are 0.3 wt% and 0.5wt% of total monomers,respectively,and reaction temperature 25 ?.Through Infrared spectrometer(FTIR)and the high performance liquid chromatography(HPLC)analysis to know the response rate of P2 was more than 98%.(3)The best synthesis conditions of P3(MMM-modified polycarboxylate superplasticizer): n(MMM):n(TPEG)=2:1,n(AA):n(TPEG)=4,n(TBHP): n(TGA)=3,the dosages of Sodium formaldehyde sodium formaldehyde sulfoxylate(reductant)and thiolhistidine acid(chain transfer agent)are 0.3 wt% and 0.7wt% of total monomers,respectively,and reaction temperature 25 ?.Through Infrared spectrometer(FTIR)and the high performance liquid chromatography(HPLC)analysis to know the response rate of P3 was more than 96%.Next,the three kinds of water reducing agents(P1,P2,P3)were compared with the three kinds of water-reducing agent P4 and P5 at the market.The compatibility index ?* was used to evaluate the fluidity of mortar system and different polycarboxylate superplasticizer by the combination of fluidity,water retention and empty time of Marsh cone,the order was as follows:P2>P4>P5>P3>P1.Comparison the effect of different superplasticizers on rheology and thixotropy of the mortar under different water-cement ratio,the average thixotropic area of the mortar with different polycarboxylate superplasticizer was obtained,the order of superplasticizers is as follows:P2>P4>P1>P5>P3.The maximum thixotropic area of cement mortar mixed with P2 is probably due to the addition of P2,the slurry at the stage of rising has more flocculation structure with larger resistance and higher torque at the same speed.At the stage of falling,some of the flocculation structure is destroyed with the free particles and less resistance.The falling stage achieves the same torque requiring for greater rotational speed,and therefore the thixotropy of the slurry has the largest and the best dispersivity.Finally,combining with the result of a series of tests,it is known that AMPS-modified polycarboxylate superplasticizers P2 is the best water-reducing agent for the five kinds of water-reducers.