Study On The Synthesis And Properties Of Polycarboxylic Acid Water Reducer At Room Temperature

With the rapid development of concrete technology,low carbon environmental protection and high performance have become the main development trend of concrete water reducing agent.At present,the synthesis temperature of polycarboxylic acid system water reducer is high,usually around 50?,the synthetic solvent is still the expensive deionized water,the synthesis process is complex,the synthesis of polycarboxylic acid system water reducer is not adaptable to clay,which seriously affects and limits the promotion and application of polycarboxylic acid system high performance water reducer.The best anionic polycarboxylic acid reducer A₅?solid content about 40%?was synthesized by free radical polymerization under the action of Jiajixi,acrylic acid and pure water as solvent.The best synthetic process of A₅ is as follows:n?AA?:n?TPEG?:n?TGA?=4:1:0.15,M?initiator?:M?TPEG?=0.6%,reaction temperature 20?,reaction time about 3 h.On the basis of the ratio of A₅,acrylated polycarboxylic acid water reducer C₁?solid content about 40%?was synthesized by replacing acrylic acid?AA?by 20%?mass percentage?of the cationic monomer DMDAAC.In the polycarboxylic acid reducer with different water quality as solvent,the polycarboxylic acid reducer with tap water as solvent was the least distributed,and the pure water and deionized water as solvent were the best.The results of infrared absorption spectroscopy show that the main functional groups of A₅ are carboxyl group,ether group,hydroxyl group and so on.The results showed that the mean molecular weight M_W of A₅ was 40100,polydispersity coefficient was 1.46,the mean molecular weight M_W of C₁ was 52000 and polydispersity coefficien was 1.6.By testing the flow degree of cement slurry and Zeta potential when adding bentonite,and comparing their adaptability to clay,the results showed that the flow value and absolute value of Zeta potential of C₁ cement slurry were higher than that of anionic polycarboxylate A₅.The controlled ratio of water ash is 0.35,the dosage of water reducer?20%solid content?is 1.2%,the initial flow of cement slurry with A₅can reach 304 mm,the initial flow of cement slurry with C₁ can reach 300 mm,the initial flow of cement slurry with 1h A₅ and the net flow of cement with C₁ is 292mm.In the concrete performance experiment,the compression strength ratio of C30concrete doped with A₅ and C₁ water reducing agent can reach 118%and 115%,respectively,and the compressive strength ratio of 7d can reach 136%and 133%,respectively.The adaptability of two water reducers was studied.The results showed that A₅ and C₁ had good adaptability to P·O 42.5 cement.The results of hydration thermal experiments show that when the amount of polycarboxylic acid water reducer increases from 0%to 1%,the retarding effect on cement hydration in the early stage of hydration is increasing,and there is little effect after 1 d.In the XRD diagram of 1d hydration of cement samples,the strength of C₂S and C₂S mixed with polycarboxylic acid water reducer had no obvious change and the strength of CH decreased.The morphology of P·O 42.5 cement hydration samples of different ages were observed by scanning electron microscopy?SEM?,confirming the reinforcing effect of polycarboxylate superplasticizers on compressive strength of concrete.