Synthesis Process And Performance Of Allylic Polyethylene Glygol Polycarboxylate Superplasticizer

Polycarboxylate superplasticize was a new type admixture with excellent performance,it was friendly to the environment, so many scholars had paid attention to it. In recent years, a large number of studies had focused on the selection of different mono-mer and the optimization of synthesis process, the cost of synthesis was rarely considered. The kinetics of polymerization was rarely reported yet. Therefore, few of synthesis process could be used to the actual production. This study aimed to reduce the synthetic cost. The simple binary polymerization system of allylic polyethylene glygol(APEG) and acrylic acid (AA) was established, the synthesis process parameters were optimized, kinetics of polymerization was discussed, the structure, dispersibility, dispersed retention, cement adaptability, stability and anti-acid rain corrosion were measured. The works and results were as follows:The polycarboxylate superplasticizer had been synthesized by binary copolymer-ization reaction, APEG and AA were monomers, ammonium persulfate-30%hydro-gen peroxide were the initiator system, thioglycolic acid was a chain transfer agent. The structure of polycarboxylate superplasticizer was characterized by IR and NMR analysis. The optimum process of synthetic reaction was that:molar ratio of monomers was AA:APEG=4:1, the amount of initiator was1.5%APS-2%H2O2(mass ratio to monomers), the chain transfer agent was1.6%of the total mass of the monomers, the polymerization temperature and time were80℃and5h, respectively. The initial fluidity of cement paste was up to300mm when the folding solid dosage of superplasticizer was0.3%and the water-cement ratio was0.29. The superplasticizer had the advantages of low dosage, high dispersibility and the dispersed retention.The radical copolymerization reaction mechanism of APEG and AA in aqueous solution was studied, the effect of the polymerization temperature, the monomer ratio and initiator percentage on polymer-ization conversion was investigated. The overall observed activation energy of copoly merization was45.048kJ/mol, the rate of copolymerization was proportional to the molar ratio of monomer to the power of0.4405, and to the amount of initiator to the power of0.7819. The kinetic relationship of copolymerization reaction of APEG with AA was established as follows:Rp∝[APEG/AA]0.4405[APS-30%H2O2]0.7819e-5418/T.The performance of polycarboxylate superplasticizer including the setting time of cement paste, water-reducing rate, compressive strength of concrete, dispersibility, dispersed retention, adaptability and stability were studied. The anti-acid rain corro-sion of mortar bar that mixed with polycarboxylate superplasticizer was researched. Polycarboxylate superplasticizer had retarding effect. Water-reducing rate had met the requirement of superplasticizer. The compressive strength of concrete mixed with polycarboxylate superplasticizer for3days,7days and28days increased. The compr-essive strength for3days increased above50%, the early strength increased signif-icantly. Polycarboxylate superplasticizer had good adaptability to different types of cement, it remained stable for2months. Mortar bar mixed with polycarboxylate superplasticizer had a certain anti-acid rain corrosion.