Synthesis And Properties Of Polycarboxylate Type Superplasticizer

Compared with the traditional water reducer, polycarboxylic superplasticizers exhibit the advantages of high water-reducing rate, cement paste fluidity and low slump loss, etc. The structure of polycarboxylates water reducing agent molecular is comb type. Because of water reducing agent can be used in the molecular design, it has high water reducing rate, low dosage, good slump stability, and have great potential in increase strength. In recent years, it attracted many researchers’ attention at home and abroad. Water reducing agent can block or destroy cement granular flocculation structure, through the surface function, complexation, electrostatic repulsion force and stereo repulsive force. Based on the application of poly carboxylic acid water reducing agent research can realize functional design of water reducing agent, so as to promote the development of high-performance concrete.At present, the polycarboxylate-type superplasticizer is generally used polyethylene glycol monomethyl ether methyl acrylic ester or allyl polyoxyethylene base as the big monomer to synthesis.Synthesis process of polyethylene glycol monomethyl ether methyl acrylic ester is very complex and difficult to control, the price is aslo expensive. While the ally] polyoxyethylene base prices are low, but reaction activity is quite low, at the same time, the molecular chain have no hydrolytic function, thus it’s a little brittle,which reflected in the cement paste fluidity is that initial water reducing rate high, but stability is poor. This paper select a more active momomer as big monomer. Prepared polycarboxylate-type superplasticizer by two different molecular weight big monomer as the long side chain and various functional groups.Compared and analysis the relation between structure and properties, promote functional design of water reducer.On the basis of molecular structure design theory and free-radical polymerization theory, the polycarboxylic-type superplastics (PC) with methallyl polyoxyethylene ethers (TPEG) of two different molecular weights as the macromonomers, and maleic anhydride (MAn), sodium methallyl sulfonate (MAS), acrylamide (AM) as the micromonomers, were synthesized through multivariate copolymerization under the action of initiator, ammonium persulfate (APS). The influence of reaction temperature, reaction time, initiator dosage and monomer dosage on the water-reducing rate, cement paste fluidity and slump loss of water reducer were investigated systematically. The relationship between structure and properties of polycarboxylate-type superplasticizers were explored. The results showed that:The initiator of quality equal to3.0%of the mass of monomer, keep the reaction temperature in the80℃or so, the reaction time6hours, and big monomer and small monomer molar ratio of1:3, the synthetic water reducing agent has good performance. The polycarboxylate-type superplasticizer is better than other ordinary water reducer. The paste flow can attain315mm and water-reducing rate was35%by using0.5%of the product.