The Synthesize Of A New Superplasticizer With Polycarboxylate

With the development of civil engineering technology and large scale application of commodity concrete, the progress of concrete additives was promoted greatly, among which the polycarboxylate type high performance water reducing agents with the characteristic of low alkali inclusion,high slushing rate , high potentiation effect , good adaptability, little slump loss,green and innocuity, meeting the demand of high dispersing performance,are becoming the focus of researching field. In our country, the research on this begins in the latter of 1990s. Most of carboxylate superplasticizer are made of co-polymerization or condensation reactions using monomers with functional group, such as sulfonic group, polyoxyethylene etc. While by reasons of the cost and technology , The polycarboxylate type super-plasticizer hasn't reached practically state in domestic .In this dissertation the mechanism of reaction between polycarboxylate superplasticizer and concrete is analyzed according to DLVO theory,electric double layer negative electyicity repulsion effect and space steric hindrance effect. Meantime the molecular of carboxylate superplasticizer is designed. Theacrylic acid,2-acrylamide- 2- methyl third sulphoacid which containing polar group(-COO^-,-SO₃^-) and PEA which containing non-polar group(-OH,-CH₂CH₂O-) are selected as reaction monomers. These monomers were grafted on molecule through -NH2 by Michael addition reaction in the aqueous solution.Finally,produced superbranched or dendritic superplasticizer with space spatial configuration. By changing monomer ratio ,polyethylene glycol ( PEG ) molecular weight, main-chain structure, a series of polycarboxylate superplasticizer with different functional group , different molecular weight superplasticizer are obtained . And the fluidity of cement grout of these products are experimented. Some factors, which affect the superplasticizers dispersal properties are analyzed. In the end the best match is screened out. the fluidity of cement grout can attain as high as 320mm by added the super plasticizer 1.5% and used water-cement ratio 0.29.