The Research Of The Synthesis And Properties Of The Polycarboxylate Superplasticizer

Polycarboxylate superplasticizer is a new grade water-reducing agent arising in the 1990s, which expresses so many performances, such as high dispensability with low addition, low loss of lump constant, high intensity in early stage, and the good compatibility with the cement. More and more efforts have been dedicated to its research over the world. However, up to now, very little research is focused on design of molecular structure, overall synthetic process and reaction mechanism, which have to been intensified. Based on the above mentioned, the optimum scheme has been investigated by appropriate molecular design, and the optimum synthetic conditions have also been given in the paper.On the basis of the design of molecular structure, the polycarboxylate superplasticizer was synthesized by polymerizing of polyethylene glycol, methl sodium allylsulfonate, acryl acid. After a series of orthogonal and signal tests were performed individually, the crucial factors in the performances and optimum processing parameters have been attained. Making a comparison between as-synthesized polycarboxylate superplasticizer and other ones according to the correlative standard rules, we find that it has better dispensing property and dispersive retentivity, and better compatibility with all kinds of cements. It meets the quality requirement of superplasticizer. Since it has a little gap in comparison with foreign polycarboxylate superplasticizer, further work is in progress.By analyzing the combined results of infrared spectrum, ultraviolet spectra, gel permeation chromatography(GPC), high performance liquid chromatography(HPLC), we find that the type and number of the functional groups, the mean molecular weight and distribution, composition and so on have an important effect on the performance. And the action mechanism was also studied. The results indicated that the water-reducing mechanism mainly depends on the adsorption and dispersion of the interactivity between the polycarboxylate superplasticizer and the cement. On one hand, in the mixed system of superplasticizer, water, and cements, the electric double layer is informed while the polycarboxylate superplasticizer is absorbed on the cement, which generated intra-particle repulsion force. On the other hand, the side chain of the polycarboxylate superplasticizer displays steric hindrance because of extension of longer branched chain. So the dispersion and stability of the dispersion is increased significantly after the polycarboxylate superplasticizer to the cement or concrete was added.