Study On The Synthesis And Properties Of Novel Functional Superplasticizers

During last decades, polycarboxylate-type superplasticizer has been widely used in various engineering projects in China. With the development of modern architecture, traditional polycarboxy-type superplasticizer can not meet the need of mechanical property and durability any more. Therefore, the research and development for higher-performance superplasticizer to improve the properties of concrete is becoming more and more important. In this paper, several functional groups were incorporated into the molecular structure, and lots of fundamental researches have been done on improving the properties of polycarboxylate-type superplasticizers to develop their early strength. Functional monomers AMPS, AM, DMAA, MAPTAC have been introduced into the molecular structure of polycarboxylate-type superlasticizer by radical polymerization. The polyamidoamine dendrimers were synthesized by divergent menthod, and dendrimers with end groups of ester group were hydrolyzed to carboxyl group. The influence of molecular structure on performance was studied.Functional groups of molecular structure were characterized by Fourier infrared spectroscopy (FTIR). The molecular structure of polyamidoamine dendrimers and hydrolysis rate were characterized by 1H-NMR. Besides, interaction between superplasticizer and cement particles were analyzed. The adsorption amount of superplasticizer on cement particles were characterized by total carbon analyzer(TOC). The Zeta potential of cement was measured by DT1200 Zeta potential measurement analyzer. Fluidity of cement paste with superplasticizer were tested to show the interaction between superplasticizer and cement, the influence of superplasticizer on hydration of cement paste were characterized by TAM Air Isothermal CalorimetryResults shows that the four kinds of functional monomers AMPS, AM, DMAA, MAPTAC were successfully introduced into polycarboxylate-type superplasticizer. Functional groups of superplasticizer affect the adsorption amount, retarding effect and dispersive capacity on cement. Carboxyl group shows the highest adsorption amount, retarding effect and dispersive capacity. Quaternary ammonium cation and sulfonic acid group show lower adsorption amount and dispersive capacity but do not have retarding effects on cement. Amide group and dimethylamino show the lowest adsorption amount and dispersive capacity but have a little retarding effect on cement. 0-3.5Generation polyamidoamine dendrimers were successfully synthesized by alternative Michael addition and Amidation. Dendrimers with the same generation but different end groups show the ability of adsording on cement, retarding the hydration progress and dispersive capacity on cement from high to low as below:carboxyl group> ester group> amino group. For dendrimers with the same end groups, the ability of adsorption on cement, retarding the hydration progress and diepersive capacity on cement increase with the increasing of generations.