硅灰是超高强混凝土(UHSC)中最难被分散的组分,超高强混凝土性能提升需要硅灰的有效分散.通过自由基反应,将乙烯基三乙氧基硅烷接枝引入了主链结构中,合成了一种含有硅烷基团的聚羧酸减水剂(PCES).采用微坍落度法研究了 PCES 对水泥-硅灰浆体流动性的影响规律.用有机碳分析仪研究了PCES在水泥净浆和硅灰表面的吸附性能.研究结果表明,聚羧酸减水剂分子结构中引入硅烷基团后,分散水泥-硅灰浆体的能力明显提高,在水泥颗粒表面吸附量增加幅度不大,而在硅灰表面的吸附量有较大幅度增加.PCES能够在含有羟基的硅灰表面同时发生物理吸附和化学吸附,硅灰表面吸附更多的减水剂分子后,其空间排斥能增加,这可能是PCES分散能力提升一个机理.相较普通聚羧酸减水剂,硅烷改性的聚羧酸减水剂更适宜配制超高强混凝土.
Silica fume is the hardest dispersing component in ultra high strength concrete (UHSC),and im-provement of UHSC performance need effective dispersion of silica fume.In this study,silanized polycarboxy-late superplastizer (PCES)was synthesized through radical copolymerization,which Vinyltriethoxysilane was in-troduced to backbone structure of polymer.The influence of PCES on fluidity of cement-silica fume pastes was analysed by mini-slumps method.Adsorption properties of PCES on surface of cement and silica fume were in-vestigated by TOC.Results shows:compared with traditional polycarboxlate,PCES showed a higher dispersing capability in cement-silica fume pastes,Adsorption amount increased marginally in cement,while sharply in sil-ica fume.The surface of silica fume existed hydroxyl,chemical adsorption and electrostatic adsorption of PCES happened simultaneously.Owing to additional chemical adsorption,more molecules existed in surface of parti-cles,they can offer stronger steric hindrance repulsive force,this may be a mechanism that PCES possessed high dispersion effectiveness in cement-silica fume pastes.Compared to traditional polycarboxlate,PCES was more suitable for ultra high strength concrete.
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