Preparation of Polycarboxylate-based Superplasticizer and Its Effects on Zeta Potential and Rheological Property of Cement Paste

A series of polycarboxylate-based superplasticizers(PCs) with different structures were synthesized and the effects of chemical structure on zeta potential and rheological property of cement paste were studied. Residual monomers in each sample of PCs were quantitatively determined. The property of the polymers in cement was tested by micro-electrophoresis apparatus and R/S rheometer. Results showed that the zeta potential and its rheological properties are related with the side-chain length and density of PCs. The PCs having shorter side chain and lower side chain density exhibit higher anionic charge density, thus resulting in higher zeta potential. The effect of side chain density on zeta potential is more notable compared with that of side-chain length, and thus affecting the initial shear yield stress and apparent viscosity of the cement paste. In addition, although increasing the side chain length will result in reduction of the anionic charge density, the steric hindrance effect is obvious, which can effectively improve the dispersion of the cement particles, and reduce the viscosity and shear yield stress of slurry.

自密实混凝土及其在印度尼西亚的应用

自密实混凝土被称为近几十年中混凝土建筑技术最具革命性的发展。为了在中国进一步推广和更好地使用自密实混凝土,介绍了采用自密实混凝土改进混凝土结构性能(即耐久性与可靠性)的趋势以及自密实混凝土在印度尼西亚高层建筑和大跨桥梁中的应用情况。由于其高流动性,自密实混凝土适合于浇筑施工困难地方和复杂截面形式,尤其是钢筋布置很密的地方。采用自密实混凝土还能减少灌注大尺寸混凝土构件所需要的时间,例如建筑物的底部或基础的灌注。自密实混凝土也会减小施工现场由于混凝土振捣产生的噪音。随着掺合剂技术在使用新一代聚羧化物基超增塑剂方面的发展,现在自密实混凝土可以大规模商业化生产,并成功地在印度尼西亚和世界各地应用。