Ming Liu;Yao Bi;Xiaodi DU;Qinglin Zhao;Jiaheng Lei;
<正>In this study,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.For characterization of the superplasticizers,1HNMR as well as GPC was carried out.The property of the polymers in cement was tested by microelectrophoresis 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 and show higher affinity to the binder surface,thus result in higher zeta potential.In addition,the effects of side chain density on zeta potential is more notable compared with side-chain length,and thus affect the initial shear yield stress and apparent viscosity of the cement paste;Although increasing the side chain length will result in reducing the anionic charge density and its adsorption capacity,the steric hindrance effect is more obvious,which can effectively improve the dispersion of the cement particles,reduce the viscosity and shear yield stress of slurry.Moreover,although PCs with higher side chain density and longer length show lower adsorption capacity,it is helpful to provide PCs compensation to adsorb on new mineral particle surface,therefore,it will be more beneficial to maintain the fluidity of cement paste. Originality PCs are widely used in high performance concrete due to their excellent water reducing capacity.The dispersing ability of these polymers are generally thought to be related to their unique chemical structure.Although the effects of PCs on the performance of concrete are frequently studied,there is not much information available on the relationship between PCs' structures and the rheological property of cement paste.So the study of rheological property and zeta potential behavior in cementitious systems to link the structure of PCs is first originality.Furthermore,detailed analysis about the synthesized PCs was not yet clarified in most studies.In this investigation,a series of PCs with different structures have been synthesized,the architecture has also been confirmed and clarified.This information generated should help to elucidate working mechanisms of PCs and this is the second originality.
polycarboxylate-based superplasticizers;;zeta potential;;cement paste;;fluidity
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