The Research On The Compatibility Between PNS And Cement

A new kind of incompatibility between cement and naphthalene-based superplasticizer (PNS) is investigated in this paper. Different from the incompatibility that has been reported before by others, the incompatibility shows some special phenomena. So, it is necessary to study at the compatibility, and find out the way to improve it effectively. On the other hand, the investigation results could be a supplement of the compatibility theory system. By examining the fresh cement pastes fluidity, the Zeta potential of the surface on cement particles, and the SO42-concentration in solution of pastes, the following conclusions are drawn: the low alkali content in cement, the high specific surface of cement, the short storing time of cement and the inappropriate phases and the dosage of the gypsum etc, are the causes that affect the compatibility between PNS and cement. The experiment results also show that the incompatible cement has a higher adsorption capacity of PNS, and that the amount of adsorbed PNS is in close relationship with the causes including the alkali content in cement,the specific surface of cement,the storing time of cement and the phases of the calcium sulfate as well as its dosage, and so on. On the base of experimental investigation, some improvements can be put forward to improve the compatibility, for example, reducing the specific surface of cement,increasing the alkali content in cement, using gypsum instead of hemi hydrate or natural anhydrite, choosing the other types of superplasticizer benefit for compatibility, and changing adding methods of PNS into delayed addition pattern etc. As each cause of the incompatibility between PNS and cement (such as the low alkali, high specific surface) is common in currently cements, the conclusions of this investigation could be a reference for improving the compatibility between other kind of PNS and cement.