A study on the impact of different clay minerals on the dispersing force of conventional and modified vinyl ether based polycarboxylate superplasticizers

The impact of three different clay minerals (montmorillonite, kaolinite and muscovite) on the dispersing force of vinyl-ether based PCE superplasticizers was studied. At first, a conventional vinyl-ether PCE was synthesized from maleic anhydride (MA), mono methoxy poly(ethylene glycol) ester of MA and 4-hydroxy butyl vinyl ether (HBVE). Additionally, a PEG-free PCE was prepared by substituting MPEG with hydroxyalkyl groups in the ester. Next, the effect of three different clay minerals on the fluidity of cement paste admixed with both PCEs was investigated. It was found that the conventional PCE is negatively affected by the clays in the order: montmorillonite >> kaolinite > muscovite. Whereas, the PEG-free PCEs were only slightly affected. The study suggests that conventional PCEs containing PEG reasonably tolerate all types of clay minerals except montmorillonite. When montmorillonite is present as a contaminant, then use of a PEG-free PCE such as described here presents a viable mitigation strategy. (C) 2014 Elsevier Ltd. All rights reserved.