A polycarboxylate as a superplasticizer for montmorillonite clay in cement: Adsorption and tolerance studies

A novel polycarboxylate superplasticizer (PCE) with a long polyoxyethylene (PEO) chain and a terminal carboxylic group was synthesized from a modified polyether (SAE-IPEG) to increase its performance in cement. The molecular structure of the PCE was characterized by infrared spectroscopy and 1H nuclear magnetic resonance (NMR) spectroscopy. The performance of synthesized PCE in cement was studied in the absence and the presence of montmorillonite (Mmt) clay. It was found that the PCE disperses in cement uniformly without aggregation, which is different significantly from the conventional PCEs. Adsorption measurements and X-ray diffraction analysis revealed that the synthesized PCE only interacted with Mmt via surface adsorption, whereas the conventional PCEs interact with the clay through the surface adsorption and the chemical intercalation. Such dramatic change could be ascribed to the introduction of an electronegative carboxylic acid group as a terminal group into the long polyoxyethylene chain of PCE, which reduced the adsorption and enhanced tolerance of PCE on Mmt.