Effect of molecular structure of polycarboxylate ether superplasticizer on its tolerance to montmorillonite

Abstract

Two groups of polycarboxylate ether (PCE) superplasticizers with different side chain lengths and densities were synthesized and characterized. Their dispersion capability was evaluated by the time-dependent rheological properties of cement pastes without and with montmorillonite (MMT). The adsorption and intercalation behaviors of these PCEs on MMT were investigated and their interactions with MMT were revealed. Results indicate that PCE with shorter side chains or higher side chain densities exhibits stronger tolerance to MMT than that with longer side chains or lower side chain densities, when they have comparable dispersion capability to cement particles. PCE with shorter side chains has lower adsorption on pure MMT and decreases the proportion of intercalated MMT. The adsorption of PCE on MMT decreases with the increase of side chain density, but the intercalation proportion shows an opposite behavior. The introduction of more side chains increases the intercalation efficiency, and decreases the consumption of MMT to PCE molecules. The adsorption kinetics of PCEs on cement or MMT system are well fitted by the pseudo-second-order adsorption kinetic equation, regardless of PCE type.