Effect of anchoring groups of polycarboxylate ether superplasticizer on the adsorption and dispersion of cement paste containing montmorillonite

Four types of polycarboxylate ether (PCE) superplasticizers with -COO- (C-PCE), -NH3+ (D-PCE), –SO3- (S-PCE) and –COOR (H-PCE) were synthesized. Their molecular structures were characterized by Gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR) and 1H nuclear magnetic resonance spectrum (1H NMR). The adsorption behavior of PCEs was investigated by adsorption amount and layer thickness on cement paste without and with montmorillonite (MMT). Time-dependent flowability and rheological properties of paste were measured and the effects of these PCEs on the hydration of paste were examined. Based on the adsorption behavior of PCEs and fresh properties of pastes without and with MMT, the sensitivity of these PCEs to MMT was also assessed. Results show that D-PCE, S-PCE and H-PCE exhibit lower adsorption amounts, but thicker adsorption layer on cement paste than that of C-PCE. S-PCE shows the best dispersion and retention capability, even in the presence of 3% MMT, and has the smallest sensitivity index. However, H-PCE is the worst one. Paste with D-PCE exhibits comparable initial flowability to that of C-PCE, but higher flowability loss.