Performance of polycarboxylate superplasticisers in seawater-blended cement: Effect from chemical structure and nano modification

Abstract

Abstract The performance of polycarboxylate superplasticisers (PCE) in cement blended with seawater (SW) depends on its molecular structure since large ions in SW significantly influenced its mechanism. The aim of this study was to investigate the effect of the molecular structure of PCE on the fresh properties of SW-blended cement pastes. A series of six PCEs with different charge densities, side chain lengths, and anchor groups were modified by introducing nanosilica and their physicochemical properties were characterised, and the performance was evaluated by determined by minislump, rheological behaviour and setting time. Finally, the potential mechanism was proposed via measurement of adsorption amount and layer thickness, and water film thickness (WFT). The results showed that the PCE with longer side chains and higher AA:HEPG ratio provided a significant improvement in the workability of cement pastes mixed with SW. According to the flow curves from the rheology experiments, analysis of the rheological behaviour of polycarboxylate superplasticisers in SW-blended cements paste by three rheological models. By adsorption measurement and WFT testing, high higher AA:HPEG ratio exhibits high sorption and WFT indicating less inhibition by ions in SW.