Heating cement to slow down its hydration: The unexpected role of PCE interpolymer bridge formation

Abstract

PCEs with specific polymer structures at dosages over 1% were shown to delay cement hydration as temperature increased. The present work investigates this unexpected phenomenon, reporting hydration kinetics of chemically admixed cement pastes at different temperatures, mineralogical changes, chemical composition of the pore solution and rheological properties.At 23 °C, a significant increase of Si, Al, Mg and Fe in pore solution of admixed samples was measured and nano-particles (polymer aggregates and/or organo-aluminates) were detected. In contrast, these nano-particles were not present at higher temperature, 70 °C, when a dramatic hydration delay was observed. This could increase the amount of free polymer available to delay silicate hydration. Molecular dynamics simulations confirmed the formation of polymer aggregates via interpolymer bridges in presence of both calcium and aluminum at room temperature, while the ability of aluminum to bridge the polymers was reduced with the increase of the temperature.