Influence of Comb-Polymer Structure on C3S Phase Hydration

The cement hydration delay due to comb-polymers (PCP) with the typical polycarboxylate structure, used as dispersing agent, was investigated by separately analyzing the effects of the polymeric parts of the PCP ar-chitecture on the reaction of the C3S phase. The focus was directed to the PCP backbone (PAA) and to the dispersing side chain parts (methoxy terminated polyethylene oxide, PEO). A linear polymer made up of PEO, Mw=1000, with a carboxylic head suitable to link the inorganic surface, was synthesized to simulate the effect of the comb-side chain. To examine the relation between structure and C3S hydration, the delay of the heat development was measured by calorimetry and the appearance of the surface was analyzed by SEM microscopy. The results show that the hydration delay is mainly ascribable to the comb-shaped structure as a whole, where PEO chain, as from considerations on energy, might assume conformations able to modify the salt concentration near the cement surface. The different hydration rates are tentatively related to the crystal growth and the surface texture observed by SEM