Early Hydration of Portland Cement Admixed with Polycarboxylates Studied Under Terrestric and Microgravity Conditions

The crystallization of ettringite at very early cement hydration (hydration period - 10 s) was studied under normal and zero gravity condition utilizing SEM microscopy. Furthermore, the impact of two polycarboxylate superplasticizers (one methacrylate ester-, one methallyl ether - based) on ettringite crystallization was investigated. It was found that under microgravity attained on parabolic flights, generally smaller, but a larger amount of ettringite crystals is formed resulting from the absence of convection and ion diffusion limited crystal growth. Furthermore, the PCE polymers were found to act as morphological catalysts for ettringite even under zero gravity condition.