Crystal growth of [Ca3Al(OH)6·12H2O]2·(SO4)3·2H2O (ettringite) under microgravity: On the impact of anionicity of polycarboxylate comb polymers

It was observed that due to the absence of convection at µg, crystal growth was generally decelerated as evidenced by the smaller size of the ettringite crystals. Highly anionic and thus strongly adsorbing PCE polymers show a strong impact on the crystal size of ettringite under both 1g and µg conditions. Whereas less anionic, weakly adsorbing PCE polymers exhibit a pronounced effect on ettringite growth only under µg conditions. For them, the diffusion-limited ion transport presents the parameter which determines the crystal size. Another remarkable observation is that under microgravity, some of the polymers change their affinity to specific crystal faces which leads to different aspect ratios compared to terrestric gravity.