Investigation of early growth of calcium hydroxide crystals in cement solution by soft X-ray transmission microscopy

The early growth of calcium hydroxide (CH) crystals in cement solution is investigated by soft X-ray transmission microscopy imaging. A quantitative analysis of the successively recorded images of the hydration process enabled to evaluate the supersaturation ratio of solution, growth rates, both kinetic and diffusion coefficients, and concentrations of solute molecules at \( \{ 10\overline{1} 0\} \) and {0001} facets of the CH crystals. It is concluded that the difference in obtained concentrations of solute molecules at these facets may be associated with solubility anisotropy of crystallographic facets of the CH. The interfacial energy of the CH nuclei in aqueous solution is evaluated to be 0.114 J/m2 that by an order of magnitude is smaller than the average free surface energy of this phase. The proposed theoretical approach is universal and, in potential, may be applied to any precipitating phase in a supersaturated solution.