A Critical Comparison of 3D Experiments and Simulations of Tricalcium Silicate Hydration
Jeffrey W. Bullard, John G. Hagedorn, Tyler Ley, Qinang Hu, Wesley N. Griffin, Judith E. Terrill
Advances in nano-computed X-ray tomography (nCT), nano X-ray fluorescence spectrometry (nXRF), and high-performance computing have now enabled the first ever direct comparison between observations of three-dimensional nanoscale microstructure evolution during cement hydration and physico-chemical microstructure simulations of the same system using HydratiCA. nCT observations of a collection of triclinic tricalcium silicate (Ca3SiO5) particles reacting in a calcium hydroxide solution are reported and compared to simulations that duplicate, as nearly as possible, the thermal and chemical conditions of those experiments. Particular points of comparison are the time dependence of the solid phase volume fractions, and both the solid phase domain spatial distribution and morphology. Comparisons made at 7h of hydration indicate that the simulated and observed amounts of Ca3SiO5 dissolution agree to within the measurement uncertainty. The location of simulated hydration product is qualitatively consistent with the observations, but the apparent volume of hydration product observed by nCT is more than ten times the volume produced by the simulations at the same time. Simultaneous nXRF measurements of the same observation volume imply calcium and silicon concentrations within the observed hydration product mass that are consistent with a sparse network of calcium silicate hydrate (C-S-H) and Ca(OH)2 that contains about 70 % occluded porosity. Moreover, the inferred molar ratio of Ca(OH)2 to C-S-H in the hydration product volume far exceeds the value required by a mass balance within the observational volume used for the computational domain. Possible origins of the anomalous amount of Ca(OH)2 and of the large occluded porosity are discussed, and some tentative strategies for simulating large volumes of occluded porosity are proposed.
, Hagedorn, J.
, Ley, T.
, Hu, Q.
, Griffin, W.
and Terrill, J.
A Critical Comparison of 3D Experiments and Simulations of Tricalcium Silicate Hydration, Journal of the American Ceramic Society, [online], https://doi.org/10.1111/jace.15323
(Accessed January 17, 2022)