Mix-, storage- and temperature-invariant precipitation characteristics in white cement paste, expressed through an NMR-based analytical model
Nabor Jiménez Segura, Bernhard Pichler, Christian Hellmich
Abstract
Proton NMR tests on hydrating white cement paste provide access to the mix-, storage-, and temperature-dependent evolutions of the hydrogen portions found in capillary and gel pores, solid C-S-H, and calcium hydroxide, respectively. The aforementioned dependencies vanish once the hydrogen molar fractions are plotted as functions of the precipitation degree, which we have introduced here as the ratio of the amount of hydrogen bound in solids, over the total amount of hydrogen. The precipitation rate is governed by one activation energy and a linear affinity function of the current precipitation degree normalized by its maximum value. The latter decreases linearly with increasing curing temperature, being consistent with the temperature-dependent water content of solid C-S-H. The corresponding water-to-silica ratio, together with the precipitation degree and the mix and storage characteristics, provide access to the volume fractions of the hydrogen-containing phases, of clinker, and of voids, as well as to the degree of hydration.