Hydration modeling has long relied on the degree of hydration as the standard variable. However, the analysis of proton nuclear magnetic resonance (NMR) relaxometry results of hydrating white cement pastes has led to the identification of a new hydration variable which has the potential to revolutionize our understanding of cement hydration, see [1]. Unlike the traditional degree of hydration, which focuses on the residual amount of cement clinker in the material, the newly introduced degree of precipitation refers to the distribution of hydrogen in the microstructure. The degree of precipitation is equal to the amount of hydrogen bound in solids divided by the total amount of hydrogen in the material. This new variable describes the evolution of hydrogen in gel pores, capillary pores, solid C-S-H, and portlandite in a manner that is independent of the initial water-to-cement mass ratio, the curing temperature, and the storage conditions (either sealed or submerged in water). In terms of reaction kinetics, the rate of the degree of precipitation is shown to be governed by one value of the activation energy and a linear affinity function of the current precipitation degree normalized to its maximum value. The maximum degree of precipitation decreases linearly with increasing curing temperature. This is consistent with the decrease in water content of solid C-S-H with increasing curing temperature. Finally, expressions describing the hydration-induced evolution of the volume fractions of gel pores, capillary pores, voids, solid C-S-H, portlandite, and cement clinker are derived. They take into account the initial water-to-cement mass ratio, the degree of precipitation, the temperature-dependent water-to-silica ratio of solid C-S-H, and the storage conditions. REFERENCE [1] N. Jiménez Segura, B. Pichler, and C. Hellmich. Mix-, storage-and temperature-invariant precipitation characteristics in white cement paste, expressed through an NMR-based analytical model. Cement and Concrete Research 172: 107237, 2023. https://doi.org/k26n