Thermo-chemical heterogeneous hydration gradient modeling of concrete and aggregates size effect on ITZ

• Calorimetric measurement of concrete specimens.
• Chemo-thermal modeling based on the modified Arrhenius's law.
• Time-dependent hydration distribution via 3D-FEM.
• Novel quasi-random geometrical spherical packing algorithm application.
• Effect of aggregates and its size on ITZ.

In the present study, the chemo-physical modeling of time dependent hydration phenomenon of the cement-based concrete materials has been achieved using the finite element method. For this study, two identical concretes have been considered with different aggregate size distribution, i.e. one contains small aggregates, 4–8 [mm] and the other contains larger aggregates, 8–12 [mm]. The experimental measurements about the heat release rate and total hydration heat have been taken into account for the numerical modeling using the modified Arrhenius's law. The numerical results confirm that the initially homogeneous hydration phenomenon across the cement paste matrix is disturbed by the existence of aggregates during the hydration period. This induced heterogeneous hydration field strongly depends on the size of aggregates. Afterwards, the hydration gradient has been scrutinized. This can readily explain not only the gap space creation which can be generally observed around the aggregates but also the particular mechanical properties and the induced hydrate product concentration at ITZ (Interfacial Transition Zone) next to the aggregates.

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