Analytical Equations and Numerical Simulation Describing the Pore and Solid Phase Distributions of Interfacial Transition Zones in Cement-Based Materials

By combining the nearest surface distribution function and hydration kinetic equation, analytical equations are proposed to determine the pore phase and solid phase evolution in the interfacial transition zone (ITZ). In addition, the numerical models for concrete with a single flat aggregate are constructed based on the CEMHYD3D hydration model. The results show that the degree of hydration is the main factor affecting the ratio of the average porosity to the matrix porosity in the ITZ. With an increase in the aggregate volume fraction and interface thickness, the volume fraction of the ITZ first increases and then decreases. The degree of overlap increases linearly with the interface thickness and the aggregate volume fraction. As the distance from the aggregate surface increases, high-density C-S-H increases, while low-density C-S-H and calcium hydroxide phases decrease. Finally, the predicted results using the analytical equations and numerical simulation are verified by testing via back-scattered electron microscopy, which indicates that the experimental results are more consistent with the predicted results of the analytical model than with those of the numerical model.

Automated summary

The study examined the evolution of pore phase and solid phase in the interfacial transition zone of concrete using analytical equations and numerical simulation. The results showed that hydration degree, aggregate volume fraction, and interface thickness played crucial roles in determining the properties of the ITZ. Experimentally verified that the analytical model predictions were more consistent with the experimental results than the numerical model.