Multiscale numerical-analytical modelling of oxygen diffusivity in partially saturated concrete: Role of interfacial transition zone

Abstract

This study presents a multiscale model to simulate oxygen diffusivity in partially saturated concrete accounting for multiscale nature of concrete and water-gas distribution in its pore structure. At microscale, 3 D microstructure of cement paste ITZ is simulated, based on which the water-gas equilibrium distribution in capillary pore structure and oxygen diffusivity at different degrees of water saturation (DWSs) are mimicked using lattice Boltzmann models. Afterwards, a (n + 1)-phase model based on effective media theory is used to predict oxygen diffusivity in non-saturated concrete at mesoscale. Results indicate that the evolution of oxygen diffusivity with the increasing DWS follows an initial drop, a plateau, a slight decrease and a sharp decrease, which correspond to the decreasing gas-filled gel pores, depercolation of gas-filled gel pores, and decreasing gas-filled capillary pores until their depercolation. The role of ITZ in oxygen diffusion in non-saturated concrete becomes more remarkable with the increasing DWS.

Keywords:

• Partial saturation
• ITZ
• moisture distribution
• transport properties
• durability

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors gratefully acknowledge the financial support from National Natural Science Foundation of China (No. 52171254 and No. 52130210) and National Key R&D Program of China (NO. 2017YFB0309904-04). The financial support provided by the Natural Science Foundation of Jiangsu Province (No. BK20220854) and Fundamental Research Funds for the Central Universities (No. 2242022R10028) to the first author is also greatly acknowledged.