Numerical modeling of multi-ionic transport with/without electrical field applied in sound and microcracked ordinary and ultra-high-performance fiber-reinforced concrete

This study focuses on developing a numerical model for the multi-ionic transport process in ordinary concrete (OC) and ultra-high-performance fiber-reinforced concrete (UHPFRC) in its sound and microcracked states. The theoretical background of multi-ionic transport was reviewed from the literature, and extended governing equations considering the influence of microcracks was proposed. The mathematical equations accounting for the coupling effects of the applied constant electrical field were first implemented in a 1D framework (MATLAB) considering idealized and simplified boundary conditions, and then in a 2D framework (TransChlor2D) considering more complex boundary variations. A unique program for detecting the microcracking distribution and modeling it with the transport process was also developed and integrated into TransChlor2D. The transport parameters and coupling effects in the numerical model were calibrated using extensive experimental data from the literature, including an innovative bending-migration test on a microcracked UHPFRC beam, measured by the digital image correlation (DIC) method. Finally, the integrated TransChlor2D model was used to simulate two accelerated migration tests on UHPFRC: one for the undamaged case and the other for the damaged case. The simulations accurately predict the influence of the distribution and opening of microcracks on the multi-ionic transport process and demonstrate the excellent capacity of the proposed model to capture the ion concentration distribution profiles in UHPFRC.