**6. Conclusions**

This paper develops a new model for predicting the effective concrete diffusivity which uses the apparent diffusion along with binding, age, temperature, carbonation, and free chloride effects. Then, the paper develops an algorithm to predict the free chloride concentration at different depths in the concrete. Different OPC and SCMs mixes prepared in the lab determined the experimental binding values which are used in the algorithm. Chloride profiles were measured on two sets of concrete blocks: one exposed daily to seawater, and the other exposed to harsh weather along the coast for two years at the east coast of Saudi Arabia. The proposed transport model proves reliability by comparing its results to the exposure site results. To completely decouple the transport model from any experimental values, the paper introduces a new binding model which relies on the oxides of cements and level of chlorides. The binding model introduces itself in the transport model, and the results compare well to the exposure site results, and the results of the transport model which uses the experimental binding data. The following remarks conclude the work:


The transport model predicts the chloride profile effectively using the new proposed binding model. Statistical analysis evidence the accuracy of the proposed model, using experimental binding data, by recording β-coefficient and R2 of 1.00 and 0.94 for coastal zone, and 0.89 and 0.89 for tidal zone; while when using the new binding model, statistical analysis show β-coefficient and R<sup>2</sup> of 0.9 and 0.93 for coastal zone, and 0.87 and 0.83 for tidal zone.

**Author Contributions:** Methodology, Project administration, Supervision; Validation, Resources, Writing—Review & editing, A.A.E.F.; Methodology, Software implementation Writing—original draft, M.O.A. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research is funded by the Deanship of Scientific Research (DSR) at King Fahd University of Petroleum and Minerals (KFUPM) through project no. IN161050.

**Acknowledgments:** The authors acknowledge the support provided by the Deanship of Scientific Research (DSR) at King Fahd University of Petroleum and Minerals (KFUPM) for funding this work through project no. IN161050.

**Conflicts of Interest:** The authors declare no conflict of interest.
