**Appendix A**

In that previous study, the data analytical process to obtain Equation (1) progressed as follows:

1. Each pair of (CS, ACP) data (i.e., ACP stands for accumulated charge passed for RCP) was treated as a data point (entry), considering the three testing time points (in terms of #days = 28, 56 and 91) and the 12 mixture portfolios of the concrete sample all together. This yields a data table of two variables, containing the 36 data points.


From the above experiment, the last SLR model in step (5) can serve as an accurate (or, accurately calibrated) predictor when one knows a concrete sample's CS value and would like to postulate the value of ACP that connotes the RCP of the sample. As CS is usually treated as a 'hardened mechanical property' but RCPT is usually a 'durability property' for the high-performance concrete (HPC) materials, and as this process has revealed a relationship between two experimental variables from two parametric categories, such a predictive model should be worthy of note.
