5.3.5 Half Cell Potential (HCP) Similar to ER, HCP technology has long been used as the indicator of corrosion progression inside concrete specimens. Equally, the condition index, with respect to corrosion activity, was defined as HCP index =
𝐴90% sound × 100 + 𝐴𝑇𝑟𝑎𝑛𝑠𝑖𝑡𝑖𝑜𝑛 × 50 + 𝐴90% Corrosion × 0 𝐴𝑇𝑜𝑡𝑎𝑙
(15)
where 𝐴90% sound, 𝐴Transition , and 𝐴90% corrosion = areas with HCP in the ranges of >200 mV, −350 to −200 mV; and < − 350 mV, respectively. Figures 54 and 55 plot the variation of condition index and damage index for the different rounds of HCP data collection efforts from BEAST and compare it against the performance curve of the representative bridge. As is clear from both figures, the HCP measurements strongly indicate that corrosion progresses within the deck components as the BEAST specimen is subjected to increased levels of live loads, brine solution, and freeze-thaw cycles.
Figure 54. Condition index calculated based on HCP measurements
