Corrosion Propagation Monitoring Using Galvanostatic Pulse on Reinforced Concrete Legacy Samples

Legacy samples were monitored. Outdoor exposed legacy samples were prepared in 1994 and have been subjected to wet/dry cycles with seawater during the wet part of the cycle. Two sets of samples were stored indoors: single rebar and three rebar specimens, these samples were prepared in 2016 and were subjected to accelerated chloride transport via a migration method at least two months after casting. The concrete composition of these samples was binary or ternary (see details in the body of the report). The indoor samples have various lengths of solution reservoir and the samples are stored in plastic bins that allow the moisture surrounding the specimens to remain above 80% RH. Although the notice to proceed was received August 2020, this report includes measurements performed February 2020 to August 2021 for the indoor samples, and August 2020 to August 2021 for the outdoor samples. Electrochemical measurements were performed using galvanostatic pulse method to monitor the legacy samples. The applied pulse current magnitude was initially 10 μA, but it was adjusted to either a smaller or larger magnitude depending on how much the rebar was polarized with the current on. Initially an anodic current was applied, but it was decided to change it to a cathodic current to minimize activation due to the galvanostatic pulse. Each measurement allowed to identify the rebar instantaneous open circuit potential (OCP), solution resistance (Rs), and polarization resistance (Rc). It was assumed that all rebars were corroding and the Icorr was calculated assuming a B constant of 26.1 mV (in the Stern-Geary equation). Ecorr vs. Icorr and Icorr vs. Rs correlations were prepared using three most recent measurements (i.e., with measurements made between April and August 2021). The findings of the Ecorr vs. Icorr correlations suggest that the slope is not the same for all sample groups, but they appear to confirm that all rebars are in an active state. It was observed that the Ecorr-Icorr value pairs of some rebars suggest less active state and deviate somewhat from the average slope. This observation is more pronounced on some outdoor samples than those exposed indoors. An interesting observation from the Icorr vs. Rs correlation corresponding to outdoor samples is that some rebars showed significantly smaller Rs with relative large Icorr values, these appear to correspond to rebars that now show cracks above the rebar.

Language

  • English

Media Info

  • Media Type: Digital/other
  • Edition: Final Report
  • Features: Appendices; Figures; References; Tables;
  • Pagination: 51p

Subject/Index Terms

Filing Info

  • Accession Number: 01891794
  • Record Type: Publication
  • Report/Paper Numbers: Project ID: 2020-FAU-02
  • Files: UTC, NTL, TRIS, ATRI, USDOT
  • Created Date: Aug 29 2023 4:29PM