Evaluation of Surface Resistivity Measurements as an Alternative to the Rapid Chloride Permeability Test for Quality Assurance PI: Tyson D. Rupnow, Ph.D., P.E. Co PI: Patrick Icenogle, E.I. Mark Morvant P.E. RAC Meeting July 2011
Background Permeability specifications required by LADOTD for LRFD designed bridges ASTM C 1202 most widely accepted test Surface resistivity test Florida DOTD study AASHTO round robin study (on-going) LTRC study Wider range of w/c ratios
Background ASTM C 1202 Sample preparation 2 days of ‘testing’ Equipment cost
Background Wenner Probe Much quicker Lower equipment cost Shorted curing time Portable!
Research Objectives Characterize surface resistivity of concrete produced at LTRC and in field conditions Characterize the rapid chloride permeability of the same specimens Comparative testing Caminada Bay Bridge Project I-10 Twin Spans Bridge Project LA 1 Bridge Project
Work Plan Measure surface resistivity and RCP on varying ages of samples Ages of 14, 28, and 56 days Sample size = 4 in. x 8 in. cylinders Over 220 test results Mixture ID w/c TIXXX 80TI-20CXXX 50TI- 50G120S XXX 90TI-10SFXXX 95TI-5SFXXX
Results – Overall Relationship
Conclusions SR measurements correlate well with RCP across a wide range of values and ages Deviations are low Able to identify great differences in w/cm User friendly Save $$$
Recommendations Test at 28-days of age Purchase 11 SR meters Training program Develop TR procedure Permeability Class 28-Day Surface Resistivity (kΩ-cm) High < 12 Moderate Low Very Low Negligible > 254
Cost:Benefit
Total cost of the research & Implementation Research: $102,878 Equipment Purchase: $30,000 (11 meters) Estimated 1 year savings DOTD - $96,000 Contractors: $1.5 million
Implementation Strategy Training Step-by-step of TR procedure and template Training video Hands on with equipment Automated template LTRC certification Demonstration Projects Equipment purchased for each district Cost/Benefit Validation Implementation Report