Evaluation of Surface Resistivity Measurements as an Alternative to the Rapid Chloride Permeability Test for Quality Assurance and Acceptance

Many entities currently use permeability specifications in portland cement concrete (PCC) pavements and structures. This project investigated the use of a surface resistivity device as an indication of concrete’s ability to resist chloride ion penetration for use in quality assurance (QA) and acceptance of concrete. ASTM C 1202 tests were conducted at various ages with the corresponding surface resistivity test and the results were compared. Samples tested included: field prepared samples, samples from the ongoing 09-4C: Evaluation of Ternary Cementitious Combinations project, and samples from the laboratory test matrix. The laboratory test matrix tested several mixtures common to Louisiana at a wide range of water to cementitious materials ratios to evaluate the range of the surface resistivity meter. The surface resistivity measurements correlate well with rapid chloride permeability measurements across a wide range of permeability values and sample testing ages. Suitable correlations were found to exist between both the 14-day and 28-day surface resistivity values and the 56-day rapid chloride permeability values. The standard deviation of the surface resistivity meter results are usually less than 3 k(omega)-cm compared to 300 to 500 Coulombs from the rapid chloride permeability test. The surface resistivity meter was also able to identify great differences in water to cementitious materials (w/cm) ratios for the same mixtures. The cost benefit analysis showed that implementation of the device will save the Department about $101,000 in personnel costs in the first year. It is estimated that contractors will save about $1.5 million in quality control costs. The cost benefit ratio for this project is estimated to be about 15. LADOTD TR Procedure, TR 233, has been developed and implementation of the surface resistivity device has begun.