Evaluation of Surface Resistivity for Concrete Quality Assurance in Missouri

This research evaluated a series of Missouri Department of Transportation (DOT) concrete mixtures to verify existing relationships between surface resistivity (SR), rapid chloride penetrability (RCP), and the AASHTO penetrability classes. Eleven mixtures that represented a range of currently allowable mixtures and several mixtures with potential use were produced in the laboratory. The classes of concrete mixtures included those used for paving, bridge deck, structural, and repair. The results showed an excellent correlation between SR and RCP that matched existing relationships provided by AASHTO and other state DOTs. The structural mixture containing 50% Class F fly ash had the best performance with very low chloride ion penetrability at 90 days. A ternary paving mixture with 20% Class C fly ash and 30% slag replacement for cement also demonstrated low penetrability as well as high compressive strength, with an average compressive strength value of over 9,000 pounds per square inch at 90 days. The two repair mixtures showed moderate to low penetrability readings and high early strength, consistent with their desired purpose. The extensive amount of SR testing (>4,500 tests) of 14 concrete mixtures at ages ranging from 3 h to 90 days by multiple laboratories, types of equipment, operators, and curing conditions verified the RCP. SR testing presents an opportunity to improve Missouri DOT concrete mixtures and specifications to increase durability without significant additional testing costs.