DETERMINATION OF ACCEPTANCE PERMEABILITY CHARACTERISTICS FOR PERFORMANCE-RELATED SPECIFICATIONS FOR PORTLAND CEMENT CONCRETE

The concrete strength has been measured for a long time; however, it is becoming increasingly desirable to the Florida Department of Transportation (FDOT) to have the ability to measure concrete's durability in addition. One test to assess durability of concrete is the Rapid Chloride Permeability (RCP) test. This test records the amount of charge passed through a sample in order to evaluate its permeability. The FDOT has the desire to make the transition from a prescriptive specification style to a performance-based specification. This research project consists of the determination of the RCP values of all classes of concrete that are specified in FDOT specifications. This goal was accomplished by taking concrete test cylinders from projects that were under construction during the study. Samples are divided by FDOT concrete class and then by composition, specifically their pozzolanic additives, for evaluation. Test value recommendations are made according to these categories. The RCP test has been around for approximately 20 years and is widely used. However, the test is labor intensive and therefore costly. For this reason, an alternative Non Destructive Test (NDT) called the Surface Resistivity test is being evaluated as a possible replacement. The Surface Resistivity test uses a Wenner 4-probe array and a small alternating current to make instantaneous readings. The readings are returned by a data acquisition unit as an indication of the concrete's ability to conduct current. This project also applied this test to the samples in order to reveal a relationship between the two tests (i.e., RCP and Surface Resistivity test) of which a good correlation has been shown. Values for Surface Resistivity as well as a table to aid in the interpretation of results have been provided. Lastly, recommendations for RCP test improvement are suggested in order to improve on the test until an appropriate alternative is arrived at and agreed upon.