Selection of Rapid Index Tests and Criteria for Concrete Resistance to Chloride Penetration

Concrete, especially for improved durability, is typically specified with prescriptive provisions. More recently there has been increasing interest in evolving towards performance-based specifications, both within state highway agencies and industry. One of the challenges in successfully implementing performance-based specifications is using test methods and criteria for concrete durability that can reliably provide the expected service life. The National Ready Mixed Concrete Association has been engaged in a state pooled fund research project to propose performance criteria for concrete that will be resistant to penetration of chlorides, cycles of freezing and thawing, and sulfate attack. This paper summarizes results pertaining to penetration of chlorides. Chloride penetration was determined by the apparent chloride diffusion coefficient test (ASTM C1556). Following initial curing, specimens were subjected to either immersion in chloride solution as required by C1556 or to a cyclic wetting and drying exposure to a chloride solution. Measured apparent chloride diffusion coefficients were correlated with results of rapid index tests that provide an indication of transport characteristics of concrete. These tests included the rapid chloride permeability, rapid migration, conductivity, absorption, and initial and secondary sorptivity. A set of rapid index tests and criteria that can more reliably classify mixtures based on their resistance to chloride penetration are proposed.