Modification of ASTM C666 for Testing Resistance of Concrete to Freezing and Thawing in Sodium Chloride Solution

About the report:

Since 1961 the Research Council has used equipment manufactured by Conrad, Inc. for exposing concrete specimens to rapid cycles of freezing and thawing. In addition, the Materials Division of the Virginia Department of Highways and Transportation sends to the Research Council specimens of concrete mixtures and related materials not previously used in the Department's construction when freezing and thawing tests are required as part of the Department's acceptance procedures. The Council’s freezing and thawing procedures are based upon ASTM Designation C666 “Standard Test Method for Resistance of Concrete to Rapid Freezing and Thawing", Procedure A (freezing and thawing in water), except that surrounding the specimens is a 2% solution of NaCl rather than water. Prior to exposure, specimens are moist cured for 14 days and air dried for 7 days. Based upon about 17 years of experience in the use of this approach at the Council, the following criteria have been established for judging acceptability. Weight loss, maximum at 300 cycles 7% Surface factor, maximum at 300 cycles 3% Durability factor at 300 cycles 60% A limited evaluation of this procedure was made using NaCl solutions with concentrations of 4%, 3%, 2% and 0% (water). Concretes of three levels of expected durability were tested. Based on these tests the following conclusions were drawn. 1. Freezing and thawing of specimens using the procedures of ASTM C666 as modified to use 2% NaCl solution as the surrounding medium rather than water is more severe and more discriminating than using water as required by the standard method. 2. Minor variations of salt concentration likely to be encountered during the progress of the testing do not significantly affect the results. 3. The period of drying between moist curing and exposure to freezing and thawing in an NaCl solution significantly improves the indicated performance. 4. Based upon ACI recommendations for durable concrete, the Council's current requirements for evaluating freezing and thawing resistance may be too lenient for concrete subjected to severe exposure conditions.

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