Extensive laboratory testing and long-term field experience have demonstrated conclusively that concrete must be properly air entrained if it is to resist the action of freezing and thawing. For more than 50 years, neutralized Vinsol resin has been used effectively for air entrainment. However, other air-entraining admixtures have been introduced in recent years and their use has increased primarily because of the higher cost and limited supply of Vinsol resin. Current test methods, such as AASHTO T 157, Air-Entraining Admixtures for Concrete, set limits on the effects that any given air-entraining admixture may exert on certain properties of the fresh and hardened concrete mixture in comparison with a similar concrete mixture containing a standard-reference air-entraining admixture such as neutralized Vinsol resin. However, experience with bridge decks, pavements, and other highway structures that were constructed with concrete mixtures incorporating newer air-entraining admixtures indicated that current test methods do not accurately assess the impact of these newer admixtures on concrete properties and durability. Thus, research was needed to address the issues associated with the use of these air-entraining admixtures in highway concrete and to develop recommendations to help improve specifications for air-entraining admixtures. Under NCHRP Project 18-10, “Procedures for Evaluating Air-Entraining Admixtures for Highway Concrete,” Construction Technology Laboratories, Inc., of Skokie, Illinois, worked with the objective of developing procedures for evaluating and qualifying airentraining admixtures for hydraulic cement concrete for highway applications. To accomplish this objective, the researchers conducted an extensive test program in which they examined the properties of concrete mixtures containing a variety of air-entraining admixtures and related these properties to freezing and thawing durability. Based on analysis of test results, the researchers developed a procedure for evaluating air-entraining admixtures that involves the testing of non-air-entrained concrete and concrete containing the airentraining admixture under simulated field conditions. Admixture evaluation is made by comparing the results from these tests against proposed evaluation criteria. The procedure includes two protocols: one for evaluating admixtures intended for use in highway pavements and the other for evaluating admixtures intended for use in highway structures. Finally, validity of the recommended procedure was confirmed by laboratory tests conducted on concrete mixtures containing five air-entraining admixtures with known performance records. The recommended test method and proposed acceptance criteria will provide a good indicator of the expected concrete properties and resistance to freezing and thawing and can, therefore, be used to evaluate air-entraining admixtures intended for use in highway pavements and structures. The test method will be particularly useful to highway agencies and is recommended for consideration and adoption by AASHTO as a standard test method. Appendixes A through C contained in the research agency’s final report are not published herein. These appendixes are accessible on the web as NCHRP Web-Only Document 101 at http://www4.trb.org/trb/onlinepubs.nsf. These appendixes are titled as follows: Appendix A: Literature Review and Survey; Appendix B: Foam Drainage and Infrared Test Results; and Appendix C: Detailed Test Results. (Author/publisher) This report may be accessed by Internet users at http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_578.pdf
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