Effectiveness of Antistripping Additives. Volume 1: Fid-Bau Portal

Effectiveness of Antistripping Additives. Volume 1

J. W. Shute / R. G. Hicks / J. E. Wilson / L. G. Scholl

Volume I of the report summarizes the findings on the extent of stripping in 32 Oregon DOT projects and discusses the significant findings from a literature review. Of the 32 projects, 10 had not used an asphalt or aggregate antistripping additive, 19 contained lime-treated aggregate, and 3 contained asphalt treated with an amine-type antistripping additive. These projects range in age from 1 to 9 years. The percent of aggregate coated wth asphalt, which was used to determine if a project was stripping, was established from breaking and visually evaluating core samples taken from each project site. Using the criteria that a coating less than 85% classified a project as stripping, the following results were obtained: 7 of 10 projects without an additive, 5 of the 19 lime-treated aggregate projects, and 2 of the 3 amine-treated asphalt projects were identified as stripping. The conclusion is that lime treatment of aggregate has proven effective in reducing the moisture susceptibility of an asphalt mixture. In addition, a review of mix design test values for the index of retained strength (IRS) (AASHTO T-165) and resilient modulus (Mr) test indicates the IRS test does not reliably predict moisture susceptible mixtures. The Mr test did provide a better indication of moisture susceptible mixtures. This assessment is based on a limited amount of data and is not statistically based; therefore, the results may change with further information. Volume II presents complete literature review.