DEVELOPMENT AND EVALUATION OF THE STRATEGIC HIGHWAY RESEARCH PROGRAM MEASUREMENT AND ANALYSIS SYSTEM FOR INDIRECT TENSILE TESTING AT LOW TEMPERATURES

Abstract

The indirect tensile testing mode is a practical method for obtaining tensile properties of bituminous mixtures from cylindrical specimens. An indirect tensile creep testing and analysis system is shown analytically to be superior to conventional methods in obtaining fundamental properties of asphalt mixtures at low temperatures in a previous study. Before extensive testing of a wide range of mixtures, however, the ability of the system to obtain accurate, reliable results was unknown. Since the introduction of the new measurement and analysis system, hundreds of field cores and laboratory compacted specimens have been tested and analyzed. Improvements to the system resulting from the testing experience are described, including how analyses of data collected from these tests were used to evaluate the accuracy of the system. Poisson's ratio values obtained with the new system were found not only to be reasonable but also necessary for the accurate determination of creep compliance of the asphalt mixtures tested--a result consistent with analytical findings. In addition, creep compliances obtained from mixtures of well-known components were found to agree with expected values and trends. Input of properties measured on 20 field sections with the new system into a mechanics-based thermal cracking model resulted in accurate predictions of thermal cracking in the field. The measurement and analysis system presented is part of the test selected by the Strategic Highway Research Program to support new mixture specifications for thermal cracking; it has been incorporated into the SUPERPAVE software.