TEST METHODS TO PREDICT MOISTURE SENSITIVITY OF HOT-MIX ASPHALT PAVEMENTS

The work conducted through the years toward development of moisture damage tests is summarized in this paper. Moisture damage has been a major concern to asphalt technologists for many years. Attempts to develop laboratory tests to distinguish between good- and poor-performing mixes in regard to stripping date back to the 1920s. The tests for identifying the moisture damage potential of an asphalt-aggregate mixture can be classified into two major categories: those on loose mixtures and those on compacted mixtures. The static immersion and the boil test, both conducted on loose mixtures, were among the first tests introduced to the paving industry. This was followed by introduction of the immersion-compression test in the late 1940s. This test was conducted on compacted specimens and was the first test to become an ASTM standard in the mid-1950s. Research in the 1960s brought considerable awareness to asphalt pavement technologists of the significant effects of climate and traffic on moisture damage. The significance of these factors was emphasized through the work of researchers such as Johnson (1969), Schmidt and Graf (1972), Jiminez (1974), Lottman (1978), and Tunnicliff and Root (1982). The Superpave system, the product of the Strategic Highway Research Program which was completed in 1993, adopted the standard test method of AASHTO T283 as the required test for determination of the risk of moisture damage. Some agencies have reported problems with this test in terms of correlation between the laboratory results and field observations. Today, it remains a challenge to asphalt pavement technologists to develop a highly reliable and practical test procedure for determination of moisture damage. An important consideration in development and acceptance of a test procedure for moisture damage should be calibration of the test to the conditions for which it will be applied. Some tests have been calibrated and implemented on a local basis (a region within a state). No test has been successfully calibrated and implemented across a wide spectrum of conditions. Reasons for this have been lack of correlation with field performance, a lack of good field performance databases, and problems with the tests such as variability and difficulty of operation.