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Evaluating Moisture Susceptibility of Asphalt Concrete Mixtures Through Simple Performance Tests

Moisture damage is a major cause of premature failure in asphalt concrete mixtures. Proper evaluation of moisture susceptibility is essential for preventing the deterioration of field mixtures. The AASHTO T 283 test method, also known as the modified Lottman indirect tension test procedure, was adopted by the Superpave® system as the required test for determining moisture damage and is currently the most widely used procedure for measuring moisture damage potential. However, this test method has two limitations: (a) its conditioning procedure does not include dynamic loading, which is different from actual field conditions, and (b) it uses strength, a parameter that is not directly used in pavement design, to determine whether unacceptable moisture damage will occur in the field. The objective of this study is to evaluate the moisture susceptibility of different asphalt mixtures with simple performance tests in conjunction with environmental conditioning procedures. AASHTO T 283 was conducted for conditioning levels of 0, 1, 3, and 6 freeze–thaw cycles and compared with results obtained from the dynamic modulus (E*) and flow number tests for the same conditioning levels. Results show that modification of AASHTO T 283 or the use of simple performance tests is a valid alternative for evaluating moisture susceptibility and may represent expected field performance better than the modified Lottman indirect tension test can. The advantages and disadvantages of each method need to be carefully considered before a new testing protocol is implemented.