Integration of Moisture Sensitivity Testing with Gyratory Mix Design and Mechanistic-Empirical Pavement Design

Abstract

Moisture damage is one of the major problems that can be faced by a pavement during its design life. It can tremendously reduce a pavement's strength and consequently its life. The test predominately specified to evaluate the moisture sensitivity of an asphalt concrete mixture is the modified Lottman test, currently specified as AASHTO T283. The problem with this test is that it assists in minimizing the problem, but it does not provide an accurate estimate of the anticipated moisture damage and in some cases it provides false results. The methodology used in this paper utilizes mixture dynamic modulus test methods, which are complimentary to the mechanistic-empirical pavement design guide (M-E PDG), in evaluating moisture damage in asphalt concrete pavements. Dynamic modulus tests are performed on both moisture conditioned and unconditioned samples and used as input parameters in the M-E PDG for estimating pavement performance. The methodology was applied on two projects and the results were compared to the results achieved using the AASHTO T283 methodology and dynamic modulus test results. The dynamic modulus test results show consistency with AASHTO T283 in identifying moisture sensitivity of a mixture. This paper outlines a method for evaluating hot mix asphalt moisture susceptibility using dynamic modulus testing and is compatible with the proposed performance testing for accompanying Superpave volumetric mix design. The results of the proposed mixture dynamic modulus moisture susceptibility method can also be used in the new M-E PDG for evaluating the moisture susceptibility effects of the tested mixtures. This in part allows for the evaluation of this environmental effect in the M-E PDG.