This synthesis will be of interest to pavement designers, construction engineers, maintenance engineers, and others interested in avoiding or limiting moisture damage in asphalt concrete. Information is provided on physical and chemical explanations for moisture damage in asphalt concrete, along with a discussion of current practices and test methods for determining or reducing the susceptibility of various asphalt concrete components and mixtures to such damage. Moisture damage in asphalt concrete is a nationwide problem which often necessitates premature replacement of highway pavement surfaces. This report of the Transportation Research Board describes the underlying physical and chemical phenomena responsible for such damage. Current test methods used to determine the susceptibility of asphalt concretes, or their constituents, to moisture damage are described and evaluated. Additionally, current practices for minimizing the potential for moisture damage are examined.

Procedures for evaluating the moisture susceptibility of asphalt mixtures were compared by performing them on mixtures having a known history of susceptibility. Data included the retained ratios, visual stripping, mechanical values (tensile strength, stability, etc.), saturation, and swell. The most promising procedures appeared to be the NCHRP 246 and NCHRP 274.

This report summarizes the results of determining the moisture susceptibility by the primary test methods: (a) Original Lottman Method. (b) Modified Lottman Method (Tex-531-C); (c) Tunniclif f-Root Method; and (d) Boiling Test (Tex-530-C). Comparisons were made between the laboratory mixtures, plant mixtures, and cores obtained from the field test sections to determine the effectiveness of the various antistripping additives and to evaluate the various methods for measuring that effectiveness.