Volume 21, Issue 1 (January 1993)
The Effect of Moisture on Laboratory-Prepared Asphalt Mixtures
This paper presents the results of a laboratory study conducted to examine the water-induced damage of compacted and loose asphalt-aggregate mixtures from Riyadh, Saudi Arabia. One asphalt cement and two typical aggregate sources (A and B) were used to prepare asphalt mixtures. Test methods used included the Marshall stability ratio, the wet-dry indirect tensile test (Lottman). and coating and stripping tests of uncompacted mixtures (ASTM D 1664, Test Method for Coating and Stripping of Bitumen-Aggregate Mixtures, and ASTM D 3625. Test Method for Effect of Water on Bituminous-Coated Aggregate-Quick Field Test).
The test results have shown superior performance of mixtures prepared from Source A aggregate in comparison with Source B Differences in physical properties of the fine fraction between the two sources appear to be responsible for the noted difference in behavior However, mixtures with water susceptible aggregate (Source B) have exhibited improved performance when natural sand. used routinely in combination with crushed sand, is reduced or eliminated.
The partial replacement of the crushed limestone filler by cement or lime had positive effects on performance of water-susceptible mixtures. Distinct improvements in 24-h Marshall stability were exhibited when 2% hydrated lime was added.
Based on the results, the test methods deployed in this study appear to do a reasonable job in detecting moisture-susceptible pavement mixtures and in evaluating the relative effectiveness of additives in minimizing water damage potential.