Utilization of Foaming Technology in Warm-Mix-Asphalt Mixtures Containing Moist Aggregates

Abstract

The objective of this study was to conduct a laboratory investigation of moisture susceptibility and rutting resistance of warm-mix asphalt (WMA) mixtures containing moist aggregates by using a foaming technology. Gyration number of various samples, indirect tensile strength (ITS), tensile strength ratio, rut depths of dry and conditioned specimens, and deformation (flow) were measured for all mixtures. The experimental design included two aggregate moisture contents (0 and ∼0.5% by weight of the dry mass of the aggregate), two lime contents (1% and 2% lime by weight of dry aggregate), one liquid antistripping agent (ASA) and non-ASA, three foaming water contents (2, 3, and 4%) with control, and two aggregate sources. A total of 42 mixtures were used and 420 specimens were tested in this study. The test results indicated that the aggregate source significantly affects the ITS and rutting resistance regardless of the foaming water content, ASA, and aggregate moisture content. In addition, the ITS and rut depth of some foamed mixtures containing moist aggregate satisfies the demand of pavement performance without additional treatment, although some mixtures need a completely dry aggregate or additional treatments. The mixture with various hydrated lime contents exhibited similar rutting and moisture resistance under dry and wet conditions. The liquid ASA used in this study is not recommended for use in foaming WMA mixtures with moist aggregates, because it is sensitive to moisture.