Hydraulic properties of asphalt concrete
This research has applied standard unsaturated flow models and laboratory methods common to soil analysis, to characterize the hydraulic properties of asphalt concrete. Wetting and drying water characteristic curves were measured for six asphalt concrete cores. From the water characteristic curves, it is proposed that asphalt concrete may require bi-modal sigmoid curves to represent drying. It is also proposed that asphalt concrete is a hydrophobic material during wetting and a hydrophilic material during drying. The wetting curves developed for the asphalt concrete were fit with power functions, while the drying curves follow a sigmoid curve as expected for a wettable material. Unsaturated hydraulic conductivity for wetting and drying was predicted according to Mualems (1976) solution. The unsaturated hydraulic conductivity of three asphalt cores was measured using an original method in the laboratory. The results of the measured unsaturated hydraulic conductivities were used to support the predicted values. The unsaturated hydraulic conductivity of the asphalt concrete during wetting was described with simple power functions; very similar to ones proposed for soils, but with a different range of exponents. The predicted values of unsaturated hydraulic conductivity during wetting, for some of the cores, fit very well with an equation derived by Parker (1989) to describe the unsaturated hydraulic conductivity of immiscible fluids. Nieber (2000) proposed that Parker's equation could be used to describe the unsaturated hydraulic conductivity of water on hydrophobic materials. This research has shown that the asphalt concrete follows Parker's equation during wetting, which supports the predictions of unsaturated hydraulic conductivity and that asphalt concrete behaves as a hydrophobic material during wetting.'
Asphalt concrete--Moisture, Asphalt concrete--Drying, Asphalt concrete--Permeability, Soils--Analysis--Methodology.
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