Field estimation of oxidative ageing in asphalt concrete pavements using non-collinear wave mixing

To facilitate the estimation of the state of oxidative ageing of the top material layer of asphalt concrete pavements, a two-dimensional 'oxidative-ageing non-linear characterisation curve', which uniquely illustrates the non-linear response of asphalt concrete mixtures with increasing levels of oxidative ageing, is presented. Because longitudinal and shear velocities and the corresponding attenuation values in asphalt concrete are dependent upon its level of oxidative ageing, and because these properties are needed for non-collinear wave mixing measurements, a methodology is presented to estimate these properties from the pavement surface only. Results from a blind study are also presented, which indicate that the proposed approach can successfully estimate the level of oxidative ageing from measurements taken from the pavement surface.