Imaging and Parameterizing Moisture in Road Sub Course Using Time Domain Reflectometry

This paper presents the experimental results of using a non-invasive time domain reflectometry (TDR) sensor to image and parameterize the moisture content of basecourse materials used in road construction. Imaging, resulting from the amplitude losses of a pulsed signal travelling down TDR transmission lines, is found to produce excellent information on the relative changes in basecourse moisture content to a spatial resolution <;5 mm in the plane of the road surface. A simple model relating the volumetric moisture content to the TDR measured propagation time is shown to provide a consistent transform between the two. The experimental data also indicate that the smallest transform error of ~0.25% in volumetric moisture content is achieved when model coefficients are separately fitted for each of the two basecourse aggregate types tested.