Poor-quality longitudinal construction joints often contribute to the poor performance of hot mix asphalt (HMA) pavements. Traditionally, the longitudinal construction joints are evaluated in terms of in-situ density measurements obtained through coring at five different locations across the joint. This approach is destructive, time consuming which limits the implementation of the quality assurance and quality control (QA/QC) plan to ensure the construction of good quality longitudinal joints in asphalt pavements. To address this problem, an innovative non destructive technique (NDT) for condition assessment of the longitudinal construction joints in asphalt pavements has been developed at the University of Waterloo in collaboration with the Ministry of Transportation, Ontario. This method involves the use of ultrasonic surface waves to assess the relative condition of the longitudinal joints in comparison to the condition of the adjacent good quality joint-free asphalt pavement surface. In this approach, novel experimental and signal processing techniques are used to minimize the variability associated with unknown limitations of wave source and receivers, wave path characteristics, and the effects of source/receiver coupling used for measuring wave attenuation across the joints. Based on the findings of the laboratory study, a field testing protocol was developed involving two types of NDT tests. A pilot field study was conducted to evaluate the suitability of the test protocol developed for field applications. Presented in this paper are the results of the pilot study which indicates that the proposed NDT test method is a viable and effective alternative to density measurements for field assessment of the longitudinal joints in asphalt pavements.
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