Acoustic assessment of pavement structural health

Determining the in-situ asset condition of a pavement is necessary to programme pavement renewal and life extension work. Concrete pavements can develop different forms of structural faults including variable types of cracking, spalling, slab rocking, corrosion of reinforcement and softening of subgrade. This paper reports on work designed to detect deterioration before it manifests at the surface, in the form of defects that would only then have been picked up through visual inspection. The approach involves non-destructive, real-time monitoring with a Close Proximity (CPX) trailer, utilising both microphones and a tri-axial accelerometer. Dependent on its condition, the concrete pavement and subgrade will respond differently to traffic induced acoustic noise and vibration from the tyres. The variability in response is analysed using specialist spectral and acoustic signal processing techniques, to detect any internal and external cracks in the pavement, as well as to assess the condition of the subgrade. By characterising the pavement into uncracked, lightly cracked and heavily cracked areas, the collected data is used to map crack locations and their severity. Repeated surveys will allow temporal changes to be monitored and its rate of decay to be predicted, enabling the scheduling of renewal and life extension to be optimised.