Structural pavement monitoring with non-destructive measuring devices

Experiences from a pilot project in Germany

Resumé

Within the last 20 years, Germany’s federal road network of 53,000 km has
become the centre of transit road freight transport in Europe. As a large part of the network is
now about 30 to 50 years old, a systematic pavement and maintenance management becomes
more and more essential for road authorities.
The existing German pavement condition monitoring and assessment and Pavement
Management System (PMS) focuses on measured surface characteristics like longitudinal and
transverse profile, skid resistance and visual damages like cracking, spalling, patching,
bleeding and is conducted in a four year cycle on the entire federal road network. A pavement
condition rating based on these surface characteristics is calculated using a standardised
procedure. No account is taken for structural bearing capacity and often there is poor
knowledge about the pavement structure, layers and thicknesses. As Falling Weight
Deflectometer (FWD) deflection measurements and coring are suitable measures for project
level assessments and require lane closures, there is a growing demand for Non-Destructive-
Testing (NDT) methods on network level at highway traffic speed without traffic disruptions.
To overcome the lack of knowledge about the structural condition and the need to detect
structural pavement deteriorations, the German Federal Highway Research Institute
(Bundesanstalt fuer Strassenwesen - BASt) conducted a project where NDT systems operating
at traffic speed of 80 km/h like the Ground Penetrating Radar (GPR) and the Danish Traffic
Speed Deflectograph (TSD) performed concerted measurements on selected highway and
trunk road sections. The testing was supplemented by FWD measurements and core samples.
In the following, an overview over the state-of-the-art in pavement condition monitoring
and the results of NDT measurements will be given as well as an assessment of different
structural pavement parameters. The observed problems and shortcomings and the advantages
and possibilities of the different techniques for structural pavement condition assessment will
be addressed and discussed.