Abstract Manager

Dowel bars are used in the construction of jointed concrete pavements to provide load transfer across transverse joints, which is a vital factor in achieving good long-term performance. Misaligned or improperly placed dowels may cause poor joint performance, which can lead to the development of distresses, such as cracking, spalling or faulting. Many agencies include requirements for the verification of dowel bar alignment at the time of construction to ensure that any misalignments can be immediately repaired.

This paper presents a forensic case study involving the novel use of two types of non-destructive testing equipment performed on an Ontario roadway to evaluate the severity and extent of errors in dowel bar placement known to have been made during a concrete paving project.  Specifically, the MIT-SCAN device, a scanner employing magnetic imaging tomography principles, and a step-frequency array Ground Penetrating Radar (also known as 3D GPR) were used to evaluate the position and alignment of the dowel bars in hundreds of transverse joints.

Using the results of the two methods of non-destructive evaluation, conformance with project construction specifications was determined and a repair plan to cost-effectively mitigate the non-compliances was developed.  The study’s outcome was specific remediation recommendations, including slab replacements, dowel bar sawcuts and dowel bar retrofits, executed to the satisfaction of both the owner and the contractor.