Dowel bars are used in the construction of jointed concrete pavements to provide load transfer, which is vital to long performance. Misaligned or improperly placed dowels may cause poor joint performance that would lead to pavement distresses, such as cracking, spalling or faulting.
Dowel bar misalignment can be categorized into five generalized categories: horizontal translation, vertical translation, side shift, horizontal rotation and vertical rotation. Depending on the type of misalignment, the impact can individual dowel bar effectiveness or globally affect free joint movement.
Different agencies have adopted different standards with regards to dowel bar alignment, tolerances for misalignments and methods of quality assurance verification. Several types of non-destructive testing equipment of are used to measure dowel and tie bar alignment in concrete pavement joints. The MIT-SCAN device, a magnetic imaging tomography scanner, and Ground Penetrating Radar (GPR) are the most common devices for measuring the position and alignment of dowel bars for quality assurance or forensic purposes.
This paper provides an overview of the usage of dowel bars in jointed concrete pavements, a review of current dowel bar tolerance standards for a sampling of Canadian and US jurisdictions and a detailed description of the state-of-practice for dowel bar alignment evaluation with North American agencies.