DETECTING DELAMINATION IN A BRIDGE DECK UNDERSIDE

OBJECTIVES

TRACE was instructed to undertake a non-intrusive structural investigation of the underside of a bridge to assess the presence and severity of concrete delamination and the risk and extent of reinforcement corrosion within the bridge deck. The investigation was required to support maintenance planning and identify areas where targeted repair or further investigation would be justified.

SOLUTIONS

TRACE carried out an investigation from the underside of the bridge via the underbridge pathway. Approximately a 1.8 m wide strip along the south side of the deck soffit was accessible and surveyed during a single site visit.

TRACE deployed a combined non-intrusive workflow using ground-penetrating radar (GPR) and iCAMM™ corrosion mapping to provide both structural condition and deterioration insight. GPR was used to identify anomalies indicative of delamination and elevated corrosion risk, while iCAMM™ was used to assess the relative corrosion condition of the bottom layer of deck reinforcement across the surveyed area.

KEY FINDINGS

The investigation successfully identified:

• Areas of concrete delamination

• Zones of increased corrosion risk

• Relative levels of reinforcement corrosion

Delamination was detected at depths ranging from approximately 10 mm to 100 mm from the deck underside and categorised by severity and confidence. Corrosion mapping highlighted localised areas of higher corrosion intensity, including zones corresponding with visible staining and moisture ingress.

BENEFITS

The investigation was completed using fully non-intrusive methods, avoiding disruptive intrusive works while providing continuous corrosion mapping rather than isolated test locations. Clear categorisation of delamination depth and severity increased confidence in targeting future intrusive inspections and repairs, reducing uncertainty in maintenance planning. By combining GPR and iCAMM™, TRACE delivered a layered understanding of bridge deck condition, distinguishing where delamination is present, where corrosion risk is elevated, and where corrosion has already progressed. This enabled targeted, proportionate intervention rather than broad, assumption-led repairs.