HAL Group Inc. was retained by WSP on behalf of Public Services and Procurement Canada (PSPC) to carry out a structural investigation of the concrete counterweight of the LaSalle Causeway Bascule Bridge in Kingston, Ontario. Delamination and disintegration had been found in earlier cores, so this Phase 1 investigation was designed to establish the condition of the counterweight and whether a more extensive examination could proceed safely.
VISUAL INSPECTION AND HAMMER SOUNDING
The cladding around the counterweight was removed and later reinstated so the full concrete surface could be visually inspected and hammer sounded. Unsound areas were marked on site, and any loose concrete was reported to PSPC for immediate attention.
GPR SCANNING
Ground-penetrating radar (GSSI StructureScan Pro, 2000 MHz antenna) was used at test locations to map the reinforcing bars and wire mesh near the exterior faces before coring.
FULL-DEPTH CORING AND BOREHOLE SCOPING
Deep cores were drilled to the centre and full depth of the counterweight, to about 3 m, while avoiding the internal reinforcement and the steel counterweight truss. Each borehole was examined with a fibre-optic endoscope to verify the integrity of the concrete and the truss.
ROPE ACCESS AND TEST PITS
Rope access was set up at the top of the counterweight to open test pits exposing the steel beam. Section loss on exposed reinforcement was measured, the counterweight geometry was recorded, and the test pits were repaired with a Sika repair mortar.
LABORATORY TESTING
The extracted cores were tested for compressive strength, carbonation depth and petrographic condition to characterise the concrete inside the counterweight mass.
WORK AT HEIGHT UNDER FULL CLOSURE
Work was carried out from two boom lifts under a full bridge closure, coordinated with the City of Kingston, MTO, Parks Canada and emergency services, with pedestrians escorted through the site.
