Project Description

Hollow Core Repair Outline

Restruction Corporation completed a project for Northern Arizona University that included repair of cantilevered hollow core planks. The planks act as walkways for the upper level of student housing located on campus. Reestablishing the structure of the hollow core planks required unique concrete formwork that was designed by Restruction Corporation specifically for this project. The finished project included updated handrail detailing to extend the service life of the repaired concrete.

Concrete Deterioration & Rebar Corrosion

The McDonald Hall student-housing complex experienced handrail failures along the elevated walkways. Concrete deterioration around the bolted handrails loosened the handrails from their position. Removal of the handrails revealed corrosion in the structural hollow core element in the walkway. Concrete deterioration and rebar corrosion were found to be widespread throughout the hollow core planks.

Concrete Excavation

The concrete topping was removed from the hollow core planks to expose the top of the structural elements. Restruction excavated the delaminated and spalled hollow core planks, tracking corrosion back to clean reinforcing rebar and to solid undamaged concrete. Reinforcing steel in the hollow core was found to have insufficient cover at the perimeter of the elements. Restruction Corporation, with permission from the structural repair engineer, cut the reinforcing steel back 2″ to allow for adequate cover at the perimeter of the hollow cores.

Concrete Formwork

Using 4″ PVC pipe and smooth-faced plywood, Restruction formed the hollow cores to match existing hollow core planks. Once concrete formwork was completed, our team pumped a fluid concrete repair material into the repair cavities. This grouting established composite action between the hollow core planks. Proper curing was achieved, once forms were stripped and repairs were cleaned, to allow for the CORE Construction to finalize the remainder of the project.