Project Type: Concrete Restoration, Precast Systems, and Waterproofing
Campus Cooling Tower Concrete Repairs, Pre-Cast Façade Repairs and Basin Waterproofing System Replacement
Issue
Vital Structures was hired to evaluate deterioration of the concrete frame structure supporting four (4) Cooling Towers as part of a University Campus Central Utility Plant. The waterproofed concrete roof slab (which serves as the ‘basin’ water collection slab below the cooling towers) and exposed concrete beams and columns exhibited severely corroded steel reinforcing, spalled concrete falling to the deck below, deteriorated pre-cast façade panels and steel support clips.
Overhead Girder Spall Repair & Corroded Reinforcing Bars.
Formwork and supplemental reinforcing for overhead repair.
Polyurea hybrid detail coating transitions completed for placement of new wall panels.
Diagnosis
With the assistance of a qualified contractor, Vital Structures performed destructive test cuts and removed core samples for petrographic analysis of the existing concrete. The evaluation concluded that the existing waterproof coating system had far exceeded its serviceable lifespan, locations of the existing structure had areas of spalled, leached concrete and poor consolidation. Corrosion and spalling were also widely related to poor securement of the reinforcing steel during original construction, causing concrete cover to be as little as 1/8”. Precast façade panel steel clips and miscellaneous steel framing needed limited replacement and restoration at all four (4) cooling towers and the adjacent screen walls.
Our Solution
Vital Structures was contracted to provide the owner with a design for restoration of the existing reinforced concrete structure and miscellaneous steel supports. The design included concrete repair at areas where the existing concrete was found to be delaminated or poorly consolidated, replacement of pre-compressed foam expansion joint seals, and replacement of the concrete roof deck waterproofing coating system with a chemical resistant Polyurea hybrid coating system. Chemical analysis of the cooling tower water was performed to confirm compatibility of coating systems. Additionally, Vital Structures provided a design for replacement of the existing precast wall panel support brackets, as the existing were found to be severely corroded.
Supplemental brackets for pre-cast concrete facade panels.
Result
The Owner required that the repair project be completed during the Winter season while the Cooling Towers were not operational. The project has been phased to accommodate Cooling Tower motor replacement, piping replacement and other mechanical upgrades in parallel with the structural/building envelope repairs. Transitional polyurea hybrid coating systems were placed at the rising walls in Phase 1 and 2 to allow tie-in of the balance of the basin slab without removing wall panels. Phases 1 and 2 (Winter 2021 and 2022, respectively) were completed on-time and within the owner’s budget.
