Wastewater Concrete Repair with Chemical Strengthening & Carbon Fiber – Murrysville, PA
Project Overview
At the Meadowbrook Road Sewage Treatment Plant in Murrysville, Pennsylvania, deteriorated concrete was identified along the upper concrete bands surrounding the nitrification towers. United Structural Systems (USS) completed the repair using a coordinated SRS system that addressed damaged concrete, corrosion at the reinforcing steel, and structural strengthening of the repaired bands.
The repair was developed around the existing conditions so the damaged areas could be restored and strengthened without replacing the affected concrete components.
The Challenge
The concrete bands exhibited cracking, localized spalling, and areas of deterioration associated with corrosion of the reinforcing steel. Before repair work began, the concrete was sounded with the engineer of record to identify unsound material and establish the limits of repair.
Because the carbon fiber reinforcement would rely on a sound, well-prepared substrate, loose and deteriorated concrete first had to be removed and the exposed reinforcing steel treated before rebuilding the damaged sections.
Repair Approach
USS removed unsound concrete and prepared the exposed reinforcing steel and surrounding substrate. SRS-4100 Steel Guard was used as part of the corrosion treatment for the reinforcing steel, while SRS-4000 Concrete Guard was applied to the concrete to reduce porosity and improve the durability of the repair substrate.
Voids and damaged areas were rebuilt with SRS-2000 Structural Repair Paste as required to restore the profile of the concrete bands and provide a suitable surface for bonded reinforcement.
The repaired bands were then strengthened with SRS-600UNI unidirectional carbon fiber fabric bonded with SRS-1000 Structural Epoxy Adhesive. The carbon fiber was installed around the perimeter of the repaired concrete bands in accordance with the approved strengthening layout. The project specification also included direct pull-off bond testing to verify adhesion of the bonded system.
Completed Repair
The completed rehabilitation combined concrete restoration, corrosion mitigation, substrate treatment, and CFRP strengthening into one repair sequence. By addressing the deteriorated concrete before installing the carbon fiber reinforcement, the repair preserved the existing nitrification tower components while providing a strengthened and more durable concrete band.
This project is representative of the type of repair approach that can be evaluated for wastewater tanks, treatment basins, clarifiers, and other concrete process structures where deterioration and structural strengthening needs occur together.
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