Chamberlin's waterproofing team helped in restoring the Northshore Austin apartments in Austin, Texas. Chamberlin is honored to have collaborated with Wiss, Janney, Elstner Associates, Inc. as the consultant for the building and to have worked under general contractor Camp Construction. Chamberlin performed PT pocket repairs, elastomeric slab edge coating and concrete repair. Originally built in 2015, Northshore is a newly renovated high-rise in downtown Austin and reaches new heights in luxury living while offering modern finishes and upscale amenities.
During a pre-purchase assessment about three years after construction, debonded and missing PT anchorage patches and protruding tendon tails were observed on the building facade, garage interior slab ends and beam ends. As part of the investigation, samples of the existing patches were extracted for petrographic studies. No material degradation was found in the samples and there was negligible carbonation. However, the laboratory study found incomplete mixing, highly variable air content, variable water to cement ratio and mortar balls within the samples. Based on field observations and laboratory findings, it was concluded that the failures were likely caused by tendon tails that were left too long, resulting in improperly seated grease caps, large voids in the pockets and poor patch material quality.
The project involved repairing all defective PT anchorage pocket patches and the application of reinforced elastomeric coating system on all exposed slab edges. To assess the viability of a precast plug repair approach, field mockups were performed. The pockets requiring repair were limited in number relative to the total number of anchorages at the building and were generally widely spaced on the building exterior.
Failure of PT anchorage pocket patches is a common condition that can occur shortly after original construction and will worsen over time if not addressed. The failures compromise the corrosion protection of the PT system and create a potential falling debris hazard. To replace failed patches, trowel-applied and precast plug repairs are two approaches that have been successfully implemented. Performing mockups and petrographic studies during the repair design phase is important to assess project-specific conditions, develop repair procedures and ultimately select a repair approach.
Depending on the project, a combination of trowel-applied and precast plug repairs may be appropriate. For both repair methods, QA/QC during construction is critical to monitor the repair installation and modify the repair details to address unique field conditions. Ultimately, the performance and durability of the PT anchorage pocket repairs is dependent on the attentiveness from the contractor, manufacturer and engineer throughout the repair work.