Multi-Level Parking Garage Assessment & Repair

Overview

Concrete Science, Inc. was brought in by the contractor, Schwager Davis, Inc., after alarming reports of concrete chunks falling from the top level of a multi-level parking garage. These falling pieces posed a serious safety hazard to users and rendered sections of the garage unusable. The building owners were eager for answers and a lasting solution to restore safety and functionality to the structure while addressing the root causes of the deterioration.

Scope of Work

Concrete Science, Inc. began the investigation with visual inspections of the structure, followed by a series of detailed diagnostic tests. Armed with advanced tools and techniques, our team worked to uncover the hidden story of the concrete's performance over time.

1. Delamination Survey:

Using hammer-sounding tests, we checked for near-surface delamination in slabs and walls. Remarkably, no delamination was identified.

2. Non-Destructive Testing:

Rebound hammer tests provided a snapshot of the concrete's compressive strength, revealing a range from 2,750 psi to 6,050 psi across different areas of the structure.

3. Corrosion Potential Survey:

Half-cell tests were performed on reinforcement within the concrete. To the client's relief, results showed no significant signs of corrosion.

4. Core Sampling and Testing:

Carefully extracted concrete cores underwent lab testing to analyze compressive strength, chloride content, and petrographic details.

5. Chemical and Petrographic Analysis:

The concrete was generally well-consolidated with excellent aggregate distribution. However, carbonation had advanced to depths of nearly 2 inches in some areas, posing a future risk to reinforcement.

Key Findings

Our testing revealed a mix of promising and concerning results. While the concrete exhibited good overall quality with low chloride levels and no delamination, one area—the U3 parking slab—stood out due to relatively low compressive strength (below 3,000 psi). Additionally, carbonation caused by exposure to atmospheric CO₂ and vehicle exhaust presented a silent but growing threat to reinforcement over time.

Solutions and Recommendations

Concrete Science, Inc. crafted a tailored repair and protection strategy to address current and future risks:

Apply a traffic coating or penetrating corrosion inhibitor to combat the effects of carbonation and protect the reinforcement.
Conduct targeted repairs on the U3 slab to improve its compressive strength and ensure long-term stability.
Regularly maintain protective coatings and monitor key areas for any signs of deterioration, safeguarding the structure's lifespan.

Fyfe Carbon Fiber Repair along Parking Structure Concrete Ceiling

Outcome

Our comprehensive field and laboratory testing results were provided to Watry Design, Inc., the project structural engineers to specify additional repairs, if necessary. By addressing issues early, the parking garage is now poised for a long and reliable service life.