FPrimeC Solutions was engaged by a client to conduct a comprehensive structural assessment of corroded reinforced concrete loading dock in Toronto, Ontario. The loading dock, featuring a suspended slab design, exhibited significant cracking and concrete spalling caused by advanced reinforcement corrosion.

The primary goal of the assessment was to evaluate the structural integrity and reliability of the dock. Additionally, the client sought guidance on a critical decision: could the loading dock be effectively repaired, or had the damage reached a point where replacement was the only viable option?

After discussions with the client and review of existing evidence, an assessment program based on non-destructive evaluation and complimentary intrusive tests was designed and executed. The following describes the assessment program:

 

Structural Assessment of Corroded Reinforced Concrete Loading Dock

The assessment combined non-destructive testing techniques with intrusive methods to provide a comprehensive evaluation of the slab. The following methodologies were employed:

1. Visual Inspection

A preliminary walkthrough inspection revealed visible signs of damage, including extensive spalling, delamination, and corrosion of exposed reinforcement. These observations guided the selection of test locations for more detailed analyses.

2. Half-Cell Corrosion Potential (HCP) Mapping

Half-Cell Corrosion Potential Mapping identified the likelihood of active corrosion in the slab’s steel reinforcement. The results were categorized into low, uncertain, and high-risk corrosion zones. The findings provided a detailed map of areas susceptible to corrosion. Learn more on corrosion assessment

Structural Assessment of Corroded Reinforced Concrete Loading Dock

3. Ultrasonic Pulse Velocity (UPV)

UPV testing was performed throughout the slab to evaluate the internal quality and uniformity of the concrete. The test involved transmitting ultrasonic waves through the slab and measuring their velocity. Lower velocities indicated areas of poor or questionable concrete quality, particularly in the central and southern regions of the slab.

4. Rebound Hammer Test

The Rebound Hammer test assessed the uniformity and surface hardness of the concrete. Measurements were taken at various stations across the slab. This test provided a rapid, non-invasive evaluation of surface concrete quality, offering an initial overview of potential variations across the structure

5. Ground-Penetrating Radar (GPR)

GPR scans were conducted to analyze rebar spacing and measure concrete cover thickness. Scans were performed in both longitudinal and transverse directions, providing detailed data on rebar configuration and potential anomalies.

Structural Assessment of Corroded Reinforced Concrete Loading Dock - GPR

6. Core Sampling

Three cores were extracted from the slab for laboratory analysis. The samples were tested for compressive strength and chloride content at varying depths. These tests validated the findings of non-destructive methods and provided additional insights into the slab’s durability.

Key Findings

The findings of this study provided critical insights into the slab’s structural health and informed recommendations for future maintenance and repair.

  1. Concrete Quality and Uniformity
  • The Rebound Hammer test demonstrated consistent surface quality, indicating generally uniform concrete across the slab.
  • Ultrasonic Pulse Velocity (UPV) testing revealed that while the concrete was fair to good quality overall, localized areas exhibited reduced quality, particularly in specific regions of the slab.
  1. Corrosion Risk
  • Half-Cell Corrosion Potential (HCP) mapping highlighted a high likelihood of active corrosion across the majority of the slab, with only a small portion showing uncertain corrosion risks. No areas were identified as having a low risk of corrosion.
  • These results underscored the widespread deterioration of the steel reinforcement, requiring immediate intervention to prevent further structural degradation.
  1. Structural Details
  • Ground Penetrating Radar (GPR) scans confirmed the presence of longitudinal and transverse reinforcement throughout the slab.
  • The slab thickness was consistent across the evaluated areas, as confirmed by both GPR data and core samples.
  1. Compressive Strength and Chloride Content
  • Compressive strength testing indicated the concrete’s ability to meet structural performance requirements.
  • Chloride content analysis revealed levels exceeding recommended thresholds, correlating with the extensive corrosion identified in the steel reinforcement.

 

Insights and Considerations

The investigation revealed several critical concerns about the slab’s condition:

  • Corrosion as a Primary Concern: The extensive corrosion of reinforcement poses a significant risk to the slab’s structural integrity. Immediate measures (extensive repair/replacement) deemed necessary.
  • Localized Poor Concrete Quality: While the concrete’s overall quality was fair to good, localized areas of poor quality warrant targeted repairs to enhance durability.
  • High Chloride Levels: Elevated chloride content highlights the need for protective measures to mitigate ongoing corrosion. These measures could include applying corrosion inhibitors or replacing heavily corroded reinforcement.
  • Rebar Configuration Insights: The detailed mapping of reinforcement provided by GPR scans will be invaluable for designing effective rehabilitation strategies.
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