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The Truth About Post-Tensioning Systems

Post-tensioning systems built throughout the 20th century were designed under construction industry standards that differ from those applied in new construction today, particularly in material specifications, grouting practices, and corrosion protection requirements.

Inspections confirm whether prestressing forces remain effective and whether post-tensioning tendons within concrete structures remain sound or need repair to sustain long-term structural performance.

Today, proven solutions are available to upgrade or modernize external post-tension tendons. These engineering methods can restore original strength and safety levels, extending its service life and improving reliability.

Post-tensioning teams

Common Issues in Post-Tensioning Systems

The performance of a prestressed structure depends heavily on the effectiveness of post-tension systems, including post-tensioned slabs in parking garages and buildings, as well as bridge decks and segmental structures.

For commercial building and infrastructure owners, the condition of external prestressing cables is a critical concern, especially in bridge decks built from prefabricated segments joined by external cables.

Routine inspections consistently reveal the same recurring deficiencies: grout voids in ducts and anchorage caps, moisture infiltration, and chloride contamination. Left unaddressed, these conditions accelerate tendon corrosion, from surface rust to full strand failure.

Voids form most often at high points in the tendon profile, where incomplete grouting leaves steel exposed to air and moisture, reducing post-tensioning effectiveness and accelerating corrosion.

Bleed water trapped during grout curing accumulates inside ducts and, without proper sealing or drainage, initiates tendon corrosion over time.

Poor joint detailing, inadequate waterproofing, or unsealed anchorage caps allow chlorides to penetrate the system. In coastal environments or structures exposed to de-icing salts, chloride ingress becomes the primary driver of accelerated corrosion.

Corrosion progresses from surface rust to section loss and wire fracture. In used post-tensioning systems built with less corrosion-resistant steel, stress corrosion cracking presents an additional failure risk.

Specialized Post-Tensioning Systems Repair

Post-tensioning systems in parking structures, bridge decks, and other prestressed concrete elements require specialized maintenance to extend tendon service life. They also require emergency repairs when a cable breaks or remaining load-bearing capacity is uncertain.

Each project begins with a detailed inspection of existing conditions, followed by structural monitoring through instrumentation. When failure risk is identified, safety measures protect workers throughout internal repair operations on post-tensioning systems. 

All work is scheduled to meet project deadlines while minimizing disruption to ongoing operations. This ensures structural safety and long-term performance.

Why Choose Freyssinet for Post-Tensioning Systems Repair

01. Expert Analysis of Structural Defects

With years of experience in repairing damaged post-tensioning systems, we provide professional assessments to evaluate the potential structural damage of your post-tensioned structures. Our team helps you understand how the cables are performing and how they are likely to behave over time.

02. Customized Monitoring Programs

We work with you to develop inspection and testing programs tailored to your structure’s specific configuration. These programs are designed to support long-term maintenance of post-tensioning systems and ensure early detection of potential issues.

03. Targeted Structural Studies

Every structure has unique characteristics. We conduct specialized laboratory and field testing to accurately diagnose the extent and severity of any deterioration or damage, ensuring that repair strategies are based on solid data.

04. Proven Strengthening Solutions

Our teams are highly experienced in working with aging or corroded external prestressing cables. We clean and treat affected areas, and when needed, replace outdated systems with modern, safer technologies that restore performance and extend service life.

Our Post-Tensioning System Repair Process

Evaluation of Cable Conditions

In addition to standard inspections, we offer advanced diagnostic techniques to support effective maintenance of post-tensioning systems. These methods help detect grout voids, corrosion, and force loss in tendons.
  • Visual inspection of anchor heads
    with ultrasonic testing to
    assess corrosion
  • Sonic and electromagnetic testing of
    accessible duct sections
  • Cross-bow testing to measure residual
    force in wires and strands

Tendon Acoustic Monitoring

For cables considered at risk, where corrosion of wires or strands could lead to full cable failure, we offer acoustic monitoring solutions. These systems help detect wire breaks in real time, track their progression, and support informed decisions about service levels and rehabilitation needs. This approach is a valuable part of proactive maintenance post-tensioning strategies.
  • Detection of wire failure
    using acoustic sensors
  • Real time alerts delivered by email
  • Support in interpreting wire
    failure progression

Maintenance Team Safety

When corrosion is suspected in external prestressing cables located in confined spaces, proper safety measures must be implemented to protect inspection and maintenance crews. We support clients in assessing risks and selecting the right protective strategies as part of a comprehensive maintenance post-tensioning approach.
  • Assessment of traffic restrictions or
    alternating traffic to maintain
    safety levels
  • Design and installation of safety straps
    to contain energy release during
    cable failure
  • Implementation of protective systems
    for safe repair operations
    in confined spaces

Cable Protection Corrosion Retrofitting

In many older structures, prestressing cables were not properly injected or were installed using outdated materials and techniques. Loose sheaths and poor-quality grout can leave tendons vulnerable to corrosion. To restore protection and extend the life of these systems, Freyssinet offers targeted preservation solutions as part of our maintenance post-tensioning services.
  • Vacuum re-injection of voids in tendons
  • Reinstate the watertightness of ducts
    and anchor caps
  • Removal of poor-quality cement grout
    where feasible

Detensioning of External Prestressing Cables

When corrosion in external prestressing tendons is too advanced, detensioning may be required to safely remove and replace the affected cables. Freyssinet offers several proven detensioning techniques, selected based on the condition of the cable, the structure, and the potential risks associated with energy release. These services are a key part of safe and effective maintenance post-tensioning operations.
  • Cable detension by cutting
  • Controlled detension of tendons
  • Tendon detension using
    elasto-plastic dampers

Evaluation of Cable Conditions

In addition to standard inspections, we offer advanced diagnostic techniques to support effective maintenance of post-tensioning systems. These methods help detect grout voids, corrosion, and force loss in tendons.
  • Visual inspection of anchor heads
    with ultrasonic testing to
    assess corrosion
  • Sonic and electromagnetic testing of
    accessible duct sections
  • Cross-bow testing to measure residual
    force in wires and strands

Tendon Acoustic Monitoring

For cables considered at risk, where corrosion of wires or strands could lead to full cable failure, we offer acoustic monitoring solutions. These systems help detect wire breaks in real time, track their progression, and support informed decisions about service levels and rehabilitation needs. This approach is a valuable part of proactive maintenance post-tensioning strategies.
  • Detection of wire failure
    using acoustic sensors
  • Real time alerts delivered by email
  • Support in interpreting wire
    failure progression

Maintenance Team Safety

When corrosion is suspected in external prestressing cables located in confined spaces, proper safety measures must be implemented to protect inspection and maintenance crews. We support clients in assessing risks and selecting the right protective strategies as part of a comprehensive maintenance post-tensioning approach.
  • Assessment of traffic restrictions or
    alternating traffic to maintain
    safety levels
  • Design and installation of safety straps
    to contain energy release during
    cable failure
  • Implementation of protective systems
    for safe repair operations
    in confined spaces

Cable Protection Corrosion Retrofitting

In many older structures, prestressing cables were not properly injected or were installed using outdated materials and techniques. Loose sheaths and poor-quality grout can leave tendons vulnerable to corrosion. To restore protection and extend the life of these systems, Freyssinet offers targeted preservation solutions as part of our maintenance post-tensioning services.
  • Vacuum re-injection of voids in tendons
  • Reinstate the watertightness of ducts
    and anchor caps
  • Removal of poor-quality cement grout
    where feasible

Detensioning of External Prestressing Cables

When corrosion in external prestressing tendons is too advanced, detensioning may be required to safely remove and replace the affected cables. Freyssinet offers several proven detensioning techniques, selected based on the condition of the cable, the structure, and the potential risks associated with energy release. These services are a key part of safe and effective maintenance post-tensioning operations.
  • Cable detension by cutting
  • Controlled detension of tendons
  • Tendon detension using
    elasto-plastic dampers

Discover Our Projects

Repairs
Maryland, United States

Montgomery College Parking Garage

When a post-tensioned floor unexpectedly sagged in a multi-level parking garage at Montgomery College in Takoma Park, our team acted quickly to complete the necessary structural repairs while keeping disruptions to garage users at a minimum.
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Repairs
Charleston, North Carolina

Cumberland Street Parking Deck

Freyssinet partnered with Charleston County to inspect and repair post-tensioned tendons at the Cumberland Street Parking Deck. The project was completed swiftly and safely, preserving access to a vital downtown parking facility.
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Repairs
South Carolina, United States

Charleston Place Hotel

Freyssinet was trusted to perform complex structural repairs at the Charleston Place Hotel, restoring post-tensioned concrete systems in a live luxury setting. The project showcased our expertise in precision engineering and discreet execution within high-profile environments.
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