Improve, preserve, secure

External Post-Tensioning Tendons

Many prestressed concrete structures built in the 20th century relied heavily on the assumed durability of reinforced concrete and bonded post-tensioning systems. At the time, these technologies were still evolving, particularly in areas like design standards, material quality, and tendon installation practices such as grouting and injection.

The primary goal of inspecting a prestressed structure is to evaluate the operational safety of the system. This includes confirming that the prestressing forces remain effective and that the tendons are in good condition to ensure long-term structural performance.

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

Bridge - External post-tensioning

Common Issues in Post-Tensioning Systems

The performance of a prestressed structure depends heavily on the effectiveness of its post-tensioning system. For owners, the condition of external prestressing tendons is a critical concern, especially in structures like bridge decks built from prefabricated segments joined by external tendons.

Routine inspections often reveal recurring issues that highlight the need for consistent maintenance of post-tensioning systems. Common problems include voids in the grout used to fill ducts and anchorage caps, moisture or water infiltration, and contamination from chlorides. These conditions can lead to corrosion of the steel tendons, ranging from surface rust to full strand failure. In older structures, stress corrosion cracking in outdated prestressing steel is also a known risk.

Voids are most commonly found at the high points of tendon profiles. These gaps in the grout can leave steel tendons exposed to air and moisture, increasing the risk of corrosion and reducing the effectiveness of the post-tensioning system.

Bleed water that accumulates during grout curing can remain trapped inside the ducts. Over time, this moisture can lead to corrosion of the steel tendons, especially if the ducts are not properly sealed or drained.

Poor detailing at joints, inadequate waterproofing, or improperly sealed anchorage caps can allow chlorides to enter the system. Chloride contamination accelerates corrosion and is a major concern in .coastal regions or environments where de-icing salts are frequently used.

Corrosion can range from minor surface rust to complete strand failure. In severe cases, wires may break due to section loss or stress corrosion, particularly in older prestressing systems that used less corrosion-resistant materials.

Specialized Maintenance and Emergency Repairs

Freyssinet performs specialized maintenance to extend the service life of prestressed tendons, along with emergency repairs when a cable breaks or when the remaining load-bearing capacity of a structure is uncertain.

Our approach prioritizes the safety of both users and workers. Each project begins with a detailed inspection of the existing conditions, followed by structural monitoring using instrumentation. When there is a risk of failure, we implement safety measures to protect workers, especially during internal repair operations.

All work is carefully scheduled to meet project deadlines while minimizing disruption to ongoing operations. This comprehensive and proactive strategy ensures the long-term performance and safety of structures requiring maintenance of post-tensioning systems.

Why Choose Freyssinet for Maintenance of Post-Tensioning Tendons

01. Expert Analysis of Structural Defects

With deep expertise in prestressing tendons and systems, Freyssinet provides thorough assessments to evaluate the structural integrity of your post-tensioned elements. Our team helps you understand how the tendons 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 Diverse Range of Solutions

Evaluation of Cable Conditions

In addition to standard inspections, Freyssinet offers 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 tendons considered at risk, where corrosion of wires or strands could lead to full cable failure, Freyssinet offers 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 tendons located in confined spaces, proper safety measures must be implemented to protect inspection and maintenance crews. Freyssinet supports 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 Tendons

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, Freyssinet offers 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 tendons considered at risk, where corrosion of wires or strands could lead to full cable failure, Freyssinet offers 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 tendons located in confined spaces, proper safety measures must be implemented to protect inspection and maintenance crews. Freyssinet supports 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 Tendons

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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