The Importance of Locating Post-Tensioned Cables in Concrete Construction Projects

When working with concrete slabs, especially in retrofitting or renovation projects, understanding and determining the location of post-tensioned cables is vital. 

Damaging these cables during drilling or cutting can have severe consequences, including structural compromise and personal injury. In this post, we’ll walk you through the steps and technologies used in the concrete construction industry to locate post-tensioned cables accurately.

Why is Locating Post-Tensioned Cables Important?

Post-tensioned cables, often called tendons in the construction world, are steel cables placed within concrete to improve the concrete's performance under service loads. Damaging these cables can lead to a weakened structure and can be a safety hazard. How, then, do you locate post-tensioned cables in a finished concrete structure? Potential tools include:

Ground Penetrating Radar (GPR)

Ground Penetrating Radar uses electromagnetic radiation to detect structures within the concrete. As the radar encounters different materials like a post-tensioned cable, it sends back a reflection to the radar device.

GPR doesn’t just detect metal; it can also detect plastic conduits, voids, and other embedded features. Plus, it provides a real-time view into the concrete, making it efficient for large areas.

Pachometer (Cover Meter)

Pachometers use electromagnetic pulses to detect ferrous materials within the concrete, such as rebar or post-tension cables. They are relatively easy to use and are specifically designed to detect metal within concrete.

Ultrasonic Imaging

This technology sends ultrasonic pulses through the concrete. These pulses bounce back when encountering an embedded object or anomaly, creating a visual representation. Ultrasonic imaging can provide more detail about the depth and condition of embedded objects than other methods.

Best Practices for Locating Post-Tensioned Cables

To ensure accuracy in locating post-tensioned cables, don’t rely on just one detection tool. Using a  combination of the tools mentioned above will provide the best results.  It is also important to:

Receive Professional Training

It is vital that whoever is operating the detection equipment is adequately trained. Misinterpretation of data can be as harmful as not checking at all.

Perform Regular Equipment Calibration

Regularly calibrate equipment to ensure its accuracy.

Mark As You Go

As you detect cables, mark their location directly on the concrete. This will provide a visual guide for anyone working on the slab later.

Document Your Findings

Always document your findings. This provides a record for future reference and can be helpful for liability reasons.

While post-tensioned cables provide many benefits to concrete structures, they require careful attention when doing any slab modification work. Experienced concrete construction professionals, like our team at Tendon Systems, ensure the safety and structural integrity of all their projects by employing the above-named methods and adhering to best practices.

For over 30 years, Tendon Systems, now a part of CMC, has been an industry-leading provider of post-tensioning, barrier cable, and restoration services across the United States. Built on a foundation of quality products, exceptional services, and engineering expertise, our team has what your project needs to succeed on time and within budget.