During a number of recent projects our technicians have discovered very shallow post-tension (PT) cables on job sites. This is a huge issue and can be incredibly dangerous, as well as resulting in costly repairs.
Our technicians have reported finding cables up 7mm below the surface, which is usually unheard of. These cables are under massive stress and should they be hit, or cut in anyway they can explode out of buildings and through the concrete itself!
What is a post-tension cable?
Post-tension cables are used in concrete construction to add strength to thin and long slabs. Concrete has very high compressive strength but lacks in tensile strength, which is where post-tension cables and rebar come in.
The cables themselves consist of steel wires within a plastic sheath which are then tensioned after pouring in the concrete. This vastly increases the load-carrying capacity of the structure meaning that less concrete can be used, and allows for fewer beams, longer spans, and thinner slabs. It is used across a wide range of structures including apartment buildings, office buildings, and bridges.
Dangers surrounding post-tension cables
When cables are drawn tight they are under thousands of pounds of pressure. If theses cables are cut, nicked, or compromised, they can rip through the concrete and cause serious injuries and damages.
Cables are usually below a layer of rebar, however, recently our technicians have reported finding PT cables at very shallow depths. This causes a lot of issues as contractors do not realize they are laid so shallow. Luckily we are able to detect them and allow those on site to avoid them.
Scanning concrete for obstructions and hidden objects
During construction there is often the need to cut or core through the concrete slab, along with the need for anchoring for pipes or walls. It is incredibly important to avoid hitting PT cables when carrying out this work.
GeoScan are Canada’s leading experts when it comes to concrete scanning and are able to scan and identify obstructions below the surface and differentiate PT cables from other in-slab targets such as rebar or conduits. Using our Xradar™ Concrete Scanning methods, we are also able to determine the depth of objects and advise on the best course of action when carrying out work.For more information on concrete scanning, or what we are currently finding when it comes to post-tension cables, get in touch with one of our expert technicians on (604) 436-7226.