When it comes to scanning concrete, distinguishing between standard rebar and Post-Tension (PT) cables is a critical task for a GPR operator. Rebar is the structural backbone that handles tension, but PT cables are under immense mechanical stress—sometimes upwards of 30,000 pounds of force. Accidentally severing a PT cable isn’t just a costly mistake; it can result in the cable snapping through the slab like a whip, causing catastrophic structural failure or severe injury.
Identifying the Difference
On a GPR screen, both rebar and PT cables appear as hyperbolas (inverted “V” shapes), but a skilled operator looks for specific patterns to tell them apart. Rebar is usually tied in a consistent, repeating grid pattern at a uniform depth. In contrast, PT cables often “drape”—meaning their depth changes as they travel through the slab to counteract specific loading forces.
