In your residential or commercial construction site, you may find a need for nondestructive means to inspect beneath the surface. This will help you not only with locating post tension cables, but also pipes, voids in the concrete, wires, ducts, and other obstacles. There are multiple methods you can use to do this, but they are not all created equal. Depending on the specifics of your job, you may want to use Ground Penetrating Radar (GPR) or Concrete X-Ray.
Ground Penetrating Radar delivers high-frequency radar pulses beneath the ground and uses the echoes from those pulses to image the ground beneath the surface. It is very useful for detecting not only post tension cables, but also other underground features like buried utility lines. Contractors commonly use this method in construction sites ranging from residential to commercial, including infrastructure like bridges and tunnels. In fact, contractors are not the only people to use GPR. Crime scene investigators have used GPR to find stolen goods and other criminal evidence. It has even been used to detect unmarked graves.
In the hands of a skilled contractor, GPR has many benefits over other subsurface location techniques and tools. It is less expensive than some other methods, including concrete x-ray. It also allows for immediate results to trained professionals who are able to interpret the machine’s readings in real time. Contractors frequently prefer GPR over other methods due to its small work site footprint and significant labor savings. When using GPR, you do not need to vacate a work site to protect workers from radiation exposure.
Like other forms of x-ray, concrete x-ray uses hard x-rays or gamma rays to capture an image of the interior of the concrete slab. Radiation is applied to one side of the slab while a film capturing the image is on the other side, and the entire setup is controlled with software via a tablet. The equipment required in order to execute concrete x-ray used to be quite cumbersome.
While X-Ray images require development in order to view, they provide a clearer picture than other methods. They also require less skilled training in order to interpret. However, the slab that is being x-rayed must be less than 300 mm thick.
Because of the presence of radiation, you must take safety precautions, including vacating the area and establishing a restricted area around the site. Because of these additional requirements, concrete x-ray is generally a more time-consuming and expensive process.
It depends! Clients sometimes assume that x-ray is always the preferred method for locating underground features, but this is not the case. One of the biggest determining factors is whether you have access to both sides of the concrete, or only one side. Because both sides of the concrete slab must be accessible to use concrete x-ray, that method is often impractical, especially for residential jobs. In these cases, you should use GPR. GPR also emits far less radiation than concrete x-ray scanners, making the method safer as well as more time- and cost-efficient.
However, concrete x-ray may indeed be the right choice for you. When both sides of the slab are accessible, it is the preferred method for locating several objects in a small area. This is frequently the case with multi-story commercial buildings, like parking garages or office buildings.
Do you need help determining which choice is right for you? Talk to our experts today.