Concrete Imaging Services (CIS) How GPR Works

The GPR system has three components which consist of the Control Unit, the Antenna and the Power Supply. The control unit contains the electronics that produce and regulate the pulse of radar energy that the antenna sends into the concrete creating ultra sound like waves. The antenna receives the electrical pulse and amplifies it then transmits it into the concrete. GPR works by transmitting a small pulse of energy into the material, recording the strength and the time required for the return of any reflected signal. A series of pulses over a single area produce what is called a scan.

Metals are considered to be a reflector which does not allow any signal to pass through; therefore targets beneath materials such as metal sheeting, fine metal mesh, or pan decking will not be visible. Water also acts as a reflector and minimizes the use of GPR; therefore, if the concrete is not fully cured or the surface is wet, the GPR will not pick up possible targets within the concrete.

Data is collected in parallel transects and placed together in their appropriate locations for the computer to process within a specialized software. The computer then produces a plain view of the survey area which allows the technician to interpret. The CIS technician will then continue to mark each target area on the scanned surface using duct tape or crayon.

Facts
·Non-destructive radar imaging technology allows inspection of concrete structures to be carried out quickly and safely without interruption of day-to-day operations or inconvenience to the public.
·GPR cannot see through wet concrete
·GPR cannot see through scanned areas which contain Styrofoam. Styrofoam acts as an insulator for the machine therefore, it is not designed to see through Styrofoam.
·GPR cannot see very well through small voids/honey combing
·It can be difficult to see through multiple mats of rebar
·Targets located directly beneath one another are challenging to see
·Plastic air filled PVC are hard to see
·Target locations are marked on the surface using duct tape or crayon
·Actual target may be 2” to each side of the CIS target mark
·GPR can be done at anytime without harm to anyone in the area.
·Core drilling can be done immediately after GPR is performed to ensure satisfactory results.
·Although CIS does not offer a 100% guarantee, we take pride in obtaining and maintaining the best equipment and technicians available. There is a minimum amount of instances that may occur, such as conduits located under rebar that the equipment cannot see, post tension cables that may be mistaken for rebar, etc. To date, CIS has a 99% success rate. The customer must understand that this equipment, like Xray will minimize, NOT eliminate the potential of striking a target.

Frequently Asked Questions

Why use GPR? There are many benefits to using GPR such as locating targets within a surface with known post tension cables or conduits. Using GPR cost far less money than having to repair conduits or cables.
How do I know where the targets are located? The CIS technician will physically mark out possible targets on the surface of each location using duct tape or crayons. Additional reports are available when requested upon job ordering.
What is the difference between GPR and XRAY? GPR uses sound waves for immediate results. Xray uses radiation and film which sometimes take hours to see the results. Additionally, since GPR uses sound waves, it is 99% safer than using a cell phone whereas Xray uses radiation which requires area evacuation.
How much does GPR cost? GPR pricing is based on several factors such as geographic location, size of area, how many areas are scanned and what type of imaging must be performed. Please call for a specific quote according to your needs.
Can GPR only look through slabs? GPR can be used on surfaces such as slabs, walls, columns and ceilings.
What size of area can you scan? CIS typically scans 2’ x 2’ areas yet has the capability to scan areas up to 100’ x 100’ if necessary.
Is there a guarantee for this type of work? We guarantee that we offer the most technologically advanced equipment and certified technicians to minimize the incident of hitting a target.

Comparisons
•Quick, easy, safe and effective way to locate buried obstructions in concrete structures prior to coring or cutting
•Faster and safer than radiography
•Only single-sided access needed
•Inspect walls, floors, decks, slabs, tunnels, balconies and garages
•Locate rebar, tension cables, conduits, voids, PVC pipes, measure slab thickness
•Many square feet of concrete can be inspected in a day
•Locate targets to a depth of 18 inches and more in concrete
•Detect and map the relative concrete condition for rehab planning
•Combine separate 3D grids into single grid