Rebar and tension cable location and depth
WHAT IS RADAR? RADIO DETECTION AND RANGING Radar first used in free space for military applications.
Early Generation Systems
Analog Paper Burning Systems (e.g., 1970’s GSSI SIR 3’s)
Digital Controllers/Laptop Driven interfaces (1980’s)
Costly and Complicated Operation System
Latest Generation
Low Cost Simple User Interfaces Targeted Applications
NDT/NDE Applications
Rebar and tension cable location and depth
Slab thickness on grade and suspended
Location of non-metallic and metallic conduits and other embedded non-structural features such as fiber networks, in-floor heating elements, and plumbing
Detection of voids and variations in the concrete matrix
What’s The Problem?
Cutting, coring, and demolition in concrete poses the same risks as those in roadway easements.
Dangers include cutting “hot” electrical lines, gas, water, fiber, network cables, telecommunication, security…
Cutting post and pre-tension cables may cause complete structural failure of an elevated slab.
Concrete slab with rebar
Concrete Slab with Rebar and Post Tension Cables
GPR Advantages
Portability GPR is non-destructive GPR is real time in the field. It is not necessary to develop and review results later Precise horizontal and vertical positioning No radiation involved as with x-ray radiography. Therefore no health risks from gamma radiation. Radiography equipment involves special handling even for transport to minimize exposure to humans GPR information is transposed immediately to the slab or site GPR can be relocated on a project without any coordination of people GPR provides depth information vs. x-ray which does not Slabs on grade cannot be x-rayed
GPR Limitations Penetration depth and ability to resolve targets at depth is strongly dependent upon the condition of the concrete and soils. Highly conductive green concrete or clay soil can render the GPR method ineffective. Concrete additives such as metal fibers can impeded performance Multi-layered rebar can be problematic with rebar over rebar Slabs on pans can be problematic since cabling or conduits are often installed in the troughs of the corrugation There must be a sufficient electrical contrast between the target and the host materials Post tension cables drape across the rebar, however, pretension cables are patterned similar to rebar Interpretation of GPR data can be subjective. The experience of the interpreter is very important
GPR – Reflection Rebar in Concrete
Tx Rx
Transmitted Wave
Received or Reflected Wave
Display Result If perpendicular to rebar
“Hyperbola” Soil layer response
Green Concrete Conditions- High Conductivity
Good Concrete Conditions-Low Conductivity
2300 MHz vs. 1600 MHz
2300 MHz
1600 MHz
SURVEY PREPARATION What is the anticipated depth and type of structures? What is the anticipated direction of the structures? What are the concrete conditions? How accessible is the site?
Collect In Real Time (2D)
Collecting Data
Marking the Slab The back up cursor lines up with the center of the antenna
Collect a Grid Project (3D)
Collecting data in a grid pattern allows you to image everything in the slab and view it from over head
Imaging of a standard Rebar Layout Collected in real-time (2D)
Rebar going North to south
Rebar Going East to West
Reflection off of the bottom of the suspended slab
Imaging of a standard Rebar Layout Collected with a Grid Format (3D) Rebar going North to South
Rebar Going East to west
Imaging of a standard Rebar Layout With Post Tension Cables Collected in real-time (2D) Data Set North to South
Data Set East to West Upper Layer of Rebar Post tension Cables East to West Post tension Cables North to South Lower Layer of Rebar
Imaging of a standard Rebar Layout With Post Tension Cables Collected with a Grid Format (3D) Upper Rebar Layer
Lower Rebar Layer
Upper Post Tension Cable
Lower Post Tension Cable
Imaging of a standard Rebar Layout and Light Fixture Collected in real-time (2D) Data Set East to West
Data Set North to South
Upper Layer of Rebar Light Fixture Lower Layer of Rebar
Imaging of a standard Rebar Layout With Light Fixture Collected with a Grid Format (3D)
Upper Rebar
Light Fixture and Conduits
Lower Rebar
Imaging of a standard Rebar Layout With Conduit Collected with a Grid Format (3D) Using the EM SENSOR function
3D Radar Data
Conduit
Layer Rebar
EM Sensor Data
Contact Information • • • • •
Matt Marcum Precision ProCut Project Manager 216-573-2400 [email protected]
Early Generation Systems
Analog Paper Burning Systems (e.g., 1970’s GSSI SIR 3’s)
Digital Controllers/Laptop Driven interfaces (1980’s)
Costly and Complicated Operation System
Latest Generation
Low Cost Simple User Interfaces Targeted Applications
NDT/NDE Applications
Rebar and tension cable location and depth
Slab thickness on grade and suspended
Location of non-metallic and metallic conduits and other embedded non-structural features such as fiber networks, in-floor heating elements, and plumbing
Detection of voids and variations in the concrete matrix
What’s The Problem?
Cutting, coring, and demolition in concrete poses the same risks as those in roadway easements.
Dangers include cutting “hot” electrical lines, gas, water, fiber, network cables, telecommunication, security…
Cutting post and pre-tension cables may cause complete structural failure of an elevated slab.
Concrete slab with rebar
Concrete Slab with Rebar and Post Tension Cables
GPR Advantages
Portability GPR is non-destructive GPR is real time in the field. It is not necessary to develop and review results later Precise horizontal and vertical positioning No radiation involved as with x-ray radiography. Therefore no health risks from gamma radiation. Radiography equipment involves special handling even for transport to minimize exposure to humans GPR information is transposed immediately to the slab or site GPR can be relocated on a project without any coordination of people GPR provides depth information vs. x-ray which does not Slabs on grade cannot be x-rayed
GPR Limitations Penetration depth and ability to resolve targets at depth is strongly dependent upon the condition of the concrete and soils. Highly conductive green concrete or clay soil can render the GPR method ineffective. Concrete additives such as metal fibers can impeded performance Multi-layered rebar can be problematic with rebar over rebar Slabs on pans can be problematic since cabling or conduits are often installed in the troughs of the corrugation There must be a sufficient electrical contrast between the target and the host materials Post tension cables drape across the rebar, however, pretension cables are patterned similar to rebar Interpretation of GPR data can be subjective. The experience of the interpreter is very important
GPR – Reflection Rebar in Concrete
Tx Rx
Transmitted Wave
Received or Reflected Wave
Display Result If perpendicular to rebar
“Hyperbola” Soil layer response
Green Concrete Conditions- High Conductivity
Good Concrete Conditions-Low Conductivity
2300 MHz vs. 1600 MHz
2300 MHz
1600 MHz
SURVEY PREPARATION What is the anticipated depth and type of structures? What is the anticipated direction of the structures? What are the concrete conditions? How accessible is the site?
Collect In Real Time (2D)
Collecting Data
Marking the Slab The back up cursor lines up with the center of the antenna
Collect a Grid Project (3D)
Collecting data in a grid pattern allows you to image everything in the slab and view it from over head
Imaging of a standard Rebar Layout Collected in real-time (2D)
Rebar going North to south
Rebar Going East to West
Reflection off of the bottom of the suspended slab
Imaging of a standard Rebar Layout Collected with a Grid Format (3D) Rebar going North to South
Rebar Going East to west
Imaging of a standard Rebar Layout With Post Tension Cables Collected in real-time (2D) Data Set North to South
Data Set East to West Upper Layer of Rebar Post tension Cables East to West Post tension Cables North to South Lower Layer of Rebar
Imaging of a standard Rebar Layout With Post Tension Cables Collected with a Grid Format (3D) Upper Rebar Layer
Lower Rebar Layer
Upper Post Tension Cable
Lower Post Tension Cable
Imaging of a standard Rebar Layout and Light Fixture Collected in real-time (2D) Data Set East to West
Data Set North to South
Upper Layer of Rebar Light Fixture Lower Layer of Rebar
Imaging of a standard Rebar Layout With Light Fixture Collected with a Grid Format (3D)
Upper Rebar
Light Fixture and Conduits
Lower Rebar
Imaging of a standard Rebar Layout With Conduit Collected with a Grid Format (3D) Using the EM SENSOR function
3D Radar Data
Conduit
Layer Rebar
EM Sensor Data
Contact Information • • • • •
Matt Marcum Precision ProCut Project Manager 216-573-2400 [email protected]
