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CX10/11 Concrete ImagingCX10/11 Concrete ImagingWith Integrated EMWith Integrated EM
Presented by:Presented by:MALA GeoScience 2040 Savage Road Charleston, MALA GeoScience 2040 Savage Road Charleston,
SC 29407SC 29407Tel: 1Tel: 1--843843--852852--50215021Fax: 1Fax: 1--843843--769769--73977397
EE-- mail: mail: sales.usa@malags.sesales.usa@malags.se
MALMALÅÅ GeoScienceGeoScience
MALÅ GeoScience USA, Inc., 2040 Savage Road, Charleston, South Carolina 29407, USATel: 1-843-852-5021 Fax: 1-843-769-7397
E- mail: sales.usa@malags.se
MALÅ GeoScience AB, Skolgatan 11, S-930 7 MALÅ, SwedenTel: +46 953-107 10 Fax +46 953 102 25 E-mail: sales@malags.se
CX Series: 1.2, 1.6 GHz with Integrated 50/60 Hz Sensor.
WhatWhat’’s The Problem?s The Problem?
Cutting, coring, and demolition in concrete poses the same risks as those in roadway easementsDangers 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
And You Thought the StreetsAnd You Thought the Streetsare Congested!are Congested!
GPR ADVANTAGESGPR ADVANTAGESPortabilityGPR is non-destructiveNo 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 humansGPR is real time in the field. It is not necessary to develop and review results laterGPR information is transposed immediately to the slab
Precise horizontal and vertical positioningGPR can be relocated on a project without any coordination of peopleGPR provides depth information vs. x-ray which does notSlabs on grade cannot be x-rayed
GPR ADVANTAGES cont.GPR ADVANTAGES cont.
GPR LIMITATIONSGPR LIMITATIONSPenetration depth and ability to resolve targets at depth is strongly dependent upon the condition of the concrete. Highly conductive green concrete can render the GPR method ineffective.Concrete additives such as metal fibers can impeded performanceMulti-layered rebar can be problematic with rebar over rebarSlabs on pans can be problematic since cabling or conduits are often installed in the troughs of the corregation
Interpretation of GPR data can be subjective. The experience of the interpreter is very important
Post tension cables drape across the rebar, however, pretension cables are patterned similar to rebar
GPR LIMITATIONSGPR LIMITATIONS
ELECTRICAL CONDUCTIVITY
Electrical conductivity is the ability of a material to conduct electricity.Signal attenuation and hence depth penetration of GPR energy is directly proportional to the conductivity of the soil/concrete.Saturated soil materials or “green concrete” with high contents of dissolved soils (e.g., salts) and soils containing clays are very conductive.
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GPR PENETRATION VS. CONDUCTIVITY
terrain conductivity in mmhos/m
dept
h in
feet
SURFACE TO METAL TARGET
EM Virtues and VicesEM Virtues and VicesAllows discrimination of “hot” conduits in otherwise busy structural components in the wall or slabThe ability to detect AC current provides obvious safety features for anyone cutting, coring, or demolishing concretePassive EM signals can be noisy and irregularBleed over to surrounding metal can be problematic for accurate pinpointing of the signal
EM Field About a Conductor
DC Constant Source
EM AC Field About a Conductor
Detection EM AC Field About a Conductor
Problem: Signal Bleed Over a Mess of Vectors
Rebar Bleed Over Noise Mitigation
CONDUCTING A CX SURVEYCONDUCTING A CX SURVEY
Estimate the general direction of the structural
members
Set up the CX system parameters
Conduct preliminary test lines
Optimize system
Acquire data
2D Scanning Mode2D Scanning Mode
Scanning Walls & Slabs
Typical 2D Scans
Rebar Tops
2D Scans in the CX Unit
Backup Cursor
Rebar Tops
3D Data Collection & Imaging3D Data Collection & Imaging
Data Collection on a Grid
Grid Project Interface
Processed Data in the Field
CX System .jpeg Export
Transposing Results to Floor
Wall Results
Standard 50/60 Hz Locating in Concrete
50/60 Hz Response
50/60 Hz GPR Combined in CX System
Conduit
EM Response
Conduit Image
Rebar Image
3D EM Image
Radar imaging combined with EM is a powerful toolBoth disruptions of service and risk of injury are reducedAs with any non-invasive tools there is no guarantee that all hazards can be detected
The Bottom LineThe Bottom Line
You Never Know What You’ll Find?
Presented by:Presented by:MALA GeoScienceMALA GeoScience2040 Savage Road2040 Savage Road
Charleston, SC 29407Charleston, SC 29407Tel: 1Tel: 1--843843--852852--50215021Fax: 1Fax: 1--843843--769769--73977397
EE-- mail: mail: sales.usa@malags.sesales.usa@malags.se
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