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Resistivity Measurement

Resistivity Measurement. Ammeter. Alternating current supply. Voltmeter. Electrodes with couplant. Equipotential surface. Current flow lines. Resistivity Equipment. Electrical Potentials. British BS 1881, Testing Concrete Pt 201 USA ASTM C876-91 German DGZP B3

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Resistivity Measurement

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  1. Resistivity Measurement Ammeter Alternating current supply Voltmeter Electrodes with couplant Equipotential surface Current flow lines

  2. Resistivity Equipment

  3. Electrical Potentials • British BS 1881, Testing Concrete Pt 201 • USA ASTM C876-91 • German DGZP B3 • Swiss SIA 2006 (most comprehensive)

  4. RESIDetermination of the potential corrosion rate based on concrete resistivity

  5. Resistivity Resistivity (kohm cm) 50 30 Corrosion Limit 20 15 Cl- (wt % concrete) 0% 10 0.045% 7 0.45% 5 5.0 3.0 4.0 Moisture Content (wt % of oven dry concrete) • If resistivity greater than 20,000ohm cm corrosion rate is negligible • Water content has major effect on resistivity Ref R.D.Browne “The mechanisms of corrosion of steel in concrete in relation to design, inspection and repair of offshore structures”

  6. Resistivity Of Sydney Concrete Resistivity Kohm cm 30 10%CSF 3% Nacl solution 3 day moist curing 285x75mmx75mm samples tested 25 using CSIRO Wenner Bridge method 25%FA+10%CSF Negligible Corrosion 20 Browne 1978 65%Slag+10%CSF 15 65%Slag 10 5 OPC Cement 0 0 10 20 30 40 50 60 70 80 90 Days Of Partial Immersion On NaCl Ref W.Gross 1992 "Marine Concrete Performance Data For NSW Materials"

  7. Concrete Resistivity Values Guideline Values Concerning Concrete Resistivity (Multiple Published Sources) Ref: R.D.Browne

  8. Resistivity Measurement • Use to assess corrosion rate • Use potentials to locate corrosion sites • Test for saturated resistivity to assess potential corrosion rate • Use to monitor change in exposure • Test a structure over a year to determine seasonal changes • Make allowance for instant changes • Use to assess moisture state • With Torrent to allow for insitu moisture content • Measurement and interpretation best left to experts

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