Résistimètre modèle C-RM-8000

The electrical conductivity of concrete is an electrolytic process that takes place by the movement of ions in the cement matrix. This ionic movement will occur when contaminants such as chloride ions or carbon dioxide are introduced into the cement mortar matrix.
A highly permeable concrete will have a high conductivity and low electrical resistance. Because resistivity is proportional to current flow, the measurement of the electrical resistance of concrete provides a measure of the possible rate of corrosion. Since carbonation seriously affects surface resistance, measurement on the concrete surface should be avoided.
The James resistivity meter, OHMCORR, has two probes spaced 5 cm (1.97 inches) apart which are placed in two holes drilled to a depth of 8 mm (3/8 inch) and filled with conductive gel. The concrete resistivity is displayed on an LCD when the control switch is activated.
The following table correlates a range of values vs. the possible rate of corrosion of the reinforcement bars.

RESISTIVITY LEVEL (K OHMS CM)	POSSIBLE CORROSION RATE OF REINFORCEMENT REBARS
<5	Very High
5 to 10	High
10 to 20	Moderate to Low
>20	Insignificant
The James OHMCORR, when used in conjunction with the James CORMAP System provides an economic and sound means of diagnoses of corrosion in reinforced concrete.

Technical Specifications
	The electrical conductivity of concrete is an electrolytic process that takes place by the movement of ions in the cement matrix. This ionic movement will occur when contaminants such as chloride ions or carbon dioxide are introduced into the cement mortar matrix. A highly permeable concrete will have a high conductivity and low electrical resistance. Because resistivity is proportional to current flow, the measurement of the electrical resistance of concrete provides a measure of the possible rate of corrosion. Since carbonation seriously affects surface resistance, measurement on the concrete surface should be avoided. The James resistivity meter, OHMCORR, has two probes spaced 5 cm (1.97 inches) apart which are placed in two holes drilled to a depth of 8 mm (3/8 inch) and filled with conductive gel. The concrete resistivity is displayed on an LCD when the control switch is activated. The following table correlates a range of values vs. the possible rate of corrosion of the reinforcement bars.