Detection of reinforcing steel corrosion in concrete structures using non-linear harmonic and intermodulation wave generation

A method of detecting corrosion on an electrically conductive member that is surrounded by an electrically non-conductive material and is unavailable to visual inspection, comprising the steps of;

• transmitting a first electromagnetic signal through said electrically non-conductive material so as to illuminate said electrically conductive member, said first electromagnetic signal having at least one fundamental frequency;
• receiving a reflected/generated electromagnetic signal from said electrically conductive member within said electrically non-conductive material, said reflected/generated electromagnetic signal comprising a reflected component made of said fundamental frequency and a generated component made of a plurality of harmonic and intermodulated frequencies of said fundamental frequency, said harmonics and intermodulated frequencies being generated by non-linear electrical characteristics attributable to said corrosion of said electrically conducive member;
• and
• determining a relative amplitude of said generated component of said reflected/generated electromagnetic signal in relation to said reflected component of said reflected/generated electromagnetic signal, said step of determining a relative amplitude comprising the steps of;
• comparing an amplitude of said generated component of said reflected/generated electromagnetic signal at said plurality of harmonic and intermodulated frequencies with an amplitude of is reflected component of said reflected/generated electromagnetic signal at said fundamental frequency by way of an electronic comparator;
• determining a quantitative difference between said amplitude of said generated component and said amplitude of said reflected component;
• and
• correlating said quantitative difference with a degree f corrosion on said metallic member;
• wherein said relative amplitude is indicative of a degree of said corrosion in said electrically conducive member.

A method of detecting and locating corrosion in reinforcing steel within a concrete structure comprising the steps of:

• positioning an electromagnetic signal transmitter adjacent to said concrete structure, wherein said concrete structure is known to contain said reinforcing steel;
• generating a first electromagnetic signal with said electromagnetic signal transmitter, said electromagnetic signal having a first frequency, and having an amplitude;
• transmitting said first electromagnetic signal through said concrete structure so as to illuminate said reinforcing steel;
• reflecting said first electromagnetic signal off of said reinforcing steel;
• causing the generation of a second electromagnetic signal from said reinforcing steel, said second electromagnetic signal comprising a plurality of harmonics and intermodulation frequencies of said first frequency, said second electromagnetic signal being generated by non-linear electrical characteristics attributable to said corrosion of said reinforcing steel, said second electromagnetic signal having an amplitude;
• positioning an electromagnetic signal receiver adjacent to said concrete structure, wherein said first electromagnetic signal has been transmitted;
• receiving said reflected first electromagnetic signal and said generated second electromagnetic signal from said reinforcing steel in said concrete structure;
• separating said first frequency of said reflected first electromagnetic signal from said plurality of harmonic and intermodulated frequencies of said first frequency within said generated second electromagnetic signal;
• and
• comparing said amplitude of said first frequency of said reflected first electromagnetic signal with said amplitude of said plurality of harmonic and intermodulated frequencies of said generated second electromagnetic signal;
• wherein a difference between said amplitude of said first frequency of said reflected first electromagnetic signal, and said amplitude of said plurality of harmonic and intermodulated frequencies of said generated second electromagnetic signal is indicative of a degree of corrosion in said reinforcing steel.

A method of detecting and locating corrosion in reinforcing steel within a concrete structure comprising the steps of:

• positioning a first electromagnetic signal transmitter adjacent to said concrete structure, wherein said concrete structure is known to contain said reinforcing steel;
• generating a first electromagnetic signal with said electromagnetic signal transmitter, said electromagnetic signal having a first frequency, and having an amplitude;
• transmitting said first electromagnetic signal through said concrete structure so as to illuminate said reinforcing steel;
• positioning a second electromagnetic signal transmitter adjacent to said concrete structure, wherein said concrete structure is known to contain said reinforcing steel;
• generating a second electromagnetic signal with said electromagnetic signal transmitter, said electromagnetic signal having a second frequency, and having an amplitude;
• transmitting said second electromagnetic signal through said concrete structure so as to illuminate said reinforcing steel;
• reflecting said first and said second electromagnetic signals off of said reinforcing steel;
• causing the generation of a third electromagnetic signal from said reinforcing steel, said third electromagnetic signal comprising a plurality of harmonics and intermodulation frequencies of said first and said second frequencies, said third electromagnetic signal being generated by non-linear electrical characteristics attributable to said corrosion of said reinforcing steel, said third electromagnetic signal having an amplitude;
• positioning an electromagnetic signal receiver adjacent to said concrete structure, wherein said first and said second electromagnetic signals have been transmitted;
• receiving said reflected first and second electromagnetic signals and said generated third electromagnetic signal from said reinforcing steel in said concrete structure;
• separating said first and second frequencies of said reflected first and second electromagnetic signals from said plurality of harmonic and intermodulated frequencies of said generated third electromagnetic signal;
• and
• comparing said amplitudes of said first and second frequencies with said amplitudes of said plurality of harmonic and intermodulated frequencies;
• wherein a difference between said amplitudes of said first and second frequencies, and said amplitudes of said plurality of harmonic and intermodulated frequencies is indicative of a degree of corrosion in said reinforcing steel.