DEVELOPMENT OF AN EMBEDDABLE MICROINSTRUMENT FOR CORROSIVITY MONITORING IN CONCRETE

The aim of this program was the development of a small and completely embeddable microinstrument for corrosivity measurement in concrete. It should contain all the electronics for the electrochemical measurements, the means for data transfer between engineer and device, and sensors sensitive to the different corrosivity parameters. The goals of the work reported here were to develop and test the required sensors and electronics in a laboratory setting. Sensors for the measurement of corrosion rate, corrosion potential, chloride concentration, and concrete conductivity were developed and tested in laboratory-scale concrete slabs. The tests included electrochemical chloride driving as a method for test acceleration and wet/dry cycling. The corrosion sensor consists of a piece of reinforcing steel as working electrode, another rebar piece or a platinized Nb-mesh as counterelectrode, and a Ag/AgCl electrode as reference electrode. The conductivity sensor is based on a modified Wenner four-pin method and made of four parallel Au wires. Both sensors work very well. Chloride introduced into the concrete electrochemically induced corrosion on the corrosion sensor, as seen by a decrease in potential and in the polarization resistance. The potentials recovered after more than 1000 h of electrochemical chloride removal, but the corrosion resistance did not regain its original value. The change in chloride content was monitored by a Ag/AgCl sensor. The only present drawback of the microinstrument is the construction of a long-term reliable reference electrode. The best candidates seem to be Ni/W galvanic couple and lead. A micropotentiostat coupled to a zero-resistance ammeter and a microgalvanostat based on operational amplifiers were designed, and the concepts tested with dummy cells and on carbon steel samples in chloride solutions. The circuits were implemented in different generations of application specific integrated circuits (ASIC), which were successfully tested. The last generation is the heart of a complete measurement system, which includes on two double surface mount boards the ASIC, a microprocessor, control circuitry, and connections to the external corrosivity sensors, as well as RF transceiver circuitry for the wireless communication with the instrument.

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• Record URL:
  • https://rosap.ntl.bts.gov/view/dot/15677
• Corporate Authors:

  University of Virginia, Charlottesville

  School of Engineering and Applied Science
  Charlottesville, VA  United States  22903

  Virginia Department of Transportation

  Office of Public Affairs, 1221 East Broad Street
  Richmond, VA  United States  23219

  Federal Highway Administration

  Turner-Fairbank Highway Research Center, 6300 Georgetown Pike
  McLean, VA  United States  22101
• Authors:
  • Kelly, R G
  • JONES, S H
• Publication Date: 1999-7

Language

• English

Media Info

• Features: Figures; Photos; References; Tables;
• Pagination: 40 p.

Subject/Index Terms

• TRT Terms: Corrosion; Electrochemistry; Electrodes; Laboratory tests; Measuring instruments; Monitoring; Reinforced concrete; Sensors; Wireless communication systems
• Uncontrolled Terms: Microinstruments
• Subject Areas: Highways; Materials; I32: Concrete;

Filing Info

• Accession Number: 00769485
• Record Type: Publication
• Report/Paper Numbers: FHWA/VTRC 00-CR1,, Final Contract Report
• Contract Numbers: 00050930
• Files: NTL, TRIS, ATRI, USDOT, STATEDOT
• Created Date: Sep 20 1999 12:00AM