An accelerated-testing method has been developed for evaluating the effectiveness of various measures taken to prevent the corrosion of steel reinforcing bars ("rebars") cast into concrete. Such measures can include chemical admixtures incorporated into the concrete, coatings, penetrants, modified concretes, new reinforcing materials, and corrosion-inhibiting chemicals that migrate after being applied. The method is an improvement of standard G 109-92 of the American Society for Testing and Materials (ASTM). In preparation for testing, concrete blocks are cast with rebars inside, along with any appropriate corrosion inhibitor(s). Holes are drilled into the blocks for measurement of electrical potentials at interior locations; other holes are drilled to promote intrusion of saltwater. During exposure of a block to a saltwater or other corrosive environment, electrical potentials are measured at rebars as well as in holes. Corrosion currents are also measured, and polarization resistances are determined. Optionally, potentials can be applied to accelerate corrosion. At the end of a test, the blocks are broken for visual examination of the rebars.
This work was done by Rupert U. Lee of Kennedy Space Centerand Joseph J. Curran of Dynacs Engineering Co., Inc. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com under the Materials category, or circle no. 122 on the TSP Order Card in this issue to receive a copy by mail ($5 charge).