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dc.contributor.authorDarwin, David
dc.date.accessioned2016-03-04T20:55:55Z
dc.date.available2016-03-04T20:55:55Z
dc.date.issued1995-05
dc.identifier.citationDarwin, D., "Corrosion-Resistant Steel Reinforcing Bars," SL Report 95-2, University of Kansas Center for Research, Inc., Lawrence, KS, May 1995, 25 pp.en_US
dc.identifier.urihttp://hdl.handle.net/1808/20448
dc.description.abstractThe corrosion of reinforcing steel in highway structures results in maintenance and replacement costs in the United States that are measured in billions of dollars. These costs would be greatly reduced and the durability and design life of reinforced concrete structures greatly enhanced if the corrosion resistance of reinforcing steel were improved. This study involves the evaluation of a concrete reinforcing steel which has shown superior corrosion-resistant properties. Previous evaluations have concentrated on the corrosion resistance of the steel in the atmosphere, which can be quite different than obtained for steel in contact with concrete. Emphasis in this study is placed on the corrosion resistance of the steel in concrete structures. The new steel differs from steel used in standard U.S. practice in a number of ways. Additional alloying elements (copper, chromium, and phosphorus) are used, along with a special heat treatment, to provide the corrosion-resistant properties of the steel. The bars possess lower carbon content than is usual, and the phosphorous content exceeds that allowed in ASTM specifications. The bars are quenched and tempered immediately following the rolling operation, a step that places the exterior of the bars in compression. The apparent corrosion-resisting mechanisms include the formation of a corrosion-retarding layer of copper chloride-<:apper hydroxide at the steel surface in the presence of chloride, the formation of phosphorous oxides, which serve as corrosion inhibitors, the formation of iron-chromium oxide at the steel surface, which is a poor conductor and, thus, reduces the corrosion rate, and the reduction of microfractures in the surface from the rolling operation due to the quenching and tempering process. The corrosion products that form are much denser than for normal reinforcing steel, which further reduces the availability of oxygen and water at the steel surface. The reduced microfractoring lowers the surface area available for corrosion. The study is carried out in four overlapping stages. Stages l and 3 are dedicated to understanding the corrosion protection mechanisms and the degree of corrosion protection when the steel is subjected to different chloride concentrations and different deicing chemicals. Stage 2 involves the evaluation and comparison of the new reinforcement to standard reinforcing steel using accepted time-to-corrosion tests. Stage 4 consists of a determination of the mechanical properties of the new steel, as affected by the alloying process. The study involves the evaluation of four types of steel, representing combinations of alloying elements and heat treatment. The steels include two conventional steels, one hot-rolled and one subjected to heat treatment immediately following the hot-rolling operation, and two forms of corrosion-resistant steel, one hot-rolled and one heat-treated. The experimental results and analyses demonstrate that the microalloying procedure improves the corrosion resistance of steel reinforcing bars cast in concrete and subjected to deicing chemicals. The resulting corrosion rate is approximately one-half of the corrosion rate exhibited by conventional reinforcing bars. The use of the quenching and tempering heat treatment following hot rolling appears to provide some additional corrosion resistance, when used in conjunction with the microalloying procedure. The heat treatment produces a reinforcing steel with higher yield and tensile strengths. A phosphorous content in excess of that allowed under current AS'IM requirements does not cause the corrosion resistant steel in this study to be brittle. The tests indicate that the new reinforcing steel should not be combined with conventional reinforcement in reinforced concrete structures. The new steel performs well when used in conjunction with an epoxy coating and offers the potential of economically providing a measurable improvement in the corrosion performance of reinforced concrete structures subjected to chlorides and deicing chemicals. Implementation of the new reinforcing steel will require additional corrosion tests to fully document the corrosionresistant properties of the reinforcement, the development of standard specif'JCations for the material, and the execution of demonstration projects in which the new reinforcing steel is applied in practice. Special attention should be given to using the new steel in conjunction with epoxy coating.en_US
dc.publisherUniversity of Kansas Center for Research, Inc.en_US
dc.relation.ispartofseriesSL Report;95-2
dc.relation.isversionofhttps://iri.ku.edu/reportsen_US
dc.titleCorrosion-Resistant Steel Reinforcing Barsen_US
dc.typeTechnical Report
kusw.kuauthorDarwin, David
kusw.kudepartmentCivil/Environ/Arch Engineeringen_US
dc.identifier.orcidhttps://orcid.org/0000-0001-5039-3525
kusw.oapolicyThis item does not meet KU Open Access policy criteria.
dc.rights.accessrightsopenAccess


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