Salts may penetrate the concrete and disrupt this protective layer, resulting in corrosion. As the steel corrodes, it expands, cracking the concrete. In the s, there was a sudden increase in the use of de-icing salts and bridge decks were exhibiting significant distress within 10 years of construction. The first bridge constructed using epoxy-coated reinforcing was built in in Pennsylvania. Since then, over 80, bridges and many other structures have been constructed using this material and approximately 10 percent of all reinforcing steel is epoxy-coated.
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Salts may penetrate the concrete and disrupt this protective layer, resulting in corrosion. As the steel corrodes, it expands, cracking the concrete. In the s, there was a sudden increase in the use of de-icing salts and bridge decks were exhibiting significant distress within 10 years of construction.
The first bridge constructed using epoxy-coated reinforcing was built in in Pennsylvania. Since then, over 80, bridges and many other structures have been constructed using this material and approximately 10 percent of all reinforcing steel is epoxy-coated.
Epoxy-coated reinforcing steel is used in marine environments to protect against seawater and in inland environments to protect against de-icing salts. Based upon a review of the past 40 years of use, bridges built with epoxy-coated reinforcing bars in areas exposed to de-icing or marine salts are predicted to last from 75 to years without major costly repairs. Welded wire fabric, covered by ASTM A, may be green or purple, based upon the purchase specification.
All standards require that manufacturers of epoxy-coated steel take steps to properly prepare the bars prior to coating, ensure that contaminants are not present, and confirm that the coatings are fully cross-linked and bonded to the bar. Just like any material used on a jobsite, appropriate handling of epoxy-coated reinforcing steel is required. Handling and storage requirements for epoxy-coated reinforcing steel may be included in contract documents by referencing ACI or ASTM D or within individual agency specifications.
Coating damage will affect the long-term performance of the coated reinforcing bar; however, even steel with damaged coatings provide better protection than uncoated bars. During coated bar manufacture, the holes that cannot be seen with the eye, termed holidays, are monitored and must be less than one per foot, and all visible damage must be repaired.
General handling and storage requirements are outlined below. During sagging, steel bars may rub on each other, causing coating damage. Nylon or padded slings should be used, and at no time should bare chains or cables be permitted. Steel should be unloaded as close as possible to the point of concrete placement to minimize rehandling, and at no time should coated steel bars be dragged, as this may result in coating damage on bar ribs. Coated and uncoated steel should be stored separately.
If the steel bars are to be exposed outdoors for more than 30 days, they should be covered with a suitable opaque material that minimizes condensation. The coated steel should be tied using a coated tie wire. This wire is typically When used with epoxy-coated reinforcing bars it is typically coated with PVC. Bars must not be flame cut. Bars may only be bent at the jobsite with the permission of the engineer responsible for the particular project, and this should be documented.
If bending is to be conducted, it must be conducted at ambient temperatures. Stands or rails used for concrete placement machines should not be welded to the epoxy-coated steel. After welding, all exposed steel should be repaired using a two-part epoxy. The epoxy-coated reinforcing industry does not recommend single component spray can systems, as these do not provide adequate coating thickness unless many coats are provided.
Repair materials should be obtained from the reinforcing steel fabricator. Repairs should be strictly conducted according to the written instructions furnished by the patching material manufacturer. Summary Epoxy-coated reinforcing steel will provide long-term protection against corrosion and its life is maximized by reducing coating damage. It should be installed with care to minimize coating damage using common-sense practices, outlined above. If damage to the coating is observed, it should be repaired using a two-part epoxy.
By following proper handling and storage, maximum life expectancy can be achieved. Featured Articles.
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The volume expansion rust expansion of steel bars in concrete structures will occur due to corrosion, which will cause the concrete protective layer to fall off, and serious longitudinal cracks will occur, which will affect the normal use of the structure. The corrosion of steel bars will also lead to the reduction of the effective section area of steel bars and destroy the bond between steel bars and concrete. It reduces the bearing capacity of the structure, and even leads to the destruction of the structure. Therefore, steel corrosion is the most important factor affecting the durability of concrete structures. High resistance to corrosion and higher specific strength. No sparks out of direct cutting. Strong anchoring strength: The strength is equaled with the bar itself.
Use And Handling Of Epoxy-Coated Reinforcing Steel
More A The surface of the steel reinforcing bars to be coated shall be cleaned by abrasive blast cleaning to near-white metal. The number and frequency of tests for coating thickness, continuity, flexibility and adhesion are specified. If the specimen for coating thickness or flexibility fails to meet the specified requirements, two retests on random samples shall be conducted for each failed test.
ASTM A775 epoxy coated deformed steel rebar HRB400