• Hill and Griffith

Do I Need to Remove Concrete Form Oil From Rebar?

No. A common misunderstanding in the concrete industry is clarified in this review of an article from ForConstructionPros.com.

Question: On several of our most recent projects, the inspector has been complicating our pour schedule when finding form oil over-sprayed on the rebar. Is it our misunderstanding that form oil on rebar shouldn’t pose a problem to the performance or the acceptance of our pre-pour inspection? Answer: Your question addresses a common problem across the construction industry. Code edition after code edition presents challenges throughout the industry to remain current with the latest acceptable practices. This is a question of appropriate code reference — ACI 332 — rather than ACI 318, and of referencing the most recent version, ACI 332-10, instead of older versions -04 or -08.

Stated in section 4.2.4 of ACI 332-10, the code provides: "4.2.4 Surface conditions of reinforcement—At the time concrete is placed, deformed bar and welded wire reinforcement shall be free of materials deleterious to development of bond strength between the reinforcement and the concrete." "R4.2.4 Common surface contaminants such as concrete splatter, rust, form oil, or other release agents have been found not to be deleterious to bond." First, during construction, nothing should be found on the reinforcement that would adversely affect the bond strength of the reinforcement in the concrete. Second, what common site conditions found on rebar are not to be considered deleterious to bond. Form oil is a surface contaminant that is not considered deleterious to bond. Deformed bar and welded wire are designed to achieve a mechanical bond with the concrete rather than a chemical or adhesive bond. The mechanical bond relies on a keying action with the deformations along the length of the reinforcement bar. As long as the surface contaminants do not effectively eliminate the presence of those deformations, they would not be considered deleterious to bond. ACI 332-10 is available through the bookstore at www.concrete.org.

To read the full article about concrete form oil on rebar go to, "Oil on Rebar."

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