Q. Do steel fibers rust?
This question is the most frequently asked and is precipitated by the fact that rebars and wire mesh are known to rust/corrode. There are a number of factors that contribute to the rusting/corrosion of rebars and wire mesh. They include the concrete's permeability, oxygen and moisture and chloride ions. The total package then produces galvanic cells at the surface of the rebars and wire mesh. The rebar or wire mesh is the conduit for the electrical current flow. The reaction is called an electrochemical process and requires moisture.

Steel fibers, more specifically carbon steel fibers, which are used to reinforce concrete and meet the requirements of ASTM A820, are typically 3/4" (19mm) to 2-1/2" (63mm) in length. These steel fibers are uniformly distributed throughout the concrete cross-section. The steel fibers are not connected and are protected by the high alkalinity of the concrete from rusting/corroding. Unlike rebar and wire mesh the steel fibers are micro reinforcing elements within the concrete and do not possess the same mass and configuration of rebar and wire mesh. Thus the steel fibers within the concrete cross-section will not rust. Any steel fibers exposed at the surface of the concrete will rust, but only that portion of the fiber exposed.

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