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Steel fibers are not a replacement of synthetic micro fibers and vice versa. Both fiber types provide very different properties to concrete so that the applications fields do not overlap. Rather than a substitute, both fiber types may be used complementary. While steel fibers offer post crack strength and thus act as reinforcement, synthetic micro fibers reduce cracking due to plastic shrinkage and improve the fire resistance of concrete. They do not provide any reinforcing effect.Did this help you?
Mechanically anchored steel fibers have been proven as reinforcement, even for structural application. Steel fibers are made from a material with well known engineering properties; e modulus, Poisson’s ratio, tensile strength and creep. The e-modulus of steel is greater than that of concrete. Thus, the steel fibers pick up the stresses quickly and affect the cracking process immediately. The long term load carrying capacity of the steel fiber reinforced concrete is significant. Steel fibers have a material specification of AStM A820. Macro synthetic fibers come in a large variety and have very different material properties. Macro synthetic fibers do not have a material specification in AStM. All macro synthetic fibers do have an e-modulus lower then that of concrete and relatively low tensile strengths. Thus, macro synthetic fibers need a certain crack width to occur prior to being able to engage in the concrete and then only moderate post crack strength values can be achieved. Macro synthetic fibers are also subject to creep which makes the long term loading capacity of the fiber lower or non existent. The rate of creep can be increased with increased ambient temperatures.
There are at least four factors to review when considering reinforcement; Modulus of elasticity, Poisson’s ratio, tensile strength and creep.
Steel fiber concrete compresses the construction schedule, allows for alternative construction methods or design solutions and increases durability. When a project is delivered quicker with fewer efforts and labor, the higher costs of the steel fibers are overcompensated by the savings.
In certain applications the volume weight of steelfibers is lower as the rebar for a similar reinforcing effect. For those applications the cost/reinforcement is lower for steelfibers.