Here's what I found. Does anyone have any comments.Note that the last benefit applies only to steel fibres but with a casual reading you m,ight miss that distinction.
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Benefits of fiber reinforcement to Engineers:
Reduces plastic cracking: Synthetic fiber reinforcement inhibits the formation of plastic shrinkage and plastic settlement cracks, contributing to the long-term durability of concrete structures. Conventional reinforcement does not function in concrete until the concrete cracks. By the time this occurs, microcracking can lead to larger macrocracks, which can affect the long-term functionality of the concrete.
Minimizes plastic settlement cracking: Plastic settlement cracks occur when fluid concrete settles around rebar and embedments. Fiber reinforcement provides a support mechanism that helps resist the migration of bleed water to the surface and the gravitation settlement of aggregates and cement. The support mechanism provided by the fibers also reduces the tendency for concrete to crack directly over traditional reinforcement and other embedments.
Provides fire resistance: Synthetic fiber reinforcement, particularly in high strength, structural concrete, dramatically improves fire resistance. In concrete, synthetic fibers reduce in volume under high temperatures forming millions of pressure relief voids in the concrete. These voids accommodate the stress created when water vapor turns to steam in the concrete.
Reduces drying and restrained shrinkage cracking: Drying shrinkage stress occurs in concrete many years after initial placement. As moisture slowly exits the concrete, a reduction in volume occurs. If concrete is free to move in all directions, the tensile stress will remain low and the concrete will not crack. If the concrete is restrained from movement, tensile stresses will develop and cracks will form to relieve stress. If steel fiber reinforcement is used and cracking occurs, the steel fibers that cross each crack will redistribute the stress to a crack-free segment of concrete. When fibers are used, cracks are held tighter and the serviceability of the concrete in severe environments is improved.
