STEEL FIBERS Steel fibers are characterized by high E-modulus (200 GPa) and high tensile strength (2500 MPa). They prevent creep of the concrete but do not counter act early shrinkage. Corrosion does not cause spalling of the concrete, justa change of color on the concrete surface. Protruding steel fibers can pose a risk of injury or damage to water – proofing membranes.SYNTHETIC MICRO-FIBERS Synthetic micro-fibers have an even lower E-modulus (3 – 5 GPa) than syn- thetic macro-fibers. They are mainly used to reduce early-age shrinkage cracking and also to improve fire resis- tance due to their low melting point (160°C). Again these synthetic micro- fibers are non-corrosive.