Experimental Study on Cracking Behaviour of Fiber Reinforced Concretes by Ring Test

In this work the influence of different kinds of fibers on Fiber Reinforced Concrete (FRC) cracking behaviour was examined. Several FRCs were prepared by alternatively using steel fibers, polypropilene macro-fibers, glass macro-fibers, hybrid or bicomponent synthetic fibers. The fibers’ dosage was always equal to 0,55% by volume. As reference, a mixture with the same mixture proportions but without fiber reinforcement was prepared and tested. Ring test according to ASTM C 1581– 04 and free shrinkage test were carried out in the same exposure conditions: 21°C and 50% relative humidity. Moreover, compressive and tensile strengths of FRCs, as well as their elastic modulus, were evaluated on cubic specimens up to 28 days of curing, and, in particular, also at the time of ring cracking. In this way, other important information could be extrapolated by introducing these experimental data in suitable numerical model of the ring concrete specimens available in the literature. This procedure enables to study the influence of the kind of fibers on the potential for early-age cracking of concrete, as well as to identify the effect of tensile creep on concrete cracking. Results obtained showed the effectiveness of the randomly dispersed fibers in counteracting the FRC early cracking