Effects of short fibers on the long-term behavior of RC/FRC beams aged under service loading

The enhanced post-cracking properties of fiber-reinforced concrete (FRC), as compared to plain concrete (PC), are extensively proven by many experimental findings. However, still limited experimental data are available on the behavior of such materials in long-term conditions and durability. This paper shows results from a study lasting for about seven years, which was for a final discussion on the behavior in the short and long-term of steel and polyester FRC beams with conventional steel reinforcement, after being exposed to sustained service loading and natural environmental agents for 72 months. After 28 days of curing in laboratory conditions, the beams were moved to the exposure site and loaded up to service conditions. The evolution of the crack pattern was monitored and recorded over time. After this long exposure the beams were subjected to a four point bending test in order to evaluate their residual mechanical behavior. Eventually, the beams were cut, in order to carry out durability tests for the evaluation of the carbonation depth and chloride penetration. The experimental results highlight the favorable effects of short fibers in reducing crack width and enhancing flexural stiffness. The presence of short structural fibers appears also to play a useful role in delaying creep effects inside the concrete beams. Finally, the experimental cracking behavior is compared with the one computed by applying the fib Model Code 2010 for the bearing capacity and crack width prediction