Durability performance of fiber-reinforced concrete in severe environments

Polypropylene (PP; 0.5%), polyvinyl alcohol (PVA; 0.75%), and hooked-end steel (1%) fibers were investigated to evaluate the durability performance of fiber-reinforced concrete (FRC) exposed to severe environments. Conventional beam specimens (100 × 100 × 360 mm3) were prepared and exposed to three types of conditioning systems for 27 months, in both un-cracked and pre-cracked conditions. Degradation of the FRC was evaluated using visual or photographic inspection, change in permeable pore space, destructive beam testing, scanning electron microscopy analysis, and depth of carbonation measurements. For each of the fiber types and mixtures evaluated, significant surface degradation and carbonation only appeared in specimens exposed to immersion in a low pH solution designed to simulate swamp water. These specimens also exhibited significant degradation in both average residual strength (ARS) and toughness. On the other hand, difficulties in the comparison between pre-cracked specimens and un-cracked specimens were found due to re-adhered or healed pre-cracked specimens from dissolved materials (salt or lime) in solutions. A relatively good resistance to saltwater immersion and w/d conditioning was observed for all fiber types. Among fiber types, steel fibers showed the highest strength to conditioning compared with PP and PVA fibers.