The need to consider flexural post-cracking creep behavior of macro-synthetic fiber reinforced concrete

The flexural creep of plastic fiber reinforced concrete (PFRC) is a controversial issue since significant doubts regarding the suitability of this type of fiber and its influence in the long-term behavior of the material still exist. The objective of this paper is to evaluate the post-cracking creep response of PFRC beams under flexural load in comparison with that of steel fiber reinforced concrete (SFRC) beams. The aim is to explore how the pre-crack opening and the environmental condition affect the long term behavior of each material and identify differences. An experimental program was conducted with 30 concrete beams with dimension of 150 × 150 × 600 mm reinforced with plastic or steel fibers subjected to a 4-point bending creep test for 5 months under 2 environmental conditions. Results showed that the flexural creep coefficient of PFRC is 2 times bigger than that of SFRC. Despite that, the use of plastic fibers as reinforcement should not be rejected as long as the additional creep is considered in the design and the crack widths are limited to reduce the risk of tertiary creep.