EXPERIMENTAL STUDY OF THE CREEP BEHAVIOUR OF STRUCTURAL MACRO-SYNTHETIC FIBERS

Synthetic fibers can be used as structural reinforcement in fiber reinforced concrete elements. After cracking, fibers bridge the crack and contribute to the element’s residual strength. However, these cracks may widen as a result of various time-dependent phenomena. Fiber creep in the crack may contribute significantly to this crack widening. This paper presents the experimental results of creep tests on individual fibers. Polypropylene fibers, that are being used in structural applications, are subjected to a sustained tensile load. Different initial fiber lengths (200 mm, 500 mm) and sustained load levels (53 %, 43 % and 36 % of the ultimate strength) are considered. The experiments have shown that no tertiary creep behaviour is present in these fibers at all considered stress levels. Creep deformation can become very large as the creep coefficient is greater than 6 for all considered load cases, and may exceed 10. The time to failure and total strain at failure depend strongly on the load levels, as well as on the initial fiber length.