Title:
Damage Mechanisms in Fiber-Reinforced Concrete Subjected to Flexural Fatigue through the Analysis of Cyclic Creep Curves
Author(s):
Vicente
Publication:
Web Session
Volume:
ws_F24_Vicente.pdf
Issue:
Appears on pages(s):
Keywords:
DOI:
Date:
11/3/2024
Abstract:
The fatigue response of fiber-reinforced concrete (FRC) can be characterized through the number of load cycles to failure. However, this parameter does not provide any information on the degradation process that the material undergoes during its fatigue life. For this purpose, it is more interesting to study cyclic creep curves, which relate the maximum strain as a function of the number of cycles. In the case of flexural fatigue, these curves represent the maximum crack opening (CMOD) versus the number of cycles. While in compressive fatigue the cyclic creep curves in FRC have a characteristic S-shape, in flexural fatigue this is not always the case. Several works indicate that, under certain fiber contents and stress levels, a double fatigue mechanism (a double S-curve) is observed. First, a damage process in which the concrete does not show macro-cracks, which is governed by the matrix (matrix fatigue). And then, once the concrete has cracked, another much more ductile damage process, dominated by the connection between fibers and matrix (fiber-matrix bond fatigue). In this work, this double fatigue mechanism appearing in FRC fatigue is studied. For this purpose, 75×75×300 mm prismatic specimens with three different fiber contents (0.3%, 0.6% and 1%) were fabricated. The specimens were subjected to flexural fatigue under the same relative stress levels. The results reveal that the probability of this dual behavior is higher the lower the fiber content. In addition, it is observed that fiber-matrix bond fatigue, being a faster damage process, has more impact on fatigue life. In this sense, a good correlation is found between the slope of the secondary branch of the cyclic creep curves and the fatigue life.