Fatigue cracking of polypropylene fiber reinforced concrete

The nucleation and growth of fatigue cracking in concrete are attributed to the inherent weakness of concrete in tension. Potentially useful improvements in the mechanical behavior of concrete fan be affected by the incorporation of fibers. In this study, the effects of several parameters that influence the composite behavior of fiber reinforced concrete (FRC) have been investigated under dynamic loading conditions. The aim was to quantify the delay in the fatigue crack initiation and further propagation in the concrete matrix due to the addition of plastic fibers. Notched and unnotched beam samples were prepared from different FRC mises and tested in the laboratory under various stress ratios Strain measurements versus number of cycles were intermittently recorded for all the beams until failure Following the laboratory testing, an analytical investigation teres performed using a finite element analysis where various material and geometrical parameters were incorporated ill different sets of numerical models. The purpose of these models was to acquire an understanding of the actual behavior of the FRC during different stages of fatigue cracking. Testing results indicated that the addition of plastic fibers to the concrete matric, in general, extended Stage Tof crack initiation by about 18 percent and prolonged Stage II of the crack propagation by 60 percent. Results from the finite element analysis on fiber reinforced concrete have confirmed the laboratory test results. It is suggested that Stage III of fatigue cracking be neglected when estimating the total fatigue life of concrete structures.