Fatigue life analysis of polypropylene fiber reinforced concrete under axial constant-amplitude cyclic compression

Abstract

Polypropylene fiber, as a micro-scale reinforcement, can effectively inhabit the continuous micro-crack propagation of concrete during service. This paper aimed at examination of the fatigue life of polypropylene fiber reinforced concrete (PFRC) as subjected to repetitive compressive stress at multiple levels. A total of 18 groups of prismatic specimens were tested for different stress levels and polypropylene fiber parameters (volume fractions and aspect ratios). A two-parameter Weibull distribution was employed to describe the fatigue life probability distribution of PFRC. The shape parameter and characteristic life parameter were derived by averaging the values estimated by graphical method, moment method and maximum likelihood estimation method. The results indicated that the addition of polypropylene fiber into the concrete matrix can remarkably prolong the fatigue strength of concrete. Compared with plain concrete, the fatigue strength of PFRC could be increased by up to 28.1% under the failure probability of 5%. The fatigue life of PFRC was increased with an increase in the polypropylene fiber volume fraction up to 0.15%. However, the fatigue life of PFRC was decreasing with an increase in the fiber aspect ratio. The PFRC specimen with a volume fraction of 0.15% and an aspect ratio of 167 possessed the highest fatigue compressive strength among all the designed specimens. The fatigue life probability distribution of PFRC also obeyed the two-parameter Weibull distribution. Finally, a single-logarithm fatigue equation for PFRC was developed with both fiber parameters and failure probabilities taken into account, which can realistically predict the fatigue life of PFRC. This research outcome provides new knowledge and database that underpin the future development of design specifications for PFRC structures.