Influence of aggregate size on flexural fatigue response of concrete

Abstract

Plain concrete used in pavements undergoes fatigue damage with repeated traffic and thermal loading. Numerous studies were conducted previously to evaluate the effect of various parameters on the fracture behavior of concrete. Nominal maximum aggregate size which is one of the parameters investigated in the past, to evaluate the fracture characteristics was focused to influence the fracture energy of concrete significantly. This could be due to a larger crack path and greater crack growth resistance offered by the larger aggregates in the fracture process zone. Hence, it is worthwhile to investigate the effect of nominal maximum aggregate size (NMAS) of aggregate on the fatigue life of concrete. This factor, if influential, might be a feasible approach for field application to control the fatigue performance of concrete. In the present study, the effect of nominal maximum aggregate size was evaluated under different stress levels (80, 85, and 90%) and different frequencies of loading (2, 5, and 10 Hz). For this purpose, flexural fatigue test was conducted on concrete beam specimens. The specimens were prepared with a blend of fine aggregate and coarse aggregate with two different nominal maximum aggregate sizes (10 mm and 20 mm, designated as S10 and S20 respectively). A total of 100 specimens of 100 mm × 100 mm × 500 mm size were used in the experimental investigation. The results show that the fatigue life of samples with S10 mixture is significantly higher compared to S20 mixture for 80% stress level but are almost similar for 90% stress level irrespective of the loading frequency. The fatigue results are in better agreement with three-parameter Weibull distribution compared to other distributions such as lognormal as confirmed by the goodness of fit test Anderson-Darling statistic. The value of β, the Weibull distribution characteristic shape parameter, obtained as less than 1.0 in this study, indicates the risk of early life failures for the considered stress levels. The survival probability plots and p-value statistics suggest that stress level influences the fatigue life estimation for both S10 and S20 samples but not the loading frequency. Based on the present study, it can be concluded that smaller nominal maximum aggregate size is more beneficial for the fatigue performance of concrete.