Papers by Ghazi Al-Khateeb
A simple quantitative method is presented which is applicable to any type of fatigue testing that... more A simple quantitative method is presented which is applicable to any type of fatigue testing that uses sinusoidal strain/stress input and which will work for experimentally identifying points of failure due to fatigue damage of any kind of material being tested. The present work utilizes strain-controlled bending beam fatigue test on asphalt mixtures to demonstrate the efficacy of this method. Distortions in the hysteresis loop or waveform are tracked to pinpoint the appearance of initial microcracks and final point of complete failure due to fatigue damage. Relationship between output signals for consecutive cycles with reference to initial stable cycle is used for computing ‘R2’. The ‘R2’ drops sharply from initial stable value of 1 to less than 0.5 and eventually to almost 0 with increasing loading cycles. The number of cycles determined from the fitted equation at ‘R2’ =1 marks the point of first fatigue failure Nfff and ‘R2’ =0 marks the point of complete fatigue failure Ncff.
The main objective of this study was to investigate the combined effect of the loading frequency,... more The main objective of this study was to investigate the combined effect of the loading frequency, temperature,
and stress level on the fatigue life of asphalt paving mixtures. Asphalt mixtures were designed using
the Superpave design procedure using a 60/70-penetration grade asphalt binder having a Superpave performance
grade of PG 64-10 and crushed limestone aggregate. The indirect tension (IDT) fatigue test was
used to determine the fatigue behavior of asphalt mixtures. The IDT fatigue test was conducted in the
stress-controlled mode of loading using five stress levels: 288, 360, 432, 504, and 576 kPa (approximately
in the range of 42–84 psi loading) representing truck or heavy traffic loadings in real-life conditions, two
intermediate temperatures: 20 and 30 C, and four loading frequencies: 3, 5, 8, and 10 Hz representing truck
speeds of about 12.5–45 km/h. Three replicates were used for each IDT fatigue test. A total of 120 IDT fatigue
tests were conducted in this study. Findings of the study showed that the increase in loading frequency
resulted in an increase in the fatigue life at the two test temperatures 20 and 30 C. In addition, the rate
of increase in the fatigue life with the loading frequency was exponential, and the difference in the fatigue
life (Nf) between the different loading frequencies was found to be higher at lower stress levels than that at
higher strain levels at the two temperatures. It was also found that the difference in the fatigue lives
between the different stress levels was much higher at higher loading frequencies than that at lower loading
frequencies for both temperatures. For the stress-controlled mode of loading, which was used in this study,
an increase in temperature provided shorter fatigue lives for asphalt mixtures.
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Papers by Ghazi Al-Khateeb
and stress level on the fatigue life of asphalt paving mixtures. Asphalt mixtures were designed using
the Superpave design procedure using a 60/70-penetration grade asphalt binder having a Superpave performance
grade of PG 64-10 and crushed limestone aggregate. The indirect tension (IDT) fatigue test was
used to determine the fatigue behavior of asphalt mixtures. The IDT fatigue test was conducted in the
stress-controlled mode of loading using five stress levels: 288, 360, 432, 504, and 576 kPa (approximately
in the range of 42–84 psi loading) representing truck or heavy traffic loadings in real-life conditions, two
intermediate temperatures: 20 and 30 C, and four loading frequencies: 3, 5, 8, and 10 Hz representing truck
speeds of about 12.5–45 km/h. Three replicates were used for each IDT fatigue test. A total of 120 IDT fatigue
tests were conducted in this study. Findings of the study showed that the increase in loading frequency
resulted in an increase in the fatigue life at the two test temperatures 20 and 30 C. In addition, the rate
of increase in the fatigue life with the loading frequency was exponential, and the difference in the fatigue
life (Nf) between the different loading frequencies was found to be higher at lower stress levels than that at
higher strain levels at the two temperatures. It was also found that the difference in the fatigue lives
between the different stress levels was much higher at higher loading frequencies than that at lower loading
frequencies for both temperatures. For the stress-controlled mode of loading, which was used in this study,
an increase in temperature provided shorter fatigue lives for asphalt mixtures.
and stress level on the fatigue life of asphalt paving mixtures. Asphalt mixtures were designed using
the Superpave design procedure using a 60/70-penetration grade asphalt binder having a Superpave performance
grade of PG 64-10 and crushed limestone aggregate. The indirect tension (IDT) fatigue test was
used to determine the fatigue behavior of asphalt mixtures. The IDT fatigue test was conducted in the
stress-controlled mode of loading using five stress levels: 288, 360, 432, 504, and 576 kPa (approximately
in the range of 42–84 psi loading) representing truck or heavy traffic loadings in real-life conditions, two
intermediate temperatures: 20 and 30 C, and four loading frequencies: 3, 5, 8, and 10 Hz representing truck
speeds of about 12.5–45 km/h. Three replicates were used for each IDT fatigue test. A total of 120 IDT fatigue
tests were conducted in this study. Findings of the study showed that the increase in loading frequency
resulted in an increase in the fatigue life at the two test temperatures 20 and 30 C. In addition, the rate
of increase in the fatigue life with the loading frequency was exponential, and the difference in the fatigue
life (Nf) between the different loading frequencies was found to be higher at lower stress levels than that at
higher strain levels at the two temperatures. It was also found that the difference in the fatigue lives
between the different stress levels was much higher at higher loading frequencies than that at lower loading
frequencies for both temperatures. For the stress-controlled mode of loading, which was used in this study,
an increase in temperature provided shorter fatigue lives for asphalt mixtures.