ABSTRACT
ABSTRACT: Top-down cracking is a commonly occurring distress in asphalt concrete pavements. Ageing of binder and effect of moisture, besides traffic loading parameters, contribute significantly to the top-down fatigue cracking of asphalt layers. Experimental investigations were conducted in this study to evaluate the effect of these parameters (ageing and moisture) on the fatigue crack initiation and propagation. Saturated Ageing Tensile Stiffness test (SATS), which is a protocol introduced recently in the European standards, has been used for ageing the asphalt mixtures. The ageing of the asphalt mix has been done for different periods: 25, 45 and 65 hours. Ageing indices of the aged mixes were calculated based on the resilient moduli of un-aged and aged mixes. Indirect Tensile Fatigue Test (ITFT) was conducted on aged and un-aged mixes. Fatigue life (load repetitions to crack initiation) of the mix aged under the combined action of temperature and moisture for 25 hours was found to be 30 percent of that of un-aged mix. Ageing the specimens for longer durations did not significantly reduce the fatigue life any further. Laboratory fatigue performance of mixes has been explained in terms of binder rheology and ageing index of mix.
