Distresses in asphalt pavements are typically due to traffic loading, resulting in rutting or fatigue cracking. The presence of water (or moisture) often results in premature failure of asphalt pavements in the form of isolated distress caused by debonding of the asphalt film from the aggregate surface or early rutting/fatigue cracking due to reduced mix strength. Tensile strength of asphalt concrete is a function of the amount of asphalt binder in the mix, mixture stiffness, absorption capacity of the aggregates used, asphalt film thickness at the aggregate interface and total voids in the mix. The presence of moisture accelerates pavement deterioration under traffic loading. This study suggests that tensile strength can be used as a design tool in the Superpave mix design stage and a modified mix design procedure is proposed based on individual tensile strength.
This research study shows that reliance on the Tensile Strength Ratio (TSR) values only may be misleading in many cases. The individual values of tensile strength of conditioned and unconditioned specimens in conjunction with TSR values should be employed in assessing the effect of water damage on the performance of pavements. This study found that a minimum tensile strength should be established for a given ESAL range. The fatigue life of mixtures decreases exponentially with decreasing tensile strength. This trend is justified by the loss in stiffness and thereby initiating cracks and stripping. A minimum tensile strength for a given ESALs level can be used as a surrogate criterion for fatigue life estimation. This research study also shows that the mixtures with lower tensile strength have higher rut depths, as the aggregate structure is affected due to moisture damage and subsequent loss in tensile strengths of the mixtures.
