This paper presents an experimental study to characterize the mechanical behaviour of bituminous mixtures containing high rates of reclaimed asphalt pavement (RAP). Two semidense mixtures of 12 and 20 mm maximum aggregate size and containing 40 and 60% RAP, respectively (S-12 and S-20, in accordance with Spanish specifications), which were used for rehabilitation of a highway section, were evaluated. First, the effect of RAP variability on the recycled mixtures was analyzed. Their mechanical properties were then studied by determining the stiffness modulus and indirect tensile strength and cracking and fatigue behaviour. Results show that high rates of recycled material can generally be incorporated into bituminous mixes by proper characterization and handling of RAP stockpiles.
Fatigue cracking in asphalt mixtures—a common, widely studied mode of distress in flexible pavements—necessitates major investments in pavement maintenance and rehabilitation. To date, research has focused on the response of bituminous mixes subjected to cyclic loading until failure. Moreover, low-temperature thermal stresses in bituminous mixes have been investigated in isolation to determine the effect of thermal gradients on materials. However, decreased temperature leads to a combined effect of fatigue distress and thermal stress. To provide insight into this phenomenon, an experimental study based on a new test procedure developed by the Road Research Laboratory of the Technical University of Catalonia, Spain, is presented. This method allows the simultaneous evaluation of the effect of thermal stresses and the fatigue response of asphalt mixtures.
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