Abstract: The recycling of the fine fractions from construction and demolition wastes is an environmental and technological challenge. In view of its incorporation as recycled aggregate in the manufacture of concretes, this work analyzes its influence on the mechanical response of these concretes to the action of variable loading, which can lead to failures due to fatigue. To do this, 3 different recycled mortar were manufactured using fine aggregate: a standardized siliceous aggregate and two others with recycled fine aggregate, coming from the crushing of out of use basalt ballast and concrete sleepers from the railway superstructure. Plain mortars have been subjected to fatigue compressive loading, following the Locati methodology, and have been characterized both by conventional methods and by micro-Computerized Tomography (µ CT) during the fatigue testing. From the observation made on the specimens, it appears that the cracks are generated, mostly, in the paste-aggregate interface and at the aggregate corner vertex of the flakiest aggregates, propagating through the weakest planes, until the failure of the concrete occurs.

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