the use of recycled aggregate to elaborate new concrete permits to reduce the quantity of construction and demolition waste and the exploitation of sources of natural aggregates, preserving the nonrenewable resources. the properties of recycled aggregates depend of both, the characteristics of natural rock and the properties of original concrete. this paper presents the physical-mechanical properties evaluated on different samples of recycled coarse aggregates, which were obtained from crushed concretes of unknown characteristics. these aggregates were employed in a 75%, by volume, by replacement of natural coarse aggregate in the elaboration of concretes of different w/c ratio. the properties in fresh and hardened states were comparatively evaluated with those of conventional concrete. the quality of recycled aggregates was lower than that of natural aggregates, due to the mortar present in those. the resistant behaviour of recycled concrete was similar to the conventional one, whereas the properties linked with the density of the material (ultrasonic pulse velocity and modulus of elasticity) were lower than those of conventional concrete.