Because of the damage they do to buildings, natural disasters such as earthquakes produce large amounts of waste concretes. Carrying waste materials away from the disaster site causes financial and environmental problems, so people try to recycle the waste concretes as aggregate in order to prevent these problems. Using waste material that was obtained from razed buildings and then was cleaned and later reduced to aggregate form is considered an appropriate solution to environmental pollution. In this study, various physical and mechanical properties of concretes were examined. These concretes were produced by the addition of C 16 (28-day compressive strength of 16 MPa) pieces as aggregate in weight percentages of (referred to total aggregate) 0, 30, 50, 70, and 100%. In the concretes, it was observed that as the amount of WCA increases, density, workability, Schmidt hardness, ultrasound velocity, and compressive strength decrease. (C) 1997 Elsevier Science Ltd.