Synopsis An artificia1 aggregate has been produced by pelletizing and firing the residues collected from incinerators used to burn domestic refuse. Tests on concretes made with this material as a coarse aggregate have been carried out forperiods of up to 4% years. The properties tested include compressive and tensile strength, modulus of elasticity, shrinkage and creep. The results so far obtained would appear to indicate that, under laboratory conditions, the material performs in a satisfactory manner. Although the material is not commercially available at the moment, it may be possible to produce it at a cost which would make it no more expensive than many lightweight aggregates currently on the market.