Used foundry sands represent the highest amount of solid wastes generated by foundries. Classified by European Union regulations as non hazardous waste, they represent a relevant source to be reused in several industrial sectors, in building construction primarily.

In present paper, the properties of mortars and concretes containing different dosages of used foundry sand (UFS) as partial replacement of sand were investigated in both fresh and hardened conditions. In particular, higher percentages of addition, but lower if referred to the whole aggregate (fine and coarse), were considered in concretes than in mortars. Both mortars and concretes were evaluated with respect to consistency of the fresh mixture and compressive strength of the hardened material. Elastic modulus determination of the hardened material was carried out on concretes.

A low (10%) amount of used foundry sand does not change the mortar's performances. In the presence of higher additions a workability decreasing can be outlined, and then a higher dosage of superplasticizer is required in order to keep it constant. Mechanical performances lower of about 20-30% than those of the conglomerate without used foundry sand are observed. The higher penalization it seems to concern to the conglomerates of better quality (i.e. lower water-cement ratio).