Copper slag is a copper industry waste that is essentially used as an abrasive for metals to remove coatings or paintings, due to its hardness, sieve distribution and rough surface, mainly in the naval industry. After the wearing process, copper slag retains most of its original properties, and remaining an environmental problem. Chemical composition of copper slag presents a high Fe, Si and Al oxide content what makes it a pozzolanic material. Thus, it is possible to use it as a partial replacement for sand and after triturating it into very small particles as a replacement for cement. After a chemical, physical, mineralogical, and environmental characterization of copper slag, its use as a partial replacement of sand on mortars was investigated. The experimental program was developed to evaluate the effect of several percentages of sand substitution in mortars. For mortars 25, 50 and 75 % of sand replacement by volume was studied. A standard 1/3 cement/sand ratio, by weight, with cement type CEM 42.5 I, was used. The type of sand and the effect of washing the slag were also investigated. Strength was measured at 7, 28, 60 and 90 days. Results obtained until now indicate that a reduction of strength occurs when the slag content increases. Additionally, it was observed a delay of the hardening process by the addition of the copper slag. As a conclusion, the use of copper slag as a sand replacement seemed to be a practical option.