The accumulation of wastes of foundry moulding sands, as well as of wastes of concrete demolition scraps after recycling of coarse aggregates, raise an important problem of stocking or of reuse to foundries and demolition contractors with respect of ecological rules and of obligations in favour of environment protection. The present research project aims at the study of reemployment abilities of these wastes in favour of the production of new building materials complying to standards, and on the bases of calcic silicatisation process, the wastes being treated and mixed with anhydre lime, and then cured in autoclave. This treatment of which feasibility must be controled, can offer a recycling way including the fixation of eventual polluting elements. The end products could be various materials such as traditional silico calcic bricks (solid or hollow), wall elements or facing panels. The project includes pilot operations of production at different levels of performances.