Construction waste, mainly those coming from crushed demolition concrete, can be used as partial or complete replacement of natural aggregates. Due to their greater porosity, recycled aggregates have lower density and higher water absorption than natural ones. This research presents different impregnation treatments of the recycled coarse aggregate obtained from concrete containing boulder, in order to improve final concrete quality and optimize their use. Three types of products were analyzed to treat the recycled aggregate (two highly used commercial products and one cement paste), as well as different time between treatment execution and its addition to the concrete. Mechanical and physical properties of concretes with 50% of natural coarse aggregate replacement by crushed concrete were studied. A petrographic study of the different samples was performed to determine the treatment influence on the morphology of the aggregate-mortar interface zone. Previous impregnation treatment of the recycled aggregate proved to be an alternative to improve concrete pore structure and to allow a similar behavior to conventional concretes. The use of waste materials reduces the amount of residues generated once the useful life of the structure ends and decreases the exploitation of non-renewable natural resources like concrete aggregates.