From 2015 till present, the Professorship for Polymer Engineering has developed the principle of structural re-use of End-of-Life (EoL) thermoset composite products. The method is based on keeping the composite structure of EoL products but machining them into smaller parts, either strips or flakes, which then act as reinforcing elements in new products. In this manner the properties of the EoL composite, like mechanical strength, stiffness and water resistance, remain unimpaired and are transferred to the new product. Because the material based on EoL composites is newly developed, safe use with respect to leaching of heavy metals and salts needed to be proven to allow for introduction in the civil engineering market. A test programme was therefore set up and carried out by an independent lab, SGS Intron, to investigate the effects of leaching in the presence of groundwater or rainwater. The diffusion tests show that the method of structural re-use of EoL composite can be safely used to create civil engineering structures.