Use of cement-bound industrial wastes and recycled materials in earthworks and road construction

For environmental reasons, it is becoming increasingly difficult and eherefore expensive to find fresh sites for wasee disposal. Investigations have shown that coal fly-ash, refuse incinerator grate ash, demolished road asphalt and concrete rubble can, when suicably treated with cement, be economically reused for road construction, for which purpose they can satisfy the same requirements as those applicable to nacural stone. As a result of these efforts, land areas for disposal can be saved and natural resources conserved. In addition to improving the mechanical properties of chese materials, cement can immobilize the harmful substances contained in them and prevent heavy metals from being washed or leached out. This immobilization is achieved by the formation of solid solutions by substitution of elements with equal ionic radius, by adsorption and by envelopment of the harmful substances by increasing the impermeability. In the Federal Republic of Germany 200,000 tonnes of cement-bound coal fly-ash has so far been successfully used in the construction of sub-bases for pavements. Fly-ash, refuse incineration ash, demolished asphalt and concrete rubble are made and used in accordance with the code of practice for soil stabilization with cement (ZTVV regulations). The experience chat has been gained in using these materials has been collected by a working committee of the German Road and Traffic Research Association (Forschungsgesellschaft für Strassen- und Verkehrswesen), evaluated and embodied in data sheets for each material separately.