Langfristige Schwermetalleinbindung in Böden und Ersatzbaustoffen durch Behandlung mit Bindemitteln

In order to conserve natural resources and landfill space, substitute building materials (recycled building materials, industrial by-products and soil material) should be used as much as possible. However, soil and groundwater must not be contaminated. The most important application of substitute building materials is in road and earthworks. Building materials containing environmentally relevant substances can still be used under certain conditions permitted by law. For this purpose, the Substitute Building Materials Ordinance will be used in the future if a political agreement can be reached. The entry of environmentally relevant substances from building materials into the soil or groundwater is mainly caused by leaching. In recent decades, numerous research projects have been performed on the environmental compatibility of building materials and on the immobilization of environmentally relevant substances. Soil treatment with binders is a well-known method in road and earthworks. In addition to improving the mechanical properties of soils or building materials, binders can be used to immobilize environmentally relevant substances by reducing their elutability. However, most studies on this topic have been performed only on freshly treated materials under laboratory conditions. The differences of elution behavior under laboratory conditions and the boundary conditions outdoor use have not been fully investigated. Moreover, the weathering of the treated material over years was not systematically investigated. The aim of this work is to assess long-term immobilization of heavy metals in binder treated soils by establishing practical elution constraints, the effects of weathering and the underlying chemical processes. These experimental works were mainly funded by the Federal Highway Research Institute (BASt) on the research project FE 05.0167 / 2011 / LRB. This work is divided into experimental studies and geochemical modeling. The experimental investigations include field studies and laboratory experiments. In the field studies, binder treated materials were taken from 10+ years road constructions and characterized to detect the status and the effects of weathering on the binders. In addition, the boundary conditions of the elution were determined on site. For laboratory testing, two binders (one cement and one lime) and two materials (a mixture of soils and a mixture of construction and demolition wastes) were selected. The binder-treated materials were investigated with different elution tests, primarily column tests, under various conditions and with artificial aging. Besides, geochemical modeling was performed. By adjusting the elution boundary conditions and using the thermodynamic databases, the relevant phases for the immobilization of heavy metals was identified. Considering the changes caused by aging or weathering, a prognosis for the long-term immobilization of heavy metals can be given in terms of simulations. Recommendations on soil treatment regarding the elution behavior are given