Technical and Economic Feasibility and Sustainability of Upcycling Excavation Materials from Tunnelling Projects

In order to promote a circular economy, the reuse of construction and demolition wastes is of great importance, especially as it makes up nearly 60% of the total waste volume in Europe. However, only 40% of it are recycled, while 30% is still landfilled, and the whereabouts of the rest of the material remains unknown. In Austria, this situation is even more acute, as 60% of the total waste volume consists of excavation materials from tunnelling and civil engineering projects, of which only 8% get recycled and the rest is landfilled. In comparison, only 1.1 billion tons of a total of 18.6 billion tons of mined raw materials worldwide are produced in Europe, while its raw material consumption lies at 6.6 billion tons, of which 2.4 billion tons are used in construction. In times of climate change, scarcity of raw materials, an accordingly increasing import dependency of Europe and an ever more unstable geopolitical situation, this is a worrying contrast. One of the main reasons excavation materials is still landfilled is its legal status as waste in most countries, that makes reuse difficult. Developments in recent years suggest that both industry and the authorities have recognized the problem, which is reflected, among other things, in the ruling of the European Court of Justice of 2022 and the draft of an ordinance dealing with excavation materials in Austria, which is expected to come into force in 2026. The remaining stumbling block on the road to implementation is the increased technical and logistical effort involved at the construction site. In order to make sure, that as much excavation material as possible is put to a high-quality reuse, chemical and mineralogical analyses have to be conducted as early as in the planning phase are necessary, with an additional quality management system in real-time during construction phase. Based on the outcomes the material can be used for far more than the common application as aggregates for the production of shotcrete and concrete. New and innovative utilizations are the fabrication of low carbon cements and calcined clays, alkali-activated materials and geopolymers, compressed raw earth bricks or the production of top soil material for agricultural or renaturation purposes. As those applications show similar properties and a lower carbon footprint than conventional construction materials, ecological benefits compared to landfilling the material with its negative impacts on the environment are certain. Furthermore, using excavation materials also bring economic advantages for the project and partners. In the cement industry for example, additives with a lower carbon footprint are constantly sought after in order to reduce expenditure due to the CO2 tax. A tunnelling site will always produce more materials than for its own needs, a market study needs to be conducted to look for potential buyers of the processed or unprocessed material, without destabilizing the local market. The added benefits of ecological and economic benefits are the basis for social acceptance of large-scale infrastructure projects, if they are presented as part of an appropriate communication strategy. These claims of ecological and ecological advantages can be proven by CERN¿s Future Circular Collider (FCC) project, one of the next major projects of the European tunnel construction industry. The FCC, a new particle collider with a circumference of 91km and a diameter of 6m will generate roughly 8 million m3 of excavation material consisting of molasse of the Geneva Basin. Since there are no industrial applications for this material so far, special attention is being paid to possibilities for using the molasse already in the planning phase. This should make the FCC a pioneering model for the use of excavated material in Europe when construction starts in 2035.