Extractive and Raw Materials Processing Industries are strongly related to the generation of large volumes of solid wastes and residues. In 2014, mining and quarrying activities in the EU-28 were accountable for 25 billions tones, almost 30% of the total waste generated and be steadily increasing the following years . This stored material feedstock in the legacy sites constitutes an opportunity that can be unlocked and valorised as secondary resource, in a sustainable way, giving a boost to the local economy. Towards this direction, the European Commission has undertaken a lot of initiatives aiming at: (a) increasing the resource productivity by applying the Roadmap for a Resource Efficient Europe, (b) increasing the resource efficiency and supply of “secondary raw materials” through recycling and reuse by applying the European Raw Materials Initiative, and (c) promoting reuse and stimulating industrial symbiosis by applying the EU action plan for a Circular Economy.
Among the different Industrial Residues of extractive industry, those derived from metallurgical activities, i.e. slags (e.g Copper Slag from Boliden with an annual production of 440,000 tn, see table 1 for info on its chemical composition), sludge, dross, etc. stand out, as they represent major streams in Europe (50-60%), with potential utilization paths as secondary resources in several industrial sectors, those of constructions and building materials, in particular. Copper slag is a by-product of copper production operations at the Rönnskär smelter. The copper slag primarily contains silica (SiO2) and iron, which have been combined to form a chemically stable, glass-like compound. The iron comes from the copper parent mineral and the silica is brought in the form of sand used to form the slag during the smelter’s processes. The copper slag also contains small amounts of copper (0.5%) and zinc (1.2%). Other present elements (primarily metals) present generally comprise less than 0.1% of the copper slag.
The recovery of valuable metals, which comprises only a small portion of the slag (<2%) has been extensively studied and although the developed processing routes are technologically feasible and promising, they suffer from economic viability. The main reason for that is the low concentration of valuable metals (100-1000ppm) that can be recovered, and the risk associated with the necessity to invest substantially in capex. However, the utilization of solid wastes/residues as a source for several components (compounds, minerals, phases etc.) for the production of construction and building materials has a lot of advantages such as:
(a) 100% utilization of wastes, avoiding the formation of downstream residues;
(b) low processing cost of the manufacturing technologies;
(c) further enhancement of the economic value of the waste stream allowing a win-win situation both, for the waste provider and the waste recycler (within the context of industrial ecology and symbiosis);
(d) minimization of landfilling; and (
e) decrease of the demand of primary raw materials.
In addition, the production of building materials with an innovative manufacturing method (3D printing) offers faster and easier production with 50% lower waste compared to the conventional precast production method as well as the manufacturing of customized products in terms of shape according to the needs of the structures which are difficult to be built with conventional methods . There are several points in e.g a tunnel that need customized products including the places at the ventilators, the exits, the Emergency phones constituting a 15% of the total tunnel surface. The project proposes a valorisation approach of the Copper Slag from the partner Swedish mining and smelting company Boliden, which leads to the production of high added value novel and smart fire-resistant photocatalytic novel materials for the construction sector. This can be achieved through materials engineering of the secondary resources, novel manufacturing technologies such as additive manufacturing and smart manufacturing of building materials through functionalization.
The project idea originates from a combination of the existing proprietary knowledge and know-how of the consortium on the development of fire resistant geopolymers through the Boliden’s Copper Slag. Crucial members of the consortium participated in the “RECOVER – EIT RM” which aimed to the design and manufacturing for a modular unit for in-situ material production. During this project a recipe for fire resistant geopolymers was designed from the Copper slag of Boliden. The designed materials proved to withstand the most severe fire scenario under two consecutive RWS – curves and were validated in terms of fire resistance. In the IDEAL project an upgraded prototype will be formed in order to be adjusted to the commercial requirements in terms of dimensions and production. To achieve the above, IDEAL project will use the modular production unit (developed in RECOVER project) and have it adapted by bringing additional processing unit operations.
The latter will allow the production of the envisaged final boards at a scale of 1x2m2 (daily production 100 m2), integrating zeolite nanocrystals of high-specific surface, being the right substrate for the photocatalytic coating. The produced boards will be functionalized with integrated photocatalytic coatings generated from ZnO (Boliden – providing) with disinfecting and air cleaning functionalities. In parallel, the developed material of the IDEAL project will be produced in such pilot scale using additive manufacturing/3D printing of the geopolymeric components.
The coatings will be sprayed on the material through a spraying system applied on both pilot production units.