## 1 Introduction  
The framework addressing the sustainability optimisation of the mining sector is currently undergoing a very significant revolution. It is abandoning the focus on the efficiency of operations, aiming to reduce the disposed waste, and shifting to a more global paradigm, encompassing not only the mining operations but also the complete life cycle of this vital industry [1]. Wastes resulting from mining operations can result either from crushing or other, more complex processing methods. The former, normally referred to as plain \"mining waste\", has been used in the construction industry (e.g., concrete, embankments) as it does not raise any special environmental concerns; the latter, usually referred to as \"mine tailings\" (MT), produces more worrying materials due to its high levels of different kinds of contaminants which can be washed away when in contact with water [2; 3; 4]. Nevertheless, the potential use of MT as a replacement for natural aggregates, which are usually obtained through an extraction process that severely affects the environment, would not only reduce the consumption of natural resources but also decrease the volume of landfilled MT. However, this waste generates acid mine drainage when exposed to oxygen and water [5], which makes it impractical as an aggregate in common applications, like embankments or roads, if not previously stabilised. Another possible use is inclusion in alkali-activated mortar and concrete, a recent research topic, with promising results in terms of mechanical and environmental performance [5; 6]. Some studies focused on the use of MT as a precursor, albeit requiring a previous thermal treatment [7; 8; 9; 10; 11], while others used a different approach by considering the MT as a filler and/or coarse aggregate in composite materials, cemented by aluminosilicate gel formed from the alkali activation of fly ash, metakalolin, waste glass, or slags [11; 12; 13; 14; 15; 16; 17; 18; 19]. Although many of the above-mentioned studies were dealing with tailings resulting from tungsten and gold mines, several studies have also been produced targeting copper mine tailings [16; 19; 20; 21; 22; 23]. From an environmental perspective, it is important to highlight that alkaline activation has already proved to be very effective for containing and neutralising different types of wastes [24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34; 35] and, specifically, wastes resulting from mine operations [36; 37; 38; 39], a capacity that reinforces the potential for this technique to stabilise mine tailings. Nevertheless, a decisive breakthrough has yet to be achieved, one might say. Alkali activation for mine tailings stabilisation, for an industrial application or landfilling, is not yet a common option because of the logistical difficulties associated with the implementation of such an operation. This is not related with its technical efficiency. For instance, for applications to roads or railway pavements we would need to consider the distance between the mine and the work site, especially if an adequate aggregate can be found nearby. A similar assessment needs to be made regarding mortar or concrete production, i.e., why not use closer and cheaper materials which do not require any sort of chemical stabilisation/enhancement, instead of this waste which, albeit a very competent material, needs to be previously treated? The obvious, most direct solution for this logistical difficulty is the installation of industrial units near the mine for the prefabrication of structural components (e.g., reinforced beams, masonry bricks) or nonstructural elements, like urban furniture or facade panels. Some studies have already started to focus on specific applications, namely, the production of bricks. [PERSON] et al. [40], when studying the production of geopolymer bricks from iron ore mine tailings, reported cost reductions of 20% to 36% relative to conventional clay bricks, as well as significant environmental benefits.