## 1 Introduction  
At the present time, roads are progressively being loaded more heavily due to the increase in heavy vehicle traffic, as these infrastructures are the essential communication links for the transport of goods over medium and short distances [1]. Therefore, roads should be built with higher quality materials, with more optimized production procedures, with a longer working life, and with better mechanical behavior. In turn, road construction is one of the most polluting activities in existence today [2]. The environmental impact caused by these infrastructures is mainly due to the modification of the landscape, the extraction of enormous quantities of raw materials, the emissions produced during their working lives by continuous vehicle traffic, as well as the waste which is obtained after the ageing of the materials which make up the road [3, 4]. It is therefore logical to think that new pavements which are more sustainable with the environment should be developed, but which at the same time do not involve a sacrifice of mechanical characteristics [5]. Different techniques are currently available to minimize greenhouse gas emissions in the bituminous mixes for roads [6]. It should be noted that bituminous mixtures are the fundamental material of the pavement, as they are the most economically expensive element and use higher quality materials. In order to manufacture these mixes in a more sustainable way, different types of binders and additives have been used to reduce the conforming temperature [7], since usually for the manufacture of hot mix asphalt, the aggregates and the binder must be heated to temperatures of around 180 \({}^{\circ}\)C, with the consequent consumption of fossil fuels and the relevant CO\({}_{2}\) emissions [8]. These techniques with lower conforming temperatures have been successfully carried out; however, in most cases they involve sacrificing mechanical properties. Therefore, the higher requirement for quality mixtures in most cases is incompatible with this technique [9]. On the other side, the waste that has been used for the conforming of the bituminous mixtures. This line has different advantages over others, on the one side, by eliminating the deposition of industrial sub-products in landfills [10]; on the other front, the use of waste in the bituminous mixtures avoids the extraction of new raw materials [11], with the consequent reduction of environmental impact; and finally, by providing a new life for the material [12,13]. In addition, the waste can provide the final bituminous mixture with interesting properties for its use, not involving a sacrifice of mechanical characteristics but an increase in its capacity and versatility [14]. There are many investigations carried out in which waste is incorporated for the manufacture of bituminous mixtures; for example, biomass ash [15], ceramic dust [16], construction and demolition waste [17], reclaimed asphalt pavement [18,19], recycled glass [20], recycled plastics [21], etc., in most cases acceptable results were obtained. In this investigation, based on the above, the wish is to obtain a high-quality bituminous mix to withstand the loads of vehicles on high traffic roads. To do this, waste will be used as raw materials, maximising their characteristics [22] and obtaining greater resistance than that provided by conventional aggregates. The waste used is ladle furnace slag and electric arc furnace slag. The slag mentioned comes from the metallurgical industry producing steel from scrap [23]. Electric arc furnace slag is derived from the first stage of the production process called the melting stage. These slags have a resistance, particle shape and size very suitable for use as a coarse and fine aggregate in bituminous mixtures. On the other hand, ladle furnace slag derives from the second stage of the steel production process, the refining stage. These slags have a small particle size, making them ideal for use as filler in bituminous mixtures.