## 1 Introduction
In the last years, many studies have been performed to determine the steelmaking slags suitability for using as aggregate in concrete in order to enhance the \"4R--reduce, reuse, recycle, and renew strategy\" and optimize the wastes management process for both environmental sustainability and cost savings in steel production [16]. Besides their use in concrete, steelmaking wastes addition to hot mix asphalt for road construction is growing year by year. Several studies have been conducted to test EAF slags performance as aggregate in asphalt concrete for pavement surface layers [11; 13]. In addition to adequate mechanical characteristics, steelmaking slags for asphalt mixes must have other suitable features related to aggregate shape, surface roughness, and texture in order to enhance the adherence and skid resistance of pavement surface layers. Adherence is the tangential force mutually exchanged on the contact surface between tire and road pavement. This phenomenon is related to many aspects including the geometrical characteristics of the micro- or macro-texture of aggregates [17]. Therefore, in order to achieve the goal of enhancing road safety it is important to evaluate the texture performance of steelmaking wastes when used as an aggregate in asphalt concrete. In particular, pavement skid resistance is strictly related to the surface texture, especially in wet conditions; consequently, the accident rate depends both on texture and friction [18; 19; 20]. More specifically, road pavements contribute to friction through a combination of micro- and macrotexture. At low speed, microtexture determines the adhesion phenomenon due to the molecular interaction forces which grow between the tire and the surface. At higher speeds the hysteresis mechanism arises: the tire repeatedly deforms, enveloping surface texture asperities [21; 22; 23; 24]. \begin{table}
\begin{tabular}{c c} \hline \hline
**Chemical Composition** & **Average Range (\%)** \\ \hline SiO\({}_{2}\) & 5–40 \\ FeO & 1.2–50 \\ CaO & 15–54 \\ MgO & 1–21.4 \\ Al\({}_{2}\)O\({}_{3}\) & 1–15 \\ Others & 0.05–5 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Chemical composition of electric arc furnace (EAF) slags (wt. %) values averaged from [2] by literature analysis. Macrotexture determines the hysteretic deformation of the rubber and the consequent development of horizontal forces which are opposed to the slipping of wheels. Surface texture can be supposed to be the superposition of \"many\" elementary components (harmonics); in particular, macro-texture is related to wavelengths (\(\lambda\)) between 0.5 mm and 50 mm, whereas micro-texture refers to \(\lambda<\) 0.5 mm [25]. Referring to the micro-texture range, surface polishing phenomenon is also a crucial issue to be investigated. In fact, surface texture and, consequently, skid resistance change over time because of many deterioration phenomena under traffic loadings related to the polishing process of aggregates. In the light of the above, this paper focuses on the evaluation of EAF slags usability as aggregate in asphalt concrete. In particular, the research is aims to analyze these type of \"second-hand aggregate\" in relation to durability, wear resistance, and polishing behavior by investigating the relationship between pavement friction and aggregates micro-texture. The EAF slag used in this study is obtained through intense oxygen injection procedures and a subsequent controlled and accelerated cooling with water spray for its complete stabilization.