# A Practice for the Application of Waste in Road Asphalt Pavements in an Eco-Friendly Way
## 2 Materials and Methods  
### Materials  
In this study, for the preparation of asphalt mixtures, four marginal materials were employed replacing both natural aggregates and fillers. The wastes were as follows:  
* Jet grouting waste (JGW) obtained from the consolidation works of an underground highway tunnel;
* Construction and demolition waste (CDW) derived from the demolition of buildings;
* Reclained asphalt pavement (RAP) originated from the milling of deteriorated asphalt pavements;
* Fly ashes (FA) generated by the coal combustion process to produce electricity;  
JGW and CDW required a grinding process of 120 min (after that, no variation in the grading curve arose) to obtain their final size, during which the materials were examined every 30 min. On the contrary, FA and RAP were adopted as replacement of filler and coarse aggregates, respectively, without a grinding transformation. The environmental compatibility of the four waste materials was assessed by the leaching test in compliance with the EN 12457-2 standard [63] (see Figure S1 in Supplementary Materials). The results of the analysis, as shown in Table S1a in Supplementary Materials, demonstrated the environmental applicability of the four wastes (JGW, CDW, RAP and FA) since the concentration of the pollutant resulted lower than the limits set by the Italian Ministerial Decree of 5 February 1998 [64]. The physical properties in terms of equivalent sand and Rigden voids and the mechanical properties expressed in terms of Los Angeles value of the limestone aggregates and waste materials are reported in Table S1b. The results of these properties allowed to made observations regarding the collocation of the waste into road pavement stratigraphy. Since the RAP exhibited poor Los Angeles value that represents the abrasion resistance of the aggregate, it was decided to use it into the base layer; on the contrary CDW was reemployed for making the binder course. In the case of JGW and FA, their mechanical properties allowed to re-use them in both binder and base layer. A total of nine asphalt mixtures were designed comprising the four wastes mentioned whose grading curve followed the requirements of the EN 13108-1 standard [65]. Three different binders were adopted; in detail, a 50/70 penetration grade bitumen was used for making hot asphalt mixtures while for the cold one, a cationic bitumen emulsion and a Portland cement 325R were used. The mechanical investigation of the four asphalt mixtures (see Figure S2 in Supplementary Materials) were evaluated by investigating the engineering performance reported in Table 1 in compliance with the EN standards. The optimum bitumen content (OBC) was identified in correspondence to the maximum S value [65] (see Tables 2-4) for the hot asphalt mixtures of the binder (see Table 2a) and base (see Table 2b) layer, while for the cold asphalt mixtures, designed only for the base layer (see Table 2b), the optimum solution was identified by considering those with the specific gravity and ITS value, assessed at the 28 th curing day [72], close to those of HMAbase (see Table 4). Therefore, the optimum cement, water and bituminous emulsion \begin{table}
\begin{tabular}{c c c} \hline \hline
**Engineering Performance** & **Standard** & **Test Temperature** \\ \hline Marshall stability (S) & EN 12697-34 [66] & 60 \({}^{\circ}\)C \\ Marshall stiffness (MS) & EN 12697-34 [66] & 60 \({}^{\circ}\)C \\ Indirect tensile strength (ITS) & EN 12697-23 [67] & 25 \({}^{\circ}\)C \\ Indirect tensile strength ratio (ITSR) & EN 12697-12 [68] & 25 \({}^{\circ}\)C \\ Indirect tensile stiffness modulus (ITSM) & EN 12697-26-Annex C [69] & 10–20–40 \({}^{\circ}\)C \\ Fatigue life (Nf) & EN 12697-24-Annex E [70] & 10 \({}^{\circ}\)C \\ Resistance to permanent deformation (RD) & EN 12697-22 Procedure B [71] & 60 \({}^{\circ}\)C \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Engineering performance of asphalt mixtures.