# A Practice for the Application of Waste in Road Asphalt Pavements in an Eco-Friendly Way
###### Abstract
In fact, the temperatures adopted for the warm process reach 100 \({}^{\circ}\)C [50], while the cold technology reaches at most 60 \({}^{\circ}\)C [51]. This last process is usually combined with the recycling of waste materials, in particular, the so-called reclaimed asphalt pavement (RAP), namely the waste produced from the removal of existing asphalt pavements. The most popular pavement rehabilitation method including 100% RAP is Full-Depth Reclamation (FDR). Not always a blend with 100% RAP performs better than a traditional HMA. RAP features significantly influence the service life and performance of recycled pavements [52]. Therefore, the cold recycling of RAP also involves the addition of cement in the mixtures. Some researchers [53] confirmed that the presence of cement improves the indirect tensile strength (ITS) and the ITSR of the final mixture. Looking at the effect of cement on cold recycled asphalt solutions, [PERSON] et al. [54] investigated different contents (0%, 2%, 4%, 6% and 8% by the mass of dry aggregates) and types of cement (ordinary Portland cement, calcium aluminate cements and calcium sulphate) added to a 100% RAP mixture; they found that, when using high quantities of Portland cement, it is possible that some cement remains non-hydrated as a solid powder, especially in the upper parts of specimens. Consequently, that amount of cement does not contribute to the performance of the asphalt mixtures. Owing to the significant environmental impact of asphalt mixtures, life cycle assessment (LCA) was performed in some works comparing alternative treatments [55]. For example, [PERSON] et al. [56] applied LCA methodology to a 5.9-km road segment to compare two different base layers with a thickness of 13 cm, which contained traditional HMAs and a cold in-place recycled mixture (CIRM) with 100% RAP produced by milling an existing asphalt base layer. A climate change (CC) impact indicator was selected to express the contribution of CO2, CH4 and N2O gases to the warming of Earth's climate due to human activities. The obtained results showed that the CC indicator of the CIRM solution was 81% lower than that of HMA. Other research works focused on developing a methodology that could identify the best alternative treatment by performing a multi-criteria decision analysis (MCDA) [57, 58]. This strategy has been widely adopted to (a) determine the most suitable technology for reusing RAP in central plant hot recycling, hot in-place recycling, central plant cold recycling and cold in-place recycling applications [59]; (b) compare various asphalt mixtures based on their engineering performance and life cycle cost indicators [60], cost, environmental and social indicators of the life cycle [61] or engineering performance and service life [62]. On the basis of the above, a new methodological tool was developed in this study for the selection of the most appropriate asphalt mixture solution containing waste materials in substitution of natural aggregates. The sensitivity analysis based on the results of a multicriteria decision analysis has been performed with the aim to bring together the goals of maximizing asphalt materials' engineering performance and minimizing both the use of natural resources and the overall environmental impacts of the life cycle evaluated through LCA methodology. A total of four marginal materials were investigated and reused, such as CDW (waste produced during construction and demolition of houses, building or other structures, made up of concrete, bricks, gypsum and other debris), RAP, JGW (waste produced during soil consolidation works) and fly ashes (FA). A summary of the research phases is reported in Figure 1.  
Figure 1: Workflow diagram of the present research study.