# A Practice for the Application of Waste in Road Asphalt Pavements in an Eco-Friendly Way
## 2 Materials and Methods
### LCA of Asphalt Road Pavement Mixtures  
LCA methodology [73] was employed (using a commercial licensed software for LCA assessments [74]) to assess the environmental impacts of the nine asphalt road pavement mixtures during their life cycles. In this process, one cubic meter of each solution (functional unit) was examined. The LCA procedure consisted of two main parts: life cycle inventory (LCI) and life cycle impact assessment (LCIA). For the designed binder course and base layer mixtures, LCI was performed to investigate the input flows of different components (including the raw materials used for the construction/maintenance of facilities and machinery) as well as water and fossil fuels, and the output flows of pollutants emitted into the air (CO\({}_{2}\), CO, CH\({}_{4}\), NOx, SO\({}_{2}\), non-methane volatile organic compounds (NMVOCs) and particulate matter) and water (chemical oxygen demand (COD), biological oxygen demand (BOD), nitrogen, sulphur and phosphorus compounds). Let M be a set of the analysed functional units with M = {1,... \(p\),... o}, o = 9 (the total number of asphalt mixtures). In this case, LCI is evaluated using Equation (1) for each functional unit. \[ \begin{array}{c}F_{p}\\ 19\times 6\end{array} =\left( \begin{array}{ccc}a_{p,1,1}&\cdots&a_{p,1,6}\\ \vdots&a_{p,r,v}&\vdots\\ a_{p,19,1}&\cdots&a_{p,19,6}\end{array} \right) \tag{1}\]  
where:  
* \(a_{p,r,v}\) is the generic entry of the inventory matrix, namely the flow of the _r_-th component during the _v_-th process of the life cycle for the _p_-th asphalt mixture solution;
* \(r\) belongs to the range [1; 19] and represents the mentioned inventory flows (5 input flows and 14 output flows);
* \(v\) belongs to the range [1; 6] and represents various macro-processes of the life cycle, such as the following: (i) Supplying secondary raw materials from the recycling facility to the asphalt plant; (ii) Production of natural aggregates and filler particles and their transport from the quarry to the asphalt plant; (iii) Production of the binders (bitumen for HMAs, bitumen emulsion and cement for CMRAs) and their transport from the refinery to the asphalt plant; (iv) Production of the asphalt mixtures and their transport from the asphalt plant to the construction site (except for CMRAs manufactured on site); (v) Construction and laying of the road pavement; (vi) Milling and waste disposal at the end of the service life. * \(p\) belongs to the range [1; 9] and represents the asphalt mixture solutions. After that, the LCIA procedure was performed using ReCiPe methodology [75] which converts the 19 flows of the specified components into 18 midpoint category indicators, where the flow of each component can affect one or more impact categories: global warming (GWP); stratospheric ozone depletion (ODP); ionizing radiation (IR); the negative effects of ozone formation on terrestrial ecosystems (OFT) and human health (OFH); fine particulate matter formation (PM); terrestrial acidification (A); freshwater eutrophication (FE); marine eutrophication (ME); terrestrial, freshwater and marine ecotoxicities (T-ECO, F-ECO and M-ECO); human carcinogenic and non-carcinogenic toxicities (CT and NCT); land use (LU); mineral and fossil resource scarcity (MR and FR); and water consumption (W). The component flows were converted into the impact category indicators using different characterization (weighing) factors to aggregate heterogeneous inventory flows (e.g., CO\({}_{2}\), CO and CH\({}_{4}\)) into homogeneous impact category indicators (e.g., GWP) expressed by specific measurement units (e.g., kg CO\({}_{2}\) equivalent for GWP) and determine the cumulative effect of different components on the environment. Therefore, each impact assessment matrix \(IC_{p}\) of the \(p\)-th asphalt solution was calculated from the inventory matrix \(F_{p}\) according to Equation (2). \[\begin{array}{c}IC_{p}= \begin{array}{c}CF\\ 18\times 6\end{array} \times \begin{array}{c}F_{p}\\ 19\times 6\end{array}