# Comparative \"from Cradle to Gate\" Life Cycle Assessments of Hot Mix Asphalt (HMA) Materials
###### Abstract
The selection of specific materials and products for a specific project, for example, should never overlook their geographical location and local availability, or the structural and functional performances that have to be provided [13]. In this sense, current practices in road infrastructure projects demonstrate that there is a need for a rigorous methodology that combines unbiased and comparable environmental criteria. This methodology should recognize that a proper environmental approach should avoid choosing a low cost material with higher environmental burden, balancing often conflicting objectives [14]. Furthermore, it should also recognize that the production chain significantly affects the environmental impact of any product [15] and, therefore, that each environmental analysis is only valid under its own boundary system and operational conditions [16]. Consequently, a more inclusive environmental approach for road projects should involve direct and indirect costs, both environmental and monetary, during the whole life cycle of the infrastructure system [17; 18; 19; 20]. This perspective makes it possible to pursue the aim of sustainability, i.e., the integration of economic [21; 22; 23] and environmental aspects [24]. It is noteworthy that an approach of this nature could be applied not only to road infrastructure projects and related facilities [25], but also to railway [26; 27], airports [28] and sidewalk infrastructure [29]. In the specific case of bituminous materials used in pavement engineering projects, there exist some limited recent efforts that have conducted comparative Life Cycle Assessments (LCA) of bituminous products (e.g., [30; 31]). Nevertheless, these works do not analyze the impact related to the characteristics of the used fuels during the production of the materials and the adopted production processes. Furthermore, these results have regional specificity and are dependent on the adopted methodologies [32]. For example, it is common that only CO\({}_{2}\) emissions are considered as part of the environmental analysis (e.g., [33; 34]), even though the best environmental solution does not necessarily correspond to that providing the lowest CO\({}_{2}\) emissions due to the complexity of the environmental problem. The aim of this paper is to assess the environmental impact of two hot mix asphalt (HMA) materials that are currently used in the Italian road industry. The proposed evaluation consists of a series of environmental indicators that, according to existing international standards, are defined to have a type III label [35]. This label is a document that quantifies the environmental impact of a product based on LCA, which is verified by a qualified third party. The methodology used to accomplish the objectives of this work is the LCA of the asphalt mixes, considering both the Life Cycle Inventory analysis (LCI) and the Life Cycle Impact Assessment (LCIA) of the materials [36; 37; 38]. The study uses a \"from cradle to gate\" boundary approach (i.e., the analysis considers the product life cycle from the resource extraction processes to the moment at which the material is ready to be transported at the factory gate), including upstream and downstream processes, as specified in the International Environmental Product Declaration, or EPD(r) system. The interpretation of the results [39] permits to compare the environmental impact of the materials, and identifying the strengths and weaknesses of the processes evaluated. This, in turn, permits to improve and update the technology used as part of the processes studied and boost competitiveness. As observed, this work overcomes some of the main limitations of existing LCA conducted on bituminous materials, which makes it a relevant contribution to the current state of knowledge on this topic.