# Comparative \"from Cradle to Gate\" Life Cycle Assessments of Hot Mix Asphalt (HMA) Materials
## 5 Conclusions  
Although the interest in environmental-related construction issues has grown fast in recent years, there is still a need for a comprehensive approach that could be universally applied to different civil works. Often, the environmental analysis is conducted using a qualitative rather than a quantitative approach, providing weak and far from reliable results. In Italy, the new Public Procurement Code requires public authorities to assess the environmental impact of construction projects in public bids.  
As a response to this need, this paper presents an application of the Life Cycle Assessment, or LCA, processes on two different hot mix asphalt materials used for the construction of road infrastructure. The method complies with current European standards concerning environmental management, and it consists of four steps: (1) the definition of the goal and scope; (2) an inventory analysis; (3) the impact assessment; and (4) the interpretation of the results.  
The presented analysis allows quantifying the environmental impact of a declared unit of 1 Mg of hot asphalt mix for the construction of binder layers in pavement structures produced at two different plant mixes (Company 1 and Company 2), using the \"from cradle to gate\" boundary system (i.e., including upstream and core production processes). The primary and secondary data used for the study were defined based on the European standard EN 15804.  
The examined mix plants differ for the use of methane as a fuel source (Company 1) instead of gasoil and low-sulfur crude oil (Company 2). The results suggest that the environmental impact of Company 1 in terms of _GWP_ and use of natural energy resources is lower than the one obtained for Company 2. The LCA of both products demonstrates that Company 2 presents a lower _ADP-fossil fuels_, energy and electricity consumption, and _HTP_. This shows that it is incorrect to consider only one indicator to select the \"greenest\" process among several alternatives. Indeed, it was found that each indicator had a different incidence in terms of its environmental impact, and that the contribution of each stage related to the LCA of both mixtures (i.e., acquisition of raw materials and fuel supplies, transportation, and manufacturing) was significantly different among indicators. This result is paramount because contracting authorities often consider _GWP_ as the only environmental criterion to evaluate or control the impact of a product or process, while the results obtained in this work demonstrate the need for considering a broader panel of environmental indicators.  
In conclusion, the \"from cradle to gate\" Life Cycle Assessment conducted to the production of bituminous concrete demonstrates that it is possible to use an unbiased tool to calculate and examine the environmental performance of a road material. Furthermore, the results from those assessments provide reliable information to identify potential actions that could contribute to reduce the environmental impact related to a construction product. Finally, it is worth mentioning that that the results obtained from this LCA could be used as reliable input data in more comprehensive environmental analyses that include road construction and maintenance or rehabilitation activities (e.g., [62]).  
[PERSON] and [PERSON] conceived and designed the experiments; [PERSON] performed the LCI and the LCIA; [PERSON] analyzed the data; and [PERSON] wrote the paper.  
The authors declare no conflict of interest.