## 2 Materials and Methods  
The authors considered four gray cements prepared by four different Italian companies, which are not named for reasons of confidentiality. All cements guarantee 32.5 MPa of 28-day characteristic cubic compressive resistance (\(R_{\mathrm{c}\lambda}\)). All powders are Portland-pozzolana cements, defined as CEM II according to [28]: they have 65-89% of clinker, 21-35% of natural pozzolana, and 0-5% of other constituents. Although each clinker content is not known by the authors, however the powders are comparable because they represent specific, detailed and homogeneous chemical and mechanical characteristics. As regard to as the environmental and social criteria, the study considers the impact categories listed in Table 1: their values refer to the production of 1 Mg of cement. According to the standard EN 15804 [29], these categories describe environmental impacts, resource use, and waste categories related to a production. They are therefore representative of environmental and human health consequences of a manufacturing process. As regard to the human health protection criteria, the authors considered the most common risks for construction industry workers [30]: noise, whole body vibrations (WBV), hand-arm vibrations (HAV), exposure to allergizing substances, exposure to Cr(VI) (hexavalent chromium), and exposure to free crystalline silica (FCS). All values are deduced from the (internal) Document of Risk Evaluation prepared by each company, as required by the Italian standard about the safety of workers [31]. As regard as the content of Cr(VI), the Italian companies comply with the European Directive 2003/53/CE [32] and doubly test their cements to increase worker safety [33]. As regard to the exposure to FCS, the weekly Permissible Exposure Limit considered in the study is compliant with the American Conference of Governmental Industrial Hygienists standards [34]. Examined risks have been classified according to the standardization proposed by the Italian Ministry of Labour [35]. For the economic issues, the authors considered the unit price of cements, listed on the pricelist of each cement plant (not herein disclosed due to privacy reasons). Table 2 lists the human health and economic data. The impact categories listed in Tables 1 and 2 have been considered as decision criteria to choose the most sustainable cement powder by mean the AHP method. It consists of decomposition of decision problem (what is the best, or most sustainable, cement?) into hierarchy of easier sub-problems, each independent from others. Each element of the hierarchy could be referred to any aspect of the decision problem (e.g., both tangible and intangible, measured and estimated variables). The method is composed of three phases:  
1. Hierarchical decomposition, which includes: * a first level, which represents the overall \"goal\" of the analysis; * a final level, which represents the alternatives to be considered; \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Impact Categories** & **Unit of Measure** & **Cement 1** & **Cement 2** & **Cement 3** & **Cement 4** \\ \hline Global Warming Potential, _GWP_ & kg CO\({}_{2}\), eq. & 737.59 & 664.6 & 785 & 611 \\ Ozone Depletion Potential, _ODP_ & kg CFC-11 eq & \(3.39\times 10^{-5}\) & \(3.41\times 10^{-5}\) & \(5.16\times 10^{-5}\) & \(1.00\times 10^{-5}\) \\ Photochemical Ozone Creation Potential, _PPCP_ & kg C\({}_{2}\)H\({}_{4}\) eq & 0.12 & 0.11 & 0.26 & 0.07 \\ Eutrophication Potential, _EP_ & kg TO\({}_{4}\) eq & 0.45 & 0.43 & 0.28 & 0.18 \\ Non-hazardous Waste, _HW_ & kg & 158 & 188 & 0.053 & 6.11 \\ Hazardous Waste, _HW_ & kg & 0.12 & 0.14 & 0.1 & 0.0307 \\ Renewable resources with energy content, _REE_ & Mj & 199 & 192.77 & 275 & 256 \\ Non-renewable resources with energy content, _nREE_ & Mj & 7185 & 6799.01 & 6525 & 3080 \\ Electricity, \(E\) & kWh & 189.41 & 183.17 & 132 & 175 \\ Water consumption, \(W\) & m\({}^{3}\) & 0.481 & 0.573 & 0.705 & 0.674 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Impact categories examined in the study.