# Environmental Impacts of Cement Production: A Statistical Analysis
## 2 Data and Methods  
After a quick introduction of the available dataset, this section provides the reader with the key concepts to investigate the behavior of the Global Warming Potential (GWP) and its connections with the production parameters, as well as a short summary of the statistical methods here employed. The examined impact categories (ICs) comply with the standard EN 15804 [21]; Table 1 lists their name and units of measure. ICs in Table 1 are available for a sample of 193 different recipes to produce 1 kg of gray cement, which can be classified into four types of cement (from CEM I to CEM IV according to [9]):  
* CEM I (i.e., Portland cement). It is the most impacting type because it contains at least 95% by mass of linker and gypsum as minor additional constituent to control the \"setting of cement\". * CEM II (i.e., Portland composite cement). It is composed of clinker with different proportion by mass (65-94%), main constituents (e.g., basfturnace slag, silica fume, pozzolana, fly ash, burnt shale or limestone), and gypsum as minor additional constituent. In the examined panel, CEM II A-LL and CEM II-BLL (i.e., portland limestone cements) are taken into account. The former has 80-94% clinker, 6-20% limestone and 0-5% gypsum by mass, the latter has 65-79% clinker, 21-35% limestone and 0-5% gypsum by mass:
* CEM III (i.e., blastfurnace cement) is composed of 35-64% clinker, 36-65% blastfurnace slag, 0-5% gypsum by mass; and
* CEM IV (i.e., pozzolanic cement). It is composed of clinker and pozzolanic constituents (i.e., basfturnace slag, silica fume, pozzolana, and fly ash). Two types of CEM IV are in the panel: CEM IV/A (65-89% clinker, 11-35% pozzolanic materials, 0-5% gypsum) and CEM IV/B (45-64% clinker, 11-35% pozzolanic materials, 0-5% gypsum). A preliminary analysis on the correlation matrix, performed to study relations between variables, is given in Figure 1. Positive and negative correlations are displayed in blue and red color, respectively, while the intensity of the color of each circle and its size is proportional to the absolute value of the corresponding correlation coefficient. Figure 1 shows that ODP, ADPf and TNRPE are pairwise perfectly correlated, that is, the corresponding correlation coefficient is equal to 1. This implies that these variables match deterministically, up to a multiplicative factor. For this reason, ODP and TNRPE are discarded in the further analysis. The remaining ICs have been used as independent variables and split into two groups, \"Emissions\" and \"Consumption\" (Table 2). \begin{table}
\begin{tabular}{c c c} \hline \hline
**Impact Category** & **IC** & **Unit** \\ \hline Global Warming Potential & GWP & kg CO\({}_{2}\) eq \\ Ozone layer Depletion Potential & ODP & kg CFC-11 eq \\ Acidification Potential & AP & kg SO\({}_{2}\) eq \\ Eutrophication Potential & EP & kg PO\({}_{4}\) eq \\ Photochemical oxidation Potential & POCP & kg C\({}_{2}\)H\({}_{4}\) eq \\ Abiotic depletion-elements & ADPe & kg Sb eq \\ Abiotic depletion-fossil fuels & ADPf & MJ \\ Total Use of Renewable Primary Energy & TRPE & MJ \\ Total Use of non-Renewable Primary energy & TNRPE & MJ \\ Use of secondary raw materials & SRM & kg \\ Non-renewable secondary fuels & nonRSF & MJ \\ Renewable secondary fuels & RSF & MJ \\ Water depletion & Water & m\({}^{3}\) \\ Electricity & El & kWh \\ Particulates & P & kg PTS \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Assessed impact categories. \begin{table}
\begin{tabular}{c c} \hline \hline
**Emission** & **Consumption** \\ \hline GWP, AP, EP, POCP, P & ADPe, ADPf, TRPE, SRM, nonRSF, RSF, Water, El \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Classes of ICs. This work will focus on the following questions:  
1. Which ones are the most relevant variables among the Consumption ICs in order to explain the behavior of GWP? 2. Are different variables important to predict GWP for the four types of cement? 3. Are the relevant variables to predict GWP also useful to predict other Emission ICs?