## 5 Results  
CO\({}_{2}\) Uptake of Concretes Manufactured with Portuguese Cements Following the Simplified Method  
Table 2 shows the summary of the Portuguese domestic data for clinker annual production, total absolute gross CO\({}_{2}\) emissions (without biomass emissions), and absolute gross process CO\({}_{2}\) emissions from cement manufacturing plants between 2005 and 2015. The theoretical uptake has been defined as 23% of all CO\({}_{2}\) emissions due to calcination for the service life period (20%) and the end-of-life plus secondary usage stage (2% + 1% = 3%), respectively [3]. Therefore, if a factor of 0.23 is applied to the absolute gross process CO\({}_{2}\) emissions shown in Table 2, this factor was proposed in the IVL simplified methodology [3], the results that appear in Figure 8 can be obtained. CO\({}_{2}\) uptake in Portuguese cement manufacturing plants has been estimated to be 8.7 million tons of CO\({}_{2}\) during the period of 2005-2015. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline
**Year** & **2005** & **2006** & **2007** & **2008** & **2009** & **2010** & **2011** & **2012** & **2013** & **2014** & **2015** \\ \hline Clinker annual production (kilotons) & 7865 & 7777 & 8018 & 7748 & 6164 & 6484 & 5351 & 4882 & 5427 & 5968 & 5626 \\ \hline Total Absolute Gross CO\({}_{2}\) Emissions (kilotons) (without biomass emissions) & 6722 & 6640 & 6811 & 6524 & 5075 & 5458 & 4455 & 4015 & 4393 & 4904 & 4621 \\ \hline Absolute Gross Process CO\({}_{2}\) Emissions (kilotons) & 4206 & 4141 & 4256 & 4146 & 3200 & 3471 & 2825 & 2588 & 2872 & 3162 & 2978 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Clinker annual production, total absolute gross CO\({}_{2}\) emissions (without biomass emissions), and absolute gross process CO\({}_{2}\) emissions (kilotons) from Portuguese cement manufacturing plants between 2005 and 2015. Figure 8: Estimation of the partial absorption of carbon dioxide that is emitted due to the process of decarbonation according to the IVL simplified methodology [3] and by applying a factor of 0.23 (20% during the service life period and 3% for the end-of-life plus secondary usage stage of the CO\({}_{2}\) emissions due to calcination). CO\({}_{2}\) Uptake of Concretes Manufactured with Portuguese Cements Following the Advanced Method  
Cement consumption and the end use of concretes from 2005 to 2015 are shown in Figure 9. The key point in this methodology is the surface per volume ratio (S/V) factor selection, which depends on the type of application. The S/V of the structural elements can be divided in several groups. The S/V ratios used in the present study were three for civil works, eight for buildings, and 20 for mortars. It was assumed that the full carbonation in mortar is achieved after 10-15 years of carbonation (year 2025). The high porosity of mortars is well-known, so their carbonation rate is much higher than that of concretes. This fact justified the assumption. The carbonation rate, k\({}_{\text{co2}}\) (mm/year\({}^{0.5}\)), can be calculated by applying Equation (5) to the experimental results. In the present study, the carbonation rate, k\({}_{\text{co2}}\), in concrete used in structures was estimated from the Portuguese data shown in the literature [17; 18]. Figure 10 summarizes the experimental Portuguese results. \[x=B\sqrt{t} \tag{5}\]  
where:  
B = carbonation coefficient (mm/y\({}^{0.5}\)). x = carbonation depth (mm). t = time of natural carbonation (years). The maximum stoichiometric amount of carbon dioxide that can be absorbed can be calculated by applying Equation (6), and the results of such a calculation are shown in Table 3.  
\[CO_{2,\text{max}}\rightarrow(CaO_{\text{reactive}}/100)\times\text{ binder}\times(M_{CO_{2}}/M_{CaO}) \tag{6}\]  
where:  
CO\({}_{2,\text{max}}\): maximum amount of carbon dioxide that can be absorbed, kg CO\({}_{2}\)/kg cement. CaO\({}_{\text{reactive}}\): kg CaO/kg binder \(\times\) 100. This value is taken as 65%. Binder: Amount of cement (kg). M\({}_{\text{CO}}\): 44.0 g/mol.