## 3 Methods
### Environmental Cost of Concrete  
It is difficult to interpret the evaluation results calculated in the various environmental impact categories and to determine their priorities because reference materials are different for each environmental impact category. Therefore, it is important to unify such evaluation results in a scientific way and express them to improve the current understanding. To address this, the concept of environmental cost was applied, in which endpoint level environmental problems caused by various environmental impact categories are listed and the damage scale is converted into a monetary value [44].  
The Korean Life Cycle Impact Assessment Method based on Damage-Oriented Modeling (KOLID) [44], a life cycle environmental impact evaluation methodology for end-point level damage calculation developed by ME, was applied to integrate the evaluation results calculated in the six environmental impact categories into environmental cost, and the environmental cost was evaluated  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Classification**} & \multirow{2}{*}{**Water**} & \multicolumn{2}{c}{**Ordinary Portland**} & \multirow{2}{*}{**Superplasticizer**} \\  & & & **Cement** & \\ \hline System Boundary & Cradle to Gate & Cradle to Gate & Cradle to Gate \\ Constructed Year & 2013 & 2003 & 2015 \\ Source & Korean LCI DB [32] & Korean LCI DB [32] & HYU LCI DB [43] \\ \hline \multirow{5}{*}{Environment} & ADP (kg-SO\({}_{\text{eq}}\)/kg) & \(1.76\times 10^{-6}\) & \(3.54\times 10^{-3}\) & \(4.45\times 10^{-5}\) \\  & GWP (kg-CO\({}_{\text{2 eq}}\)/kg) & \(1.02\times 10^{-4}\) & \(9.44\times 10^{-1}\) & \(2.05\times 10^{-3}\) \\ \cline{1-1}  & ODP (kg-CFC11\({}_{\text{eq}}\)/kg) & \(2.78\times 10^{-15}\) & \(5.23\times 10^{-9}\) & \(2.17\times 10^{-11}\) \\ \cline{1-1} Impact Unit & AP (kg-SO\({}_{\text{2 eq}}\)/kg) & \(1.95\times 10^{-7}\) & \(1.00\times 10^{-3}\) & \(5.45\times 10^{-8}\) \\ \cline{1-1}  & POCP (kg-C\({}_{\text{2}}\)H\({}_{\text{4 eq}}\)/kg) & \(1.64\times 10^{-9}\) & \(6.61\times 10^{-4}\) & \(5.45\times 10^{-8}\) \\ \cline{1-1}  & EP (kg-PO\({}_{\text{4}}\)\({}^{\text{3-eq}}\)/kg) & \(3.34\times 10^{-8}\) & \(1.04\times 10^{-4}\) & \(5.21\times 10^{-7}\) \\ \hline \hline \end{tabular} ADP: abiotic depletion potential, GWP: global warming potential, ODP: ozone depletion potential, AP: acidification potential, POCP: photochemical ozone creation potential, EP: eutrophication potential.  
\end{table}
Table 4: LCI DB Information for Water, Ordinary Portland Cement, and Superplasticizer.  
using Equation (2). KOLID is a methodology in which the endpoint level damage caused by the six environmental impact categories (GWP, AP, EP, ODP, POCP, and ADP) is identified in terms of 16 categories (that include categories such as cancer, heat stress, infectious disease, malnutrition, and cataract) associated with four protection targets (human health, social assets, biodiversity, and primary production) and the environmental cost is calculated through their marginal willingness to pay (MWTP). Table 5 shows the environmental cost factor associated with each environmental impact category.  
\[\text{EC}=\Sigma(\text{EI}_{\text{i}}\times\text{ECF}_{\text{i}}) \tag{2}\]  
where EC is the environmental cost evaluation result, \(\text{EI}_{\text{i}}\) is the environmental impact evaluation result associated with the environmental impact category (i), and \(\text{ECF}_{\text{i}}\) is the environmental cost factor associated with the environmental impact category (i).