# Proposal for the Evaluation of Eco-Efficient Concrete
## 3 Proposed Assessment Method for the Eco-Efficiency of Concrete
### Eco-Efficiency Assessment Method of Concrete
#### 3.4.3. Durability Performance (DP)  
Durability performance assessment of concrete was assumed to assess the service life of concrete used on a reinforced concrete (RC) structure based on carbonation. In addition, the covering thickness was 30 mm. For our purposes, service life was defined as the duration of utility until the carbonation depth of concrete reaches the outermost reinforcement. The most appropriate equation was selected as the standard specification for concrete to indicate that equations other than the proposed equation should be used. For this, service life was assessed on covering thicknesses of 30 and 40 mm with a water-binder ratio of 60%. (1) Selection of prediction equation for the service life of concrete  
Service life was assessed for covering thicknesses of 30 mm and 40 mm with a water-binder ratio of 60%. Although conditions for the calculation of service life differ, concrete comprised of ordinary Portland cement was assessed under outdoor conditions in order to apply identical parameters. As shown in Table 7, an equation from the Architectural Institute of Japan (AIJ) [37] was used to deduce the results of assessment. The AIJ formula is appropriate because it yields results that are closest to the average service life of concrete. (2) Prediction factors of the service life of concrete  
Among existing carbonation prediction equations, Equations (13) and (14) (originating from the Architectural Institute of Japan) were used to derive the service life of concrete in order to assess the durability performance of concrete. However, because conditions of temperature and humidity in Japan (as presented in the values of the equations) are different from the values in Korea for an average year, more apt coefficients for the conditions of Korea were derived with annual average values provided by the Korea Meteorological Administration. \[Durability_{pf}\ \ T\ =\ (C/A)^{2} \tag{13}\]  
\[A\ =\ K\times\alpha 1\times\alpha 2\times\alpha 3\times\beta 1\times\beta 2 \times\beta 3 \tag{14}\]  
Here, \(T\) is the service life (year), \(C\) is the carbonation depth (mm), \(A\) is the carbonation velocity coefficient, \(K\) is the Kishitani coefficient, \(\alpha 1\) is the coefficient by type of concrete, \(\alpha 2\) is the coefficient by \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Substance** & **Unit Price** & **Unit** & **Reference** \\ \hline Ordinary Portland Cement & 3410 KRW & 40 kg & National information \\ Aggregate & 13,000 KRW & ton & National information \\ Electric & 110 KRW & Kwh & National information \\ Diesel & 1700 KRW & L & National information \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Unit price of raw materials and energy used in the production of concrete (example). \begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Prediction Formula**} & \multicolumn{2}{c}{**Coating Thickness**} \\ \cline{2-3}  & **30 mm** & **40 mm** \\ \hline [PERSON] [38] & 42 years & 76 years \\ [PERSON] [39] & 60 years & 109 years \\ [PERSON] [40] & 43 years & 78 years \\ [PERSON] [41], JSCE [42] & 63 years & 114 years \\ This study (AIJ) & 43 years & 87 years \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Service life evaluation results according to carbonation prediction equations (W/C 60%). type of cement, \(\alpha\)3 is the coefficient by the water-cement ratio, \(\beta\)1 is the coefficient by temperature, \(\beta\)2 is the coefficient by moisture, and \(\beta\)3 is the coefficient by the concentration of carbon dioxide. Selection of covering thickness  
Korean structural design standards for reinforced concrete have similar criteria to the code of the American Concrete Institute (ACI) [43]. Item 7.7.1 of ACI 318 suggests a covering thickness of 1.5 inches (38 mm) for reinforcement No. 14 and No. 18, and 3/4 inches (19 mm) for reinforcement No. 11 and below in the case of slabs, walls, and joint structures.