# Sustainability Enhancement and Evaluation of a Concrete Dam Using Recycling
## 4 Results and Discussion
### Construction Stage  
#### 4.1.1 Environmental Impacts  
Figure 3 demonstrates the carbon footprint distribution across different components and processes involved in the production of concrete. Cement is shown to be the most significant contributor, accounting for nearly 90% of the total emissions, aligning with the typical findings in the literature [16] that highlight cement's high environmental impact due to energy-intensive production. Aggregates, both fine and coarse, contribute a smaller but notable amount, reflecting the environmental cost of extraction and transportation. Admixture production and transportation have measurable impacts, suggesting that logistics management and minimizing admixture quantities can further reduce emissions. Concrete batching, although a relatively minor component, also adds to the footprint, emphasizing the need for efficient batching processes. \begin{table}
\begin{tabular}{c c c} \hline
**Material or Operation** & **Value (ton)** & **Transportation (km)** \\ \hline Concrete & 2142 & 30 \\ Steel and rebar & 0.35 & 550 \\ Blasting & 4.14 & 620 \\ Fuel oil & 66.3 & 150 \\ Wood & 27 & 150 \\ Earth and rock excavation & 192 & 25 \\ \hline \end{tabular}
\end{table} 
Table 1: LCI database for the construction stage. \begin{table}
\begin{tabular}{c c} \hline
**Construction Material or Operation** & **Unit Cost (\$)** \\ \hline Concrete (USD/ton) & 45 \\ Wood (USD/ton) & 345 \\ Fuel oil (USD/ton) & 407 \\ Steel and Rebar (USD/ton) & 1050 \\ Earth and rock excavation (USD/ton) & 200 \\ Transportation (USD/ton.km) & 0.25 \\ Blasting materials (USD/ton) & 599 \\ Landfill (USD/ton) & 23 \\ Recycling concrete (USD/ton) & 55 \\ \hline \end{tabular}
\end{table} 
Table 2: Price of each operation and construction materials. The analysis' outcomes, as presented in Table 3, outline the environmental impacts throughout the entire construction phase of 1 m width of the dam. Moreover, Figure 4 presents the distribution of environmental impacts during the construction phase of the dam based on the IMPACT 2002+ method. The bar chart delineates the influence of six components--concrete, transportation, diesel fuel, wood, blasting materials, and steel and rebar--on the overall environmental impacts. The results reveal that the total carbon dioxide equivalent (CO\({}_{2}\) eq) emissions amount to approximately 355 ton CO\({}_{2}\) eq/m, with the primary contributors being concrete production and fuel usage. Concrete, as one of the most extensively used materials in dam construction, accounts for over 305 ton CO\({}_{2}\) eq/m, indicating its substantial role in greenhouse gas emissions. Fuel use, largely associated with transportation and machinery, contributes an additional 33 ton CO\({}_{2}\) eq/m. Additionally, aquatic ecotoxicity is primarily driven by the use of blasting materials, which also contribute heavily to terrestrial impacts and land occupation. These findings point to the need for improved practices in material selection and handling to mitigate ecological damage. \begin{table}
\begin{tabular}{l c} \hline \hline
**Impact Category** & **Total** \\ \hline Carcinogens (ton C\({}_{2}\)H\({}_{3}\)Cl eq) & 2.405 \\ Non-carcinogens (ton C\({}_{2}\)H\({}_{3}\)Cl eq) & 5.059 \\ Respiratory inorganics (ton PM2.5 eq) & 0.269 \\ Ionizing radiation (B\(\,\)C–14 eq) & 2,384,000 \\ Ozone layer depletion (ton CFC-11 eq) & 0.00006 \\ Respiratory organics (ton C\({}_{2}\)H\({}_{4}\) eq) & 0.126 \\ Aquatic ecotoxicity (ton TEG water) & 58,727 \\ Terrestrial ecotoxicity (ton TEG soil) & 16,074 \\ Terrestrial acid (ton SO\({}_{2}\) eq) & 6.253 \\ Land occupation (m\({}^{2}\)org.arable) & 62,759 \\ Aquatic acidification (ton SO\({}_{2}\) eq) & 1.348 \\ Aquatic eutrophication (ton PO\({}_{4}\) P-lim) & 0.042 \\ Global warming (ton CO\({}_{2}\) eq) & 355 \\ Non-renewable energy (MJ primary) & 5,700,000 \\ Mineral extraction (MJ surplus) & 5215 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: The environmental impacts throughout the entire construction of 1 m width of the dam.