## 4 Results
### Life Cycle Assessment of Crumb Rubber Use in Concrete  
Incorporating sustainable materials into construction is a growing priority, particularly in the context of reducing the environmental impact of resource-intensive industries, such as concrete production. Calculations performed using the OpenLCA software 2.0.2 demonstrate the environmental benefits of substituting traditional river sand with crumb rubber, a recycled material derived from ELTs. The weight disparity between river sand (2300 kg/m\({}^{3}\)) and crumb rubber (1050 kg/m\({}^{3}\)) allows for a lighter and more sustainable alternative. By treating crumb rubber as a waste product with negligible environmental impact during its life cycle, the substitution results in a substantial reduction in Global Warming Potential (GWP100a). Table 4 highlights substitutions of river sand and crumb rubber, as all other parameters for the cement composite, such as cement, chemical admixtures, water, electricity, and transportation, remain constant. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{1}{c}{**Scenario Outcome**} & \multicolumn{1}{c}{**Input per 1 t of ELT**} & \multicolumn{2}{c}{**Output per 1 t of ELT**} & \multicolumn{1}{c}{**Avoided Products per**} & \multicolumn{1}{c}{**References**} \\ \hline Landfill & Transport—50 t/km & & & **1 t of ELT** & **References** \\ GJ/t & Front loader—10 m\({}^{3}\) & - & - & [14; 47] \\ CO\({}_{2}\)/t & ELT—1 t & & & \\ \hline \multirow{4}{*}{Incineration (RE)} & Transport—50 t/km & & & \\  & Front loader—5 m\({}^{3}\) (1 t) & & & \\  & ELT—1 t & Energy, & Coal—1.28 t & \\ GJ/t & Renewable & recovered—32 GJ & Natural gas—800 m\({}^{3}\) & [3; 26; 48] \\ CO\({}_{2}\)/t/m\({}^{3}\) & electricity—100 kWh & & & \\  & Natural gas—3 m\({}^{3}\) & & & \\ \hline \multirow{4}{*}{Incineration (CO\({}_{2}\), RE)} & Transport—50 t/km & & & \\  & Front loader—5 m\({}^{3}\) (1 t) & & & \\  & ELT—1 t & Energy, & Coal—1.28 t & \\ GJ/t & Renewable & recovered—32 GJ & Natural gas—800 m\({}^{3}\) & [3; 26; 32; 34; 36; 38; 48] \\ CO\({}_{2}\)/t/m\({}^{3}\) & electricity—100 kWh & & & \\  & Natural gas—3 m\({}^{3}\) & & & \\  & CO\({}_{2}\)—1.68–2.27 t & & & \\ \hline \multirow{4}{*}{Car tire recycling (RE)} & Transport—50 t/km & & & \\  & Front loader—5 m\({}^{3}\) (1 t) & & & \\  & ELT—1 t & T textile—0.1 t & & \\  & ELT—1 t & & & \\  & Renewable & & & Steel wire—0.1 t & [32; 36; 49; 50] \\ CO\({}_{2}\)/t & electricity—350 kWh & & _Saved material_: & & \\  & Water—0.3 m\({}^{3}\) & Carbon black—0.2 t & & \\ \hline \multirow{4}{*}{Truck tire recycling (RE)} & Transport—50 t/km & & & \\  & Front loader—5 m\({}^{3}\) (1 t) & & & \\  & ELT—1 t & T textile—0.01 t & Natural rubber—0.15 t & [32; 36; 49; 50] \\ CO\({}_{2}\)/t & Renewable & & _Saved material_: & & Steel wire—0.2 t & \\  & electricity—350 kWh & & & \\  & Water—0.3 m\({}^{3}\) & Carbon black—0.3 t & Aggregates—0.07 t & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: OpenLCA calculation results of the impact on the environment. As shown in Figure 4, the GWP reductions for various substitution scenarios by volume are as follows: reference mix with 0%, then 10%, 20%, and 50% river sand was replaced with crumb rubber by volume of materials. The results indicate a 24.06% reduction in GWP when replacing 50% of the sand by volume with crumb rubber, showcasing the material's significant potential to reduce carbon emissions and promote sustainable construction practices. Despite these environmental advantages, the physical-mechanical properties of the material show a 26% decrease, requiring further testing and refinement to ensure structural integrity. Balancing these environmental benefits with functional performance remains challenging, underscoring the need for continued innovation to optimize crumb rubber for sustainable construction applications. In life cycle assessment (LCA), the treatment of energy inputs for recycled materials varies depending on the chosen methodology.