## 2 Materials and Methods
### Solar Reflectance Index
For comparison, the common albedo value for asphalt is 0.05-0.10, which increases to about 0.10-0.20 over time due to the polishing effect of vehicular traffic and the subsequent exposure of aggregates. The effect of decreasing albedo and SRI of precast concrete pavements with age can be observed clearly in Table 3. The new mix design (Glacier 5 and 6) of concrete sections appears much lighter (0.59-0.64) than the existing aged concrete (Figure 1). Although precast concrete pavements start out with a relatively high albedo, i.e., solar reflectance (Glacier 3 and 4), and are not as prevalent as asphalt in pavements, it is a worthwhile endeavour to improve the solar reflectance of pavements. Some research studies reported that even a small increase of 0.01 in albedo has an important environmental benefit. Therefore, it is recommended to use cool pavements (i.e., concrete pavements), which have made an effective contribution to climate change mitigation by reducing the Earth's surface temperature. Considering an albedo of 0.10 for asphalt pavements as reference value, we can calculate the \"carbon dioxide equivalent\" reduction by replacing this conventional type of pavement with concrete pavements. An increase in albedo of 0.1 causes a variation of 34.1 W m\({}^{-2}\) and an average decrease in \"carbon dioxide equivalent\" of 25 kgCO\({}_{2}\)/m\({}^{2}\) of pavement. Table 4 shows the reduction in carbon dioxide emissions by using the tested concrete pavements, taking as a reference the asphalt pavement's albedo. Madrid Central is a low-emission zone located in the center of Madrid (4.72 km\({}^{2}\)). More specifically, in the hypothetical case that it could be covered with high-reflectance materials (albedo > 0.5), a yearly equivalent reduction in carbon dioxide of 0.43 gigatons could be reached. The stadium was built on 88,150 m\({}^{2}\) of land near the city center. The use of concrete pavements of albedo 0.30 instead of asphalt pavements will contribute to combatting climatic change by reducing about 4500 tons of carbon dioxide each year. This positive effect could be increased by using high-reflective concrete pavements with albedos over  
Figure 5: Albedo in some pavement applications: (**a**) Wanda 1 (0.30); (**b**) Titanium (0.57); (c) Dolomite (0.54). 0.5. In this case, the mitigation will become 8800 tons of carbon dioxide by pavement areas of 88,000 m\({}^{2}\) (Table 4). Climate change is having an alarming impact worldwide and the problem continues to grow because of ever-increasing global temperatures. Accordingly, extreme weather events are becoming more common. Atmospheric carbon dioxide levels reached more than 400 parts per million. Therefore, urgent action is needed to combat climate change and to reduce the ever-increasing climate-related hazards. Albedo of the tested precast concrete pavements can be up to six times higher than that of asphalt pavements (Table 3). Thus, they reflect between 60 and 160 W m\({}^{-2}\) of the incident radiation with respect to asphalt pavements. Accordingly, a reduction in the Earth's surface temperature, equivalent to a decrease of 45-118 kgCO\({}_{2}\)/m\({}^{2}\), is expected.