## 2 Materials and Methods
### Solar Reflectance Index
By contrast, the highest albedo was measured in the titanium sample (0.57), which was made with white Portland cement. This specimen shows a clear grey color with a slight white tinge. The second highest albedo was recorded in the dolomite pavement (0.54), which was made with grey Portland cement. In this case, it presents a clear grey color with a slight yellow tinge. Figure 3 shows the solar reflectance index (SRI) as a function of the wavelength. Dolomite and titanium samples present a maximum SRI between 50 and 60 in the range between 500 and 1500 nm, whereas there was a downward trend in the samples with the lowest albedo (from 30-35 to 20) in the same range of wavelengths. There is a linear correlation between the solar reflectance index (SRI) and albedo. Figure 4 shows the marked correlation between the SRI and albedo. As the trend line shows, there is a significant correlation between the two. The following Equations (6)-(8) show the strong correlation (R\({}^{2}\) > 0.999). \[\text{For h}_{\text{c}}=5\text{: }\text{y}=134.03\text{x}-9.2667\text{; }\text{R}^{2}=0.9993 \tag{6}\]  
\[\text{For h}_{\text{c}}=12\text{: }\text{y}=133.81\text{x}-8.1937\text{; }\text{R}^{2}=0.9997 \tag{7}\]  
\[\text{For h}_{\text{c}}=30\text{; }\text{y}=133.59\text{x}-7.4259\text{; }\text{R}^{2}=0.9999 \tag{8}\] \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline
**Denomination** & **Rm** & \(\alpha\) & \(\epsilon\) & **Ts (hc = 5)** & **Ts (hc = 12)** & **Ts (hc = 30)** & \(SRI\) (hc = 5)** & **SRI (hc = 12)** & **SRI (hc = 30)** \\ \hline BLACK & - & 0.95 & 0.9 & 376.2 & 355.4 & 334.3 & 0.0 & 0.0 & 0.0 \\ WHITE & - & 0.2 & 0.9 & 322.2 & 318.0 & 313.9 & 100.0 & 100.0 & 100.0 \\ \hline GLACIER 1 & 0.281 & 0.719 & 0.897 & 360.6 & 344.2 & 328.1 & 28.9 & 29.8 & 30.3 \\ GLACIER 2 & 0.291 & 0.709 & 0.894 & 360.0 & 343.8 & 327.8 & 30.1 & 30.9 & 31.5 \\ GLACIER 3 & 0.309 & 0.691 & 0.888 & 399.0 & 343.0 & 327.4 & 32.0 & 33.0 & 33.8 \\ GLACIER 4 & 0.295 & 0.705 & 0.888 & 359.9 & 343.7 & 327.8 & 30.2 & 31.2 & 31.9 \\ GLACIER 5 & 0.359 & 0.641 & 0.882 & 355.6 & 340.6 & 326.1 & 38.2 & 39.4 & 40.3 \\ GLACIER 6 & 0.404 & 0.596 & 0.886 & 352.2 & 338.3 & 324.8 & 44.5 & 45.6 & 46.4 \\ \hline DOLOMITE & 0.535 & 0.465 & 0.891 & 342.5 & 331.6 & 321.2 & 62.5 & 63.5 & 64.1 \\ TITANIUM & 0.572 & 0.428 & 0.893 & 339.7 & 329.7 & 320.2 & 67.7 & 68.6 & 69.1 \\ \hline \end{tabular}
\end{table} 
Table 3: Albedo average results (Rm), solar absorptance (\(\alpha\)), thermal emittance (\(\epsilon\)), the temperature that each sample would reach (\(T_{s}\)) and its solar reflectance index (\(SRI\)) for three convection coefficients (\(h_{c}\)), corresponding to three wind speeds. The Wanda Metropolitan Stadium in Madrid, Spain, was built between 1990-1993 with Glacier precast concrete pavements (Figure 5). Precast concrete pavement named Glacier was collocated into the surrounding ground with a solar reflectance index (SRI) about 0-30 and albedo 0.28-0.29 (Table 3). It has been estimated that ageing will reduce concrete albedo of this pavement by about 0.1. Figure 5 shows several pavement applications of the tested precast pavements with their albedo values: (a) Wanda Stadium (0.30); (b) titanium precast concrete pavement (0.57); (c) dolomite precast concrete pavement (0.54). The photograph on the left is a pavement made with white cement and a very fine and clear aggregate (dolomite precast concrete  
Figure 4: Correlation between the solar reflectance index (SRI) and albedo. Figure 3: Solar reflectance index (SRI) as a function of the wavelength. pavement). Consequently, it presents a very high albedo of 0.54. The second photograph also shows an example of high-reflectance concrete pavement with a solar reflectance index (SRI) of 0.68-0.69 and albedo of 0.54 (Table 3). In fact, the use of cool-colored materials, namely titanium and dolomite (Figure 5b,c), increases albedo substantially without altering visual appearance. Typical albedo values for new concrete range between 0.35 and 0.40, and between 0.25 and 0.30 for weathered concrete [4].