The albedo of crushed-rock layers and its implication to cool roadbeds in permafrost regions

• A simplistic method for measuring the albedo of a crushed-rock layer is provided.
• The albedo of a crushed-rock layer decreases with the increase of aggregate size.
• Incorporating light-colored aggregates on the highway surface layer cools the roadbed.

The construction of roadway embankments may destabilize the thermal stability of roadbeds in permafrost regions. One mitigating strategy is to face the embankment side slopes with a crushed-rock layer, which promotes convective cooling and cools the underlying permafrost. While research on the convective cooling of the crushed-rock layer is fairly plentiful, the solar absorption of this layer remains unknown in the current stage. Measuring the albedo of a crushed-rock layer is crucial to estimate the thermal performance of the roadway embankment. This study proposes the theory and procedure for measuring the albedo of crushed-rock layers. The albedo of crushed-rock layers with different sizes of aggregate is measured in sunny and cloudy weather. It was found that the albedo of crushed-rock layers decreases with the increase of the aggregate size. The reason for this correlation is that at a rough surface, some photons leaving the surface return to it, increasing its absorption. Incorporating light-colored aggregates on a highway surface or side slope layer may raise the highway albedo and cool the underlying permafrost.