Thermal stabilization and permanent deformation resistance of LWA/PCM-modified asphalt road surfaces

- PCM modified resistant to overheating asphalt mixture AC 16 W 35/50 has been proposed.
- Analysis of heat transfer from the asphalt surface has been performed.
- Rutting tests for binding and new designed packet layers have been performed.
- The results of theoretical thermodynamic considerations were experimentally verified.
- Temperature lowering for asphalt packet layers in moderate laboratory conditions reaches 4 °C.

This paper presents the results of attempts at reducing the problem of solar overheating of asphalt road pavement surfaces, resulting in weakening and accelerated destruction of the aforementioned structures.To protect pavement surfaces against periodic overheating, standard asphalt mixture AC 16 W 35/50, used for binder course, has been modified by replacing one of the aggregate fractions from the mineral mixture with lightweight aggregate (LWA) soaked in phase-change material (PCM). This modified asphalt mixture, placed under the thin standard asphalt wearing course without any modification (no LWA and no PCM), serves as a temperature and permanent deformation stabilizer of the asphalt surface layer.To ensure maintaining the highest possible resistance to permanent deformation the newly design asphalt mixture has been verified with the rutting tests. Two different asphalt packet layers have been tested. First the configuration contained only the binder course and the second test configuration-double-layered ones - comprised of binder course covered by thin wearing course.To verify the correctness of conclusions drawn from theoretical thermal considerations, experimental temperature simulation tests were conducted under laboratory conditions on two asphalt specimens with dimensions of 0.30 × 0.30 × 0.10 m. The first one, standard AC 16 W 35/50, served as reference specimen, while the second one, PCM AC 16 W 35/50 containing LWA with PCM (LWA/PCM), was tested. In both cases a binder course was covered by a wearing course from stone mastics asphalt SMA without LWA/PCM. The simulations have confirmed that 3% wt. addition of PCM, in relation to the weight of the asphalt mixture for binder course, reaches a reduction in surface temperature of about 4 °C in moderate laboratory conditions, within the tested temperature range between 30 and 60 °C.