# Road Pavement, Road Pollution, and Sustainability under Climate Change Increased Temperature
## 3 Materials and Methods
### Procedures to Evaluate Particles Retention at High Temperature  
The Wheel Tracking Test (WTT) required that the specimens were placed in the Wheel Tracking Machine 6 h before the test start, as specified by the standard. The temperature targeted for the test was programmed. The first 4 h are required for the testing equipment to reach the set temperature, and 2 additional hours are needed for all parts of the slabs to reach the target temperature and to stabilize. This latter stage is called temperature conditioning. After this conditioning, the wheel is rolling and compressing the slab during a period of 6 h, which corresponds to 1 \(\times\) 10\({}^{3}\) load cycles, or until a rut depth of 20 mm is reached. During testing, the temperature is constant with variations within \(\pm\)3 \({}^{\circ}\)C and the slab surface shape is measured and recorded by laser, at least at three cross-sections. After test completion and cooling down to room temperature, the slabs were removed from the equipment. For the purposes of studying road pollutants and the control of road runoff pollution discharges, a particle-based approach is frequently used to represent the physical processes of pollutant detachment, deposition, build up, and wash-off [22, 41]. Furthermore, the simulation of rainfall and wash-off of pollutants from road pavements, in laboratory and field conditions, as well and road dust collection (sweeping, use of vacuum cleaners, wet vacuuming, etc. ), are procedures used to study road dust, as well as pollution accumulation and removal from pavements (e.g., [36, 40, 43].) Two procedures were designed to assess the retention of particles by the specimens, using the WTT device already described. One was based on spreading an amount of soil all over the slab and, after the WTT, removal of the excess of soil (not retained by the specimen) using water. The second procedure, based on dry removal of the excess of soil, focused only on the strip of the slab that would be compressed during the WTT. The two procedures are described in detail below, and are illustrated in Figure 4.  
Figure 2: Characterization of the soil mass used in the tests in accordance with the accumulated fraction for different size ranges. 1. **Wet removal of excess soil** A total of 30 g of soil was weighed and manually spread, as homogenously as possible, on the entire surface of the specimen that would undergo the WTT, cf. Figure 3b,c. After the test conclusion and when room temperature was reached, each slab was placed inside an inox container of 35 \(\times\) 50 cm, supported by a metallic basis with a slope of 2.5%, similar to common pavement cross-section slope. Then, the surface was washed out with 500 mL of deionized water, during 5 min, trying to remove as much of the surface soil as possible. The specimen was taken to the dry room for some days, until it reached constant weight. During the different stages, each specimen was weighted and several pictures were taken. Figure 3: Wheel Tracking equipment (**a**). Test with 30 g of soil over the specimen (**b**,**c**). Test with 5 g of soil over a 5 cm strip (**d**). The inox container was taken to an oven at constant 100 \({}^{\circ}\)C until the soil was dry, and at that time the dry soil was weighted. 2. **Dry removal of excess soil** A total of 5 g of soil was weighed and manually spread only over the 5 cm strip of the specimen that would be directly under the rubber wheel during the WTT, cf. Figure 3d. After the test conclusion and when room temperature was reached, the slab undertook a process of soil removal: (i) Vacuum aspiration (900 W power device); (ii) Brushing; (iii) Vacuum aspiration, repeated twice. The vacuum equipment was weighed before and after this particle removal process, allowing to estimate the removal of soil from the specimen. In order to have an indicator of the sensitivity to temperature, tests were performed at 40 \({}^{\circ}\)C and 60 \({}^{\circ}\)C. The latter aimed to simulate the wearing course behavior under the climate change scenarios.