During the 1990s, a few airfield pavements paved with SMA mixtures were constructed in Norway. Various binders and additives were used, depending on the climatic zones in which they were placed. The biggest of these airfields with an SMA pavement is Gardermoen near Oslo. On Gardermoen’s runways, 4-cm thick SMA mix of 0/11 mm were placed on the western runway) and 4-cm thick SMA mix 0/16 mm was placed on the eastern runway. Two SMA runways, 3300 m and 2950 m long, were constructed there with styrene-butadiene-styrene (SBS) modified binders (Larsen, 2002).
13.1.3 Johannesburg Airport
In 1999 the following comparative trial sections of different mixes applied in new asphalt wearing courses were laid down at the international airport in Johannesburg, South Africa (Joubert et al., 2004):
• 0/19 mm asphalt concrete (continuous graded coarse mix)
• 0/9 mm SMA with tested parameters: binder content 7.1% (40/50 Pen type), voids in mix 5.7%, stability 6.7 kN, flow 4.0 mm, passing by sieve 2.36 mm 17%, density in place 92%
• 0/13 mm porous asphalt concrete
These mixes were also compared with the existing old wearing course of continuously graded mix.
All sections were located in the landing area, a zone of heavy dynamic loads. Tests were aimed at determining the practicality of various mixes, assuming ungrooved pavements. The surface integrity of the section of pavement and its surface properties were inspected periodically. Special attention was paid to antiskid properties, lifespan, and the buildup of rubber with time (worn-off the airplane tires). The results for the SMA section were as follows:
• Grip number—initially 0.64, after 5 months 0.71
• Surface texture—initially 1.33 mm, after 5 months 0.9 mm
The summary of SMA’s performance on the trial section pavement proved that the surface properties of the tested SMA layer were better than the other mixes tested in the trial sections. The porous mix was also recognized for its good characteristics, with the exception of its durability, which was the lowest of those tested here. The conventional asphalt concrete pavement demonstrated poor antiskid properties and therefore needed grooving (Joubert et al., 2004).
