Can Coarser Aggregates Improve Frictional Properties of Runway Surfaces Without Compromising Other Properties

This paper describes how the main purpose of runway pavements is to carry traffic loads conveniently, economically, and safely during its design life. Pavement safety is usually evaluated through several components including skid resistance, rutting susceptibility, light reflectivity of the surface, debris of foreign objects, and area boundary. Pavement slipperiness in terms of skid resistance is the most critical component that affects pavement safety. Adequate runway surface friction is essential in operating the antiskid braking systems installed in most modern aircraft. Lack of skid resistance can cause a serious safety problem if water exists in any form on the runway. The main objective of this paper is to attempt to improve the skid resistance of hot mix asphalt concrete (HMAC) surfaces for airfield pavements without compromising their mechanical properties. In order to achieve this objective, three different airfield mixes were designed using the Marshall mix design method. Sufficient quantity of each mix was fabricated according to the Canadian Specification ASG-06. Test specimens were prepared including slabs and cores. The slabs were tested for their frictional properties using the British pendulum tester, while the core specimens were tested for their indirect tensile strength, moisture sensitivity and shear strength. Test results showed that using coarser aggregates could improve the frictional properties and the mechanical properties of HMAC for airfield pavements. This paper provides details of the testing program and results, and shows the effect of using coarser aggregates to design safer mixes for runways.