TABLE OF CONTENTS The mechanical properties of asphalt need to be designed to cope with the nature and speed of site traffic under the prevailing climatic conditions. Basically slow-moving heavy goods vehicles with high axle loads will impart significantly higher load stresses on asphalt than a fast moving car. For example, the slow lane of motorways will receive much higher stress levels than the outside lane so for this reason is more prone to rutting, particularly during the warmer summer months.
Because bitumen properties are temperature susceptible due to it's viscoelastic nature, this means that asphalt behaves in a similar manner. In simple terms asphalt will soften during periods of warm/hot weather and become harder or stiffer during cold winter months. This means that the asphalt engineer has to take this into account when designing asphalt so that it doesn't rut under traffic loading during summer months or crack during colder periods and, importantly, to ensure the asphalt road achieves its design life. Polymers help to reduce the temperature susceptibility of bitumen by elevating the softening point and lowering the brittle point, thereby reducing the risk of asphalt rutting and cracking. Polymers also reinforce the binder, making it tougher with enhanced cohesive strength.
Probably the most important mechanical property for asphalt is elastic stiffness. There are a number of variables which influence asphalt stiffness, however, the bitumen grade and content and aggregate type are especially significant assuming adequate compaction is achieved. The thermal history of...
