Prediction models for fatigue resistance of local hot mix asphalt

Abstract

The performance of asphalt concrete pavement depends on the bitumen properties, asphalt concrete mixtures, volumetric properties and external factors such as traffic volume and environment. Higher traffic volume produces high stress within pavement layer, which is one of the main causes for pavement distress. Fatigue cracking is considered to be the most important type of distress affecting the performance of asphalt concrete pavements on major state highways. This distress reduces the service life of the pavement and increases the maintenance cost. This paper describes the results of a laboratory study of the fatigue response of a typical asphalt concrete mixes to define the effects of degree of compaction (as measured by air-void content), asphalt content, temperature and ageing on the performance parameter. To achieve the objective of this research, the Nottingham flexural fatigue test is considered and super pave mix design requirements are employed. Test specimens (400 mm length by 63 mm width and 50 mm height) were sawed from slabs of the mixes prepared to the target air-void contents by rolling wheel compaction. Controlled-strain flexural fatigue tests were conducted using the Nottingham flexural fatigue test equipment and procedure. The tests were conducted at temperatures of 10 ± 1°C (50 ± 2°F), 20 ± 1°C (68 ± 2°F) and 30 ± 1°C (86 ± 2°F) and at a frequency of loading of 10 Hz. The long-term ageing experiment employed a full factorial design as well, with three asphalt contents, two ageing periods, two air-void contents and three test temperatures for a nominal total of 36 tests. Local material properties, stress-level and environmental impacts were considered for this aspect. In addition, field data are collected from different-aged pavement sections to check the applicability of fatigue prediction in the field through testing cores of (400 mm length × 300 mm width); laboratory results that are judged to be simulation of field compaction conditions were analysed. Fatigue life of hot mix asphalt and stiffness models for super-pave-compacted asphalt concrete wearing course mixtures were developed using statistical analyses by the aid of a software as a function of: degree of compaction (air-void content), temperature, ageing and asphalt content. Finally, a series of recommendations are presented for enhancing the fatigue performance of pavements, including changes to current construction quality assurance procedures.