Time dependant volumetric behaviour of asphalt pavements under heavyloading and high temperature

摘要

Permanent deformation and fatigue cracking are two common signs of failure in a flexiblepavement. High ambient temperature and heavy loading are two major factors that cause early failure by reducingthe percentage air voids in a pavement mix with time. This behaviour depends on the in situ air void content,bitumen type, aggregate quality and hot mix asphalt (HMA) properties. A field study on two pavement sectionswas carried out in Pakistan to investigate the volumetric behavior of HMA under severe loading conditionsexperienced in this region. Section 1 was paved at the start of the winter (i.e. the start of the 6 month coolerseason) and Section 2 was paved at the start of the summer (ie at the start of the 6 month hot season). Theinitial air void content of the mix was close to 6.0%. Air void content was measured by taking cores everythree months. The seasonal development of permanent deformation was also monitored on both sections overthe 2 year test period. The study clearly illustrated that the rate of change in the development of air voids inthe mix was different for each section and followed a seasonal trend related to temperature. The study alsorecorded the reduction in air void content in the pavement hot mix material with depth. Data is presented whichcorrelates season (temperature) and depth (magnitude of applied stress) to the reduction in air void contentin the bituminous mixes. Some conclusions are drawn on the efficient design and construction of bituminouspavements in Pakistan.