Domains of permanent deformation coefficient alpha and mu for hard grade asphalt concrete mixtures

Permanent deformation coefficients,such as alpha (a) and mu show influence of mixture's properties on flexible pavement probable rut development. assessment of these coefficients requires a data bank of mixture parameters (aggregate type,gradation,binder type,contents and mixtures volumetric),temperature and loading conditions. a comprehensive laboratory study was carried out on six mixtures ranging from fine to coarse with three hard grade asphalt cements,which are used in typical hot weather areas of pakistan. the specimens were subjected to cyclic loading on utm-5p in order to study resistance against permanent deformation of the mixtures at 25,40 and 55°c and permanent deformation coefficients alpha and mu. it was revealed from the current study that alpha and mu has opposite trends in all the six mixtures under the specified load and temperature domains. at low temperature (25°c) and stress levels (100 kpa),the mixtures showed same resistance to permanent deformation,while at high temperature (55°c) and stress level (500 kpa),mixtures with polymer modified asphalt showed better performance.