A CONSTITUTIVE MODEL FOR BINDER-AGGREGATE MIXTURES: A COMBINED MACRO- AND MICRO-MECHANICS APPROACH

DEVELOPMENT OF A CONSTITUTIVE LAW FOR BINDER-AGGREGATE MIXTURES HAS BEEN A MAIN YET ILLUSIVE OBJECTIVE OF RESEARCHERS IN PAVEMENT TECHNOLOGY. A GOOD CONSTITUTIVE LAW WILL LEAD TO BETTER MIX DESIGN AND PROLONG THE SERVICE LIFE OF PAVEMENTS THUS SAVING THE GOVERNMENT BILLIONS OF DOLLARS ANNUALLY. AT THE SAME TIME, NEW AND POTENTIALLY LARGE COMMERCIAL SOFTWARE MARKETS WILL APPEAR. BINDER-AGGREGATE MIXTURES EXHIBIT HIGHLY NONLINEAR BEHAVIOR. THESE MATERIALS DILATE, ARE RATE AND TEMPERATURE DEPENDENT, INELASTIC, AND BECOME DAMAGED. THE FOLLOWING TWO FACTORS PLAY AN IMPORTANT ROLE IN PAVEMENTS' SERVICE LIFE EXPECTANCY: RUTS, WHICH DEVELOP AT HIGH TEMPERATURE; AND CRACKS, DUE TO CYCLIC LOADING (MECHANICAL AND THERMAL). TO DATE, NO UNIFIED MODEL THAT ACCOUNTS FOR BOTH FACTORS HAS BEEN PROPOSED. RESEARCHERS ARE DEVELOPING A NONLINEAR VISCOPLASTIC CONSTITUTIVE LAW WITH DAMAGE THAT WILL ACCOUNT FOR BOTH ASPECTS. THE MODEL IS BASED ON FUNDAMENTAL PRINCIPLES OF CONTINUUM MECHANICS, AND THE (LOCAL) DAMAGE MODEL IS BASED ON MICRO-MECHANICAL CONSIDERATIONS. TO ENABLE A PROPER INCORPORATION OF DIRECTIONAL DAMAGE, A FINITE DEFORMATION FORMULATION IS BEING ADOPTED FROM THE ONSET AND THE MODEL INCORPORATED INTO A FINITE ELEMENT PROGRAM TO SIMULATE BINDER-AGGREGATE PAVEMENT BEHAVIOR.