IMPROVING THE STABILITY AND THE VISCOELASTIC RELAXATION OF BITUMINOUS MIXTURES

VERBESSERUNG DER STANDFESTIGKEIT BZW. DES VISKOELASTISCHEN RELAXATIONSVERHALTENS VON BITUMEN- ODER ASPHALTMISCHUNGEN IM STRASSENBAU

STABILITY CANNOT BE ACCURATELY DEFINED PHYSICALLY, AS IT IS SPLIT INTO TENSILE, COMPRESSION AND SHEAR STRESSES ACCORDING TO THE SHAPE OF THE SAMPLE. AN INCREASE IN STABILITY IS ASSOCIATED WITH A DECREASE IN DUCTILITY. THIS LEADS TO CRACKS IN THE ROAD SURFACING, PARTICULARLY DURING COLD WEATHER. A SERIES OF TESTS WAS UNDERTAKEN TO TRY AND ELIMINATE THIS DISADVANTAGE BY MODIFYING BITUMEN AND TECHNOLOGY. ONLY SOME OF THE DEVELOPMENT WORK COULD BE TRANSLATED INTO PRACTICAL TESTS. EXPERIMENTAL SECTIONS OF ROAD WHICH DID NOT HAVE MEASURING DEVICES INCORPORATED INTO THEM PROVIDE ADEQUATE INFORMATION ON MIXING AND LAYING TECHNOLOGY; THEIR LONG TERM BEHAVIOUR CAN ONLY BE ASSESSED HOWEVER BY THE HUMAN EYE, AND NOT BY MEASUREMENTS, AND CANNOT BE ESTIMATED WITHOUT A KNOWLEDGE OF THE BASIC MECHANICAL AND TECHNOLOGICAL FACTS. THE POSSIBILITY NOW EXISTS TO ELIMINATE THIS DEFICIENCY AND TO ARRIVE AT PRINCIPLES WHICH FACILITATE THE SELECTION AND/OR ADAPTATION OF AN OPTIMUM METHOD FOR AUSTRIAN CONDITIONS, OR TO DEVELOP A NEW METHOD. A HIGH-SPEED MIXER TEST RIG SHOULD FACILITATE THE TRANSFER OF THE PARAMETERS TO PRACTICAL CONDITIONS. DETERMINATION OF THE PHYSICAL CHARACTERISTIC VALUES IS TO BE FOLLOWED BY THE TRANSFER OF THE INFORMATION OBTAINED TO BITUMINOUS MIXTURES AND PRACTICAL TESTS ON PILOT FACILITIES.