EFFECT OF PRIMARY FEATURES OF AGGREGATES ON THE BEHAVIOUR OF ASPHALTS - PART B: FINE CONSTITUENT FORMATION FROM SANDS AS A RESULT OF DYNAMIC STRESS

EINFLUSS VON PRIMAERMERKMALEN DER MINERALSTOFFE AUF DAS VERHALTEN VON ASPHALTEN - TEIL B: FEINTEILNACHBILDUNG AUS SANDEN INFOLGE DYNAMISCHER BEANSPRUCHUNG

SO-CALLED "HEAT DAMAGE" TO BITUMINOUS SURFACINGS FOLLOWING THE HOT SUMMER OF 1976 LED TO NUMEROUS STUDIES ON CORES AND SAMPLES TAKEN FROM VARIOUS PARTS OF THE ROAD (CRAWLER LANES, TRAFFIC LIGHTS, BUS STOPS, ETC). THESE SHOWED THAT LATERAL DISPLACEMENT OCCURRED AS A RESULT OF STRONG SHEARING FORCES (E.G. ACCELERATION FORCES) OR INCREASED STRESS ON THE ROAD STRUCTURE CAUSED BY THE GREATER NUMBER OF PARKED VEHICLES. THE CAUSES OF THESE UNDESIRABLE DEFORMATIONS ARE COMPLEX. A MAIN REASON IS PROBABLY THE TRAFFIC-INDUCED INCREASE IN BITUMINOUS MORTAR THROUGH THE REPRODUCTION OF FINE CONSTITUENTS (FILLER AND SAND) FROM SAND, CHIPPINGS AND REFINED CHIPPINGS. FACTORS INFLUENCING THIS PROCESS ARE TO BE DETERMINED AND THEIR MAGNITUDE ESTIMATED. BITUMEN-BOUND AND UNBOUND MIXTURES AND INDIVIDUAL FRACTIONS OF SAND ARE TO BE EXAMINED IN A PULSATOR WHICH SIMULATES THE FREQUENCY AND FORCE OF LORRY TRAFFIC WHICH IS MAINLY RESPONSIBLE FOR THE STRESS ON THE ROAD.