EVALUATION OF AGGREGATES IN THE CONSTRUCTION OF BITUMINOUS PAVEMENTS

BEWERTUNG VON GESTEINSMATERIALIEN IM BITUMINOESEN DECKENBAU

95 PERCENT OF BITUMINOUS SURFACINGS CONSIST OF AGGREGATE, AND THE DURABILITY OF THE SURFACINGS DEPENDS ON THE QUALITY OF THE AGGREGATES USED. STUDIES HAVE BEEN CARRIED OUT ON THE STRENGTH PROPERTIES OF A LARGE NUMBER OF THE CHIPPINGS NORMALLY USED IN BITUMINOUS WEARING COURSES, AND RESULTS ARE AVAILABLE. THE OBJECT OF THIS RESEARCH WAS TO FIND A RELATION BETWEEN THESE DATA AND THE BEHAVIOUR OF THESE AGGREGATES IN PRACTICE. 44 SECTIONS OF ROAD WHICH HAD BITUMINOUS SURFACINGS CONTAINING 20 DIFFERENT KINDS OF REFINED CHIPPINGS WERE OBSERVED FOR FIVE YEARS DURING SPRING AND AUTUMN. THE OBSERVATIONS WERE SUPPLEMENTED BY CORES 50 MM IN SIZE TAKEN FROM THE SURFACINGS TO ESTABLISH ABRASION. SKIDDING RESISTANCE BEFORE AND AFTER STRESS BY STUDDED TYRES WAS MEASURED ON CORES 200 MM IN SIZE WITH A SKIDDING RESISTANCE PENDULUM. A DETAILED PETROGRAPHIC DESCRIPTION OF THE CORES WAS UNDERTAKEN TO PROVIDE SCIENTIFIC EVIDENCE OF THE RELATION BETWEEN THE LABORATORY TESTS AND PRACTICAL MEASUREMENTS, A DISTINCTION BEING MADE BETWEEN CONDITIONS DURING THE AUTUMN AND THE SPRING. A NUMERICAL RELATION BETWEEN PRACTICAL RESULTS AND LABORATORY FIGURES WAS NOT FOUND.