STUDIES OF THE CHANGE IN THE PROPERTIES OF CHIPPINGS AND GRAVELS WHEN THEY PASS THROUGH THE DRYING DRUM OF HOT MIXING PLANTS

AENDERUNGEN DER EIGENSCHAFTEN VON SPLITTEN UND KIESEN BEIM D URCHGANG DURCH DIE TROCKENTROMMEL VON HEISSMISCHANLAGEN

THE TEMPERATURES OCCURRING IN THE DRYING DRUMS OF HOT- MIXING PLANTS, TOGETHER WITH THE TEMPERATURE GRADIENTS, MAKE GREAT DEMANDS ON THE HEAT RESISTANCE OF THE AGGREGATES USED FOR THE HOT MIXTURE. THEREFORE IN MANY CASES OF EARLY DETERIORATION OF ROAD STRUCTURES, THERE IS SOME BASIS FOR THE SUSPICION THAT HEAT STRESS DURING THE MANUFACTURE OF THE HOT MIXTURE HAS LED TO A DETERIORATION IN THE QUALITY OF THE AGGREGATE, AND THAT THIS CAN BE REGARDED AS AT LEAST ONE OF THE CAUSES OF THE DAMAGE. RECOMMENDATIONS , SPECIFICATIONS AND INSTRUCTIONS RELATING TO HOT MIXTURES THUS REQUIRE SUFFICIENT HEAT RESISTANCE OF THE AGGREGATES USED, WITHOUT GIVING ANY DETAILED INFORMATION ABOUT THIS. BEFORE THE PREPARATION OF A METHOD OF TESTING THE HEAT RESISTANCE OF CHIPPINGS, SANDS AND GRAVELS, IT IS ESSENTIAL THAT THE ACTUAL REDUCTION IN QUALITY WHICH OCCURS DURING THE PASSING THROUGH THE DRYING DRUMS IS DETERMINED. THE AIM OF THE RESEARCH PROJECT IS TO STUDY THE MIXTURES OF CHIPPINGS, SAND AND GRAVEL USED IN SURFACINGS OR ROADBASES BOTH BEFORE AND AFTER THEY HAVE PASSED THROUGH THE DRYING DRUMS OF A HOT MIXING PLANT, SO THAT CHANGES IN THEIR TECHNICAL PROPERTIES CAN BE DETERMINED. THE MATERIALS ARE TO BE A REPRESENTATIVE CROSS SECTION OF AGGREGATES USED IN AUSTRIA FOR THE PRODUCTION OF HOT MIXTURES.