INVESTIGATIONS INTO THE POLISHING OF BITUMINOUS MIXES IN THE LABORATORY

THE INVESTIGATIONS CARRIED OUT CONFIRM THAT THE TEST EQUIPMENT AND METHOD DEVELOPED AT DRESDEN TECHNICAL UNIVERSITY FUNCTION WELL. THE INFLUENCE OF THE POLISHING OF BITUMINOUS MIXES ON GRIPPING BEHAVIOUR IS PROVED QUANTITATIVELY. INITIALLY AFTER A SHORT TIME IN WHICH IT RISES TO A MAXIMUM VALUE, THE SKIDDING RESISTANCE REDUCES DIFFERENTIALLY DEPENDING ON THE DURATION OF POLISHING DOWN TO A CONSTANT VALUE MY(P300) WHICH CAN BE REPRODUCED. THIS BASIC POLISHING BEHAVIOUR SHOULD BE APPROPRIATELY TAKEN INTO ACCOUNT WHEN ASSESSING THE SKIDDING RESISTANCE OF PAVEMENTS. THE RESISTANCE TO POLISHING OF THE BITUMINOUS CONCRETES TESTED IS SIGNIFICANTLY INFLUENCED BY THE MATERIAL PROPERTIES, AND IN PARTICULAR THE PETROGRAPHICAL PROPERTIES OF THE TYPE OF STONE USED IN EACH MIX. A DIFFERENT POLISHING BEHAVIOUR RESULTS FROM A CHANGE IN BINDER CONTENT. THIS INFLUENCE IS NOT SO SEVERE FOR THE ORDER OF MAGNITUDE STIPULATED FOR THE DEVIATION FROM THE OPTIMUM DETERMINED FOR EACH ON THE BASIS OF STABILITY TESTS, BUT SUFFICIENTLY RECOGNISABLE, AS IS THE REDUCTION IN SKIDDING RESISTANCE EXPERIENCED WHEN THE BINDER CONTENT IS TOO HIGH. IT MUST THEREFORE BE POINTED OUT THAT AN EXCESS OF BINDER MUST BE CAREFULLY AVOIDED WHEN PRODUCING BITUMINOUS MIXES. RELATIONS BETWEEN THE POLISHING BEHAVIOUR AND OTHER CHARACTERISTICS, FOR EXAMPLE MARSHALL STABILITY AND ABRASION RESISTANCE, CANNOT BE PROVED FROM THE RESULTS. FOR EXAMPLE GOOD POLISHING RESISTANCE CAN EXIST WITH LOW STABILITY AND VICE VERSA. IN ACCORDANCE WITH THE STATED REQUIREMENTS, OPTIMUM MATERIAL PROPORTIONS ARE NECESSARY CONSIDERING ALL THE QUALITY CHARACTERISTICS FOR EACH SEPARATE CASE, IN ORDER TO ACHIEVE BETTER ECONOMICS IN MATERIAL USAGE. WITH THIS IN MIND THE INVESTIGATIONS WILL CONTINUE TO DEVELOP PAVEMENTS HAVING PERMANENT SKIDDING RESISTANCE.