LIMESTONE DUST AS A FILLER MATERIAL IN ROAD CONSTRUCTION

THE RHINE LIMESTONE WORKS AT WULRATH HAS PUBLISHED A NEW LEAFLET ON FILLERS IN WHICH THEY DESCRIBE THE CONSIDERABLE INFLUENCE OF FILLERS ON BITUMINOUS MORTARS AND HENCE ON ASPHALT ROAD CONSTRUCTION. THE PERFORMANCE OF ASPHALTIC CONCRETE ROAD SLABS CAN BE FURTHER INCREASED WITH COST REDUCTIONS. IN DETAIL THE AUTHOR DEALS WITH THE DETRIMENTAL EFFECTS WHICH SOMETIMES CONSIDERABLY WEAKEN THE STABILITY OF THE FILLER; FOR EXAMPLE THE SELF-FILLER WHICH IS OFTEN OF DOUBTFUL QUALITY AND HAS DAMAGING EFFECTS. THE RANGES OF TOLERANCE FOR FILLER QUANTITIES ARE TOO WIDE AND ARE NOT IN PROPER RELATIONSHIP TO THE DEVIATIONS IN BINDER MATERIAL QUANTITIES. IN ADDITION THERE ARE ERRORS IN COMPACTION, ESPECIALLY WITH GRAIN STRUCTURES WHICH ARE NOT READILY COMPACTABLE IN WHICH THE HIGH COMPACTION EFFORT ASSISTS THE INGRESS OF WATER INTO THE BITUMEN AND THE DESTRUCTION OF THE GRAINS. THE GOOD QUALITIES OF LIMESTONE DUST ARE ESPECIALLY IMPORTANT. CAST ASPHALT (GUSSASPHALT) IS MAINLY PRODUCED USING LIMESTONE DUST, WHICH IS ALSO REGARDED AS THE MAIN MATERIAL AS A FILLER IN ASPHALTIC CONCRETE. A HIGH-GRADE LIMESTONE DUST MUST FULFIL 5 REQUIREMENTS TO BE SUITABLE IN PRACTICE. THESE ARE DESCRIBED BY THE AUTHOR. FINALLY TECHNICAL GUIDELINES CONCERNING THE USAGE (FILLER TO BITUMEN RATIO APPROXIMATELY 2 : 1) ARE GIVEN AND GENERALLY INFORMATION ON THE RIGDEN VALUE WHICH IS NOT ONLY USED FOR ASSESSMENT.