Bitumen Durability-Measurement by Oxygen Absorption

THE ABSORPTION OF OXYGEN BY BITUMENS IN THE LIGHT AND IN THE DARK WAS MEASURED AT AMBIENT TEMPERATURE WITH STIRRED SOLUTIONS IN AN INDIFFERENT SOLVENT TO AVOID PROBLEMS DUE TO DIFFUSION EFFECTS. THE RATE OF ABSORPTION WAS CONSIDERABLY INCREASED BY LIGHT (FLUORESCENT LIGHTING) AND BY TRACES OF CERTAIN METALS. ALL CHEMICAL-TYPE FRACTIONS PREPARED FROM BITUMENS BY CHROMATOGRAPHIC SEPARATION OXIDIZED IN THE LIGHT, BUT ONLY THE ASPHALTENES AND RESINS ABSORBED OXYGEN IN THE DARK, THIS REACTION PROBABLY BEING INITIATED BY THE STABLE FREE RADICALS PRESENT IN BITUMENS. THE CONCENTRATION OF REACTIVE COMPONENTS IN DARK-COLORED BITUMENS IS HIGHER THAN IN LIGHT-COLORED ONES, BUT IN PRACTICE THE DARK COLOR ACTS AS A PROTECTION AGAINST EXCESSIVE OXIDATION IN THE LIGHT. FEW OF THE COMPOUNDS KNOWN TO INHIBIT OXIDATION REACTIONS APPEARED TO AFFECT BITUMEN OXIDATION. THOSE THAT WERE ACTIVE ACCELERATED OXYGEN ABSORPTION IN THE LIGHT BUT HAD HARDLY ANY EFFECT IN THE DARK. THE EFFECTS FOUND WITH THESE SUBSTANCES IN THE LIGHT EXPERIMENTS WERE CHECKED WITH WEATHER-O-METER EXPERIMENTS. /AUTHOR/