Dependence of carbonyl, sulphoxide and hydroxyl functional group formation on oxygen concentration during the oxidation of roading bitumen

•Autoxidation of bitumen at 50 °C was measured in the fast and slow reaction rate regions.•Carbonyl, sulphoxide and hydroxyl formation rates depended on oxygen concentration.•Oxygen reaction orders were unchanged over the fast and slow reaction rate regions.•Oxygen dependence was inconsistent with previously proposed oxidation mechanism.