The use of diffuse reflectance infrared spectroscopy to monitor the oxidation of UV irradiated and naturally aged bitumen and asphalt

Between 2013 and 2014 it cost £4.2 billion to repair roads in England [Department for Transport, Statistical Release. (2014). Road conditions in England 2014. Retrieved from https://www.gov.uk/government/uploads/system/uploads/attachment]. Currently, road surface quality is monitored visually and repairs effected when visible damage arises. At this point, repair is unfeasible and costly and time-consuming resurfacing is required. Hence the ability to perform non-invasive monitoring and prediction of road surface degradation could provide a significant advance in highway maintenance.The oxidation of bitumen in road surfaces is known to promote failure of road surfaces as it reduces the cohesion between bitumen and aggregate. This paper reports the use of non-contact, diffuse reflectance infrared Fourier transfer (DRIFT) spectroscopy to monitor the oxidation process in bitumen and asphalt.We outline the comparison between natural and enhanced, artificially promoted ageing of bitumen and asphalt samples using UV light. The IR spectroscopic results show the evolution of oxidation product functional groups and allow the ageing of the samples to be monitored. After 4 weeks of UV ageing and a total exposure of 350 kW/m2 the area of the carbonyl feature had increased from 0.17 to 3.25 and the combined carboxylic & sulphoxide feature had increased from 0.93 to 8.97, while the C–H feature had decreased from 8.16 to 1.18, indicating an increase in the oxidation of the bitumen.