Influence of refinery processing methods on ageing of bitumen

This investigation reports the influence of processing condition (air rectification and component blending) on ageing and stress relaxation behaviour in bitumen. FTIR spectra were recorded on two samples of bitumen at unaged, short-term aged and long-term aged conditions. Indices such as aliphaticity, aromaticity, carbonyl and sulphoxide calculated from the FTIR spectra were used in the analysis. It was seen that the ageing compounds in the air-rectified bitumen were higher at the end of the production process compared with the blended bitumen while the rate of oxidation compounds formed during short-term and long-term ageing was higher in the blended bitumen. In addition, a stress relaxation test was performed at 25°C in the unaged, short-term and long-term ageing conditions. Since the formation of ageing compounds leads to change in ‘stiffness’ and hence a change in the stress relaxation behaviour of the material, it is seen that the stress relaxation results are in line with the material behaviour as seen from the FTIR tests.