Efficacy of Polyphosphoric Acid in Reducing the Degree of Thermal Aging of Agbabu Natural Bitumen

Abstract

Bitumen is a complex mixture of hydrocarbons which occurred naturally or obtained from crude oil distillation. The degradation of bitumen causes its rapid aging leading to deterioration of asphalt based pavement readily induced by cracking, rutting, potholes etc. Aging in bitumen is attributed to chemical oxidation of its molecules and exposure to environmental factors, such as heat, moisture and sunlight. This study therefore investigates the viability of using polyphosphoric acid (PPA) to reduce the oxidative degradation effect of heat (60 o C) on constituents of Agbabu natural bitumen (ANB) with a view to making it more durable when used for road pavement. Modification of ANB with PPA was carried out at 150-55 o C using melt blend technique. Thereafter, the PPA modified and neat (unmodified) ANB samples were thermally aged in a hot air oven at 60 o C. Fourier Transform Infrared (FTIR) Spectroscopy was used to evaluate the changes in the structure of ANB and aging indexes of neat and PPA modified samples of ANB were calculated. The neat and PPA modified ANB samples aged as a result of their exposure to temperature at 60 o C. However, the aging indexes of PPA modified samples of ANB were found to be lower compared with that of the neat sample of ANB. This implies that the rate of aging (60 o C) of the neat ANB was faster than that of PPA modified ANB samples. Thus, a good potential for reducing thermal aging in ANB was found in PPA.