Microwave spectroscopy: A potential technique to analyse bitumen dielectric and physical properties

Bitumen is a complex mixture of high molecular weight organic compounds, predominantly hydrocarbons, with carbon numbers greater than C₂₄. It has high carbon to hydrogen ratios, and also contains small amount of metals such as nickel, iron and vanadium. The application of bitumen in the pavement industry is mainly as a binding agent for road construction/surfacing. Hence, this paper discusses the use of microwave spectroscopy (MS) as a potential technique to analyse bitumen's dielectric properties to indicate change in some of its physical properties after its interaction with both treated and untreated coarse rubber in the field of pavement engineering. A comparison of the existing techniques for the quantitative and qualitative analysis of bitumen is given. The drawbacks of the existing techniques are also discussed and the paper addresses how the MS technique can overcome these drawbacks. The MS technique is investigated by analysing different bitumen samples including pure bitumen and samples taken from rubber-bitumen blends. Each of the blends used rubber with different surface properties which have different effects on the properties of the resulting bitumen. The paper highlights the novelty and advantages for the MS technique in reducing analysis time, solvent usage and potential take-up by the industry.