Determination of physico-chemical parameters for bitumens using near infrared spectroscopy

Bitumens are usually characterised by using time-consuming empirical or functional physico-chemical tests. This paper reports a method for the determination of various physico-chemical properties (viz. viscosity at 60 and 135 degreesC, density at 15 degreesC, softening point and Fraass breaking point) and the chemical composition (viz, n-heptane-insolubIe asphaltenes, asphaltenes + insoluble polar resins (IPR), saturated hydrocarbons, aromatic hydrocarbons and resins) of bitumens using near infrared (NIR) spectroscopy in conjunction with partial least-squares regression (PLSR). The proposed method surpasses existing alternatives in expeditiousness; also, it allows the simultaneous determination of several parameters from a single spectrum and is amenable to implementation in the continuous mode. Its accuracy and precision are essentially identical with those of reference methods; the relative standard deviation ranges from 0.2% for density to 14% for the Fraass breaking point. (C) 2001 Elsevier Science B.V. All rights reserved.