Repeatability and sensitivity of FTIR ATR spectral analysis methods for bituminous binders

Abstract

Bituminous binders as organic materials are prone to aging mainly by oxidation. Aging changes the viscoelastic behavior of the material over time towards higher stiffness and brittleness. FTIR has been increasingly used lately to investigate impacts of oxidative aging on the chemical structure of bitumen. Especially the carbonyl and sulfoxide bands are affected by aging and commonly used to describe changes due to evolving oxidation of a binder. However, spectra obtained from FTIR can be analyzed in fundamentally different ways and the analysis method applied to a spectrum has an impact on the gathered results and especially on the repeatability and sensitivity with regards to oxidative changes. For the presented study, two bituminous binders, a PG 64-16 and an SBS modified PG 76-22 PM were aged by RTFO and PAV and subsequently measured by FTIR. The obtained spectra (up to 90 individual spectra per aging state) were analyzed employing various methods using either the original or a normalized spectrum, a band maximum or integration based calculation of indices from an absolute or tangential baseline. By analyzing the coefficient of variation of the different analysis methods, it was found that not all analysis methods exhibit the same repeatability and sensitivity. From the findings of the study it can be recommended to work with normalized spectra, use an absolute baseline and work with integration of areas for index production in favor over band maximum based methods.

Effect of Cereclor as Rejuvenator to Enhance the Aging Resistance of Reclaimed Asphalt Pavement Binder

“…In the previous studies of FTIR spectra of asphalt binders, investigators mainly recognized two functional chemical groups produced during aging through oxidation at the intensity of peaks for carbonyl at 1700 cm −1 and sulfoxide at 1030 cm −1 [14,37,38]. The aliphatic groups are used as a reference as it is estimated that these groups are stable and do not change due to aging [39].…”

FTIR spectral analysis of bituminous binders: reproducibility and impact of ageing temperature

“…A recent round robin test was performed between seven laboratories using RTFOT aged binders [43]. This study compared Attenuated Total Reflectance (ATR) and transmission spectroscopy and recommends working with transmission spectroscopy since it produces more repeatable results.…”

On the Applicability of ATR-FTIR Microscopy to Evaluate the Blending between Neat Bitumen and Bituminous Coating of Reclaimed Asphalt

“…The past years, increasing attempts have demonstrated the ability of non-destructive tests to evaluate this problem. Attenuated total reflectance (ATR) spectra obtained by Fourier transform infrared (FTIR) spectroscopy is a widely utilized non-destructive test to study bitumen and especially to trace ageing evolution [16][17][18], to evaluate rejuvenation [19,20] or to evaluate the modification of bitumen [21,22]. ATR-FTIR spectroscopy is suitable to evaluate homogeneous individual components but not a heterogeneous composite material (such as an asphalt mixture), since it can only be applied in a single spot averaging the measuring spectra.…”