Attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) is an essential tool for the analysis of bituminous binders due to its cost-effectiveness, user-friendliness, and non-destructive nature. However, its effectiveness is often hampered by challenges such as non-informative regions, lack of standardized analysis methods, and inconsistent baselines in spectral data. Addressing these challenges, this study aims to comprehensively evaluate the impact of various data pre-processing (DP) methods on ATR-FTIR spectra from diverse bituminous binder types, sources, and aging conditions. Using partial least squares discriminant analysis (PLSDA) classification, the study assesses the effectiveness of baseline correction, normalization, and their combinations. The methodology involves analyzing peak areas, indices, entire spectra, and first derivative spectra to determine the most effective pre-processing strategies. Key findings reveal that the effectiveness of DP methods is influenced by the classification goals, characteristics of the spectral dataset, and the specific methods employed for input data preparation. The study demonstrates that using entire spectra or their first derivatives leads to higher classification accuracy compared to indices or specific spectral peak areas. The choice between peak area and indices calculation methods should align with the study’s objectives. For efficient and rapid selection of DP methods, tools like PLSDA are recommended. Among the normalization methods, normalization to constant vector length (NCV), normalization to change the maximum to 1 (NMO), robust scaling (RS), and normalization to sum (NTS) are suitable for peak area or indices-based classification. For entire spectra and their first derivatives, NTS, NCV, autoscaling (AS), pareto scaling (PS), and standard normal variate (SNV) methods are recommended. Regarding baseline correction, Adaptive Smoothness Penalized Least Squares (aspls) is suitable for studies focusing on gradual material changes, such as multi-level aging studies, but not for additive
detection studies. The findings of this study provide valuable insights and practical recommendations for selecting appropriate DP methods, thereby enhancing the classification accuracy and reliability of ATR-FTIR spectral analysis of bituminous binders. This contributes significantly to the design of experiments, reduces operational risks, and optimizes resource utilization in the field.@en

Bituminous binders naturally age, affecting the properties and performance of asphalt pavements. The physical and chemical characteristics of binders are influenced by environmental factors, leading to a decline in their performance and durability. Therefore, it is essential to understand the mechanisms of binder environmental aging to design more resilient and long-lasting asphalt pavements. This study examines the effects of temperature, liquid, and vapor water on binder aging to develop more durable pavements. Aging was induced at three temperatures (60°C, 70°C, 85°C) under dry air, 90% relative humidity, and water immersion conditions. Field-aged samples were also analyzed to compare with laboratory-aged samples. Fourier-transform infrared spectroscopy (FTIR) and dynamic shear rheometer (DSR) were used to assess chemical and rheological changes. To assess the similarity between samples and identify the lab aging protocol closest to field aging, Hierarchical Cluster Analysis (HCA) was employed for data analysis.

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Asphalt pavements are subjected to various environmental factors such as rainfall, sunlight, humidity and wind that causes oxidative aging of bitumen, leading to reduced structural and functional performances in the longer run. Antioxidants are often added to asphalt binders to enhance their resistance to oxidative ageing. In the current study, two different antioxidants, Zinc Diethyldithiocarbamate and Lignin were evaluated for their effectiveness in improving the performance of asphalt binders. The laboratory mixing procedures were conducted at two different percentages, and laboratory aging were performed. Rheological and chemical tests were then conducted to evaluate the performance of the binders at different temperatures. The current study provides valuable insights into the use of antioxidants for improving the performance and service life of asphalt pavements, which will help in the development of perpetual asphalt pavements in the future.

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The rejuvenation efficiency of aged bitumen is the main concern when developing rejuvenating agents. It is necessary to develop a method to assess the efficiency of rejuvenators using rheological parameters in the whole frequency region. To this end, the 2S2P1D micromechanics model is adopted to fit the entire G∗ master curves of various rejuvenated bitumen, and the influence of rejuvenator type/dosage and aging grade of bitumen on the whole G∗ master curve and chemical indices are investigated. Critical parameters for evaluating rejuvenation efficiency derived from viscoelastic models and chemical characterizations are proposed. Furthermore, the potential relationships between the rheological model-based parameters (E _∞, δ, β, and τ) and chemical indices (carbonyl index CI and sulfoxide index SI) are explored. The results indicate that rejuvenators restore the δ, τ, CI, and SI values of aged bitumen towards the virgin bitumen level. The E _∞ parameter is not applicable to evaluate the rejuvenation efficiency of engine-oil and naphthenic-oil rejuvenators, but the positive E _∞R values of bio-oil and aromatic-oil rejuvenated bitumen are detected. All rejuvenators fail to restore the β parameter of aged bitumen. The τ and CI parameters are selected as critical evaluation indicators from the perspective of viscoelastic models and chemical characteristics. Linear correlations between all rheological parameters and chemical indices are observed and established.

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