Petroleum Asphalt Testing

Hou, Xiangdao, et al. Fuel 226 (2018): 230-239.

Aging of asphalt binders during the construction and service life of asphalt pavements leads to structural deterioration, primarily caused by exposure to sunlight, oxygen, water, and varying temperatures. Understanding the aging resistance of asphalt is critical for improving pavement durability. Traditional methods such as rheological tests, Fourier transform infrared spectroscopy (FTIR), and gel permeation chromatography (GPC) are effective but often complex and costly. This study introduced spectrophotometry as a novel, cost-effective method to characterize asphalt aging.

A 2 g/L "toluene-heptane" asphalt suspension was prepared, and absorbance in the 700–900 nm range was measured to assess aging characteristics. Results demonstrated that increased absorbance correlates with higher asphaltene content, indicating asphalt oxidation during aging. FTIR analysis confirmed the accuracy of spectrophotometry in detecting changes in asphalt composition.

Eight asphalt samples at three aging levels (Virgin, RTFO, PAV) were analyzed. The percentage of asphaltene increased significantly after aging treatments, confirming that asphaltene content is a key indicator of asphalt aging. Further analysis showed that harder asphalt samples (#70) exhibited higher aging susceptibility (slope of 0.0055) compared to softer samples (#90) (slope of 0.0046). This study highlights the potential of spectrophotometry as a reliable and practical technique for assessing asphalt aging, offering a simpler alternative to conventional methods while providing accurate insights into asphalt durability and performance.

Li, Jin, et al. Measurement 198 (2022): 111361.

Accurate characterization of asphalt's SARA (Saturates, Aromatics, Resins, and Asphaltenes) fractions is critical for assessing pavement performance and improving road durability. This study introduced a rapid and precise method for determining SARA fractions in asphalt using Mid-Infrared (MIR) spectroscopy combined with Partial Least Square Regression (PLSR).

A total of 84 asphalt samples with varying SARA fractions were prepared through blending and progressive aging. The SARA content and MIR spectra (4000–600 cm^-1) were measured using standard methods. Quantitative calibration models were developed for each SARA fraction using the PLSR method, demonstrating high consistency between predicted and measured values, with strong reproducibility and repeatability. The most informative spectral regions were identified at 3100–2500 cm^-1 and 1800–1000 cm^-1. Key absorbance peaks included 2920 cm^-1 and 2852 cm^-1 (CH₂ groups), 2962 cm^-1 (CH₃ groups), 1700 cm^-1 (carbonyl groups), and 1030 cm^-1 (S=O in asphaltenes or resins). Aromatic C-H vibrations were evident between 870 cm^-1 and 720 cm^-1.

The MIR-PLSR method allows faster SARA analysis compared to traditional techniques through a single MIR spectrum, facilitating real-time quality control during asphalt production and in-situ quality inspection using portable devices. This method enhances the efficiency and accuracy of asphalt quality evaluation, providing valuable insights into the aging and performance of asphalt binders in road construction.

da Silveira, Géssica Domingos, et al. Journal of Chromatography A 1457 (2016): 29-40.

Accurate determination of organosulfur compounds in asphalt is essential for understanding its aging behavior and improving pavement performance. This study developed a highly sensitive ultra-high-performance liquid chromatography–atmospheric pressure photoionization tandem mass spectrometric (UHPLC-APPI-MS/MS) method for characterizing organosulfur compounds in Brazilian asphalt cements.

The method enabled the detection of 14 organosulfur compounds, including sulfoxides, sulfones, thiophenes, and aromatic sulfides, with sulfoxides and sulfones showing higher ionization sensitivity. The optimized chromatographic flow rate improved detection accuracy, and the matrix effect of asphalt cements was within an acceptable range (70.58% to 119.18%). The method demonstrated excellent linearity and recovery, ranging from 83.85% for thianaphthene to 110.28% for 3-methylbenzothiophene. Importantly, the APPI source was used without a dopant, eliminating interference from polycyclic aromatic hydrocarbons (PAHs).

Characterization revealed the presence of dimethyl sulfoxide, di-p-toluyl sulfone, and dibenzothiophene, among others. After RTFOT + SUNTEST aging, an increase in sulfoxides and sulfones was observed in the asphaltenic fraction, highlighting their role in asphalt aging. Differences in sulfur speciation among samples were attributed to the asphalt's origin from different refineries.

The UHPLC-APPI-MS/MS method offers a rapid, accurate, and reproducible approach for analyzing organosulfur compounds in asphalt without complex pretreatment. This facilitates real-time monitoring of asphalt quality and enhances understanding of the chemical changes driving asphalt aging.