Classification of bitumen using chemical and rheological properties
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School of Engineering |
Master's thesis
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en
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65
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Abstract
Bitumen is characterized by its chemical and rheological properties. These properties play a role in determining the performance, durability, and behaviours of bituminous materials under varying environmental and loading conditions. The classification of bitumen based on both chemical composition and rheological behaviour is essential for ensuring its suitability for specific applications. This research aims to classify the different bitumen based on the rheological and chemical properties. Dynamic Shear Rheometer (DSR) and Fourier Transform Infrared Spectroscopy (FTIR) tests were performed on bitumen samples. Bitumen samples were found to contain chemical compounds like carbonyls (C=O), sulfoxides (S=O), aliphatic hydrocarbons (CH_3,CH_2), and aromatic C-H compounds, with their absorbances increasing with increasing bitumen grades. Susceptibility to oxidation decreased with increasing bitumen grades. Bitumen samples with the same IDs as some Fourier transform infrared spectroscopy (FTIR) samples were tested to determine their rheological properties. The sample data were combined to generate datasets for grades 35, 50,70, 100, 120 and 160. Master curves showed smooth curves depicting sample consistency and can visually evaluate the rheological behaviour of different binders. Black diagrams showed that samples were unmodified by generating smooth curves (thermo-rheologically simple bitumen). Cole-Cole curves extensions described the balance between the elasticities and viscosities of the bitumen samples. Complex modulus master curves showed that all bitumen samples exhibited similar low temperature properties but varying high temperature properties whereas phase angle master curves showed similar viscoelastic properties at both low and high frequencies and temperatures. Principal component analysis (PCA) was used to determine the bitumen binder classification using DSR and FTIR parameters with the principal components (PCs) according to sample grades and sources. PCA of FTIR components generated a 51% cumulative variance between PC1 and PC2 which did not satisfy the required 80% cumulative variance between PC1 and PC2. PCA of DSR however generated a cumulative variance of 91.4% which satisfies the PC1 and PC2 variance requirement. Analysing the DSR parameters according to grades and sources revealed that the storage, complex and loss moduli correlated with PC1 while the phase angle correlated with PC2. FTIR components analysis in PCA according to grades and sources also revealed that both PC1 and PC2 captured the variations related to hydrocarbon chain structure (CH3 and CH2) and oxidation susceptibility (C=O & S=O). This explains the minor variation in the principal components. DSR and FTIR samples with the same IDs were analysed with PCA, it was revealed that the aliphatic hydrocarbons with the higher peaks (CH_3,CH_2) around wavelengths 2750 cm-1 – 3000 cm-1 and carbonyl peaks (C=O) correlated with the storage, complex, and loss modulus. The first aliphatic hydrocarbon peaks (CH_3,CH_2) around 1250 cm-1 – 1500 cm-1 and sulfoxide (S=O) correlated with phase angle. The balance between the FTIR parameters on both principal components after the combination (between FTIR and DSR) indicates that the DSR parameters were paramount in classifying the bitumen samples. PCA can classify bitumen by source and by bitumen grade. However, FTIR parameters cannot be used as a standalone classification parameter.Description
Supervisor
Raitanen, NinaThesis advisor
Cannone Falchetto, AugustoZhang, Fan