FTIR spectroscopy and multivariate discriminant analysis for classifying bituminous mastics: Exploring aging states and mastic composition

This study aimed to differentiate among various bituminous mastics through the analysis of FTIR spectroscopy data. The mastics, incorporating three filler types, a 50/70 penetration index binder, and foamed bitumen, underwent chemical examination via FTIR spectroscopy after exposure to various aging cycles. Employing different multivariate discriminant analysis approaches, the investigation identified an optimal method, i.e., PLSR-LDA, which achieved a prediction precision of 100 % in distinguishing between various types of mixtures. The governing wavenumbers in the classification were determined through PLSR-LDA analysis by calculating VIP scores. Next, integrals associated with the highlighted wavenumber regions served as input to the DT classifier, resulting in classification with the prediction precisions of 96 % and 88 % for mastic types and aging states, respectively. The subsequent analysis underscored the significance of the CaCo₃ absorption band in discriminating between different mastic types. Similarly, C-H stretching of CH₃ and carbonyl bands were identified as pivotal regions governing the classification based on aging states.