Hyperspectral imaging applied to the identification and classification of asbestos fibers

HyperSpectral Imaging (HSI) is a powerful technique suitable to develop analytical protocols for materials identification difficult to handle and investigate through classical chemical based analytical approaches. Asbestos fibers can be considered one of these products. Asbestos, largely utilized in the past for its characteristics (i.e. heat resistance, sound absorption, thermal insulation and easily binding with building materials such as gypsum, lime and cement or polymers), is one of the most harmful and risky materials to handle in respect of human health. Asbestos fibers become very dangerous when dispersed in friable matrices. Dispersion effects, due to material fragmentations, and fiber release, can thus represent a high risk factor. Selected samples of cement-asbestos fibers, of different nature, were collected and analyzed by HSI in the short wave infrared (SWIR: 1000-2500 nm). Analytical strategies were then developed, implemented and set up to detect absorption effects related to the presence of CaCO3, iron and magnesium hydroxides, indicating the presence of asbestos, that is of specific phyllosilicates (i.e. chrysotile, crocidolite, amosite, anthophyllite, tremolite and actinolite) characterized by an asbestiform habit (i.e. 1:20 average aspect ratio). The obtained results were also validated analyzing and mapping the same samples by micro-X-ray fluorescence using a Bruker M4 Tornado device.