Characterization of cement-based materials by infrared spectroscopy

This work describes the advantages and limitations of Fourier transform infrared spectroscopy (FT-IR) for analyzing cementitious materials (anhydrous Portland clinker phases, hydrated mineral phases, building materials containing cement paste (such as mortars and concretes). Unlike the analysis of organic products, polymers and coatings such as paint or varnish, FT-IR spectroscopy is relatively little used to study cementitious and hydraulically-setting materials. Indeed, other analytical methods such as thermogravimetric analysis (TGA) or X-ray diffraction (DX) are often preferred when it comes to characterizing these materials. However, FT-IR spectroscopy was already used in the 1970s to characterize the anhydrous phases of clinker, and has a number of advantages that make it an interesting addition to the range of methods for characterizing cementitious materials.

In this article, a number of applied results will be described, together with relevant bibliographical references for those wishing to delve deeper into the subject. Firstly, the main analysis modes generally available on a FT-IR spectrometer will be briefly described: (i) the transmission mode (Tr); (ii) the attenuated total reflection mode (more commonly referred to as "ATR"); and (iii) diffuse reflectance spectroscopy (more commonly referred to as "DRIFTS"). The advantages and limitations of IR-FT spectroscopy in the study of cementitious materials will then be explained. In a second section, an overview of the scientific literature will be presented, together with results for several types of application (anhydrous clinker phases, hydrated cementitious phases, mortar containing recycled materials, raw or coated concrete surfaces). Finally, a third section will describe some of the analytical techniques that can be used to complement FT-IR spectroscopy to analyze these cementitious materials.