Fourier-Transform Infrared (FT-IR) spectroscopy shows several advantages that make it interesting to investigate cementitious materials: from clinker or hydrated phases to the bulk or the surface of hardened concrete. The FT-IR analyses in Transmission mode need only a few milligrams of material to provide its composition while other techniques (such as thermo-gravimetric analysis, X-ray diffraction, X-ray fluorescence) need a few grams. Moreover, FT-IR analyses are rapid and give results after a few minutes while other methods need at least a few hours to study one sample. The analyses done in Attenuated Total Reflection mode allow studying the surface of materials without any specific sampling methods (such as cleaning with solvent or storage under vacuum), which can alter the final composition. Clinker and anhydrous cement phases were already studied in 70s to establish the specific peaks of alite, belite and calcium aluminate. The study of major hydrates has been largely performed for the last two decades. FT-IR spectroscopy highlights easily the presence of portlandite (Ca(OH) 2 ), which is detected by a thin unique peak. Moreover, the shift of the peaks assigned to Calcium Silicate Hydrate (C-S-H) can be detected using transmission mode, in order to study the polymerization of the silicates according to the conditions of cure and ageing. AFt and AFm phases (such as ettringite, sulfoaluminate or hemicarbonate) can also be studied using FT-IR spectroscopy. Finally, this method is also able to detect organic demolding agents or CaCO 3 efflorescences at the surface of hardened concrete and can be used to study the interface between the hydrated paste and the polymers or coatings.
Plasma oxidation of plasma deposited polystyrene (pPS) films was performed in an inductively coupled plasma reactor. Reconstruction of the oxygen concentration depth profiles based on angle‐resolved XPS data showed that two competitive mechanisms (functionalization and etching) happened during the oxygen plasma treatment. Static water contact angle measurements confirmed this result. Oxidized pPS films were also not stable with time; a loss of hydrophilicity was observed and reorganization of the topmost functionalized surface occurred involving diffusion of oxygen groups from the surface towards the bulk and re‐contamination by reaction of trapped radicals with hydrocarbon molecules present in ambient air.
Concrete surfaces were studied by two spectroscopic techniques, FT-IR (in ATR mode) and Raman, to establish a nondestructive method to analyze the distribution of hydrated and organic phases. The surface composition of ordinary clinker, polished concrete, concrete after demoulding, and coated concrete as used in building construction was studied. The clinker's mineral phases and the polished concrete were first analyzed by Raman spectroscopy to determine a spectrum database of the specific phases located on the surface of the concrete. Then, both spectroscopic techniques were used to analyze, directly, the surface of hardened concrete after demoulding. No impact of roughness or porosity was highlighted using Raman spectroscopy; many cementitious, or hydrated phases (alite, belite, tricalcium aluminate, ferrite, portlandite and ettringite) were clearly identified. FT-IR in ATR mode only identified some hydrated phases: portlandite and CaO-SiO 2 -H 2 O (C-S-H), but organic residues from the demoulding oil were characterized by this technique. Furthermore, the convenience of using these techniques together was tested by analyzing the composition of concrete surfaces coated by different organic post-treatments. FT-IR spectroscopy was useful to identify the main organic groups at the concrete surface, whereas Raman spectroscopy was especially able to characterize the mineral/hydrated phases under a thick post-treatment layer (constituted of polyester varnish). Due to their own specificities, these complementary techniques should be used together to easily identify all the mineral phases and organic residues/coatings on concrete surfaces.
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