Near-infrared spectroscopy investigation on the hydration degree of a cement paste

Abstract

NIR Infrared spectroscopy is a fast and easy-to-perform technique characterized by a high sensitivity towards water containing systems and for this reason it is a suitable tool for investigating structural modifications of hydrating cementing materials, even if the lack of knowledge in this field makes the interpretation of NIR vibrational bands very difficult.In this paper the NIR spectrum of a hydrated ordinary Portland cement is deeply investigated and an interpretation of the different bands is proposed on the basis of both experimental evidences and literature reference.The obtained results have been then applied to the investigation of the cement hydration advancing up to 28 days, analyzing the variations detectable in the shape of the spectrum as the reaction goes on. The entity of this variation, quantified through area calculations of main significant bands, revealed a good agreement with the hydration degree of the paste measured by thermal method.The findings of this research supply a solid base for future in-field application of NIR spectroscopy, for example for investigations on cements with different hydration behavior or to evaluate the effect of additives on cement pastes and, at a further level, for cement quality control.

Near-Infrared (NIR) Spectroscopy of Synthetic Hydroxyapatites and Human Dental Tissues

“…The 4500–5800 cm −1 region contains combination bands of water and surface P–OH (Table II). 12,13,31,–34 We found that the water band, located in the 4600–5400 cm −1 range, is broad and asymmetric, with extra features indicative of its inherent complex structure (Fig. 1b).…”

“…24,–27 For the synthetic apatites, they are dominated by bands of water and various OH groups. 12,13,31,–34 Figure 1a shows the spectra of samples HA100–HA800. There are three main spectral regions to discuss: 4500–5800, 6200–8000, and 10 000–10 500 cm −1 .…”

“…Particles of nanoapatite are covered by an extensive hydrated surface layer, incorporating water and P–OH groups, and they are also rich in structural water that fills the HA channels together with structural OH groups. 28,–30 So far, there have been only a few reports on NIR studies of apatites, 12,13,31,–34 and they are focused only on selected bands. Some spectral features, such as a band at 5314 cm −1 , still need to be interpreted.…”

Application of Fourier Transform infrared spectroscopy (FTIR) coupled with multivariate regression for calcium carbonate (CaCO3) quantification in cement

“…In this context, it is essential to: (i) quantify the carbonation reaction products, (ii) control the carbonation process and (iii) understand its effects on the cement integrity and properties. Thus, techniques such as phenolphthalein test, X-ray florescence (XRF), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray microtomography (MicroCT), thermogravimetric analysis (TGA), nuclear magnetic resonance (NMR) spectroscopy and infrared (IR) spectroscopy are widely applied in the literature to characterize carbonated cementitious materials and their composites [32,[35][36][37][38]. Among the characterization methods, the analysis of CaCO 3 in cementitious materials can be performed in the following way: (i) qualitative, by means of phenolphthalein, TEM and SEM methods, (ii) semi-quantitative, using the IR, MicroCT, XRD and XRF instruments and (iii) quantitative, through TGA analysis [11,[35][36][39][40].…”

Study of the Microstructure Evolution of Low-pH Cements Based on Ordinary Portland Cement (OPC) by Mid- and Near-Infrared Spectroscopy, and Their Influence on Corrosion of Steel Reinforcement

“…In this region three bands (or groups of bands) can be identified. The feature between 7000 and 7300 cm −1 is the first OH overtone (2ν 1 , 2ν 3 , and ν 1 + ν 3 ) and it has many components [ 32 , 33 ]: one easily detectable at 7083 cm −1 corresponding to OH stretching vibrations in portlandite, a broader but less precise shoulder at 7200 cm −1 related to C–S–H gel and a band around 7100 cm −1 related to the presence of Al-bonded O–H groups in ettringite. Although the overlapping of these bands/shoulders complicates the identification of the three components, the portlandite band is only recognizable in the Ref paste where increases its intensity from 2 to 90 d. However, in the low-pH cement pastes this band is not easily detectable and a very broad band related to structural water in C–S–H gels is observed, confirming the CH consumption.…”