Abstract
Establishing the carbonation profile is of great significance to the prediction of the service life of reinforced concrete structures. In our previous work, Raman spectroscopy was shown to be an efficient tool for characterizing calcium carbonate (CaCO3) polymorphs and their profile in plain Portland cement (PC) matrices. However, as supplementary cementitious materials (SCMs), particularly fly ash (FA) and ground granulated blast furnace slag (GGBS), are widely used in concrete, establishing the carbonation profile without considering the possible effects of these SCMs could be of little significance to the real world. This paper, thus, investigated the effects of FA and GGBS on the working capacity and reliability of Raman spectroscopy for establishing the carbonation profile in PC blends containing SCMs. The thermogravimetry (TG) analysis was also conducted to verify the results from Raman spectroscopy. The results show that Raman spectroscopy demonstrated a good capacity for differentiating the variation of CaCO3 contents in FA or GGBS blends. However, the incorporation of FA and GGBS into the PC system caused some adverse effects on the quantification of CaCO3 by Raman spectroscopy, which could be attributed to the darker color and weak scatter nature of FA and the high content of glassy phases in GGBS.
Highlights
Published: 5 April 2021Concrete is inevitably exposed to carbonation attacks during its service life owing to the presence of carbon dioxide (CO2 ) such as that in the atmosphere
The Signal-to-Noise Ratio (SNR) values of the Raman spectra were calculated using the υ1 CO3 peak of the samples obtained at the depth of 0–2 mm according to the method recommended in American Society for Testing Materials (ASTM ) E579-04 as follows: SNR = Signal level/Noise (RMS) level where the signal level is the peak height/intensity after subtracting the background and the noise level is obtained by the root mean square (RMS) method, which is the standard deviation of the intensity values of a selected Raman shift region on the spectrum after subtracting the background
To identify the possible effects that fly ash (FA) or ground granulated blast furnace slag (GGBS) might impose on the qualitative and, the quantitative working capacity of Raman spectroscopy for establishing carbonation profiles in blended cementitious systems, the experiment work was organized into two parts and the results are reported as follows: 1
Summary
Published: 5 April 2021Concrete is inevitably exposed to carbonation attacks during its service life owing to the presence of carbon dioxide (CO2 ) such as that in the atmosphere. Subtraction adopting the baseline correction using Origin 2018 (OriginLab, Northampton, MA, USA) This procedure can remove the strong fluorescence background, allowing the Raman peaks to be clearly observed. The SNR values of the Raman spectra were calculated using the υ1 CO3 peak of the samples obtained at the depth of 0–2 mm according to the method recommended in American Society for Testing Materials (ASTM ) E579-04 as follows: SNR = Signal level/Noise (RMS) level (1). Where the signal level is the peak height/intensity after subtracting the background and the noise level is obtained by the root mean square (RMS) method, which is the standard deviation of the intensity values of a selected Raman shift region on the spectrum after subtracting the background. The CaCO3 quantity was calculated by following its decomposition to CaO and CO2 at a temperature of around
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