PSI - Issue 67

I. Flores-Vivián et al. / Procedia Structural Integrity 67 (2025) 80–89 Ismael Flores-Vivián / Structural Integrity Procedia 00 (2024) 000 – 000

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Figure 6 shows the micrograph obtained by SEM of the synthesized NaY zeolite. Synthesized NaY zeolite has irregular shapes; however, spherical particles of different sizes can be observed deposited on the surface. The presence of hierarchical spherical nanoparticles can be intuited, which due to the scale and resolution of the equipment used could not be observed.

Figure 6. Synthesized NaY zeolite micrograph. Amplifications a) x500, b) x1000, c) x2000 and d) x4000

3.2. Fourier transform infrared spectroscopy The Fourier transform infrared (FT-IR) spectroscopy technique was used to evaluate the evolution of the reaction in the pastes and the effects of the zeolites. In addition to aiding in the characterization of functional groups of geopolymers, FT-IR spectroscopy can also be used to provide information about the transition of vibrations due to small structural changes, therefore, it can give us information about the polymerization process. By means of this technique, the different pastes were analyzed, making a comparison between the zeolites, reference pastes and the pastes with zeolite replacement in the precursor. A comparison of the effects obtained due to variation in NaOH Figure 7 shows the FT-IR spectra of ZN (Figure 7.a) and NaY (Figure 7.b) zeolites compared with reference pastes and pastes added with zeolitic materials at the ages of 3 and 7 days. In the spectrum, it can be observed that both zeolites and pastes have bands located between 3000 cm -1 and 3700 cm -1 , which correspond to the symmetrical stretch of the – OH group and indicate the presence of water (Villa, Pecina, Torres, & Gómez, 2010). Within this range, the band at 3600 cm -1 can be observed in ZN, which is attributed to acidic zones of the Al (Al-OH) frames (Chester & Derouane, 2009). In the case of MK, this band has disappeared in the calcination process due to the dehydroxylation of kaolinite. The presence of water (H-O-H) can also be identified in the band at approximately 1600 cm -1 , which has weak bonds, and may be trapped in cavities or adsorbed on the surface. Similarly, it can be observed in all spectra, except ZN, the presence of the band located near 1400 cm -1 , which is attributed to Na 2 CO 3 , a product due to the carbonation of sodium, mainly from the AA, when reacting with CO 2 in the atmosphere (Belmokhtar, Ammari, Brigui, & Allal, 2017 ) (Villa, Pecina, Torres, & Gómez, 2010). molarity was also performed. 3.2.1. Effect of Adding Zeolites