## 1 Introduction
### Factors Affecting Bond Vibrations
[8] showed that asymmetric stretching for Al-O and Si-O existed within the mid-infrared and, therefore, assigned 1100 and 1210 cm\({}^{-1}\) for asymmetric stretching of Si-O, just as 470 cm\({}^{-1}\) was assigned to O-Si-O/Si-O-Si bending vibrations. They further characterized tetrahedral Al-O stretching bands existing within polymerized calcium aluminate (CaAl\({}_{2}\)O\({}_{4}\)) glass at 820 and 680 cm\({}^{-1}\), while Si-O bond vibrations in silica (SiO\({}_{2}\)) were noted at 1100/1200 and 810 cm\({}^{-1}\). Additionally, O-Al-O/Al-O-Al had a detectable deformation mode at 425 cm\({}^{-1}\). Both Al-O and Si-O are very prominent modes in geopolymers and AABs, as they define the aluminosilicate framework that governs the strength characteristics. Since the strength of materials depends on their microstructural composition and framework, researchers began to study the strength performance through qualitative analysis of the silica and alumina bonds present in a CB. Moreover, the bending of S-O could be noted at the band at 450, 600, and 680 cm\({}^{-1}\), while the stretching was reported to occur at 1080-1140 cm\({}^{-1}\). The possibility of noting S-O bonds in FTIR spectra has given the opportunity to study concrete durability and its setting time due to the presence of sulfate in ettringite (Aft) formation in OPC binders. [PERSON] et al. [61] reported that the strength of a binder will decrease with the formation of ettringite (S-O), noted via FTIR spectra. Similarly, the study of the carbonation of concrete paste due to environmental exposure can be corroborated by observing C-O spectra using FTIR. Further, CO\({}_{3}\)\({}^{2-}\) bending in-plane and out-of-plane were reported at wavenumbers 680-740 and 860-880 cm\({}^{-1}\), respectively, while stretching O-C-O in CO\({}_{3}\)\({}^{2-}\) and CO\({}_{2}\) were 1410-1510 and 2350-2390 cm\({}^{-1}\), respectively [62]. This provides adequate information for characterizing AAS and GP [5]. Many other researchers [63; 64; 65] investigated and reported on the qualitative durability of sodium and magnesium sulfate in 2005, and [PERSON] et al. [66] and [PERSON] et al. [28] followed suit. FTIR was used to observe that there was more leaching of alkali in Na sulfate than observable in Mg sulfate [28; 66]. Furthermore, the four main binders, which include Portland cement (PC), AAS, GP, and a mix of GP-AAS, were identified and characterized by the FTIR method by [PERSON] et al. [63]. They asserted that C-S-H in OPC is semicrystalline, while AAS, GP, and AAS-GP are amorphous in nature. Due to this, it is quite difficult to completely distinguish various phases in AAB and GP by using X-ray diffraction (XRD) techniques. In 2006, [PERSON] [10] published a review on the application of FTIR to organic compounds and adumbrated other various factors that could affect the vibrational frequencies of organic compounds--aromatic compounds, olefinic groups, and saturated aliphatic bonds. They also reported organic siloxane (Si-O-Si) at wavenumbers of 1095-1075/1055-1020 cm\({}^{-1}\). [PERSON] [6] published a book titled _Geopolymer Chemistry and Application_ in 2008, where the chemistry of geopolymer binder was discussed in distinction from alkaline-activated binders and OPC. He also discussed the application of FTIR, XRD, and NMR for the characterization of cementitious binders, and subsequently wrote a specific review on the synthesis of Ca-based geopolymers or alkaline-activated slag (AAS) due to the proliferation of Ca-like compounds (calcium aluminosilicate hydrate (CASH)) present in ground granulated blast furnace slag (GGBFS) and Class C fly ash. It was established by both [PERSON] et al. [63] and [PERSON] [6] that FTIR could indicate the disparity between CASH, NASH, and CSH products in AAS, GP, and OPC, respectively. In 2008, [PERSON] [67] studied the disparity between CSH and NASH and asserted that depolymerization occurs due to a reduction in the pH of the binder.