Scanning Electron Microscopy/Energy-Dispersive X-ray Spectroscopy (SEM–EDS) Analysis

The SEM–EDS analysis of all concrete mixes was performed on hardened fragments in the form of slices of cement paste using a JSM-IT100 scanning electron microscope. Isopropanol was used to dry the fragments of hardened paste using the solvent exchange method. After that, all specimens were examined for changes in morphology and composition.

### Nitrogen Adsorption Isotherm Technique

In addition to the SEM–EDS study, N2 sorptiometry was conducted on all the tested concrete mixes. The surface area and pores of the powdered specimen (weighing approximately 0.3 g) obtained from the 91-day cured hardened paste were measured by N2 sorption analysis (NOVA2200e, Quanta chrome, Boynton Beach, FL, USA) at 273 K. First, the samples were degassed to remove airborne contaminants that had absorbed during curing. Afterward, N2 adsorption was performed at ambient temperatures and controlled pressure on the specimens.

#### Fourier Transform Infrared (FTIR) Analysis

All the mixes studied were additionally characterized using FTIR using a PerkinElmer Spectrum Two FTIR spectrometer to determine their individual phases. The powdered samples of all of the studied mixes were dried and examined under an infrared light source, and the IR spectra were taken in the wavenumber range 400 to 4000 cm<sup>−</sup>1.

#### Thermogravimetric Analysis (TGA) of Cement Pastes

To perform TGA of all the concrete mixes, the powdered specimens obtained from 91-day cured pastes were placed in ceramic vessels fitted with thermogravimetric analyzers. The specimens were heated inside the thermal gravimetric analyzer to a temperature of 20 to 1000 ◦C at a rate of 10 ◦C/min, using N2 as a medium under static conditions. Moreover, alumina powder was used as a reference for thermal stability at elevated temperatures. Finally, a comparison plot was developed using the built-in software to show the loss of weight of various paste specimens in various temperature ranges.
