Preparation and characterization of eco-friendly composite based on geopolymer and reinforced with date palm fiber

2.3.1 Compressive strength

The compressive strength (CS) was assessed by subjecting cylindrical specimens (40x70 mm³) of the geopolymer matrix and geopolymer composites reinforced with date palm fiber to compression test. Four specimens for each composition were tested using a mechanical CONTROLS testing machine operating at a speed of 3 mm/min.

2.3.2 Flexural strength and flexural modulus

The flexural strength (FS) and flexural modulus (FM) of geopolymer matrix and geopolymer composites were determined using a three-point bending tests, employing a WSM-10kN universal testing machine at a displacement rate of 1.5 mm/min. Four specimens measuring 140 × 50 × 20 mm³ from each composition were tested and the flexural strength ( $\mathit{\sigma }$ ) was calculated using the equation (Alomayri and Low, 2013):

The flexural modulus ( $\mathrm{F}\mathrm{M}$ ) can be obtained either graphically by measuring the slope of the linear segment of a typical stress–strain curve or determined using the equation (Alomayri and Low, 2013; Alzeer and MacKenzie, 2018):

2.3.3 Water absorption and thickness swilling

Water absorption (WA) and thickness swilling (TS) were conducted on specimens measing 40x40x20 mm³, immersed in a cold-water bath at the laboratory’s ambient temperature. The tests were carried out at various immersion durations, including 6 h, 24 h, 72 h, and 168 h. These physical properties are calculated using the following formulas (Akinyemi et al., 2019; Andiç-Çakir et al., 2014):

• Structural and microstructural properties

2.3.4 FTIR spectroscopy

FTIR spectra of mining residue, geopolymer matrix, and various geopolymer composites samples embedded in KBr were acquired using a Bruker Optics Vertex 70 spectrophotometer. The analysis was performed at a resolution of 4 cm⁻¹ and 32 co-addition scans in a frequency range of 4000–400 cm⁻¹. The pellets were prepared with a mixture of 300 mg KBr and 5 mg of finely ground powders, using a hydraulic press. Nicolet software was employed for spectra analysis, allowing the comparison of absorbance bands corresponding to each functional group.

2.3.5 X-ray diffraction (XRD)

X-ray diffractograms of mining residue, the geopolymer matrix, and geopolymer composite samples were obtained using PHILIPS X'Pert diffractometer. The instrument is equipped with a copper anticathode Cu Kα with a wavelength 1.54A° to scan the samples from 5.00° to 70.00° 2- theta angles. The XRD analyses were performed on finely ground powders of mining residue and extractions from the fracture surface of the geopolymer matrix and geopolymer composites.

2.3.6 Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX)

The microstructure of the samples was examined using a Tescan Vega Microscope device equipped with a tungsten filament electron gun. Apart from conventional secondary electron (SE) and backscattered (BSE) detectors, the device features an X-ray detector (a silicon-lithium (SiLi) diode) for non-destructive in-situ elementary chemical analysis (EDS, Energy Dispersive Spectroscopy). SEM and EDX analyses were conducted on the fracture surfaces of the geopolymer matrix and geopolymer composites.

3.1.1 Compressive strength

Fig. 4 illustrates the change in compressive strength (CS) as a function of fiber content for the formulated geopolymer composites with mining residue and date palm fiber (DPF). As demonstrated in this figure, the CS values exhibits a gradual increase within the range of 0–5 % (wt/wt) fiber content. Nevertheless, beyond this value, there is a noticeable and steady decrease in SC as the fiber content continues to increase. The geopolymer composite, formulated with 1 % (wt/wt) fiber content, exhibited a relatively small increment in CS of approximately 13.70 % (wt/wt) compared to geopolymer matrix. This modest gain is primarily attributed to the limited quantity of fibers incorporated into the geopolymer matrix, and is also a consequence of inadequate fiber distribution, which result in more unreinforced areas within the geopolymer matrix. Andiç-Çakir et al., (2014) have studied the effect of coir fiber content on the mechanical properties of geopolymer composites, and their findings indicated that the CS of geopolymer composites containing less than 1.5 % (wt/wt) coir fibers is similar to that of geopolymer matrix. This suggests that the geopolymer composite structure exhibits lower density in specific region, attributed to the absence of fiber (Andiç-Çakir et al., 2014).

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Fig. 4

Mean compressive strength of the geopolymer composites reinforced with date palm fibers.

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More interesting are the results of CS found for the geopolymer composite formulated with 5 % (wt/wt) of fiber content, which was doubled compared to that of geopolymer matrix. This significant increase, approximately of 115 %, can be attributed to the optimal distribution of fibers within the geopolymer matrix, enhancing the overall compactness of the composite and reducing porosity and cracks. This distribution enhances the interfacial bonding force and bridging stress between the matrix and fibers, as elucidated by (Andiç-Çakir et al., 2014). In a similar study, Liu and Lv, 2022 elucidate the enhancement in CS, noting that the interface between the linen fabric and the geopolymer matrix is not subjected to shear loads. This condition allows to reduce the linen fabric separating or delamination from the geopolymer matrix under high loads (Liu and Lv, 2022). It is worth noting that the optimal value of added fibers to reinforce the geopolymer matrix, vary from a study to another, and depends on the nature of the fibers and the geopolymer matrices (Assaedi et al., 2015). For example, Assaedi et al., (2015) has found the maximum CS of 91 MPa when the flax fiber content was 4.1 % (wt/wt) for the metakaolinite-based geopolymer composites (Assaedi et al., 2015). However, the CS of geopolymer composites decreases when the fiber content exceeds 5 % (wt/wt). This decrease is mainly attributed to the elevated fiber content hindering the uniformity of the fiber–matrix interface and contributing to the formation of fiber clusters. These clusters, in consequence, compromise the adhesion between the fiber and matrix interfaces, as indicated by Liyana et al., (2013). The addition of fibers beyond the optimal quantity leads to a further increase in the porosity of the geopolymer composites, consequently causing a reduction in CS (Liyana et al., 2013).

3.1.2 Flexural strength

The flexural strength (FS) of geopolymer composites reinforced with date palm fiber versus fiber content is illustrated in Fig. 5. The increase of incorporated fibers quantity led to a notable improvement in FS of the formulated geopolymer composites, highlighting the effectiveness of date palm fiber as reinforcing agent. The results demonstrate that the FS of the geopolymer composites experienced a notable increase when the fiber content was below 8 % (wt/wt), but beyond this value, a subsequent decrease is observed. Of particular interest are the results of the formulations incorporating only 1 % and 2 % (wt/wt) of date palm fibers exhibited a 30 % and 45 % increase in FS, respectively. More interesting are the results obtained for the formulations made with 8 % and 10 % (wt/wt) of added fibers, in which the FS of the reinforced geopolymer composites was more than two times higher than that of geopolymer matrix. These results suggest that incorporating date palm fiber enhances the FS of the formulated geopolymer composites. This enhancement can be attributed to the exceptional intrinsic flexural strength of date palm fiber, effective dispersion of fibers within the geopolymer matrix, and strong adhesion between the fibers and the geopolymer matrix. Certainly, the strong adhesion and the effective dispersion play a crucial role in overcoming discontinuities in the geopolymer matrix.

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Fig. 5

Mean flexural strength of the geopolymer composites reinforced with date palm fibers.

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Similar to compressive strength, the maximum flexural strength value achieved with optimal fibers amount for reinforcing the geopolymer matrix varies across studies and depends on both fibers and geopolymer matrices characteristics. For instance, Alomayri et al., (2013) reported a maximum FS of 11.7 MPa with the addition of 0.5 % (wt/wt) cotton fiber to the low calcium fly ash geopolymer composites, whereas the incorporation of 1 % (wt/wt) led to a decrease in this property (Alomayri et al., 2013). The same authors reported a maximum FS of approximately 31.7 MPa when reinforcing geopolymer composites with 8.3 % (wt/wt) woven cotton in a subsequent study (Alomayri et al., 2014b). This notable increase, form 8.2 MPa to 31.7 MPa, was almost four times higher than that of geopolymer matrix. They attribute this remarkable enhancement to the lower density of woven cotton, facilitating the formation of numerous reinforcement layers capable of resisting shear failure and supporting applied loads effectively. This, in turn, enhances stress transfer between the matrix and the woven cotton fibers, resulting in improved FS (Alomayri et al., 2013). In a more recent study, Zhang et al. (2021)found that incorporating 15 % (wt/wt) of kenaf fibers into the geopolymer matrix resulted in a maximum flexural strength of 11.8 MPa. This result is due to the good interface between the geopolymer matrix and kenaf fibers Huang et al., 2021).

It is important to highlight that incorporating more than 8 %-10 % (wt/wt) of date palm fibers into the geopolymer matrix led to a decrease in FS of the geopolymer composites. As reported for the compressive strength, this decrease is mainly due to the higher fiber content hindering the uniformity of the fiber–matrix interface and contributing to the formation of fiber clusters. These clusters compromise the adhesion between the fiber and matrix interfaces, as indicated by Liyana et al., (2013). The addition of fibers beyond the optimal amount further increases the porosity of the geopolymer composites, rendering the material less dense. This, coupled with the formation of the fiber agglomerates, results in a reduction of FS (Liyana et al., 2013).

3.1.2.1

3.1.2.1 Flexural modulus

Fig. 6 illustrates the flexural modulus (FM) of the geopolymer composites reinforced with date palm fibers versus fiber content. Generally, as the loading of date palm fiber increased the FM of the reinforced geopolymer composites exhibited a corresponding increase. Achieving the optimal fiber content of 8–10 % (wt/wt), corresponding to the optimal flexural strength, results in an almost twofold enhancement in FM compared to the geopolymer matrix. For geopolymer composites with 15 %–20 % (wt/wt) fiber content, the increase reaches approximately 150 % when compared to the geopolymer matrix. These results indicate that incorporating date palm fibers enhances the stiffness of geopolymers composites. A similar trend has been observed by other authors (Alomayri et al., 2014b; Low et al., 2014). For example, Low et al., (2014) noticed an increase in FM with rising fiber content for geopolymer composites reinforced with cotton fabric. This increase is attributed to the crack bridging facilitated by the existing long continuous fibers, resulting in a higher FM compared to the geopolymer matrix. These fibers possess the capacity to sustain greater loads and can undergo multiple cracks during the loading process, thereby preventing the brittle failure of geopolymer composites (Low et al., 2014). In a similar study, Alomayri et al., 2014b) demonstrated a consistent increase in FM with an increase in cotton fiber content. For comparison, the addition of 4.5 %, 6.2 % and 8.3 % (wt/wt) of cotton fibers resulted in increasing the FM to 0.87GPa, 1.23GPa, 1.4GPa and 1.74GPa, respectively. This significant improvement in FM can be attributed to the higher intrinsic flexural modulus of the cotton fibers, influencing the flexural modulus of composite materials when reinforced with such natural fibers (Alomayri et al., 2014b). In our case, the remarkable FM achieved can be also attributed to the higher intrinsic flexural modulus of date palm fiber. These fibers act as bridges for cracks, resulting in a higher FM compared to the geopolymer matrix. Furthermore, with an increase in fiber content, the risk of brittleness diminishes, as the fibers exhibit resistance to higher loads.

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Fig. 6

Mean flexural modulus of the geopolymer composites reinforced with date palm fibers.

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3.2.1 Water absorption

Water absorption is a critical characteristic in geopolymer composites incorporating natural fibers, given their sensitivity to water related to their hydrophilic nature. Therefore, it is essential to evaluate this property in geopolymer composites formulated with mining residue and reinforced with date palm fiber. This assessment allows for the measurement of the quantify of water absorbed under specific environmental conditions and within a defined time. The water absorption or moisture diffusion depends on various factors such: void/pore structure, humidity, temperature, fiber volume fraction, and matrix viscosity (Radzi et al., 2019).

The results of water absorption (WA) of geopolymer composites immersed in a water bath for durations of 6 h, 24 h, 72 h, and 168 h are illustrated in Fig. 7. The results indicate that an increase in fiber content corresponds to a higher WA in the geopolymer composites. This is can be attributed to the significant amount of date palm fibers in the geopolymer composites, containing hydrophilic compounds like cellulose and hemicelluloses. The presence of hydroxyl groups and other oxygenated groups in cellulose and hemicelluloses emerges as a primary factor contributing to the elevated WA. Consequently, this factor enhances the overall hydrophilic nature of geopolymer composites, resulting in increased WA. Moreover, the incorporation of excessive fiber content beyond the optimal amount promotes the cracks formation, contributing to the higher WA through capillarity phenomenon. The same behaviour was reported by several researchers, where WA exhibited elevated value with higher fiber content in geopolymer composites reinforced with cotton fabric (Alomayri et al., 2014a; Low et al., 2014; Alzeer and MacKenzie, 2013). According to their findings, the higher WA is primarily attributed to the hydrophilic nature of the used cotton fabric fibers and the poor interfacial area between fibers and matrix. In a recent study, Huang et al. (2021)studied the influence of fiber content and emersion time on the WA property of geopolymer composites reinforced with rice straw Huang et al., 2021). Their results demonstrated a positive correlation between elevated WA and higher fiber content. They attributed this increase to the presence of micro-cracks in the geopolymer composites, promoting capillary water transport within the composites and facilitating water storage in the fractures, thereby gradually enhancing water absorption.

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Fig. 7

Mean water absorption of the geopolymer composites reinforced with date palm fibers. the utilized rice straw fibers.

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3.2.2 Thickness swelling

The thickness swelling (TS) was performed on geopolymer composites containing mining residue and reinforced with date palm fiber to evaluate changes in their dimensional stability. Fig. 8 illustrates the thickness swelling of geopolymer composites in relation to the fiber content. The results exhibit a similar trend to water absorption, indicating an increase in TS with a rise of fiber content. The TS values remained low, staying below 1 % for all formulated geopolymer composites with fiber content below the optimal fiber content of 8 %, even during prolonged immersion times. However, surpassing the optimal fiber content led to a noticeable difference in TS values for all tested immersion times. For instance, in geopolymer composite with 15 % (wt/wt) fiber content, the TS increased from 1 % to 2.2 % after immersion times of 12 h and 168 h, respectively. Alternatively, the TS exhibited greater stability after 12 h immersion time, but a significant increase occurred after 72 h of immersion when the fiber content exceeded the optimal value of 8 % (wt/wt). This increase is likely attributed to the large gaps between the fiber and the geopolymer matrix, facilitating water movement into the composites. These findings are in agreement with those reported by other researchers, suggesting that natural fibers contribute to increased TS (Alomayri et al., 2013; Gholampour et al., 2022; Huang et al., 2021). Furthermore, a poor interface between fiber and matrix and inefficient fibers dispersion within the geopolymer matrix significantly decrease the dimensional stability of the composites when the fiber content exceeds the optimal value. In a different study, Huang et al. (2021)found that TS continued to increase with prolonged immersion time, even in composites with a good interface between fiber and matrix and an efficient fibers distribution within the geopolymer matrix Huang et al., 2021). This phenomenon may be attributed to the potential presence of cracks and the higher hydrophilic nature of the utilized rice straw fibers.

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Fig. 8

Mean thickness-swilling of the geopolymer composites reinforced with date palm fibers.

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3.3.1 X-ray diffraction

The X-ray diffraction (XRD) patterns showing the composition of mining residue, geopolymer matrix and geopolymer composites reinforced with varying date palm fiber contents of 2 %, 5 %, 8 %, and 12 % (wt/wt), are presented in Fig. 9. In this figure, it is evident that mining residue is predominantly a crystalline material, with major crystalline phases identified as quartz, calcite, dolomite, muscovite, albite and hornblende. The XRD peaks of the mining residue closely resemble to those of other raw materials used in geopolymers such as fly ash, metakaolin (Alomayri et al., 2013; Alomayri et al., 2014a; Low et al., 2014; Alomayri and Low, 2013). For example, Alomayri et al., 2014b) found that the main crystalline phases of fly ash include quartz, mullite, muscovite, dolomite, and hematite (Alomayri et al., 2014b). In another study, Ahmari and Zhang (2012) indicated that mine tailing is mainly a crystalline material with substantial amount of silica (Ahmari and Zhang, 2012).

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Fig. 9

XRD patterns of A) Mining residue, geopolymer matrix, and geopolymer composites, and B) main changes after geopolymerisation reaction.

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Following the geopolymerisation reaction of mining residue using a highly concentrated alkaline solution, there is a decrease in intensity of the crystalline peaks in the 0 to 22° region. However, these crystalline peaks in XRD patterns are still present, due to the partial dissolution of the mining residue particles. Comparing the XRD pattern of the original mining residue with that of the hardened geopolymer material in Fig. 9(B), it is noticeable that the crystalline phases remain largely unchanged, except that their intensities were decreased. This can be attributed to the activation of the mining residue, as reflected in the formation of an amorphic bump characteristic in the cured geopolymer matrix, appearing in the region of 28°-30° in 2θ position. These results confirm that the crystalline phases are minimally affected by the geopolymerisation reaction, while the amorphous phases located between 0°–22° and 28–30° in 2 θ are strongly involved in the activation of the mining residue. Similar findings have been reported by several authors, suggesting that crystalline phases act as inert fillers in the geopolymer network and do not actively participate in the geopolymerisation reaction (Alomayri et al., 2014b; Alomayri and Low, 2013; Liyana et al., 2013). Additionally, a decrease in the intensity of the peaks related to the crystalline phases due to the partial dissolution of mining residue particles has been previously reported (Ahmari and Zhang, 2012; Zhang et al., 2021).

3.3.2 Infrared spectroscopy

Fig. 10 displays the FTIR spectra of mining residue, geopolymer matrix, and geopolymer composites reinforced with different percentages of date palm fibers (1 %, 5 %, 8 % and 12 %). These spectra highlight both similarities and differences among the mining residue and its geopolymer forms. The following bands and peaks are consistently observed in all spectra: The two broad bands at 3480 cm⁻¹ and 1650 cm⁻¹ are attributed to the stretching and bending vibrations of —OH, respectively. These bands are a result of the presence of physically absorbed free water molecules by powder and reaction products (Yan et al., 2016). The bands at 1796 cm⁻¹, 1465 cm⁻¹, and 875 cm⁻¹ corresponding to the presence of calcium carbonate (Somna et al., 2011). Within the range of 930–1200 cm⁻¹, there exist various bands that can be attributed to the Si—O—Si bonds of (Si—O)_n units. This particular structure is commonly found in calcium aluminosilicate hydrate (C—A—S—H) gel (Clayden et al., 1999). The band at around 1037 cm⁻¹ related to the asymmetric tensile vibration of Si—O—Si and Si—O—Al, which is considered as evidence of the existence of three-dimensional aluminosilicate hydrate gels (Ahmari and Zhang, 2012; Murmu and Singh, 2014). The band between 780 and 800 cm⁻¹ is assigned to Si—OH stretch and Al—OH bond (Ettahiri et al., 2023; Hermann et al., 2022). The peaks around 520–530 cm⁻¹ corresponding to stretch symmetrical vibration of Al—O—Si band, and 445–480 cm⁻¹ are assigned to symmetrical stretch vibration of Si—O—Si and O—Si—O bands (Chuewangkam et al., 2022; Ismail et al., 2014; Tang et al., 2018; Wu et al., 2023).

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Fig. 10

A) FTIR spectra of mining residue, geopolymer matrix and the geopolymer composites. B) Main changes after geopolymerisation reaction.

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The comparison between the spectra of mining residue and its geopolymerized forms revealed that all the absorption bands of asymmetric stretching of Si-O-Si, Si-O-Al, Si-OH, and Al-OH, which are considered as the characteristic peaks of aluminosilicate raw materials, are shifted to low wave numbers (Fig. 10B). This is due mainly to the substitution of the [AlO₄]^3- groups into [SiO₄]^4-, confirming the occurrence of the geopolymerisation reaction under highly alkaline conditions (Chuewangkam et al., 2022). On the other hand, the FTIR spectra of geopolymer composites are similar to that of geopolymer matrix, except the —OH band at 3480 cm⁻¹ that is shifted to the long wave number and its width is decreased, and also the appearance of a small band at around 2341 cm⁻¹ attributable to the C—O band. This suggests that mining residue are involved in geopolymerisation and aid in the formation of N-A-S-H and C-A-S-H gels.

3.3.3 Scanning electron microscopy (SEM) and EDX (Energy Dispersive X-Ray)

Fig. 11 shows SEM images of both geopolymer matrix and geopolymer composites reinforced with different date palm fiber contents (1 %, 8 %, 10 %, and 12 %). In Fig. 11(a and b), it is evident that the geopolymer matrix exhibits a granular appearance, loose structure and less compact matrix. The presence of voids and pores in the geopolymer matrix explain the observed low mechanical properties for geopolymer matrix. In Fig. 11(b), the SEM image illustrates the surface fracture of a geopolymer composite reinforced with a lower fiber content of about 1 wt% (wt/wt). In this image, matrix-rich regions are predominant compared to the geopolymer composite with higher fiber content (Fig. 11e and f). The presence of less compacted matrix-rich regions indicates that the matrix lacks adequate fiber reinforcement. As a result, there are insufficient fibers to resist the load from the matrix, leading to the lower mechanical properties in geopolymer composites reinforced with lower fiber content (Akinyemi et al., 2019; Asasutjarit et al., 2009; Maragkos et al., 2009). The fiber surfaces shown in Fig. 11 (e, f) are smooth with a clear texture, while the fibers illustrated in Fig. 11 (d) possess rough surface and are covered by a layer of matrix particles. This observation suggests that the geopolymer composites exhibit stronger adhesion compared to the geopolymer matrix Huang et al., 2021).

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Fig. 11

SEM images at the fracture surfaces of geopolymer matrix and geopolymer composites.

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The SEM image in Fig. 11(c) illustrates the fracture surface of geopolymer composite with a fiber content of 8 % (wt/wt), exhibiting the obtained higher mechanical properties. The fibers are tightly embedded in the matrix, and no cracks or voids are observed at the fiber–matrix interface. Additionally, the pulled-out fiber is coated with geopolymer matrix, indicating strong adhesion between fiber and geopolymer matrix. Consequently, this enhances the bending strength in the longitudinal direction Huang et al., 2021). The SEM images in Fig. 11(e and f) illustrate the fracture surfaces of geopolymer composite filled with higher fiber content of about 12 % (wt/wt). It can be observed the presence of gaps between fiber and matrix, along with signs of debonding at the interface between the fiber and matrix Huang et al., 2021). Furthermore, the presence of holes left after the fibers were pulled out, local fiber-rich regions and aggregations as shown in Fig. 11 (e, f), indicate that fibers separated from the matrix inadequately absorb the load transmitted by the matrix. As a result, geopolymer composites filled with 12 % (wt/wt) fiber content exhibit reduced mechanical properties compared to that filled with the optimal fiber content of 8 % (wt/wt) (Assaedi et al., 2015; Huang et al., 2021).

Fig. 12 illustrates the EDX spectrum for the fracture surface of the geopolymer composite with 8 % (wt/wt) fiber content, while Table 2 provides a summary of the corresponding weight and atomic mass percentages. These results align well with the results of previously presented X-ray diffraction (XRD) and X-ray fluorescence (XRF) analyses, indicating that the geopolymer composite matrix comprises inorganic materials, with silicon (Si), aluminium (Al) and calcium (Ca), as major components. In contract, sodium (Na) and magnesium (Mg) are present in minor quantities. The Si element is derived from silica (SiO₂) and silicon derivatives like Muscovite and Albite, while Al element originates from the aluminum oxide (Al₂O₃) found in mining residue. Ca is derived from calcite and calcium carbonate, and Mg is present in the sample due to magnesium oxide (MgO) and dolomite. Na is detected in minor quantity within the binding phase of the geopolymer composite, serving as the primary element in the activator solution containing NaOH (Kourti et al., 2010; Utama et al., 2022). It is worth noting that the higher proportion of oxygen and the moderate quantity of carbon in the analyzed geopolymer composite can be attributed, to a lesser extent, to mining residue and predominantly to the organic origin of the natural fibers used in formulating the geopolymer composite.

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Fig. 12

EDX (Energy Dispersive X-Ray) of geopolymer composite at 8% (wt/wt) fiber content.

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The results obtained from the EDX spectroscopy analysis reveal an interesting composition of the geopolymer gel derived from mining residue. It appears that there is a significant amount of silicon and a moderate quantity of both calcium and aluminum. Specifically, the percentages of Si, Ca, and Al are 23.54 %, 10.61 %, and 10.18 % (wt/wt) respectively, with a Si/Al molar ratio of 2.22. These findings align with previous studies, suggesting that the resulting geopolymer material conforms to the expected range of 1 to 3 (Toniolo et al., 2018). The higher concentration of Ca compared to Na confirms that the geopolymer gel formed from mining residue primarily undergoes the C-A-S-H (calcium-alumino-silicate-hydrate) process, rather than the sodium-alumino-silicate hydrate (N-A-S-H) process (Ariffin et al., 2013; Mijarsh et al., 2014). This is a positive indication of the geopolymer composite's mechanical properties. Furthermore, the data also reveals a low Ca/Si ratio of 0.32 in the formed gel, which is believed to play a crucial role in enhancing the strength of the geopolymer composite. These findings contribute to our understanding of the geopolymer gel's composition and its potential for robustness.