## 3 Results and Discussion
### Flexural Strength
The residual compressive strength of the test specimens is shown in Figure 7. The results for the specimens heated at 400 \({}^{\circ}\)C show that the control OPC mix has 38.40%, 41.55%, 49.71%, 49.79%, and 50.83% more residual compressive strength than GPC-A, GPC-B, GPC-C, GPC-D, and GPC-E, respectively. Among the GPC mixes, GPC-A has 4.95%, 6.98%, 7.09%, and 8.78% higher residual compressive strength than GPC-B, GPC-C, GPC-D, and GPC-E, respectively, at 400 \({}^{\circ}\)C. The residual compressive strength of the GPC mixes, i.e., GPC-A, GPC-B, GPC-C, GPC-D, and GPC-E, after heating at 800 \({}^{\circ}\)C was further decreased by 14.41%, 12.32%, 3.5%, 2.07%, and 15.9%, respectively, compared to the compressive strength of their respective specimens at 400 \({}^{\circ}\)C. The residual compressive strength test results of the specimens exposed to elevated temperature are in agreement with the previous research. The compressive strength significantly decreased after the temperature escalated from 200 to 800 \({}^{\circ}\)C. The basalt-reinforced geopolymer foams showed better properties after exposure to high temperature. The compressive strength significantly improved after exposure to temperatures higher than 600 \({}^{\circ}\)C [55]. The test results show that strength is decreasing persistently by the replacement of SG with QRD, and the minimum residual strength was observed in the GPC-E specimens with 20% QRD content. The test results for the weight loss of all types of mixes are shown in Figure 8. It can be observed that the control OPC mix is the most fire-resistant since it has the lowest weight loss among all the mixes. The weight loss in the QFS-GPC mixes was observed to be more with a rise in temperature. Among the QFS-GPC mixes, GPC-A has the lowest weight loss as compared to the other QFS-GPC mixes. Geopolymers revealed the reduction in the mechanical strength when exposed to elevated temperatures [56; 57]. It is in agreement with the existing literature. Blended ash geopolymer concrete in the previous research showed a decrease in strength at higher exposure temperatures (400-800 \({}^{\circ}\)C). However, the strength increased up to 200. It could be attributed to the stable mix of blended ash geopolymer as compared to the ordinary Portland cement concrete [58]. At 400 \({}^{\circ}\)C, the weight loss of the GPC-A specimen was 29.55% higher than the OPC mix. Among the QFS-GPC specimens, the weight loss of GPC-A was 7.27%, 10.45%, 58.64%, and 70% lower than the GPC-B, GPC-C, GPC-D, and GPC-E specimens, respectively. At 800 \({}^{\circ}\)C temperature, the weight loss of GPC-A was 20.35% higher than the control mix. The QFS-GPC mixes, GPC-B, GPC-C, GPC-D, and GPC-E have 2.36%, 3.64%, 28.73%, and 33.64% higher weight loss than the GPC-A specimens, respectively. It can be observed that the weight loss of the QFS-GPC specimens increased with the increase in QRD content from 0% to 20%. It can be concluded from the above observations that the damage extent and strength reduction appeared to be higher in those specimens with the higher calcium content. The product of CaCO3 decomposition resulted in the rise of volume, initiating the progress of cracks [57]. This phenomenon can be ascribed to two distinct processes occurring in the specimens as the temperature rises, i.e., the strength improvement due to the continuance of the geopolymerization process and strength loss as the thermal conflict of specimens to resist temperature elevation [53; 59]. [PERSON] et al (2010) reported that the  
Figure 8: The weight loss in OPC and QFS-GPC specimens after exposure to 400 \({}^{\circ}\)C and 800 \({}^{\circ}\)C temperatures. Figure 7: The residual compressive strength of OPC and QFS-GPC specimens after exposure to 400 \({}^{\circ}\)C and 800 \({}^{\circ}\)C temperatures. thermal variability between the geopolymer matrix and aggregates is the outcome of a heavy loss of geopolymer concrete at high temperatures. The control OPC mix has maximum residual compressive strength among all the mixes.