## 4 Results and Discussions  
### Performance of Slabs upon Exposure to Fire  
When the slabs were exposed to fire in the furnace, internal and external thermocouples data were monitored for determining the heat transfer behavior in different types of slabs. The five external thermocouples were placed at the surface of the slab, which was unexposed to the fire. The purpose of the installation was to assess the insulation characteristics of different slab types; the average reading of all five thermocouples indicated the temperature at the end of 120 min of fire exposure at the non-fire surface of the slab. Fire standards defined insulation as the ability of a media, in this case, concrete slab, to restrict the temperature rise at the unexposed face within the specified level. From this context, insulation failure occurs when the mean temperature of the unexposed surfaces reaches 140 \({}^{\circ}\)C above its initial temperature, or if any of the unexposed surface thermocouples records 180 \({}^{\circ}\)C above the primary mean temperature of the unexposed face. Figure 5: Fire test furnace **(a)** Furnace interior **(b)** with slab. Figure 6: Furnace temperature during the tests of different slabs and standard fire curve for hydrocarbon fire according to BS 476-20: 1987. Figure 7 shows the temperature of external thermocouples recorded at the end of 120 min of fire exposure in the furnace. This temperature indicates the insulation characteristics of different concrete mixes. Where; TE represents the thermocouple number. In X-axis, M, PF, and BF represent the mix identification number, PVA fiber, and Basalt fiber, respectively. The number associated with BF and PF represents the percentage of fiber in the concrete mix, as listed in Table 2.  
It has been found from Figure 7, a concrete slab made of concrete mix M1-0F (slab with no fiber) shows the highest surface temperature from all five thermocouples. The highest temperature was recorded as 58.5 \({}^{\circ}\)C, whereas the average of all five thermocouples is 55 \({}^{\circ}\)C. It is the control mix that did not include fibers. When basalt and PVA fibers added to concrete, the recorded temperature is reduced at the unexposed surface. The lowest temperature was measured as 38 \({}^{\circ}\)C, and the highest obtained was 52 \({}^{\circ}\)C, whereas the mean is calculated as 45 \({}^{\circ}\)C. It could be concluded that the addition of fibers resulted in an average reduction of 10 \({}^{\circ}\)C in the unexposed surface temperature, which may be considered a significant effect. One of the reasons is that both basalt and PVA fibers are excellent heat insulators. Figure 8 shows the internal thermocouples results, which were installed throughout the thickness of the slab at a 25 mm interval. It is worth mentioning that the location of thermocouples measured from the unexposed surface of the slab, i.e., temperature reading at 25 mm, means it is the farthest point from the fire, whereas 275 mm is the nearest point from the fire. By observing the temperature readings of the internal thermocouples, the entire thickness of a slab can be divided into three zones; near zone, middle zone, and the far zone. The first 100 mm slab thickness at the fireside is called the near zone, the middle zone is the middle 100 mm thick part of the slab, and the far zone is the 100 mm thick part of the slab at the unexposed side. Figure 7: The temperature of external thermocouples measured at 120 min of fire exposure (at the unexposed surface). Figure 8 shows the temperature distribution within the entire slab thickness for all concrete mixes after 120 min to fire exposure. A common observation is made that the thermocouples within the near zone showed a very high temperature.