# Efficacy of Fire Protection Techniques on Impact Resistance of Self-Compacting Concrete
## 3 Results and Discussion  
### Residual Compressive Strength and Mass Loss of SCC after Exposure  
#### 3.1.1 Residual Compressive Strength  
Figure 6 presents a graphical representation of the residual compressive strength and mass loss observed in different SCC specimens exposed to varying durations of heating. The residual compressive strength of SCC cube specimens can be classified into distinct phases based on the duration of exposure and their corresponding strength levels. Unprotected specimens of FA and GGBFS without CPP (FA/EPA, FA, GGBFS/EPA & GGBFS) exhibit two phases: 0 to 30 min and 30 to 120 min. Conversely, CPP specimens of FA and GGBFS (FA/EPA/CPP, FA/CPP, GGBFS/EPA/CPP & GGBFS/CPP) display three phases: 0 to 30 min, 30 to 60 min, and 60 to 120 min. Notable differences in residual strength between the two phases of FA and GGBFS specimens without CPP protection are evident. The initial phase (0 to 30 min) exhibits a substantial strength gain, followed by a sharp decline in the second phase (30 to 120 min). The strength gains during the first phase (0 to 30 min) of unprotected specimens (FA/EPA, FA, GGBFS/EPA & GGBFS) range from 12% to 26%. This increase in strength can be attributed to secondary hydration resulting from the autoclave effect on unhydrated clinker [32].  
As the duration of temperature exposure extends beyond 30 to 120 min, the decline in strength becomes increasingly pronounced. The most substantial reduction in strength is observed at 60 min (925 \({}^{\circ}\)C), with a maximum decay of 16%. Furthermore, unprotected specimens (FA/EPA, FA, GGBFS/EPA & GGBFS) experience a higher loss of approximately 63% at 120 min (1029 \({}^{\circ}\)C).  
The deterioration of the dense structure and the decline in strength in SCC become significant when exposed to temperatures above 500 \({}^{\circ}\)C, primarily due to the decomposition of calcium hydroxide. During this phase, the strength reduction occurs due to the complete dehydration of the CSH gel, resulting in the loss of its inherent binding ability [33].  
The protected specimens of FA and GGBFS (FA/EPA/CPP, FA/CPP, GGBFS/EPA/CPP & GGBFS/CPP) display distinct variations in strength patterns based on the duration of exposure. In the initial phase (0 to 30 min), all specimens exhibit a minimal reduction of less than 1% in strength. From 30 to 60 min, a gradual strength gain ranging from 16% to 30% is observed following the initial decline. The CPP-coated FA and GGBFS specimens demonstrate improved performance compared to the unprotected specimens at higher  
Figure 5: Schematic representation and view of impact strength test setup.  
temperature exposure. Even after 90 min of temperature exposure, the CPP specimens of FA and GGBFS exhibit a strength gain of 12% and 2%, respectively. This enhancement can be attributed to the thermal insulating capability of the perlite mineral, which limits the heat flux into the concrete core, thereby enhancing the performance of the protected specimens [34].  
In the final phase of temperature exposure (60 to 120 min), a gradual decrease in strength is observed for FA and GGBFS specimens, with a strength loss ranging from 10% to 5%, even lower than that of the unprotected specimens. Based on the results of residual compressive strength, it can be concluded that the perlite mineral can be effectively utilized as a sacrificial coating (CPP layer) on the surface of SCC and as an internal thermal-resistant filler. At 120 min of temperature exposure, the maximum reduction in strength is observed, ranging from 32% to 34% for FA/CPP and GGBFS/CPP specimens, respectively. The observed strength loss for FA/EPA/CPP and GGBFS/EPA/CPP specimens is minimal, with values of 3% and 10%, respectively [14; 15; 16].