PSI - Issue 68

6

Rami Hawileh et al. / Procedia Structural Integrity 68 (2025) 259–265 R. Hawileh et al./ Structural Integrity Procedia 00 (2025) 000–000

264

0,00 0,20 0,40 0,60 0,80 1,00 1,20

y = -7E-07x 2 + 0,0001x + 1 R² = 0,9222

HSC-ST HSC-ST+PP

EuroCode - 1.2 Poly. (HSC-ST) Poly. (HSC-ST+PP)

y = -4E-06x 2 + 0,0011x + 1 R² = 0,9195

Reduction Factor (R)

0

200

400

600

800

1000

Temperature (ºC)

Fig. 3: Compressive strength versus temperature for both mixes

3.3. Mass loss The average mass loss per sample is an indicator to the level of spalling and deterioration that the concrete experiences after the exposure to elevated temperatures. The major concern that is evaluated in this study is explosive spalling and its severity. Upon evaluation of the results presented in Fig. 4, a linear correlation between temperature increases and mass loss is noted. Furthermore, HSC-ST experienced a higher level of mass loss compared to HSC ST+PP. As predicted, HSC-STPP demonstrated remarkable resilience against spalling, supporting the findings from the literature, particularly those discussed by (Kodur & Banerji, (2021)) Its superior performance highlights the effectiveness of combining steel and PP fibers for enhanced fire resistance.

10 12

y = 0,009x R² = 0,8391

0 2 4 6 8

HSC-ST HSC-STPP Linear (HSC-ST) Linear (HSC-STPP)

y = 0,0055x R² = 0,8558

Precentage Mass loss (%)

0

200

400

600

800

1000

Temperature (ºC)

Fig. 4: Compressive strength versus temperature for both mixes

4. Summary and conclusions

This study investigated the degradation of compressive strength in high-strength concrete (HSC) under elevated temperatures, particularly focusing on the effect of polypropylene (PP) fibers in improving its fire resistance. Two mix designs were tested: one with 1% steel fibers and another with 1% steel fibers combined with 0.1% PP fibers. The following conclusions can be deduced from the study: • The study found that the mix with only steel fibers exhibited the highest compressive strength at room temperature but suffered from more pronounced degradation in strength after being exposed to high temperatures. Meanwhile, the mix that included both steel and PP fibers showed comparable compressive strengths with less severe degradation in strength, demonstrating the positive impact of PP fibers on fire resistance.