PSI - Issue 82

Asad Zia et al. / Procedia Structural Integrity 82 (2026) 234–238 A. Zia, I. Holly/ Structural Integrity Procedia 00 (2026) 000–000

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the internal pore connectivity, thereby restricting water penetration. These results highlight the potential of hybrid fiber systems to enhance the long-term durability of concrete by reducing water absorption.

Fig. 2. Water absorption test results

3.2. Carbonation Due to a testing error, precise carbonation depth measurements could not be obtained; however, the corresponding weight changes of specimens exposed to accelerated carbonation for 21 days are presented in Fig. 3. Previous studies reported that weight gain during carbonation is correlated with carbonation depth, as it reflects the extent of carbon dioxide uptake within the matrix (Pareek et al., 2023). Hence, the observed weight variations can be used as an indirect indicator of carbonation resistance.

Fig. 3. Weight increases due to carbonation

Among the tested mixes, the hybrid fiber-reinforced concrete containing 0.70% combined industrial and tire derived fibers (0.7CTF) exhibited the lowest weight gain of 2.56%, representing a 15% reduction compared to the industrial fiber-only mix (0.5HIF). This suggests that, in addition to reducing water absorption, the inclusion of hybrid fibers enhances resistance against carbonation, thereby contributing to improved protection of embedded steel reinforcement and extending the service life of structural concrete. 3.3. Tensile strength results The split-tensile strength results for 599-day-old specimens are presented in Fig. 4. The findings reveal that the hybrid fiber-reinforced concrete exhibited a noticeable improvement in tensile performance with increased fiber