PSI - Issue 68

Asad Zia et al. / Procedia Structural Integrity 68 (2025) 231–237 A. Zia et al. / Structural Integrity Procedia 00 (2025) 000–000

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6EF7R was minimal, showing a decrease of only 0.2% and 1.4% compared to plain concrete. This suggests that the inclusion of both industrial steel fibers (ISFs) and end-of-life tire steel fibers (EFs) has a negligible effect on the compressive strength of recycled aggregate concrete (RAC). However, despite the minimal impact on compressive strength, significant improvements were observed in the compressive total energy (CTE) and compression toughness index (CTI). The CTE for 6IS7R and 6EF7R increased by 6% and 1%, respectively, compared to the plain concrete, indicating that both fiber types contributed to the concrete's ability to absorb more energy during compression. The CTI values further demonstrate the enhanced toughness of fiber-reinforced concrete, with 6IS7R showing a 27% increase and 6EF7R a 16% increase compared to 0F7R. These results highlight the fact that while fiber addition does not significantly affect compressive strength, it greatly enhances the energy absorption capacity and toughness of the concrete. This improvement in toughness is beneficial for applications where enhanced durability and resistance to dynamic loads are required.

Table 2 Compressive strength test results Properties

units MPa

0F7R 30.46 100 6.3 100 1.24 100 0.201

6IS7R 30.40

6EF7R 30.03

Compressive strength Standard deviation

%

99.8

98.6

4

6.9

CTE CTE CTI CTI

MPa

0.213

0.203

%

106 1.57 127

101 1.44 116

-

%

3.3. Split Tensile Test Results The split tensile strength test results, summarized in Table 3, reveal a notable improvement in the tensile strength of fiber-reinforced concrete compared to plain concrete containing 75% RCA replacement (0F7R). The plain concrete exhibited a tensile strength of 2.62 MPa, while the industrial steel fiber-reinforced concrete (6IS7R) showed a substantial increase to 3.83 MPa, representing a 46% improvement. This significant enhancement in tensile capacity is attributed to the bridging effect of the industrial steel fibers, which effectively restrict crack propagation and improve load-bearing capacity under tensile stress. In the case of the end-of-life tire fiber-reinforced concrete (6EF7R), the split tensile strength was measured at 2.89 MPa, which marks an increase of 10% compared to plain concrete. Although this improvement is smaller compared to the industrial steel fibers, it still indicates that waste tire fibers provide a reinforcing effect, enhancing the tensile strength of recycled aggregate concrete (RAC). Both fiber types demonstrate their effectiveness in enhancing tensile performance, with the industrial steel fibers (6IS7R) outperforming the end-of-life tire fibers (6EF7R) in this regard. However, given the sustainable advantage of using recycled tire fibers, the moderate improvement in split tensile strength still supports their potential use in applications where sustainability and moderate tensile performance are prioritized. Additionally, the lower standard deviation in 6EF7R indicates consistent performance, further reinforcing its viability as a sustainable reinforcement option.

Table 3 Split tensile strength test results Property

Units MPa

0F7R 2.62 115 0.09

6S7R 3.83 169 0.47

6R7R

2.89 127 0.16

Split tensile strength Standard deviation

%

%