PSI - Issue 68

Eyad Shahin et al. / Procedia Structural Integrity 68 (2025) 238–244 E. Shahin et al. / Structural Integrity Procedia 00 (2025) 000–000

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Fig. 2. (a) RCPT equipment; (b) cut cylinders used for RCPT investigation.

3. Results and discussion 3.1. Uniaxial tensile performance of GGBS-ECC

The uniaxial tensile tests conducted on GGBS-ECC aimed to evaluate the tensile strain-hardening behavior of the material, providing key data on its performance. Table 4 summarizes the ultimate tensile strength, ultimate tensile strain, first crack strength, and their averages for each mixture with varying GGBS contents (30%, 60%, and 90%). The tensile stress-strain curves in Figure 3 provide further insight into how each mixture performed under tensile loading. The tensile strain-hardening behavior was clearly observed in GGBS-ECC, with tensile strain capacities reaching between 1.2% and 3.8% at 28 days of curing. This level of ductility is remarkable, being 100 to 200 times greater than that of conventional concrete, which typically exhibits brittle failure when loaded in tension. Even though the ultimate tensile strain of GGBS-ECC was lower than that of ECC made with fly ash, Holschemacher et al. (2010), Li et al. (2001), it still demonstrated significantly better ductility compared to normal concrete and conventional fiber-reinforced composites (FRCs), Swaddiwudhipong et al. (2003), Shkolnik (2008). The first crack strength, which marks the point where microcracks first form in the material, decreased as the GGBS content increased. Specifically, as the GGBS content increased from 30% (G30) to 90% (G90), the first crack strength dropped from 3.60 MPa to 3.35 MPa. However, this decrease in first crack strength did not affect the overall load bearing capacity of the material. After the first crack, the GGBS-ECC mixtures continued to resist increasing loads through the formation of multiple microcracks, which is a hallmark of strain-hardening materials. This behavior demonstrates the material's capacity to distribute stresses across multiple cracks rather than localizing failure to a single crack, which contributes to its high ductility and toughness. Additionally, the tensile stress-strain curves for each mixture (G30, G60, and G90) provide a visual confirmation of this strain-hardening behavior, with the curves showing increasing tensile stress even after initial cracking. Each mix exhibited different peak stresses and strain capacities, with G30 showing the highest peak stress, followed by G60 and G90. Despite differences in tensile strength and first crack strength, all mixes demonstrated similar pseudo strain-hardening behavior, a key feature of ECC materials. This characteristic ensures that the material can undergo substantial deformations without losing its load-carrying capacity, making it suitable for applications requiring high durability and resilience under tensile stresses.

Fig. 3. Tensile stress-strain curves of (a) G30 dogbones; (b) G60 dogbones; and (C) G90 dogbones.