Issue 74

V. J. Kalyani et alii, Frattura ed Integrità Strutturale, 74 (2025) 89-114; DOI: 10.3221/IGF-ESIS.74.07

In the GG specimen prepared using Sikadur 30 LP, failure occurs at the concrete - adhesive interface. For the GSG, SGS, and GGG specimens bonded with Sikadur 30 LP, the failure primarily involves the concrete substrate near the specimen edges with debonding of strengthening layer. For the SS specimen bonded with Sikadur 330 exhibits tearing of the SSWM layer at the central slit without any evident debonding. For all other Sikadur 330 specimens, clear debonding between the concrete and laminate is observed, along with concrete failure at the specimen edges. These failure modes suggest that the concrete fails before the full-strength utilization of the strengthening materials, particularly when using Sikadur 330.

SS

SG

GS

GG

SSS

SGS

GSG

GGG

(a) strengthening using Sikadur 30 LP

SS

SG

GS

GG

SSS

SGS

GSG

GGG

(b) strengthening using Sikadur 330 Figure 19: Typical failure patterns of dumbbell specimens during bond test.

The capacity utilization ratio, calculated as the ratio of the average ultimate load on one side of the dumbbell bond specimens to the average ultimate load from tensile coupon tests is presented in Tab. 8, for various strengthening configurations using Sikadur 30 LP and Sikadur 330. The results reveal that specimens strengthened exclusively with GFRP (GG and GGG) utilize only around 40% of their material tensile capacity in load resistance. In these cases, failure occurs due to concrete crushing and subsequent debonding of laminate layer with concrete surface, before the full strength of the strengthening material is utilized. In contrast, specimens strengthened with SSWM (SS and SSS) demonstrate significantly higher capacity utilization, exceeding 83% with Sikadur 330 and approaching 90% with Sikadur 30 LP. This indicates a strong bond between the SSWM and the concrete surface. It further suggests that nearly the full tensile capacity of SSWM is effectively engaged, especially when bonded using Sikadur 30 LP. While hybrid specimens show moderate capacity utilization (around 45% to

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