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High-strength strain-hardening cementitious composite (HS-SHCC) has been proven effective in strengthening reinforced concrete (RC) beams experiencing steel rebar corrosion. However, for beams reinforced with large rebars ( \(\varPhi 25\) or larger), the maximum steel area loss ratio that is compensable is 20% or below. In practical scenarios, the loss of steel area can be much higher, necessitating additional reinforcement to restore the load-carrying capacity. Carbon fiber-reinforced polymer (CFRP) is a kind of promising composite for structural repair applications due to its high strength-to-weight ratio. Compared to the external CFRP bonding method, near-surface mounted (NSM) CFRP reinforcement is more efficient and cost-effective. However, plate-end cover separation failure may occur in NSM CFRP strengthened RC beams due to the complex stress condition in the plate-end region, limiting the effectiveness of repairs. This study hypothesizes that the combination of SHCC and NSM CFRP reinforcement can be a viable solution for repairing RC beams experiencing significant loss in load-carrying capacity, through the synergistic interaction of SHCC and CFRP and delayed cover separation failure. In this research, CFRP-SHCC repaired RC beams with discontinuous tensile steel rebars (representing 100% loss of loading capacity due to severe localized corrosion) are investigated. The lower part of the middle span (from the bottom surface to 20 mm above the tensile rebars) is replaced with SHCC, incorporating a sand-coated CFRP strip under the tensile bars. Four-point bending tests reveal that the flexural capacity of the repaired beam achieves 64% of that of the original RC beams. Besides, the maximum strain in the CFRP strip at the plate-end area reaches 2500 με without inducing cover separation. This study demonstrates the feasibility of using a hybrid repairing system involving NSM CFRP strips embedded in SHCC patches for repairing severely deteriorated RC beams, and offers a much easier and more efficient structural repairing approach.

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Strengthening Beams with Severely Corroded Rebar Using CFRP and SHCC: An Experimental Study Focusing on Plate End Cover Separation

  • 会议论文

  • 发表日期：

    2025年

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  • Zhenghao Li,
  • Xuanyi Lu,
  • Haroon Younas,
  • Shenghan Zhang,
  • Christopher K. Y. Leung

摘要

High-strength strain-hardening cementitious composite (HS-SHCC) has been proven effective in strengthening reinforced concrete (RC) beams experiencing steel rebar corrosion. However, for beams reinforced with large rebars ( \(\varPhi 25\) or larger), the maximum steel area loss ratio that is compensable is 20% or below. In practical scenarios, the loss of steel area can be much higher, necessitating additional reinforcement to restore the load-carrying capacity. Carbon fiber-reinforced polymer (CFRP) is a kind of promising composite for structural repair applications due to its high strength-to-weight ratio. Compared to the external CFRP bonding method, near-surface mounted (NSM) CFRP reinforcement is more efficient and cost-effective. However, plate-end cover separation failure may occur in NSM CFRP strengthened RC beams due to the complex stress condition in the plate-end region, limiting the effectiveness of repairs. This study hypothesizes that the combination of SHCC and NSM CFRP reinforcement can be a viable solution for repairing RC beams experiencing significant loss in load-carrying capacity, through the synergistic interaction of SHCC and CFRP and delayed cover separation failure. In this research, CFRP-SHCC repaired RC beams with discontinuous tensile steel rebars (representing 100% loss of loading capacity due to severe localized corrosion) are investigated. The lower part of the middle span (from the bottom surface to 20 mm above the tensile rebars) is replaced with SHCC, incorporating a sand-coated CFRP strip under the tensile bars. Four-point bending tests reveal that the flexural capacity of the repaired beam achieves 64% of that of the original RC beams. Besides, the maximum strain in the CFRP strip at the plate-end area reaches 2500 με without inducing cover separation. This study demonstrates the feasibility of using a hybrid repairing system involving NSM CFRP strips embedded in SHCC patches for repairing severely deteriorated RC beams, and offers a much easier and more efficient structural repairing approach.