Steel corrosion is a major cause of deterioration for reinforced concrete structures which may lead to significant area loss of rebars that affects structural safety. The most common repair approach is to splice additional reinforcements to the corroded rebars, which is time consuming and costly, as a large volume of sound concrete beyond the corroded part must be removed to provide sufficient lap lengths. In this research, a new repair technique using high strength strain-hardening cementitious composites (SHCC) in the aforementioned situation is proposed and explored.

To verify the proposed repair technique in terms of load-capacity recovery, the development of high strength SHCC was first described. Then, rebars with reduced area were embedded inside high strength SHCC block...[ Read more ]

Steel corrosion is a major cause of deterioration for reinforced concrete structures which may lead to significant area loss of rebars that affects structural safety. The most common repair approach is to splice additional reinforcements to the corroded rebars, which is time consuming and costly, as a large volume of sound concrete beyond the corroded part must be removed to provide sufficient lap lengths. In this research, a new repair technique using high strength strain-hardening cementitious composites (SHCC) in the aforementioned situation is proposed and explored.

To verify the proposed repair technique in terms of load-capacity recovery, the development of high strength SHCC was first described. Then, rebars with reduced area were embedded inside high strength SHCC blocks with different bond lengths, and were tested under direct tension, in order to determine a suitable bond length for the repair procedure. Further, beams containing rebars with reduced area and patched with high strength SHCC were tested under four-point bending, together with control beams without patching. The test results verify the feasibility of the proposed repair technique.

Further investigations attempt to address several issues identified from the aforementioned structural test. Issues directly related to the structural performance of the repair include the bond between high strength SHCC and rebars as well as the feasibility of lapping additional rebars using high strength SHCC when the steel loss is very severe. The investigations demonstrate good bond between SHCC and rebars, and the effectiveness of the enhanced lapping method. In addition, bond between SHCC and concrete, shrinkage of SHCC and its reduction as well as effect of internal curing are also studied. The results show strong bond between SHCC and concrete, effective shrinkage reduction with the use of shrinkage reducing agent and/or calcium sulfoaluminate cement as well as the mechanical benefit of internal curing, which are promising for improving the repair quality.

In order to promote the application of the novel repair method, a guideline based on the research findings is proposed, with considerations including design approach, procedures and workmanship.