Investigation of the axial compressive performance of locally defective reinforced concrete columns strengthened using cementitious grout

Abstract This study examined the axial compressive behavior of deficient strength reinforced concrete (DSRC) columns with local defects strengthened using cementitious grouting materials, based on axial compression tests and numerical simulations of nine reinforced concrete specimens. The effects of defect location and grout thickness on compressive performance were evaluated. The results show that, after grouting, local compressive failure still initiated in lower‐strength regions along the column height under axial loading. The ultimate bearing capacity of strengthened specimens increased by up to 35.4%. Grout strengthening effectively reduced cracking in defective regions and delayed reinforcement yielding. However, strengthening exhibited boundary effects, and the recovery of bearing capacity was more sensitive to grout replacement thickness, while defect location had a limited influence on the ultimate capacity. Considering the lateral confinement provided by grout and stirrups, a calculation method for the axial bearing capacity of locally strengthened DSRC columns was proposed. The predicted results showed good agreement with the test data.