Analysis of Axial Compressive Bearing Performance of Defective Concrete Short Columns Replaced With Cement‐Based Grouting Material

ABSTRACT Reinforced concrete (RC) columns may develop defects due to long‐term material degradation or construction deficiencies such as honeycombing and voids, which substantially reduce their load‐bearing performance. To address this issue, defective zone replacement using cement‐based grouting material (CGM) has been proposed as an effective strengthening technique. In this study, nine axial compression tests were carried out to investigate the failure characteristics, load–displacement responses, strain distribution, and stiffness degradation of RC columns. The effects of varying defective zone replacement thicknesses and locations on the axial compression performance were experimentally evaluated, whereas numerical simulations were conducted to further examine the influence of replacement thickness, grout strength, and defective concrete strength on ductility, load‐bearing capacity, and energy dissipation capacity. The results demonstrate that replacing defective concrete with CGM effectively mitigates stiffness degradation in strengthened columns during the plastic stage. Columns strengthened at the lower defective region exhibit higher recovery efficiency in axial load‐bearing capacity compared to those strengthened at the midheight defective region. Among the parameters investigated, CGM replacement thickness is identified as the most significant factor influencing strengthening effectiveness. As the replacement thickness increases, the axial compressive bearing capacity and energy dissipation capacity of the strengthened columns improve by approximately 39.9% and 74.8%, respectively, whereas ductility decreases by about 11.3%. Furthermore, after strengthening, the region of high‐stress concentration shifts from the defective zone to the intact concrete zone. It is recommended that the strength of the grouting material should not exceed 2.5 times that of the original concrete, and the cross‐sectional replacement ratio should be limited to no more than 90%. Based on both experimental and numerical findings, a calculation method for the axial compressive bearing capacity of RC short columns is proposed, incorporating the lateral confinement effect of the outer grouting material on the defective concrete. The predicted results show good agreement with the experimental data.