The Impact of Rehabilitation of Reinforced Concrete Columns: an Investigating of Column Size and Load-Bearing Capacity

Abstract This study presents an investigation on the column square size effect in concrete structures. It has been observed that most jacketing material fails to fully restore the original load of square columns due to the presence of poorly confined concrete regions within their cross sections. This study investigates the influence of varying square cross-sectional dimensions on the performance of Ultra High-Performance Fibre Reinforced Concrete (UHPFRC) as a strengthening material. A total of 18 reinforced concrete column specimens, with dimensions of 100 x 100, 125 x 125, and 150 x 150 mm, were fabricated and subjected to axial compression tests to evaluate their load-bearing capacities and failure modes. The results indicated a direct correlation between the load-bearing capacity and the cross-sectional area of the columns. The application of UHPFRC jacketing resulted in significant enhancements in load-bearing capacity, with increases of 63%, 39%, and 34% for the respective column sizes. However, the degree of improvement showed a diminishing trend with larger column sizes, emphasizing the necessity of optimizing the ratio of column size to jacketing thickness. This study concludes that UHPFRC substantially enhances the structural performance of reinforced concrete columns, particularly in smaller sizes. The findings highlight the critical importance of customized strengthening strategies that account for the geometric characteristics of columns to maximize the benefits of UHPFRC in structural rehabilitation projects.