Paper Title
Repairing and Strengthening of Damaged Reinforcement Columns Using Concrete (Covering) Jacketing

Abstract
This research aims to investigate the efficiency of repairing damaged concrete columns using thin concrete jacketing. experimental program included casting of nine reference 300mm long reinforced concrete column specimens: three specimen had a cross-sectional dimension of 100mm× 100 mm, three specimens had a cross-sectional dimension of 150mm× 150 mm, and three specimens had a cross-sectional dimension of 170mm× 170 mm. A total of 36 identical column cores were cast with similar cross sections of 100mm× 100mm and a height of 300 mm. (ese cores were damaged by loading them with approximately 90% of their actual ultimate axial load capacities. (the columns were repaired and strengthened by applying two jacketing materials, which were 25 and 35mm thick, on all four sides. Group 1 consisted of 18 column cores jacketed by normal strength concrete with a maximum aggregate size of 4.75mm and steel reinforcement, whereas Group 2 consisted of 18 column cores jacketed using ultrahigh performance fibre-reinforced self-compacting concrete with steel reinforcement. (The experimental program showed that the Group 1 specimens had ultimate load capacities more than twice those of the unjacketed reference columns and the same axial capacity as the monolithically cast reference columns. (e Group 2 specimens showed a significant increase in ultimate load capacity, which was approximately 3 times that of the unjacketed reference column and 1.86 times that of the monolithically cast reference columns. Moreover, using the shear studs was found to be the most effective among the three surface preparation techniques. Keywords - Reinforcement, corrosion, Concrete Jacketing, Strengthening, Repair, Damaged RC Columns,