Strengthening of RC columns by ultra-high performance fiber reinforced concrete (UHPFRC) jacketing

It is the objective of this study to investigate the axial behavior of circular reinforced concrete (RC) columns strengthened with ultra-high performance fiber-reinforced concrete (UHPFRC) jackets. For this purpose, 14 circular base column specimens, each 120 mm in diameter and 500 mm in height, were cast whose contact surfaces were prepared through longitudinal or horizontal grooving, sandblasting, and abrasion techniques. Moreover, 10 specimens were strengthened with UHPFRC jackets 15 mm in thickness and containing either steel fibers or synthetic (barchip) macro-fibers, while three more were strengthened with full or intermittent glass fiber-reinforced polymer (GFRP) hoop wraps. The specimens subjected to the novel longitudinal grooving surface treatment were found to exhibit a monolithic compression behavior with average increases of 33% and 34% recorded in their load-carrying capacity and energy absorption, respectively, compared to those achieved by the specimens subjected to the common sand blasting technique. Using the data thus obtained, a model was finally proposed for predicting the stress-strain relation of RC columns strengthened with UHPFRC jackets. Verification of the model against the results reported elsewhere shows its great prediction accuracy. (C) 2019 Elsevier Ltd. All rights reserved.