Use of HPFRC Jackets for Strengthening Concrete Columns - Experimental and Numerical Assessment

Economic, environmental and sustainability reasons bring a growing need to act upon existing structures to extend their working lives, preferably through efficient strengthening solutions, in which the least amount of material and better ways are used to calculate the resistance of a structure or section. Such an approach not only conserves resources but also minimizes the environmental impact associated with the production of new materials and the construction of new structures. This paper unveils the result of theoretical-experimental research on using High-Performance steel Fibre-Reinforced Cementitious Composite (HPFRC) to increase the load-bearing capacity and strain capacity of concrete columns subjected to centred compression. Additionally, it proposes a novel way to determine the parameters of Mazar's damage model. The study introduces a new approach for determining the parameters of Mazar's damage model when limited material behaviour data is available. In practical scenarios, the lack of exhaustive data is often a challenge, and this approach could facilitate more accurate and practical assessments across various structural situations. Six cylindrical concrete specimens were tested to validate this procedure. These specimens were divided into three groups: two as reference models, two with an external HPFRC jacket covering the full height, and two with partial-height jacketing. The jacket is made of a thin layer of HPFRC without additional longitudinal or transverse reinforcement bars. The test results show that significant improvements can be made in circular cross-section elements strengthened over the entire height even if the reinforcement has a reduced thickness, making it thus both a feasible and economical solution. The results indicated that the maximum load achieved in the columns reinforced with HPFRC was more than twice that of the unreinforced standard specimen, underscoring the effectiveness of this technique in enhancing structural performance in terms of load-bearing capacity and durability. Furthermore, the numerical study carried out with finite element software demonstrated a good agreement with the experimental results obtained, which open up possibilities for their application in the analysis and design of future structural reinforcement.