Developments in the use of Ultra High Performance Fiber Reinforced Concrete as strengthening material

Ultra High Performance Fiber Reinforced Concrete (UHPFRC) is a novel material which has been developed the last few decades and has been applied in applications that require high strength, ductility and durability. Recently, the material has been applied in strengthening applications. The present study aims to investigate new techniques for the application of UHPFRC as strengthening material and to provide an insight into the parameters affecting the performance of elements strengthened with UHPFRC. The present research investigates for the first time the effectiveness of the use of dowels at the interface between UHPFRC and concrete to improve the connection between these two materials. Additionally, the effectiveness of the use of UHPFRC jackets for the strengthening of Reinforced Concrete (RC) beams has been examined. In the present research, a systematic experimental study has been conducted together with numerical study. The results demonstrate that both examined techniques are effective and should be taken into consideration when UHPFRC is applied for strengthening applications. The dowels result in better bonding at the interface and can delay the formation of cracks in the post elastic phase, leading to reduced interface slip values and subsequent enhanced load bearing capacity. This technique should be taken into consideration to eliminate the risk of premature de-bonding of the strengthening layer. The construction of UHPFRC jackets on the other hand, results in a dramatic increase of the stiffness and the load carrying capacity of the strengthened elements and should be preferred in cases of heavily damaged RC members.