Strengthening of Short Reinforced Concrete Columns by Using Natural Fiber Ropes as Confinement Composite Materials: Experimental Investigation

It is widely known that concrete is one of the most used construction materials worldwide. However, strengthening or repair is an essential part of its lifecycle because it ages. The use of synthetic fiber-reinforced polymer (FRP) in strengthening RC structures has been proven to be effective. Recently, researchers have started investigating the use of natural FRPs (NFRPs) as an environmentally friendly alternative. However, the literature is still limited, and the efficiency of using different types of natural materials has not been confirmed, especially for concrete strength higher than 30 MPa. In the current study, three types of locally available NFRPs, including jute, cotton, and sisal, have been used to strengthen short-circular RC columns (fc` = 37.42 MPa). Ten columns have been prepared, cast, and tested under monotonic axial loading until failure. The effects of the number of confinement layers (1, 2, and 4 layers) have also been investigated. The results show that NFRPs can significantly improve the axial strength of short RC columns. Sisal NFRPs provided the greatest enhancement in axial strength (83%), followed by jute (43%) and cotton (35%). In general, increasing the number of confinement layers increases the axial strength of RC columns. However, more confinement did not show a clear pattern on the deformation performance.