Experimental and Numerical Study on Compressive Behaviour of Circular Reinforced-Concrete Column with Pre-fabricated Self-compacting Mortar Stay-in-Place Formwork Strengthened with CFRP Layers

This research introduces an experimental and numerical study of the axial compressive performance of novel RC composite columns consisting of a pre-fabricated self-compacted mortar stay-in-place formwork (SCM-SIP), unwrapped and wrapped with carbon fibre-reinforced polymer (CFRP) layers, and post-cast core concrete. Fourteen scaled columns, including two references, four unwrapped composite columns, and eight CFRP-wrapped SCM-SIP formwork composite columns, were tested axially. The investigated variables were the formwork thickness, the number of CFRP wrapping layers, and their interaction effects. Finite element (FE) analysis was performed to simulate the axial compressive performance of the column using ABAQUS software. The load–deflection behaviour, stress–strain relationship, and failure mode were analysed. It was found that both the formwork thickness and number of CFRP layers improved the axial load capacity and ductility values; however, the CFRP effects were more pronounced. No peeling failure was observed at the interface surface between the core concrete and the pre-fabricated formwork, indicating efficient bonding between them and better composite column integrity. The developed FE model was sufficiently accurate, with good agreement between the predicted and measured load–strain curves.