PERFORMANCE OF PREFABRICATED FERROCEMENT SHEET TO RETROFIT RC TIED COLUMNS

Abstract

The durability and performance of reinforced concrete (RC) structures are often compromised due to aging, environmental exposure, poor construction quality, and extreme loading conditions such as earthquakes or cyclones. In developing countries like Bangladesh, where a significant portion of the built

environment is vulnerable and maintenance resources are limited, a cost- effective and structurally efficient retrofitting technique is urgently required. In

this regard, this research explores the feasibility and effectiveness of a retrofitting method using prefabricated ferrocement sheets (PFSs) to strengthen partially damaged tied RC columns. In this study, an experimental investigation was conducted to assess the structural performance of eighteen one-third-scale column specimens representing three concrete strength levels (20 MPa, 24 MPa, and 28 MPa), divided into control, damaged, and retrofitted groups. The retrofitting involved bonding prefabricated ferrocement sheets, comprising single or double-layer wire mesh, onto the damaged columns using epoxy adhesives and mechanical anchors. All specimens were tested under axial displacement-controlled loading, and key performance indicators such as ultimate load capacity, initial stiffness, energy absorption, ductility index, and failure patterns were determined and evaluated. The results obtained from the investigation indicate that the retrofitted columns outperformed both the control and damaged specimens across all measured parameters. Notably, columns retrofitted with double-layer ferrocement jacketing exhibited up to 164% of axial strength, an improvement of initial structural stiffness of 54% and energy absorption increased by 152% over partial damage specimens for column concrete strength with 28 MPa. Subsequently, the respective values for the PFSs retrofitted column with a single layer are: 123%,

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40% and 105%. The ductility index also improved substantially for both retrofitting scenarios, while failure modes shifted from brittle longitudinal splitting to ductile diagonal crack propagation with a delayed collapse. These similar scenarios are equally true for column specimens with lower concrete strength. Apart from that, the methodological approach of this study demonstrates prefabricated ferrocement sheet wrapping as a structurally sound, less labour-intensive, time-efficient and economically scalable retrofitting technique for deteriorated RC columns, especially for a developing country like Bangladesh.