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Research Project: Thin overlays to replace the need for conventional reinforcement in additively manufactured concrete structures

Supervisor: Behzad Nematollahi

Construction is one of the UK’s largest industry sectors, representing 7% of the country’s GDP and employing over 9% of the workforce. However, construction has shown poor productivity gains relative to other sectors, attributable to its limited use of automation and digital technologies. Three-dimensional concrete printing (3DCP) provides an opportunity to introduce digital construction technologies. 3DCP allows construction of 'free-form' concrete structures with complex geometries 'without' using expensive and waste- generating formwork. The benefits of 3DCP include waste, time, and cost reduction due to the elimination of formwork. The formwork contributes to 35-60% of the cost and forms a major part of construction waste. There is also a significant community benefit, as 3DCP meaningfully increases construction safety by replacing dangerous low-skilled construction work with safer high-skilled work, boosting productivity. Although 3DCP is being developed in an increasing number of places around the globe, there are challenges that need to be addressed to allow widespread and large-scale applications of this technology in the construction industry. Integrating conventional steel reinforcement in the 3DCP process is very challenging.

Novel reinforcing methods for 3D-printed concrete structures should be developed. Steel reinforcement in concrete structures serves the following purposes: 1) provide ductility to prevent brittle failure in the case of natural disasters, 2) spalling failure mechanism during fire events, and 3) transmit tensile forces. All these requirements may be provided when a thin cementitious overlay, containing mechanical fibres, is applied to the 3D-printed structure, or a layer of mild steel is added on the external side of the structure and bonded to the structure using shotcrete. This project aims to develop such novel overlay.