Knitting bespoke reinforcement for new concrete structures

Emissions data suggests that 30-50% of all carbon emissions arise from activities in the built environment. The global population is expected to reach 9bn by 2050, with 67% living in urban areas. Meeting strict emissions reductions targets (in the UK - an 80% reduction by 2050) and facilitating global low-carbon design is therefore a major challenge for structural engineering.

Concrete is the world's most widely used man-made material. The manufacture of cement accounts for a large proportion of global raw material expenditure and at least 5% of global CO2 emissions. Recent research has made it possible to cast geometrically complex concrete structures, capitalising on a key advantage of this fluid material. These developments allow new architectural expression, and the new geometries allow us to save considerable amounts of material through design optimisation.

This new potential is being held back by current methods for reinforcing concrete. Although the steel rods that we use can be bent into standardised shapes, any further complexity adds considerable cost to the construction process.

With the goal of achieving low carbon concrete design, two major challenges exist: 1) to reinforce structures with complex geometries and 2) to provide durable and resilient structures. Meeting both challenges would allow us to capitalise on the fluidity of concrete to meet long-term emissions reductions targets. This will require a completely new approach to design and construction of concrete structures.

This proposal will completely replace internal steel reinforcement with a knitted composite reinforcement cage made from carbon fibre tows. By fabricating this reinforcement in exactly the right geometry, we will provide exactly the right strength exactly where it is needed. This will be transformative for concrete construction, and will greatly simplify the reinforcing of more efficient concrete structures to help the UK meet its ambitious targets for emissions reductions.

This proposal will provide new technical and practical methods for the reinforcement of low-carbon concrete structures with novel geometries, with its outcomes and long term impacts potentially affecting all users of the built environment. The ambition of the proposal is to provide a prototype design and construction method to act as the founding blocks of a longer-term research effort to fully realise the potential of the woven cage system. These impacts will be seen in the order of years after this initial project is complete.

Researchers in concrete formwork technology will benefit through the provision of a feasible construction process for the all-important internal reinforcement. This research will help those engineers and architects working on novel geometries of concrete structures to understand how they may be reinforced with materials other than steel - a step that may be important to provide alternative, commercially viable, construction processes. This will help to enhance the UK's economic competitiveness in the construction industry and will provide a new avenue of both academic research and industrial development.

This proposal will provide initial steps towards a design method for the distributed woven carbon fibre internal reinforcement. Verification by structural testing will provide initial evidence for the method's efficacy - but much more research will be required before codified approaches are made available. This will impact colleagues working in structural engineering, and advanced composite design processes.

The societal impacts of this proposal will be seen in the medium-long term, and are found in its provision of an alternative method for the reinforcement of geometrically complex concrete structures. In this way it has the potential to reduce the contribution of the built environment to carbon emissions, which in turn will positively impact our quality of life. These steps will be crucial if we are to meet government targets for an 80% reduction in carbon emissions by 2050.

This project will provide design and construction guidance for the woven carbon fibre cage, which will be a trigger for additional research in the process that will in turn lead to a more widespread use of optimised concrete structures. This will be a significant impact in the race to reduce the carbon emissions of the built environment.

In the longer term the initial research completed here will be developed into a completely automated system for the fabrication of entirely bespoke reinforcement cages for concrete structures of any geometry. This will bring new potential for architectural, engineering, and construction industries.