Sustainable and durable maintenance of civil infrastructures has become a global need, especially for developed countries like the UK with large amount of aged and deteriorated structures. The recent failure of RAAC structures causing closing down of schools and hospitals is a good example. To address this global issue, I have been working on structural strengthening/repair using advanced composite materials, including fibre reinforced polymer composites (FRP) and engineered cementitious composites (ECC). FRP is formed by continuous fibres embedded in a polymer matrix, which shows light weight, high strength and has excellent fatigue and corrosion resistance. Also FRP is an application-oriented material whose properties are designable according to different applications, resulting in reduced cost and improved performance. ECC is a class of ultrahigh performance fibre reinforced cementitious composite. Unlike the typical trial-and-error development methodology, ECC is developed based on micromechanics and fracture mechanics theories. ECC is ‘bendable’ because it is similar to metals with a tensile strain capacity of more than 5%. ECC shows strain-hardening with micro-crack width less than 0.1 mm, making it highly durable under harsh environmental attacks.

Above figure is a demonstration showing strengthening of concrete bridge with carbon fibre fabrics which are bonded to the soffit of the beam. Other innovative and high performance materials are also developed for strengthening purpose, like the bendable concrete shown in the figure. Bendable concrete is ductile and can be bent like metal under flexural loading.