Development of GFRP-reinforced GFRC for thin permanent formwork applications Available to Purchase

A major impediment for the development of precast concrete permanent formwork and other thin structural elements such as cladding is the minimum cover requirement to the reinforcement. For aggressive environments, this can be up to 50 mm, which results in minimum 100 mm thickness units. Currently, glass-fibre-reinforced concrete or cement (GFRC) is used to address that problem in small non-structural elements. However, the structural capacity of GFRC is limited and fibre-reinforced plastic (FRP) reinforcement can be used to structurally reinforce GFRC to enable the development of much larger units. The ‘skin and rib' concept for the design of such units has been developed by the authors and has been used for the design of precast units. The main issues relating to GFRP-reinforced GFRC are bond, anchoring, tension stiffening, deflections and shear capacity of thin panels. This paper presents experimental and analytical work undertaken to address all the above issues. Pull-out tests confirm that the pull-out resistance of FRP is greater in GFRC than in concrete. Flexural capacity and deformations can be predicted provided the tensile properties of the GFRC are determined and modelled correctly. Finally the shear resistance of the elements is examined and design proposals are made. The work demonstrates that it is possible to develop 1 cm thick GFRC permanent formwork for bridge or building applications – spanning unsupported up to 3·85 m and up to 10 m with intermediate supports, thereby providing a durable and economic alternative to metal decks.