FRP Structural Stay In Place Formwork for Concrete Slabs

Abstract

Development in the use of fibre reinforced polymer (FRP) in the construction industry has led to the development of FRP structural stay-in-place (SIP) formwork system. The concept of using FRP composites for structurally integrated SIP formwork maximises the advantages of both FRP and concrete while simplifying the construction process and reducing construction time and labour cost. FRP SIP formworks plays role of a formwork when concrete is in plastic stage and as reinforcement when concrete has hardened. This thesis investigates the feasibility of FRP plank manufactured in India as structural SIP formwork. The selected plank is a GFRP (glass fibre reinforced polymer) profile consisting of base plate integrated with T-shaped ribs. Experimental investigation regarding the suitability of the plank as SIP formwork was performed in three stages. In the first stage, the FRP plank was selected out of the two commercially available planks. The selection was based on the material and geometrical properties of the plank, viz. moment of inertia, longitudinal tensile strength test and fibre volume fraction test. Further, sand and concrete loading tests were conducted to check if the deflections under concrete weight were within the permissible limits, so that it can be used as a formwork during casting of concrete. In the second stage, the bond between FRP plank serving as structural SIP formwork and cast-in place concrete has been investigated. Bond development between plank and concrete is critical for FRP tension element to be effective. Two different shear tests were used for investigation of bond- Push Tests and Pull Tests. The above mentioned shear tests were performed to investigate two types of bond treatments: aggregate bonding and adhesive bonding. Performance of three different types of adhesives has been compared. The adhesives to be compared were selected based on their viscosity, modulus of elasticity, elongation at break, ease of application and pot life.