GFRP reinforced concrete : environmental and movement characteristics
For the last few decades, research has been conducted in order to come over the problem of corrosion in steel reinforced concrete. Consequently, methods such as cathodic protection, epoxy coatings, concrete additives, etc., have been tried. Unfortunately, non of these methods has totally solved the corrosion problem. The outstanding characteristics of fibre reinforced plastic (FRP) suggest that these materials may be the solution to the problem of steel corrosion. It is believed that the widespread application of glass fibre reinforced plastic (GFRP) reinforcement faces some challenges such as lack of design codes, brittle behaviour of FRP resulting in reduced structural ductility, low bond capacity to concrete, and lack of knowledge of durability issues and long-term behaviour of concrete reinforced with composite reinforcement. In this investigation, some properties of GFRP rebars were investigated, namely flexural and compressive characteristics, bond strength with concrete with different concrete strengths, and micro-structural features such as porosity and pore size distribution using mercuryi ntrusion porosimetry( MIP), together with observations of the micro-structure of the material under the scanning electron microscopy (SEM). Moreover, monitoring of changes in both the flexural characteristics and the microstructure of the material under high alkalinity and salinity solutions at high and moderate temperatures for different periods of aging up to 270 days were carried out. The results suggested that bond strength increased with high concrete strength, and alkalinity at high temperature(i . e. 60°C) was the most damaging medium. Furthermore,the influence of GFRP and steel rebars with different reinforcement ratios on elastic modulus and creep in compression, and drying shrinkage of concrete with and without SRA were considered and compared to concrete specimens with no reinforcement. Finally, a comparison between theoretical values and experimental measurements of elastic modulus, creep and drying shrinkage was made. The use of GFRP reduced the movement restraint due to low stiffness. Therefore, movements are greater for GFRP reinforced concrete than for steel reinforced concrete. Also SRA reduced compressive strength, creep, drying shrinkage and elastic modulus. Hence, concrete cracking is either avoided or delayed and reduced.