FRP reinforcing bars and tendons are relatively new products and require extensive testing before they can be recommended for widespread application in concrete construction.
This should not, however, preclude carefully controlled and monitored demonstration projects.
It is paramount that complete product reliability be assured in these projects.
It is anticipated that there will be significant obstacles and criticism in the introduction of these materials in concrete construction.
Such questions and criticisms need to be considered in the overall research program, and efforts made to answer as many pressing questions as possible.
For the research results to be universally acceptable, it is imperative to standardize the test methods for evaluating such basic properties as ultimate strength, modulus of elasticity, elongation at failure, coefficient of thermal expansion, creep, relaxation, fatigue, bond, etc.
Considering the dynamic nature of these materials and the fact that new commercial materials will frequently enter this field, standardization plays an important role in streamlining and effectively categorizing FRP reinforcements for inclusion in design specifications and standard codes.
The research needs of FRP reinforcing bars and tendons can be divided into three main categories: (1) materials behavior; (2) concrete element behavior; and (3) analysis and design guidelines. FRP bars and tendons generally have higher strengths than steel.
However, the modulus of elasticity of most FRP, particularly GFRP, reinforced materials, is less than that of steel.
This shortcoming can pose a problem with regard to serviceability considerations and could limit the application of FRP.
Therefore, studies are needed on basic properties of constituent materials, such as the resin and fibers, for improved stiffness of FRP bars and tendons.