Durability and bond durability of composite rebars

ABSTRACT

GFRP rebars have been developed to solve the corrosion problems often encountered with steel reinforcement. Durability tests on GFRP rebars under different conditions and in different applications throughout the world provide no uniform conclusions regarding the permissible design stress levels in GFRP bars. Long term field tests in Canada have shown excellent long-term properties of certain bars, while the results of tests on the same materials in a hotter climate are inferior The first coherent approach to bringing the results of the various test series together was developed by the fib. In this procedure secure design values of the tensile strength for any GFRP material is derived under any given environmental condition. The resulting values apply to any type of structure in environments ranging from Canada to the Arabian gulf region The bond between the GFRP bar and the surrounding concrete is also of great importance. It must be proven that the brittle material has a ductile bond behaviour. Furthermore it must be shown that the bar can transfer its force into the concrete and vice versa over the full design lifetime of the structure. The results of long-term bond tests under different environmental onditions for a specific GFRP rebar are discussed. Bond creep curves for up to 2000 hours are presented Using the newly developed approach of the fib and applying it to a modern material it is possible to define safe, yet not exceedingly conservative, design values for any possible application of any particular GFRP rebar