DURABILITY OF CARBON PRETENSIONED ELEMENTS IN A MARINE-ENVIRONMENT

This paper presents results from a 3-year exposure study to evaluate t he durability of carbon fiber reinforced polymer (CFRP) pretensioned e lements which were used as piles in a marine environment. Ten CFRP pre tensioned beams, designed to fail in flexure by rupture of the pretens ioning rods, were precracked and then exposed to wet/dry cycles in sal t water to simulate tide change. Exposed beams were periodically remov ed and tested for failure to determine their service and ultimate resp onse. Changes in response compared to unexposed control specimens were used to evaluate durability. The results of the study indicate that w hile concrete's alkaline environment had no effect on the CFRP rods, t he mode of failure was sensitive to the extent of precracking damage s ustained prior to exposure. The bond between CFRP and concrete showed evidence of degradation in severely damaged specimens, possibly due to moisture absorption by the epoxy matrix. In less damaged specimens, t here was no commensurate bond degradation. Thus, if CFRP is used to re place steel in pretensioned piles, driving stresses should be carefull y monitored to prevent any damage.