DURABILITY OF ARAMID PRETENSIONED ELEMENTS IN A MARINE-ENVIRONMENT

This paper presents results from a 3-year exposure study to evaluate t he durability of aramid fiber reinforced plastic (AFRP) pretensioned e lements used as piles driven in a marine environment. The aramid/epoxy composite ARAPREE was used in the investigation. Ten AFRP pretensione d beams designed to fail by rupture of the pretensioning rods were pre -cracked and then exposed to wet/dry cycles in saltwater to simulate t ide change. Exposed beams were periodically removed and tested to fail ure to determine their service and ultimate response. Changes in respo nse relative to that of unexposed control specimens were used to evalu ate durability. The results showed that exposure had a relatively mino r effect on the ultimate capacity of the AFRP pretensioned beams. Howe ver there was evidence of bond deterioration in the failure mode of sp ecimens exposed for two or more years. More importantly, characteristi c bond splitting cracks developed in one beam that had been exposed fo r 3 years. This suggests that while AFRP may have adequate chemical re sistance to concrete's alkalinity, its bond with concrete is vulnerabl e under wet/dry cycles. Thus, AFRP is not the ideal candidate for repl acing steel in pretensioned piles driven in tidal waters.