Mechanical splice of GFRP rebar

[TehMightyEngineer]

So, ran into an issue where we specified a continuous GFRP rebar in the interior of the top slab of a underground steam pit structure. Construction of the cast in place slab has just finished and we were about to begin casting the precast walls and top slab. All concrete will use GFRP (fiberglass) rebar as the design life of this structure is 100 years. Steam and condensation cause serious serviceability issues with carbon steel rebar in these pits we've found and they need this particular pit to last as it's cost them about $700/sq.ft. to replace these pits. Due to the potential of steam leaks and high temperatures reducing the bond strength (90% loss of bond strength calculated) we had all the bars developed away from areas that could see high temperature steam in the event of a gasket or pipe lets go. However, we just discovered that the bars delivered have be setup for a 4 ft splice right along the interior of the top slab, the worst spot for high-heat. At 10% normal bond strength I calculated a required splice of over 300 inches (hah, not happening).

So, my long-winded question is has anyone had any experience with mechanically splicing FRP rebar? Anyone got any good ideas for increasing the bond strength of GFRP rebar at 300 degrees?

Attached is a picture of the bars for those who haven't seen GFRP rebar up close. It's fibers in a vinyl ester epoxy binder with what appears to be sand or something else on the exterior surface to roughen the bars and develop the bond.

Maine EIT, Civil/Structural.

 

[precast78]

Last time I wanted to use FRP for slab, I had a hard time trying to get the shear to work. The code gives you a such lower # for concrete shear strength compared to steel. How did you get the shear to work?

 

[TehMightyEngineer]

Had the same issues, we made the slab 14" thick.

Maine EIT, Civil/Structural.