Some early and a few more recent segmental bridges erected by span-by-span erection in the US utilized Type B joints between precast segments primarily to reduce cost, reduce construction time and eliminate potential problems with epoxy applications. The structures were generally designed with only external post-tensioned tendons protected by polyethylene ducts. No reinforcing or prestressing steel extended across the joints. For some bridges rubber tubes, rubber gaskets, compression seals, etc., were used in a transverse recesses formed in the segment joint face in an attempt to keep moisture from penetrating through the joint.
After the first few bridges were completed, various signs of undesirable performance began to be detected. This included such items as leakage through the joint into the box and spalling of the top slab concrete at the joint. Also, opening of the joints was possible under some load conditions such as seismic, thermal gradient, temperature, creep, shrinkage and overloads. After performance information was known some states prohibited the use of Type B joints. General conclusions were that the use of Type A joints would improve the performance of the structure by keeping moisture from leaking through the joints into the interior of the box section and most future designs included epoxy joints (Type A).
Early editions of The AASHTO Guide Specifications for Design and Construction of Segmental Concrete Bridges and the AASHTO LRFD Bridge Design Specifications included provisions for Type B joints as an option. The provisions for Type B joints and their use were at the discretion of the owner or designer. A change was made to both the AASHTO Specifications to delete provisions for Type B joints by the AASHTO Subcommittee on Bridges and Structures in 2002. Accordingly, the current specifications do not include provisions for Type B joints for segmental construction and require the joints between precast units to be either cast-in-place closures or match cast with epoxy (Type A joints). The background for the change was based primarily on the prevention of water leakage through the joint into the box and possible impact the water leakage may have on the durability of external post-tensioning tendons. Type A epoxy joints provide lubrication to assist in the fit up and alignment of segments and minimize the effect of hard points of contact between segments.
