Precast concrete products and structures, namely, voided concrete slabs, concrete girders, concrete abutments, concrete bent caps, concrete pile caps, and concrete wingwalls; girders, not of metal; prestressed concrete products and structures, namely, voided concrete slabs, concrete girders, concrete abutments, concrete bent caps, concrete pile caps, and concrete wingwalls;

prefabricated metal bridges; construction implements, primarily made of metal, namely, fully welded, pre-engineered, pre-fabricated, modular unit bridges, with steel decks or fittings for concrete forming