19 Concrete, clay and composite building materials and articles, namely, bricks and blocks; pavers, namely, segmental pavers; concrete poles, piles and bridge components; concrete bearers, stumps, beams and girders; boardwalks made of concrete; treads made of concrete for boardwalks, decking, promenades, access ways, jetties, wharfs and crossings; concrete decking and access ways; crossings, wharfs, promenades and jetties, made of concrete