19 Building materials (non-metallic), non-metallic rigid pipes for building, building panels, not of metal, cement slabs, joists, not of metal, framework, not of metal, for building, railway sleepers, not of metal, concrete sleepers, in particular concrete switch sleepers, railway sleepers, not of metal, concrete building elements, paving blocks, not of metal, paving slabs, not of metal, crash barriers, not of metal, for roads, support rails, retaining walls, concrete and cement tiles