Constructions and construction elements not of metal, namely, bridges, tunnels and underpaths; constructions and construction elements of concrete, namely, beams, desks, slabs, plates and boards; modular construction elements of concrete, namely, slabs, bricks and walls; prefabricated concrete elements for the building industry and for public or private works, civil engineering and agricultural engineering, namely, prefabricated concrete walls, prefabricated concrete slabs, prefabricated concrete desks, prefabricated concrete rails and prefabricated concrete struts; transportable non-metallic constructions and construction elements; transportable concrete constructions and construction elements; rigid non-metallic pipes and conduits for buildings and their parts sold as a unit; concrete pipes and conduits and their parts sold as a unit for the building industry and for public and private works, civil engineering and agricultural engineering