19 Concrete building materials, namely, beams, poles, blocks, bricks and slabs; Building construction materials, namely, cement mixes, mortars, limestone, gypsum, sandstone and gravel; Road construction materials, namely, asphalt composition paving; Transportable non-metal scaffolding; Non-metal gutter pipes; Non-metal underground diaphragms in the nature of structural supports used in the construction of bridges, roads and tunnels