This object is an inflatable rubber culvert balloon (also known as a pneumatic rubber core mold or inflatable mandrel), which is used as a temporary internal formwork to cast hollow concrete pipes, culverts, and tunnels.Function: Inflated with air to support wet concrete during casting, then deflated via the valve system and pulled out once the concrete cures.Material: Heavy-duty reinforced rubber layers integrated with high-strength fabric for elasticity and pressure retention.
