Rubber inflatable mandrel use the most beautiful encounter, octagonal-shaped rubber balloon wall thickness of 3.2mm, made of two layers of natural rubber and a layer of hot-rolled 12MPA anti Labrador vulcanization step molding steel with high tensile strength, elastic and air tightness, to form a cavity concrete elements, mainly used in the bridge plate precast tunnel ditches production in prefabricated concrete hollow member, the inner mold into a steel cage, and start using the pump inflated, inflated After having sufficient strength to withstand the pressure of concrete, pouring concrete, until the initial setting of concrete, open the valve deflated balloon mold, and can be withdrawn from the mold cavity. octagonal rubber balloon as a bridge building site construction lightened offer a must. Use; (1) After it stops, open the inlet valve, air compressor inflated. Inflated with air pressure gauge control monitoring, octagonal-shaped rubber balloon inflation pressure in accordance with the model set, when the pressure to use the pressure, the valves are closed to stop inflation. (2) Note that no excessive pressure when inflated. (3) for the first time before the examination inflated, each measuring up to full time use pressure to determine the required number of compressor according to the initial setting time of concrete to ensure that vertical ribs and the upper plate girder concrete initial setting of concrete in its lower Before you start pouring avoid construction joints, to ensure the integrity of each piece of plate girder concrete. The field test with 6m3 / min air compressor inflatable, each octagonal rubber balloon inflation time of 15 ~ 20min, takes less time, less impact on the formation of concrete construction joints. Precast Slab process, the concrete heat, hot vulcanized air bag, do not open plastic. The product can meet the long and large diameter hollow member, shaped cross-section of the hollow member pouring requirement Product is simple, lightweight, easy to use, with good anti-aging properties, a wide range of application and can be reused many times, can greatly reduce the cost and improve the construction schedule.