Rubber-inflated core mold, a type of expandable and contractible cylindrical bag, made by vulcanizing rubber with a fiber-reinforced layer, boasts high tensile strength, elasticity, and airtightness. It is used to form cavities in concrete components. During the production of hollow structures, it is placed in the center and filled with compressed air. Once inflated, it has sufficient strength to withstand the pressure of concrete, replacing traditional wooden, bamboo, or steel molds. Upon opening the valve, the bladder contracts and can be removed from the cavity. Easy to use, cost-effective, and durable, it can be reused multiple times. Deflated, it can be softly contracted, folded, or curled. Suitable for creating holes in reinforced concrete components, including piles, trusses, roof panels, columns, beams, civil engineering, and hydraulic engineering (shipyards, shipways, docks). Construction practices have proven that the bladder hole-punching process is simple, saves materials, and offers versatile shapes such as circular, elliptical, rectangular, arched, octagonal, trapezoidal, and more. It can also create straight holes and variable cross-section holes, making building structures lighter, thin-walled, and hollow, and altering the properties of concrete, thus replacing the traditional rigid molds. This is a cost-reducing and time-saving concrete product accessory.
Manufacturing Process:
Rubber inflatable core molds, in terms of manufacturing, early production used cold bonding techniques. Over time, however, this was gradually replaced by the one-step molding process of heat pressing and vulcanization due to continuous practical experience. Some manufacturers still use this method due to its relatively lower production costs. However, a critical drawback of the cold bonding process is that the adhesive joints can fail when overheated, significantly reducing the lifespan compared to core molds produced using the heat pressing and vulcanization one-step molding process.
The rubber and anti-pull fabric are heat-pressed and vulcanized into one piece using a single molding process, ensuring a smooth surface without any seams and capable of withstanding sufficient concrete heat and pressure.
Next, the choice of raw materials in the same production process can greatly vary the quality of the rubber inflation core mold. The selection between natural rubber and synthetic rubber, as well as the tensile strength of the anti-pull fabric, all directly affect the quality and service life, or the number of times the product can be recycled.
Construction Method:
1. Place the core mold inside the steel cage, ensuring the longitudinal joints are facing up, inflate to the specified pressure, and close the valve. To prevent the concrete from floating upwards during vibration, it is necessary to secure the top, bottom, left, and right sides according to the construction process. Use formwork tension bolts to apply pressure and counteract the upward float.
2. Cast concrete using a high-frequency insert vibrator, vibration from both sides simultaneously to prevent the core mold from shifting left or right. The end of the vibrator must not touch the core mold to avoid piercing and causing leakage.
3. Once the concrete has initially set, the core mold can be removed, and the mold can be demolded (open the air valve).
