| 摘要 |
The intention is to form a cavity in concrete or the like by means of a reusable shuttering apparatus, it being possible to pull out said shuttering apparatus conveniently after the concrete has hardened. The intention is, however, to avoid sagging of the shuttering apparatus. For this purpose, the shuttering apparatus exhibits a rigid or stiffened inner body (12) and a flexible outer body (14). The outer body can be expanded by a pressure medium, can be enclosed within the hardening material and determines the shape of the cavity to be formed. The inner body (12) imparts the required rigidity to the structure. It is narrower than the cavity. Once the material has hardened, the shuttering apparatus can be relieved of stress. It can then be removed from the cavity for reuse. <IMAGE>
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