| 摘要 |
A plurality of formwork elements are provided, each of which is curved according to an arc of a circle and which are assembled to form an inner formwork wall and an outer formwork wall. Each of said formwork elements have two vertical edges provided with angled portions which form engaging faces, which engage engaging faces of horizontally adjacent formwork elements of the same formwork wall. Said angled portions of said formwork elements of said outer formwork wall extend outwardly. Said angled portions of said formwork elements of said inner formwork wall extend inwardly. |
