| 摘要 |
The pipes or moulded parts are surrounded by rings of plastic foam which are kept compressed to 15-25% of their initial volume by rings made of a material such as asbestos cement, reinforced with fibre, which forms a good bond with mortar. The gap between the holding rings and the brickwork is then filled out with mortar. The pipes or moulded parts are preferably made of hard PVC. |
