What are the various methods for leaving ducts during the post-tensioning construction of prestressed concrete? What issues should be noted?
Thread Content
I would like to ask everyone: in the post-tensioning construction of prestressed concrete, how many methods are there for creating ducts? What issues should be noted? Last edited by Lailai on 2009-3-23 12:43]
①Steel pipe core extraction method: The steel pipe must be straight, with a smooth surface; it should be rust-free before being embedded, coated with oil, and firmly secured to the rebar framework. The tube extraction sequence should follow a top-to-bottom order; the speed at which tubes are extracted should be consistent, with drilling and rotation occurring simultaneously. ②Rubber tube core-pulling method: One end of the rubber tube is sealed, while the other end is inflated. Before pouring concrete, the hose is filled with water and air at a pressure of 0.5–0.8 N/mm2. The tube extraction time is slightly later than that of core extraction for steel tubes. Before removing the tube, release water to reduce pressure; once the cross-section of the rubber tube shrinks and it separates from the concrete, the tube can be removed. The order of removal is generally from top to bottom, and from curved sections to straight sections. ③The embedded bellows method: When using this method for construction, it is advisable to mark lines on the side formwork of the component in advance. Repeated bending should be avoided as much as possible when employing this method, to prevent cracks in the tube walls ； At the same time, it is necessary to prevent the pipe wall from being burned by welding sparks. After installation, check for any damage to the pipe walls and ensure that the joints are sealed properly.