A small amount of pan-slurry is necessary to ensure the construction quality, because it shows that the solid particles have sunk and the castable has shrunk and become dense. Especially when the low-moisture castable is vibrated, it often means that the castable is dense and can stop vibrating. A small amount of pan-slurry can also prevent the surface of castable from drying too fast, which is convenient for surface finishing.
A large amount of water immersion is harmful, because water immersion weakens the strength of castable on the surface of hardened castings and produces a large number of "powder layers" that are easy to peel off. If the castable is poured in layers, if the laitance on the surface layer is not removed, the bonding force between the layers of castable will be destroyed.
Operating conditions:
1. Concrete layer formwork, steel bar, top embedded parts and pipes have all been installed, which meet the design requirements after inspection, and the concealment and pre-inspection procedures have been handled.
2. Shelves and. After the concrete pouring is completed and passed the inspection.
3. Cement, sand, stone and admixture meet the requirements of relevant standards after inspection, and the laboratory has issued a notice of concrete mixture ratio.
4. The scale (or automatic feeding system) has been tested accurately, and the vibrator (rod) has passed the trial operation.
5. The foreman has conducted comprehensive construction technical training for the operation team according to the construction scheme, and the application for concrete pouring has been approved.
Extended data:
Column pouring:
Before pouring the 1. column, the bottom should be filled with semi-stone concrete with a thickness of 5- 10 cm, which is the same as the concrete mixture ratio. Column concrete should be vibrated in layers, and the thickness of each layer should not exceed 50cm when using internal vibrator. Vibrating rods shall not touch steel bars and embedded parts. In addition to vibrating above, someone should knock the template at any time below.
2. If the height of the column is less than 3m, it can be directly poured under the ash at the top of the column. When the column height is more than 3m, measures should be taken to cast the column in sections with string tubes. The height of each section shall not exceed 2 meters.
3. Column concrete should be poured at one time. If construction joints are needed, they should be left under the main girder.
Precautions:
1. When concrete is poured into formwork, formwork or steel skeleton shall not be dumped centrally. When the pouring height is more than 2M, the string tube and chute should be used for discharging, and the free falling height from the discharging nozzle to the pouring layer should not be greater than1.5m.
2. Concrete must be poured within 5 hours (from the start of the train). In order to prevent cold joint during concrete pouring (cold joint refers to the construction quality joint formed when the time interval between the upper and lower layers of concrete pouring exceeds the initial setting time), the concrete pouring time for two times shall not exceed 65438 0.5 hours, and the joint shall be continuously stirred with a vibrating rod.
3. When pouring, the vibrating duration should make the concrete surface appear laitance, no bubbles and no sinking. The insertion points of vibrators are arranged evenly in plum blossom shape, and move in the order of determinant, and the distance of moving position should not be greater than 40CM. Make sure there is no vibration leakage, but no vibration.
4. When pouring beam slab concrete, beam concrete should be poured first, starting from the beam-column joint, so as to ensure the vibrating compaction of the beam-column joint, and then circulating pouring with the slab by grouting method, but no cold joint can occur.
5. When concrete pouring is about to be completed, estimate the remaining concrete quantity and the remaining concrete quantity, and contact the mixing station for reasonable scheduling.
Integral pouring concrete lining is the main construction method of forming lining, which is widely used in underground projects such as railway tunnels, highway tunnels and hydraulic tunnels. This shaped lining is convenient for mechanized construction and has good integrity and impermeability; In full-face excavation, it is beneficial to use metal formwork trolley to pour concrete. Disadvantages are many processes, slow construction progress, unable to bear the load immediately after pouring concrete, and poor chemical stability.
References:
Baidu encyclopedia-concrete pouring