Cement pipes are not uncommon around life. Some things we can see, some things we can't see, and those invisible cement pipes, their tasks are generally very heavy. And there are some things that cannot be replaced by cement pipes, such as some special sewer pipes and gas pipes. Today's cities attach great importance to the construction of groundwater. Cement pipes are often used, so the underground system will be perfected. It is also a place where urban high-rise houses can be drained. It is related to pipes in terms of drainage. Therefore, the quality of the cement pipe is very important. At the same time, the cement pipe is also particular about the time of the installation. Let us understand the common quality problems and solutions of cement pipes, how to extend the service life of cement pipes?
I. Common quality problems of cement pipes and their causes
1. Pipe wall crack
Reinforced concrete well pipes are formed by centrifugal process, and after steam maintenance, they are formed by water cultivation. Abnormalities in the mix of raw materials, centrifugal operations, and maintenance systems can all lead to cracks. Causes of cracks in the wall of cement pipes:
(1) In the mix ratio, the water-cement ratio is too large, resulting in a large water-cement ratio after molding. During steam maintenance, due to high temperature, part of the water is transpired, resulting in shortened appearance and cracks on the inner wall of the well pipe.
(2) The well tube after centrifugal molding, because the steam delivery system is not tightly controlled during steaming. For example, when the heating rate is too fast, on the one hand, the water on the pipe wall is transpired too fast, and a large humidity gradient occurs; A large temperature difference occurs inside the pipe wall, and a water film and pores are easily formed at the interface between the aggregate and the cement mortar, and these water films and pores constitute a concentration place of temperature gradient and temperature gradient stress. Therefore, it is easy to guide the occurrence and development of cracks. When it is severe, even the inner wall of the well tube is bubbling, with a depth of 3 ~ 8mm, which severely affects the appearance quality of the well tube and even cannot be used.
(3) After the centrifugal molding is completed, when lifting into the pond for steaming, cracks occur due to the collision of the cement well pipe mold due to factors such as operators, machinery and the like.
(4) After the steam curing is demoulded, the well pipe is hung into the steam curing tank without cooling, and the sharp temperature difference will cause shortening cracks in the pipe wall.
(5) The demolding strength is too low, which causes cracks due to external force during demolding.
2.The inner wall is exposed with stones and rough.
The main reasons for the formation of exposed stones and rough surfaces on the inner wall are: raw material ratio, well pipe mold, process operation, and other factors. The sand content in the raw materials is low or the water-cement ratio is too small. During centrifugal molding, the resistance between the mixture increases. When the centrifugal force is less than or equal to its comprehensive resistance, the coarse aggregate and cement mortar are difficult to delaminate, and the mixture is difficult. Dense, the inner and outer surface can not form a cement-rich slurry layer, and then constitute the shortcomings of exposed walls and rough inequality. When the water-cement ratio is too large, because the coarse aggregate and the cement mortar are likely to form a water film, the cement slurry and water are discharged together during centrifugation, making the internal and external surface cement slurry lacking and rough.
3, exposed ribs, hidden ribs, end steel hoop deflection
Regarding the general production process, the steel frame uses a combination of machinery and craftsmanship. When exposed ribs are present, plastic gaskets are generally not installed or less installed or are not installed in the correct position, forming a reinforced cage that is biased to one side during centrifugation, and then there are exposed or hidden ribs after the well tube is formed. The reasons for the formation of internal exposed tendons are mostly due to improper operation when forming by technology, so that the reinforced cage exhibits internal ribs, or the concrete mixture is not evenly arranged during centrifugal forming, the lack of internal protective layer shows exposed tendons, and the end steel hoop is formed. The deflection is mainly caused by the unevenness of the end of the skeleton forming machine or the deformation of the reinforcing cage caused by external forces.
4 Rough mucosa and outer wall
The normal well tube requires the outer wall to be lubricated without the disadvantages of rough inequality. The main reasons for the formation of the mucous membrane are the dirty cleaning of the cement well pipe mold, the uneven release of the release agent or the failure of the release agent, and the low release strength of the concrete. Excessive modification of the release agent will affect the normal hydration of the external concrete and constitute the disadvantage of rough appearance; the slump of other concretes is too low, and it will show the defects of numbness and incompact mixture.