Just like our common honeycomb coal, sometimes we will see a lot of cracks in some coals, and some even lack a piece. These may not be important for coal, as long as they can be burned. But let's think about what happens if this kind of work happens on the large-diameter cement pipes we usually use! At this time, we should think about why this happens.
In fact, the main reason is presented during production. Let's take a look with Xiaoxin Xiaobian now. In the production of large-diameter cement pipes, the causes of cracks? Let's take a look at them together.
First, the cause of cracks in the appearance of concrete
The cracks on the concrete surface are mostly caused by shrinkage, which can be divided into two categories:
1. The surface moisture of the freshly poured concrete is caused by transpiration and drying. The freshly poured concrete often has high external temperature and relatively low relative humidity in the air, so its surface will be dry and dry, but its interior is still plastic. Body, which leads to cracks.
2. It is caused by the temperature difference between the surface and the surface of the concrete due to the hydration heat when the concrete is hardened. Regarding the deeper concrete, during the pouring of the upper concrete, it will continuously settle due to its own weight. Then, when the concrete is initially set but not set before it is subjected to the reinforcement or the connecting bolts of the formwork, the settlement will be blocked and cracks will occur.
Second, the solution of concrete surface cracks
First, we need to effectively control the heating rate inside the concrete. We can mix the appropriate amount of mineral fly ash in the concrete production to slow down the heat release rate of hydration. Second, we can control the temperature of the raw materials. The cooling pipe is used to pass water to release the heat of hydration.
When concrete has cracks, we usually use cement paste or low-viscosity polymer for sealing to prevent water intrusion; if the crack is deep or wide, we use pressure grouting technology to repair it.