What are the reasons for the oblique cracks in the building floor wall and the cracks in the cast-in-place concrete floor?

1. Cracks caused by the shrinkage of concrete itself: Because the volume of concrete shrinks when it condenses and hardens in air, when the surrounding consolidation cannot shrink freely, tensile stress will be generated, resulting in cracks.

2. Because the grace of the wall is relatively large, and the thickness of the cast-in-place surface of the floor slab is generally between 8- 10cm, although the strength meets the requirements, the stiffness of the floor slab to the wall is reduced, so some weak parts, such as sudden changes in section, construction joints and threading pipes, often appear first, and cracks appear there.

3. The main reason for the oblique cracks in the wall under the window sill is the uneven settlement of the foundation. Secondly, due to the large openings of doors and windows in the longitudinal wall (some engineering openings are not lintels when they are more than 2M, and the foundation has not been treated accordingly), the stiffness of this part is obviously weakened, which leads to the stress concentration at the four corners of the window opening and causes the wall to crack. In addition, the splayed cracks under the windowsill are often more on the sunny side (south wall) than on the shady side (north wall), so the influence of temperature change stress cannot be ruled out.

At present, the structural forms of residential buildings are basically the same, and there is not much change. Designers tend to focus only on strength and ignore deformation. There is no joint where expansion joints are set, and the foundation treatment is not careful, which often leads to excessive settlement and deformation of residential projects, resulting in cracks in walls and floors.

Because the construction period is too short, the project was put into use before the foundation and main structure settled. In the process of use, the deformation of foundation and ground continues to deform, resulting in some projects without cracks when delivered, but cracks appear after a period of use. This phenomenon often occurs in the engineering of artificial foundation treatment.

6. In order to catch up with the construction period, some construction units removed the formwork when the concrete failed to meet the strength requirements, and the construction load was too early, which led to internal cracks in the hardening process of concrete, which is also one of the reasons that can not be ignored.