Concrete is a highly disordered, multi-phase, porous heterogeneous material, in the process of cement gel coagulation and hardening, it is inevitable that some structural defects such as pores and micro-cracks will be formed inside, and then affected by factors such as ambient temperature, humidity, external load, action between components, construction links, etc., visible cracks are easy to appear.
As a brittle material, the tensile capacity of concrete is far less than its compressive capacity, and the tensile stress caused by restraint during the shrinkage and deformation of concrete is the most important reason for its cracks, and it will not crack without constraint.
There are two ways to solve this problem, one is to enhance the tensile capacity of concrete, and the other is to disperse the tensile stress of concrete. After hundreds of years of development, the concrete industry has many mature standards and specifications to solve this kind of problem. However, in actual engineering, problems still emerge one after another, mainly due to the lack of an effective mechanism to integrate the achievements of different fields and improve the overall level of the industry.
In the concrete floor, there is often a phenomenon of hollow drum cracking of the screed, if you learn from some mature processes of laminated panels, you can greatly reduce the occurrence of problems, and it is a good choice for those projects with higher quality requirements.
In the Code for the Design of Concrete Structures GB 50010-2010, it is said that it is:
The thickness of the laminated concrete of the laminated plate should not be less than 40mm, and the concrete concrete strength grade should not be lower than C25. The surface of the prefabricated plate should be made with a rough surface with a concave and convex difference of not less than 4mm. For the laminated plate and the prestressed laminated plate that bear a larger load, it is advisable to set the structural reinforcement extending into the superimposed layer on the prefabricated bottom plate. “
Although in the construction of concrete flooring, the base layer is also required to take measures to make a rough surface, but the roughness is not as high as 4mm. The laminated slab is also provided with structural reinforcement that runs through the new and old concrete, which disperses the internal tensile stress;If such a reliable connection method is used on the floor, the effect is definitely much better than laying reinforcement mesh sheets in the floor.
Problems that are difficult to solve in one dimension may not be a matter in another dimension, and the cost may not increase much, and if there is a quality accident, the loss will be greater.