Among them, the main construction factors are too large protective layer of negative reinforcement of slab (serious collapse of reinforcement), insufficient protective layer of concrete at the bottom of slab or excessive chloride content of sand.
Then analyze the treatment methods of various cracks:
First, thoroughly deal with the destructive cracks caused by unqualified cement stability or chemical reaction of different cement varieties in concrete, that is, knock out the concrete and pour it again.
Second, for cracks caused by stress, targeted reinforcement measures can be taken according to the causes of cracks. If there are cracks in the floor that have affected the structural safety, in addition to flushing the V-shaped groove along the cracks, epoxy resin liquid is poured into the cracks by pressure, and measures such as sticking flat steel or carbon fiber cloth are also adopted to strengthen the floor.
When strengthening with carbon fiber cloth, for a single crack, in addition to sticking along the seam, it is necessary to expand the width at intervals perpendicular to the direction of the seam; For multiple intersecting seams, paste them into a hash shape with the same spacing and width. (The width of the cloth is about 300 mm)
Three, caused by temperature, concrete shrinkage, construction and other factors of non-stress crack treatment is as follows:
1. For cracks on the surface of general concrete floor, the cracks can be cleaned first, and then filled with epoxy resin liquid or closed by surface painting after drying. If cracks are found before final setting during construction, they can be treated with plastering.
2. For the treatment of other general cracks (the width is between 0.05 mm and 0.2 mm), the construction sequence is as follows: after the slab joints are cleaned, they shall be leveled and maintained with 1: 2 or1:kloc-0/cement mortar, and sealed to restore the look and feel. (Limited to a few short and non-penetrating joints)
3. When the crack (width greater than 0.2mm) is large, a splayed groove should be chiseled along the crack. After cleaning, smooth it with 1: 2 cement mortar, or repair it with epoxy putty. (Limited to a few short and non-penetrating joints)
4. When there are large cracks in the floor, static load test should be carried out on the floor to check its structural safety. If necessary, a layer of steel wire mesh can be added to the floor to improve the integrity of the floor. Or seal the board with epoxy resin liquid (waterproof layer is also acceptable), and stick carbon fiber cloth at the bottom of the board into a well shape with equal spacing and width.
5. For the long and penetrating dangerous structural cracks with the crack width greater than 0.2mm, the treatment method is also: in addition to flushing the V-groove along the joint, epoxy resin liquid is injected into the joint under pressure to seal it, and measures such as sticking flat steel or carbon fiber cloth are adopted to reinforce the floor.
When strengthening with carbon fiber cloth, for a single crack, in addition to sticking along the seam, it is necessary to expand the width at intervals perpendicular to the direction of the seam; For multiple intersecting seams, paste them into a hash shape with the same spacing and width. (The width of the cloth is about 300 mm)
6. When the number of cracks with long length, long length and non-long length is too large, the bottom of the plate is only pasted vertically and horizontally.
Extended data
Classification definition
Cast-in-place reinforced concrete floor
Its floor has good integrity, durability, earthquake resistance and high rigidity, and can adapt to various shapes of building planes. It is convenient for equipment to leave holes or set embedded parts, but the template consumption is large and the construction period is long. According to the different structure, cast-in-place floor can be divided into the following four types:
Cast-in-place reinforced concrete floor slab: When the distance between load-bearing walls is not large, such as the kitchen and bathroom of a house, the reinforced concrete floor slab can be directly placed on the wall without beams and columns. The span of the board is generally 2-3 meters, and the thickness of the board is about 70-80 mm. ..
Reinforced concrete multi-ribbed floor: also known as beam slab floor, is the most common form of cast-in-place floor. It consists of a main board, a secondary beam and a main beam. The main beam can be supported by columns and walls. All plates, ribs, main beams and columns are cast-in-situ after formwork support. The general span is 1.7-2.5m and the thickness is 60-80mm.
Flat slab without beam: it is a flat slab with equal thickness directly supported on columns with column caps, and there are no main beams and secondary beams. Its structure is conducive to lighting and ventilation, and it is also convenient to install pipes and arrange wires. Under the same clearance condition, the height of the building can be reduced. Its disadvantage is low stiffness, which is not conducive to bearing a large concentrated load.
Floor slab: it is a floor slab that is cast-in-place into a flat slab without beam and directly supported on the wall. It is the simplest form, and is suitable for rooms with small plane size (such as kitchens and bathrooms of mixed-structure houses) and corridors of public buildings. Slab floor can be divided into one-way slab, two-way slab and cantilever slab according to the surrounding supporting conditions and the ratio of long and short sides of slab plane.
Precast reinforced concrete floor slab
The use of this kind of floor is to divide the floor into several components, such as beams and plates, prefabricate them in the prefabrication factory or construction site, and then install them. Its advantages are that it can save formwork, improve working conditions during production and speed up construction progress; However, the integrity is poor, and certain hoisting and installation equipment is needed. With the improvement of building industrialization, especially the extensive use of prestressed concrete technology, its application will be more and more extensive. According to its structure, it can be divided into the following categories:
Solid flat plate: The solid flat plate is simple to manufacture and saves templates, and is suitable for corridor plates, platform plates and other parts with small spans.
Trough plate: it is a kind of beam-slab composite member, which consists of panel and longitudinal rib. The load acting on the trough-shaped plate is transferred from the plate to the longitudinal ribs, and then from the longitudinal ribs to the walls or beams at both ends of the plate. In order to increase the rigidity of the trough-shaped plate, transverse ribs should be added between the two longitudinal ribs, and the two ends of the plate should be closed with end ribs.
Hollow slab: the upper and lower surfaces are smooth, and the sound insulation effect is good, which is widely used in the floors and roofs of civil buildings. According to the shape of its holes, there are square holes, oval holes and round holes.
References:
Baidu encyclopedia-floor