Concrete cracks are a common phenomenon in concrete structures. Concrete has become a popular structure because of its wide range of materials, low price, high compressive strength, and the ability to be poured into various shapes. It also has good fire resistance, is not easy to weather, and has low maintenance costs. The most widely used building material in building structures in the world today. Its appearance will not only reduce the impermeability of the building and affect the use function of the building, but also cause corrosion of steel bars, carbonization of concrete, reduce the durability of the material, and affect the load-bearing capacity of the building. Therefore, concrete cracks must be treated Carefully study and treat them differently. Most of the early cracks in concrete complained by customers in the civil market are due to shrinkage strain caused by water loss during drying before and after initial setting and thermal strain generated by hydration heat. Usually, 2/3 of concrete stress comes from temperature changes, and 1/3 comes from temperature changes. Dry shrinkage and wet swelling. To this end, targeted analysis and processing must be carried out, and various effective preventive measures must be taken during construction to prevent the occurrence and development of cracks and ensure the safety of buildings and components.
1. Polymer immersion method
Gravity penetration method Low viscosity liquid resin can be used to seal cracks of no less than 0.1mm in pavement and bridge decks. Apply concrete admixture resin to the surface, or build a temporary embankment along the crack on a horizontal surface to allow the resin to overflow on the crack surface.
The vacuum infiltration method is more suitable for sealing multiple irregular surface cracks. First seal the crack surface and remove the vacuum to remove all air in the cracks and pores. Pure epoxy resin slurry is then injected into the crack surface under atmospheric pressure.
2. Grouting method
Ordinary cement grouting cracks in the rock foundation of large-volume dams, thick concrete walls, or hydraulic structures is sometimes sealed by injecting Portland cement mortar. .
Polymer grouting is a grouting material based on urethane or acrylamide polymers that reacts with water to form a solid precipitate or foam material that seals cracks. Can be used in humid environments.
3. Resin infusion method Epoxy resin is a common crack infusion material. It has high mechanical strength and can resist most chemical attacks encountered by concrete. The resin can be poured into cracks of 0.05mm.
4. Nailing method When it is necessary to restore the tensile strength of the main crack section, it is more appropriate to use the nailing method. It is particularly suitable for locking movable cracks in situations where the surrounding structure will not be damaged.
5. Surface sealing method This is a simple and common crack repair method. It is used to repair static cracks that have little impact on the structure and prevent the intrusion of water vapor, chemicals and carbon dioxide by sealing the cracks.
6. Drilling and caulking method This method is usually used to fill cracks in walls. If sealing and waterproofing are required, the hole should be filled with flexible asphalt instead of mortar; if the role of the plug is more important, the hole should be filled with epoxy resin.
7. Flexible sealing method It is usually more appropriate to convert movable cracks into moving joints. Cut a groove along the edge of the crack and fill it with a suitable flexible material. Use insulation at the bottom of the joints.
8. Paste method This method can be used when the movement does not act on more than one plane, or when the excessive movement exceeds the allowable range of a normal-sized groove, or when the groove cannot be cut. Cover the crack with flexible sealing tape, taping only the edges of the tape.
9. Additional steel bar method: Seal the crack, then drill holes through the crack plane in a direction of about 90°, inject epoxy resin into the hole, and then insert the steel bar into the hole to bond it into a whole.
10. Dry embedding method: mortar with a low water-cement ratio is continuously inserted into the cracks by hand to form a dense mortar that is closely connected to the original concrete structure. First, groove the crack surface, clean it, apply interface agent, and continuously embed low water-cement ratio mortar.
11. Laminated surface method When there are a large number of cracks on the surface of the structure, and it is too expensive to treat each crack individually by other methods, this method is very effective to seal and cover (not repair) the cracks. This method is very effective for the occasional large-area network cracks.
12. Self-closing method Concrete relies on itself to close cracks, which is called “self-closing”. This is a phenomenon that occurs when moisture is present and there is no tensile stress. Mainly used to repair structures in damp environments.
13. Coatings and other surface treatments A wide range of surface-impregnating sealants and coatings can be used to repair cracked concrete structures. If concrete cracks have stabilized, they can be successfully repaired with paint. But it is not suitable for operation in low temperature areas.
The early curing practice of concrete has proved that most of the common cracks in concrete are surface cracks of different depths. The main reason is that the sudden temperature drop in cold areas caused by the temperature gradient also easily forms cracks. Therefore, the insulation of concrete is particularly important to prevent early cracks on the surface
The above are the methods and precautions for treating concrete cracks with concrete admixtures. I hope it will be helpful to you.
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