How to deal with cracks on the surface of concrete, and why cracks appear inside and outside the con

For the cracks on the surface of the general concrete floor slab, the cracks can be cleaned and repaired with epoxy resin repair glue after drying.

Concrete cracking is caused by untimely curing, and this situation can only be treated with caulk.

Summary. The causes of concrete cracking include defects in structural design, uneven settlement of the foundation, untimely maintenance after pouring, premature demoulding, problems with the concrete mix ratio, excessive drying and calendering of concrete, etc., and the cracking caused by different reasons is not the same treatment method.

The causes of concrete cracking include defects in structural design, uneven settlement of the foundation, untimely maintenance after pouring, premature demoulding, problems with the concrete mix ratio, excessive drying and calendering of the concrete in the concrete of the Mixed Tomb, etc.

Causes of cracks and cracks in concrete floors: During the hardening of concrete, the cement emits a large amount of heat of hydration, and the internal temperature rises continuously, causing tensile stresses on the surface. In the later cooling process, due to the constraints of the foundation or the old concrete, tensile stress will occur inside the concrete.

The decrease in air temperature can also cause a large amount of tensile stress on the concrete surface. Cracks occur when these tensile stresses exceed the concrete's ability to resist cracking. Due to the uneven raw materials, the unstable water-cement ratio, and the segregation phenomenon in the process of transportation and pouring, the tensile strength of the same concrete is uneven, and there are many weak parts with very low tensile capacity and easy to crack.

There are several main methods for repairing concrete cracks:

1. Surface repair method: This method is very simple, the cracks on the concrete surface can be directly coated with concrete, or other repair materials can be used. The premise of using this method is that this kind of crack will not affect the bearing capacity, of course, it can also be used for leakage prevention of small cracks with a relatively large area.

2. Hair dryer repair method:

1) Use a hair dryer to blow off the floating dust inside and outside the trench.

2) Scrub the inner surface of the trench and the sanded area with absorbent cotton silk dipped in acetone or alcohol, with the aim of completely removing concrete powder and dust inside and outside the trench.

3. Structural completion method: Generally speaking, the cracks generated will reduce the durability of concrete due to overload or long-term failure to repair cracks, in which case it can be solved by structural reinforcement method.

How to deal with cracks in concrete:

1. Surface treatment method.

This includes both surface coating and surface patching. The scope of application is fine and shallow cracks that are difficult to penetrate in the slurry, cracks of hairs that do not reach the depth of the surface of the steel bar, cracks that do not leak, cracks that do not stretch, and cracks that are no longer active.

The surface patching (geomembrane or other waterproof sheet) method is suitable for anti-seepage plugging of large-area water leakage (honeycomb surface, etc., or it is not easy to determine the specific leakage location and deformation joint).

2. Filling method.

Fill the cracks directly with repair materials, which is generally used to repair wider cracks, which is simple to operate and low in cost. Cracks with a width less than and shallow depth, or cracks with filling, cracks that are difficult to achieve by grouting method, and small-scale cracks can be treated with a V-shaped groove and then filled.

3. Grouting method.

This method has a wide range of applications, from fine cracks to large cracks, and the treatment effect is good.

4. Structural reinforcement method.

Structural reinforcement method can be adopted for cracks caused by overload, reduction of concrete durability caused by cracks left untreated for a long time, and cracks caused by fire. Including section reinforcement method, anchor reinforcement method, prestress method, etc.

5. Post-pouring concrete cover-up.

For the follow-up construction of concrete such as leveling layer, post-pouring layer, surface layer, etc., the cracked concrete surface can be haired or chiseled into a rough surface, and after cleaning, flushing and wetting, the infiltration of cement slurry when the post-poured concrete is vibrated is used to bridge the cracks.

The following measures should be taken for cracks caused by geological reasons: 1. Elastic waterproof measures should be taken for cracks caused by geological reasons; 2. For cracks caused by thermal expansion and contraction, because they will not continue to develop, waterproof mortar can be used to repair, but if the cracks are in the toilet or other places that are prone to water accumulation, waterproof measures should be taken (JS waterproof paint).

1) During the hardening of concrete, the cracks caused by the limitation of volumetric deformation due to drying shrinkage can sometimes be large in width and even penetrate the entire component.

2) Because a large amount of hydration heat is not fully released during the hydration process of large concrete, the internal temperature and internal temperature of the concrete flush stove soil change dramatically, which leads to the deformation of the concrete beyond the limit, resulting in the cracking of the concrete.

3) Cracking due to plastic collapse of concrete in large-thickness components.

4) Under the constraint conditions, the volume expansion due to the thermal expansion and contraction of the concrete due to the restraint, will form temperature stress inside, while the tensile strength of the concrete is low, and it is likely to crack due to the tensile caused by temperature. In construction, cracks due to sun exposure are also relatively common.

5) After adding water and stirring, the lye in the cement reacts with the silicon oxide in the active aggregate to form a colloidal alkali, that is, silica gel, which expands and expands in the environmental medium, and the volume increases by three times, causing the concrete to crack.

6) In high temperature and strong wind weather, due to the rapid evaporation of water on the surface layer of concrete, the hydration heat inside the concrete increases, and the concrete still maintains plastic deformation for several hours after pouring, and it is easy to crack plastic shrinkage.

7) Cracking caused by the overload of the component, such as: the component will produce cracks perpendicular to the longitudinal direction of the component under the design average load or concentrated load, and form inclined cracks under the action of large shear, and extend downward.

8) When non-uniform settlement occurs in the foundation of the structure, cracks will occur and allow it to continue to expand.

9) When the reinforced concrete is corroded in the harsh environment such as water, the thickness of the concrete protective layer is limited, especially the density of the concrete with concrete, the chloride ions in the environment and the oxygen dissolved in the water will corrode the steel bar, thereby producing iron oxide, thereby producing rust, and the rust will expand, which will lead to the cracking of the concrete.

In conclusion, there are many reasons for concrete cracking. The usual approach is elastic waterproofing or waterproofing in places prone to water accumulation.

There are many remedies for concrete cracking, and generally surface repair, glue potting, concrete replacement and other methods can be used.

1. Surface repair method

As the name suggests, surface cracks are treated and applied directly with concrete or other repair materials. Usually such cracks do not affect the bearing capacity. It can also be used for leak prevention of large areas of fine cracks.

2. Glue filling method

This method can be used when cracks that affect the integrity of the structure, or when there is a high requirement for impermeability. Use pressure equipment to pressurize and press the grout glue into the crack, so that after the glue is dried and hardened, the crack is blocked, and the original concrete becomes a whole.

3. The method of concrete replacement

This method can be used if the concrete is badly damaged. This method is more effective for such situations. Remove the damaged area and replace it with new concrete or other repair materials.

Causes of concrete cracking

1. Cracks caused by temperature.

When the external environment or the internal temperature of the structure changes, the concrete will be deformed, and if the deformation is constrained, stress will be generated in the structure, and therefore cracks will occur. Sudden cooling, heat of hydration, improper construction measures during steam curing or winter construction, concrete quenching and sudden heating, uneven internal and external temperatures, and cracks are prone to appear.

2. Cracks caused by load.

In the design calculation stage, the structure is not calculated or partially omitted; The calculation model is not reasonable; The assumption of structural stress does not match the actual force; under- or under-calculation of loads; The reinforcement is set too little or arranged incorrectly; insufficient structural stiffness; Failure to construct according to the design drawings, changing the construction sequence of the structure without authorization, changing the stress mode of the structure, and not checking the fatigue strength of the structure under machine vibration are all causes of cracks.

3. Shrinkage cracks.

In practical engineering, cracks caused by shrinkage of concrete are the most common. Among the types of concrete shrinkage, plastic shrinkage and shrinkage shrinkage (dry shrinkage) are the main causes of concrete volume deformation. After the concrete is hardened, the moisture gradually decreases as the surface moisture gradually evaporates, and the volume of concrete decreases.

Because the moisture loss of the surface layer of the concrete is fast and the internal loss is slow, it produces uneven shrinkage with large surface shrinkage and small internal shrinkage.

Concrete cracking is a common problem, but if timely measures are taken to remedy it, further damage and poor performance can be avoided that affects the structural safety of the building. Here are a few common concrete crack remedies:

1.Surface repair method: For the case of small surface cracks, polymer cement mortar, polymer repair agent and other materials can be used for surface repair. These materials have good adhesion and crack resistance, which can effectively fill cracks and prevent water leakage.

2.Tensile reinforcement method: For deeper or longer cracks, the method of tensile reinforcement can be used to remedy them.

This method requires drilling holes on both sides of the crack to extend the rebar into the crack, and then using epoxy resin or other adhesive to hold the rebar in place, so as to achieve the effect of reinforcement and reinforcement.

3.Prestressed strand method: For large-area cracks or buildings with high structural safety requirements, the prestressed steel strand method can be used to remedy.

This method needs to stretch the prestressed steel strand into it after drilling holes on both sides of the crack, and then fix the steel strand with epoxy resin and other materials, so as to achieve the effect of reinforcement and reinforcement.

It should be noted that there can be many reasons for concrete cracking, such as material quality, construction technology, environmental factors, etc., so it is necessary to find out the specific cause and solve it before remediation. At the same time, the damaged area needs to be cleaned and treated before any restoration work is carried out to ensure the adhesion and compactness of the repair material.