How to deal with concrete shrinkage cracks, and how to prevent and control concrete shrinkage cracks

Hello, glad to answer for you.

The principles and methods of dealing with concrete shrinkage cracks are roughly as follows:

1. For some subtle cracks, it will not affect the use, and there is no need to deal with them, and some subtle cracks can heal on their own over time.

2. For the cracks that appear in the initial setting of concrete, the cracks can be healed by the method of secondary calendering, and then the maintenance can be strengthened.

3. Surface repair is a simple and common repair method, which is mainly suitable for the treatment of surface cracks and deep cracks that are stable and have no impact on the bearing capacity of the structure.

4. For cracks that affect the safety of the structure, after inviting the design or experts to inspect, discuss and determine the treatment plan, the methods are: grouting, pouring epoxy resin, etc., or structural reinforcement, using bonded steel, carbon fiber reinforcement, etc. It is necessary to come up with a special structural reinforcement plan, and ask a professional team to carry out the construction.

The formation of concrete shrinkage cracks is closely related to the design reinforcement ratio, concrete water-cement ratio, concrete pouring, vibration, maintenance and construction load. There are many reasons for the formation, and the treatment depends on the actual situation and whether the building has strict requirements to control cracks. In general, only the surface is hung with net plastering, and larger gaps need to be caulked or filled.

Hello, expansion joints of concrete.

You can fill the foam board first and then pour it with asphalt.

Concrete shrinkage cracks mostly appear on the surface of newly poured and exposed structural components, and there are shrinkage cracks such as plastic shrinkage, subsidence shrinkage, and dry shrinkage. Today we have summarized its prevention and control methods, let's take a look.

Preparation before construction.

1) Under the condition of satisfying the operating performance, try to reduce the slump of precast concrete. (2) In the case of meeting the requirements of the net spacing of structural reinforcement, try to select stones with larger particle size and strictly control their mud content, so as to reduce the amount of water used during mixing, thereby reducing the deformation of precast concrete. (3) Try to avoid using cement with high strength, because too fine cement hydrates quickly and is easy to crack.

4) Repeated wiping pressure before and after initial coagulation to heal the plastic shrinkage cracks that have appeared.

Cement. Different varieties of cement have different shrinkage, and cement varieties with small shrinkage should be selected. The smaller the strength grade of cement, the smaller the amount per unit volume, the smaller the shrinkage.

Aggregate. Aggregates include stones, sand, etc., and aggregates have a limiting effect on the shrinkage of cement, so aggregates with high elasticity and good grading without impurities should be selected. In addition, the smaller the aggregate particle size, the higher the sand rate and the greater the shrinkage.

Water. Excessive water consumption in precast concrete can cause excessive shrinkage of precast concrete, so too much water should not be added.

Admixtures and admixtures.

The addition of admixtures can make the precast concrete obtain the characteristics of early strength and high strength retardation, and the superplasticizer can be added to the precast concrete to greatly reduce the water consumption, so as to improve the strength and reduce shrinkage. In addition, admixtures such as fly ash can reduce the amount of cement while maintaining the same strength of precast concrete, and thus shrinkage.

Mix ratio. The shrinkage of precast concrete is different with different mix ratios, and the construction should be mixed in strict accordance with the construction mix ratio, and the precast concrete mix ratio should not be changed at will. The water-cement ratio should be strictly controlled, and the larger the water-cement ratio, the greater the shrinkage.

Maintenance conditions. Extended moist curing can delay the onset of shrinkage but has little effect on shrinkage size, whereas enhanced early curing can reduce the chance of shrinkage crack cracking or delay the appearance of cracking. Therefore, after the precast concrete is poured, it should be covered with film or geotextile in time to protect the moisture of the surface of the precast concrete, and the higher the humidity, the greater the temperature, and the longer the curing time, the smaller the shrinkage of the precast concrete.

Rational construction measures.

Appropriately increase the reinforcement ratio of precast concrete components, and the gripping force between the steel bar and the precast concrete can also partially resist the shrinkage of the precast concrete; Setting up the spring pouring belt can also reduce or eliminate the occurrence of shrinkage cracks.

Reasonable construction methods.

Precast concrete shall not be segregated in transportation and pouring, and it should be noted that the temperature should not be too high during construction in summer and too low during construction in winter; Before pouring precast concrete, the base and formwork should be poured thoroughly with water. Large-volume pre-formal shed concrete to be layered or sectional construction, in order to prevent the internal and external temperature difference is too large, can also be buried in the precast concrete inside the cold water pipe, so that the precast concrete internal and external temperature difference is less than 25.

Concrete is a heterogeneous mixture composed of a variety of materials, and the changes in water content and temperature during the hardening process will cause uneven volume deformation to form cracks.

The volumetric deformation in the process of concrete hardening can generally be divided into two types: one is the plastic shrinkage of the concrete before hardening, and the other is the volumetric deformation caused by the temperature rise formed by the heat of hydration during the condensation process.

The hydration process of cement is accompanied by the common change of temperature and humidity, and the heat exchange and humidity exchange also occur at the same time, so the temperature shrinkage deformation caused by the action of temperature and the humidity shrinkage deformation caused by the action of humidity occur at the same time, and the two are intertwined and work together, and it is difficult to make a clear distinction between them and separate them from each other.

1. Check the size of the cracks in the concrete, if it is very small, choose to repair it by grouting it, this method is relatively simple and convenient, and the cost of filling is relatively low.

2. If the crack of the concrete is cracked, you need to clean the gap around, then fill it with the crack of the epoxy slurry tank, apply it nearby and wait for it to be completely injected, and wait for it to melt before applying it to the crack.

3. If there are many cracks, you can choose to fill them with a professional crack repair agent, and this method should also clean the edges of the cracks, remove the surrounding sand and dust, and then use a roller to touch the repair agent for treatment.