Crack analysis, treatment and prevention of building exterior paint finishes!

With the continuous development and progress of social economy, buildings are more and more pursuing external aesthetics, which requires complex exterior wall decoration to reflect, and deepening of exterior wall decorative line coating stone and so on is more and more essential

1.

After investigation and research, combined with the current construction specifications, the reasons for cracks were summarized and summarized: cracking at the grass-roots level, unqualified raw materials, environmental factors, and management problems

1.

Common causes of grassroots cracking are as follows:

1.

In order to ensure the needs of building appearance when designing the building façade compartment seam, designers usually only design the dividing seam at the upper and lower horizontal lines of the door and window openings, resulting in an excessive area of the wall compartment block, and the mortar plaster base layer is very easy to crack due to thermal expansion and contraction caused by temperature changes

1.

The raw materials for the base mortar include cement, sand, water and other major materials

1.

Temperature, bottom base treatment, maintenance and other grass roots construction processes can cause cracking

1.

The grass-roots mortar is not cleaned according to the requirements of the construction code, the pulp is brushed, the reinforcement is filled, the layering is smeared and other cutting-edge behaviors, resulting in poor quality of the grass-roots construction and cracks

There are many types of exterior wall coatings, the quality is uneven, some varieties even have no quality standards, no engineering experience, some product instructions are too simple, no mixing ratio instructions, no use of environmental instructions, etc.

3.
Environmental factors

3.
1 Low temperature
.
The low temperature is not conducive to the growth of the strength of the mortar base layer, nor is it conducive to the growth of the adhesive strength of
the coating.

3.
2 high temperature
.
The temperature is too far away from the mortar base layer inside and outside can not be synchronously deformed, easy to produce cracks
.

3.
3 Humid
.
Excessive humidity can easily lead to some types of coatings with slow adhesion strength and even flow.

3.
4 Direct sunlight
.

Some substances in the paint may decompose under sunlight, causing aging and causing a decrease
in strength.

4.
Management factors

4.
1 Construction management personnel, operator quality, labor skills factors
.
At present, most of the people on the construction line are older migrant workers, with poor labor skills, weak quality awareness, and lax
quality acceptance procedures.
Young and middle-aged people are not keen on manual labor, resulting in a serious loss of skilled personnel and worrying
quality of personnel.

4.
2 The effect of construction technology is poor
.
At present, many construction workers do not attach importance to the labor skills training of labor workers, and the construction is more and ignores the education and training work
.

5.
Crack prevention measures

5.
1 The division of the grass-roots design is unreasonable
.
In order to solve this problem, the façade of the building should be designed with horizontal compartments and vertical compartments, and the area is best controlled by 3 to 5, so that the area effectively reduces the crack problem of the mortar plastering base layer due to excessive size, and the decorative effect brought by the wall paint is also greatly strengthened
.

5.
The raw materials of the base mortar are unqualified
.
The cement with qualified quality is selected, and the strength, volume stability, coagulation time, fineness and other indicators of cement are qualified
.
The sand should be used as much as possible in the middle sand river sand, which should be cleaned before use, and the mud content is up to standard
.
Water as far as possible to use drinking water, the minerals refer to the standard
.
Lime is used after curing to a specified time
.

5.
3 Bottom base cleanup
.
The bottom layer is flat, the garbage is cleaned up, there is no oil stain, and the sprinkler is wet
.

5.
4 Mix mortar
according to the prescribed proportion or test ratio.
Accurate measurement of raw materials, in strict accordance with the specified proportion of mortar category or test ratio for deployment, do a good job of sand moisture content testing, sand moisture content should be subtracted
.

5.
5 Strict construction process to control the quality
of plastering.
Do a good job of ash cake and reinforcement before plastering, shake the pulp and brush the hair, and start plastering after the hair is pulled to a certain strength, control the amount of ash mixed, and do it with the mixing
.
Pay attention to the convergence of the timing of each layer of plastering, and start to do the lower layer plastering at the upper layer when the upper layer strength reaches 70%-80% of the design strength
.

5.
6 Try to choose the time when the construction environment conditions are good
.
The adverse effects of bad weather such as high temperature, severe cold, rain and snow on the quality of construction should be avoided

6.
Exterior wall paint

At present, most of the construction has not paid much attention to the construction process of exterior wall coatings, so that the exterior wall coatings crack and fall
off within a short period of time after the completion of the project.

6.
1 Reasons

6.
1.
1 Factors influencing raw materials

The quality of the exterior wall paint used in construction is poor, and the durability and adhesion are greatly reduced; The putty used is made of white cement, talcum powder and 107 glue, so that the water resistance and alkali resistance of such putty are not good, the strength of the adhesion performance is also greatly weakened, and it is easy to appear coating bulging, cracking and shedding
.

6.
1.
2 Influencing factors at the grassroots level

Because the plastered base layer of the building façade does not get sufficient maintenance time, resulting in an increase in water content and alkali content, the adhesion between the coating and the base layer is reduced, and the durability of the paint is also reduced; Problems such as cracks and loosening at the base or surface are not dealt with in time; The surface of the base layer contains a large number of impurities, and mud or floating slurry will have an impact on
quality.

6.
1.
3 Weather Influencing Factors

If the weather temperature during coating is too low, the emulsion-type paint cannot have a high-quality film-forming effect; If the weather humidity is too large, the drying of the coating film is not complete

6.
1.
4 Influencing factors of painting

If the coating layer is too thick at one time, the coating is easy to crack; The time interval between the two coating layers is too short, and the first time the paint is not completely dried out on the second time, and the paint is not easy to stick firmly
.

7.
Prevention

7.
1 Selection of exterior wall coatings

Exterior wall coatings should choose excellent products made by regular manufacturers and refuse to use inferior coatings

7.
2 Plastering base layer maintenance

The maintenance time of the external wall plastering base should be sufficient, and the normal temperature state needs at least fourteen days; The water content of the base layer needs to be detected to be less than 8 percent, and the PH value is less than 10 to be constructed
.

7.
3 Pay attention to temperature and humidity

The temperature should be considered before painting, if the emulsion-type paint is used for coating, the temperature should not be less than 5 °C; Paint should not be performed in foggy weather or if the humidity in the air exceeds
85%.

In order to put an end to the cracking phenomenon of exterior wall paint finish, you need to put the quality of the most critical in the stage, whether it is plastering or painting, material quality and construction quality are extremely important, no matter how subtle the problem, in the quality of the building and aesthetics are huge hidden dangers, we should pay attention to it, do our best to do everything well, if everyone in the industry will be in all stages of construction meticulously believe that not only the architectural paint problem, the construction project can be a breakthrough in the stage problem
。