First, the causes of cracks in the wall
Cause 1: cracks appear in the foundation.
Cracks caused by uneven settlement of foundation. All the load of the building is finally transferred to the foundation through the foundation, and the uneven settlement of the building foundation occurs due to the diffusion of stress; When the temperature of the upper foundation soil drops below 0℃, the upper foundation soil begins to freeze, and the lower water rises continuously due to capillary action to form ice crystals in the frozen layer, which expand in volume and make the soil uplift upward.
Reason 2: cracks caused by temperature changes.
Thermal expansion and cold contraction are the basic physical properties of most objects. Masonry is no exception. Due to uniform temperature change, uneven contraction of masonry, or uneven expansion and contraction constraints of masonry, the temperature stress exceeds the strength of masonry, which leads to cracking of masonry.
Reason three: cracks caused by materials.
Due to the introduction of national measures to protect cultivated land, the use of clay solid bricks and clay hollow bricks is generally prohibited and restricted, and various blocks are widely used. However, cracks and water seepage generally exist in cement block walls. The wet expansion and dry shrinkage of the block are very obvious, especially in the external wall. When the drying shrinkage of the block is large, the wall is prone to cracks.
Reason 4: Cracks caused by construction.
Poor construction quality is another important aspect that leads to wall cracking. In the process of construction, masonry workers' low technical level, low quality awareness and contractors' intention to cut corners may all lead to wall cracking.
Reason five: cracks caused by design reasons.
The main manifestations are: unreasonable foundation design or insufficient drilling, resulting in uneven settlement and cracks; Due to the consideration of funds, there is no thermal insulation layer on the roof, which leads to the temperature difference between the roof structure layer and the wall, the temperature strain difference and the fission. The lintels and sill beams are not designed at the window sill, which leads to cracks in these weak stress areas, and the building is too long without expansion joints.
Second, the wall crack treatment scheme
Scheme 1: grouting reinforcement method:
Preconditions: fine cracks, few cracks and basically stable cracks.
Specific practice: make two or four test masonry columns with the same material. Divided into two groups, one group is first fractured by a press, then grouted, and then the failure tests of the two groups of masonry columns are compared. If the grouted masonry strength is basically the same as the original masonry strength, it is considered that the reinforcement is qualified. Cracks with a width of about 3.0mm can be filled; When the actual crack width is greater than 5.0mm, cement mortar can be used; When the cracks are small, pressure grouting can be used.
Solution 2: Embedding method
Prerequisite: the cracks are wide, but the number is small.
Specific practice: the mortar joint at the intersection of cracks can be filled with high-grade mortar and fine steel bars, or the embedded method can be adopted, that is, reinforced concrete wedges or hacksaws are used to reinforce the cracks at both ends and in the middle. Wedges or hacksaws can be as thick as the wall, or 1/2 or 1/3 of the wall thickness.
Scheme 3: Steel-reinforced pull rod method
Prerequisites: The wall will flash outward due to horizontal thrust, uneven settlement, expansion and contraction caused by temperature change and other reasons, resulting in large cracks in the wall or poor binding between the outer longitudinal wall and the inner transverse wall.
Specific practice: steel tie rods should be long and tied, and set along both sides of the wall. In the middle of the iron dragon rod, a bright blue screw should be added to tighten the pull rod, and the extension of the pull rod should be welded. The pull rod or pad nut exposed outside the wall can be properly treated before construction, and the pull rod and pad should be painted with antirust paint.
Scheme 4: Ring beam method.
Prerequisites: the wall is severely cracked. In order to increase the overall rigidity of the house,
Concrete practice: the strength grade of ring beam concrete is C 15-C20, and the section is at least 120× 180mm. Every 1.5-2.5m, supports (or bolts, anchors, etc. ) should be inserted into the wall and bound, and bear the weight of the ring beam. When pouring ring beam, the wall should be cut and watered to strengthen bonding.
Classification of wall cracks:
Wall cracks are cracks in the wall of the building structure, which are divided into the following four types according to the different materials.
1, concrete wall crack;
2, brick masonry wall cracks;
3. Cracks appear in new partition boards such as 3.GRC board and gypsum board;
4. Cracks often appear in walls made of different materials, such as cracks between concrete and brick masonry, such as cracks in construction holes;
How to prevent wall cracks;
1, reasonably handle the original wall.
In order to prevent the wall from cracking in the future to the greatest extent, it is best to completely eradicate the original wall, whether it is a new house or an old house. Because, if the quality of the building materials used in the original base of the new house is not good or the products are shoddy, it will cause the subsequent plastering to be not firmly bonded with the base, leading to cracking of the wall.
2, strictly control the construction process
(1) Strictly follow the wall painting standard: brush the interface agent once → treat the cracks on the wall → level gypsum → paste → scrape putty for 2-3 times → polish → brush the primer → touch-up polish → brush the top coat twice.
(2) Strictly follow the wall leveling work: leveling can't be completed at one time, but it should be carried out several times. Where the error is large, it is generally leveled with gypsum first, and then leveled with putty for 2-3 times.
(3) Control the amount of water when daubing: add a small amount of water according to the manufacturer's instructions, too much water will lead to wall cracking in the future.
3. Choose high-quality materials
When selecting materials, we must purchase them through formal sales channels, select qualified building materials products and use them in strict accordance with the product specifications.
4. Pay attention to details.
Tip: The joints of different bases are prone to cracks, so special treatment is needed during construction. For example, if the seam between the wooden frame and the wall of the wardrobe is not treated, cracks are likely to appear after the four seasons exchange. In the process of construction, the method of sticking wood veneer is usually used to cover up possible cracks. Be very careful.
The above is the relevant content of wall cracks, I hope to help everyone! Tubatu decoration network, high-quality materials, standardized technology, unified management, and after-care service make you feel at ease. Click the link below this page to enjoy exclusive free house viewing, free design quotation and other value-added benefits.
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