Causes of cracks in concrete hollow block walls

　　Reasons for cracks in concrete hollow block walls:

　　1. Reasons for raw materials.砼Small hollow blocks are concrete made of coarse aggregates of gravel or pebbles, which have the brittleness of concrete. At the same time, the block has the important characteristics of shrinkage. After 28 days of natural curing, the dry shrinkage is about 60%. Therefore, such a small hollow block is inevitable cracks in the wall; Cement, lime, sand and other materials in blocks and masonry mortars have a wide range of sources, and their performance is not stable enough, so it will also affect the quality of blocks and masonry mortar.

　　2. Design reasons. The block is very sensitive to the uneven settlement of the foundation. If the uneven settlement of the foundation is insufficiently estimated in the design, it is easy to produce stepped cracks in the wall and vertical cracks in the wall of the bottom sill. In addition, most of the roofs currently have no insulation measures at the cornice, resulting in stepped cracks in the top wall. The random selection of the roof insulation material without regard to the effect of reducing the temperature difference can also lead to the occurrence of cracks. At the junction of the concrete column and the small hollow block, there is a lack of corresponding measures to control the crack.

　　3. Construction reasons. The difference in technical level between masonry workers causes the quality of masonry to be unstable, which is an important factor in the quality of the wall. During the construction, the mortar used is low in strength, the surface ash and other dirt on the block are not cleaned, and the ash is too large during the masonry. The adhesion between the mortar and the block will be poor, resulting in cracks. Secondly, the block The factory storage period is not enough. When the volume shrinkage of the block is not completed, the wall is built and shrinkage cracks are generated. The arrangement of the blocks is unreasonable, and no ribs or steel mesh are added as required in the horizontal gray joints, resulting in cracks. There is no reliable connection between the vertical and horizontal walls between the wall, the ring beam and the floor. At the construction site, the stacking site and rain-proof measures for small hollow blocks are not implemented according to the specifications, which will cause horizontal cracks in the wall.