What is a Concrete Masonry Unit?

When the block is used as the main material of the building, the radionuclide limit should comply with the "Radionuclide Limit for Building Materials" (GB6566-2010).

Concrete block

Right!

When the block is used as the main material of the building, the radionuclide limit should comply with the "Radionuclide Limit for Building Materials" (GB6566-2010).

Chinese name

Concrete block

General technical requirements

Radionuclide limit

Sexual performance

Workability

Composition of material structure

Cement, coarse aggregate (crushed or pebble)

When the block is used as the main material of the building, the radionuclide limit should comply with the "Radionuclide Limit for Building Materials" (GB6566-2010). When the specific radioactivity of the natural radionuclides radium-226, thorium-232, and potassium-40 in the building's main material satisfies IRa 1.0 and Ir 1.0 at the same time, its production and sales and use range are not limited. For the main building materials with a hollow ratio greater than 25%, the specific radioactivity of the natural radionuclides radium-226, thorium-232, and potassium-40 satisfies IRa 1.0 and Ir 1.3 at the same time. limit.

The Ministry of Finance and the State Environmental Protection Administration's document "Caiku [2006] No. 90" stipulates that when state agencies, institutions and organizations at all levels use financial funds for procurement, they must purchase environmentally labeled products first, and must not purchase products that endanger the environment and human health. product. The building blocks implement the "Technical Requirements for Building Blocks of Environmental Labeling Products" (HJ / T207-2005) standard, and their main technical contents are as follows:

Waste and industrial by-products used in products (such as straw, wood chips, slag, fly ash,

The main items are as follows:

Causes of cracks in concrete block walls

1. Raw material reasons. Small hollow blocks are concrete made of coarse aggregate with gravel or pebble, which has the brittleness of concrete. At the same time, the block has the important characteristics of shrinkage. After 28 days of natural curing, the shrinkage is about 60% complete. Therefore, it is inevitable that such a small hollow block will crack in the wall; it is used for small hollow 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 block and masonry mortars.

2. Design reasons. The block is very sensitive to the uneven settlement of the foundation. If the uneven settlement of the foundation is underestimated in the design, stepped cracks in the wall and vertical cracks in the bottom sill wall are likely to occur. In addition, most roofs are not insulated at the cornices, resulting in stepped cracks in the top wall. The random selection of roof insulation materials without considering the effect of reducing the temperature difference will also cause cracks. At the junction of concrete columns and small concrete hollow blocks, there are no corresponding measures to control the generation of cracks.

3. Construction reasons. The difference in the technical level between the masonry workers causes the instability of the masonry quality, which is an important factor causing the quality problems of the wall. During construction, the strength of the mortar used is low, dirt such as floating ash on the surface of the block is not treated cleanly, and the ash is spread too large during masonry, and the poor adhesion between the mortar and the block will cause cracks; second, the block The factory storage period is not enough, and the wall is built before the shrinkage of the block volume is completed, resulting in shrinkage cracks. The arrangement of the blocks was unreasonable, and no tie bars or reinforcing meshes were added in the horizontal gray joints in accordance with regulations, resulting in cracks. There is no reliable connection at the intersection of vertical and horizontal walls between walls, ring beams and floors. The stacking site of small hollow blocks at the construction site, rain-shielding measures, etc. have not been implemented in accordance with the requirements of the specifications, which will cause horizontal cracks in the wall.

4. Reasons for use. After the project is completed, when the user renovates the buried pipeline, the wall is randomly drilled, which destroys the integrity of the wall and causes the wall to open. 1. In addition to strengthening the inspection of the main specifications of concrete hollow blocks, auxiliary specifications should be added. The age of the blocks provided by the component factory should be guaranteed to be more than 28 days; strengthen the detection of the stability of the cement and control the mud content of the sand, preferably the blocks of manufacturers with good product quality and reputability Resolutely refuse to use substandard products.

Concrete block prevention measures

1. Do design optimization. In order to reduce the adverse effect of the temperature stress caused by the temperature difference on the upper wall, it is recommended to install reinforced concrete wall strips or reinforced wall strips along the internal and external walls and gables at the windowsills at the ends of the building. The key to controlling cracks in the top wall is to reduce the temperature difference between the roof and the wall. Therefore, both the thermal insulation layer and the thermal insulation layer must be used, and the thickness of the thermal insulation layer at the eaves must meet the requirements of the allowable temperature difference. At the same time, the insulation layer should be fully covered, and no gaps should appear at the cornice. Separate joints should be provided at appropriate locations on the roof. Reinforced concrete window sill beams are installed at the windowsills on each floor to reduce cracks caused by pressure differences. At the same time, the strength level of the masonry mortar under the windowsill of the bottom layer is improved. If the foundation is uneven, increase the rigidity of the ground circle beam, and set 4 steel bar spot welded mesh panels in the second and fourth skin gray joints of the bottom sill wall to control the occurrence of vertical cracks.

2. Construction control measures. Masonry workers should be certified to work. Before starting the post, you should make a technical explanation, and require that the same part of the wall on each floor should be constructed by the same person. During construction, the determined mix ratio of masonry mortar shall be strictly implemented. When laying horizontal mortar joints, use the mortar method to spread the mortar. When laying vertical joints, first spread the small block end up with mortar, then squeeze the wall tightly, and use a trowel to insert and compact in the vertical joints. Follow the construction and sew along to ensure that the wall has sufficient tensile and shear strength. If it is necessary to move the small block that has been built or the small block that has been hit, it should be repaved to control the generation of cracks around the block. The inner powder of the top layer should be carried out after the construction of the roof insulation layer and insulation layer to reduce the influence of temperature difference. The external wall stucco should be constructed after the structure is capped, and after the wall shrinkage is basically stable, to prevent future stucco cracking. During the decoration and use process, the integrity of the wall shall not be arbitrarily destroyed without the consent of the relevant management department.