What are aerated concrete blocks?
Aerated concrete block is a new type of building material with lightweight, porous, thermal insulation, good fire resistance, nailable, sawn, plannable, and has an individual seismic capacity. As early as the early 1930s, China began to produce this product, and it was widely used in high-rise frame structures. It is an excellent new building material and has the advantages of environmental protection.
Advantages of Aerated concrete blocks
1. Light bulk density, generally 500 kg/m3 to 700 kg/m3, is only equivalent to 1/4 to 1/3 of clay bricks and sand-lime bricks, and 1/5 of ordinary concrete; due to weight reduction, it will bring a series of benefits to construction projects.
a) Improve the seismic performance of buildings;
b) Reduce the cross-section size and reinforcement of building beams and columns, and reduce project cost;
c) The weight of the building is reduced, which can reduce the necessary investment;
d) Increase the use area of buildings;
e) The same structure can increase the height of the building and add floors.
2. Large strength utilization rate. Due to the lightweight of the aerated concrete block, each block can be equivalent to the volume of more than ten red bricks, so the overall strength is high, and the strength utilization rate is improved. Its strength utilization factor is 0.7-0.8, while the clay The brick strength utilization factor is 0.2-0.3, which is far smaller than the aerated concrete block.
3. Good heat insulation and heat preservation performance. Due to the structural characteristics of aerated concrete block, the thermal conductivity is significantly reduced compared to clay bricks. The thermal conductivity of aerated concrete block is 0.11～0.15W/MK, and its thermal insulation performance is five times that of clay bricks. Therefore, it can be used in the internal and external walls of buildings, roof insulation, freezer and air-conditioning rooms to improve thermal insulation Effect, thereby reducing energy consumption.
4. Good sound absorption and sound insulation performance. Aerated concrete block is a porous structure with an individual sound absorption capacity, which fully meets the proper insulation requirements.
5. Good anti-permeability. Because the aerated concrete block are closed and independent spherical structure, the water seepage has the characteristics of fast and slow. The shower nozzle is used to continuously spray the 240mm thick aerated concrete wall and 240mm thick clay brick wall. The clay brick wall is fully penetrated after 12 hours, and the water seepage depth after 72 hours of spraying on the aerated concrete wall. It is 80mm～100mm, so the exterior wall made of aerated concrete is especially suitable for the construction structure in the rainy season in the south.
6. Durability, the long-term strength of aerated concrete is stable. Exposing a 150mm×150mm×150mm specimen to the atmosphere will increase the compressive strength by 25% after one year and remain stable after ten years. According to the freeze-thaw test, if one cycle can represent the life span of 5-10 years, the strength of 15 freeze-thaw tests of aerated concrete does not decrease, indicating that its durability is better.
7. The seismic performance is good. Because the building is built with lightweight materials, the horizontal thrust during the earthquake is significantly reduced. In the great Tangshan earthquake in China in 1976, the two 5-story residential buildings of Baiwanzhuang, Beijing Building Materials Bureau, which used aerated concrete bricks, had a good structure after the earthquake and were intact. The brick-concrete dormitory building near the building has cracks of varying degrees.
8. Good processability
a) Aerated concrete blocks can be processed by sawing, and the effect is better than that of clay bricks processed with brick cutters; b) It can be nailed, and the nails can be directly nailed into the wall with a hammer, and objects of 2 to 5 kg can be suspended vertically;
c) Expansion bolts can be fixed. Generally, 6-8mm expansion bolts are punched and fixed. The bolts can bear a vertical force of 35kg and a horizontal force of 15-20kg;
d) Wooden bolts can be used to fix objects that are not subject to stress;
e) Use an electric or manual chucking device to pull out the required groove pipe on the wall to facilitate the installation of the line pipe;
d) To fix the doors and windows, you can drill holes first, then put the expansion bolts, and tighten the screws to set them on the wall.
9. Good heat and fire resistance. Aerated concrete blocks are non-combustible materials, and their fire resistance is much higher than that of ordinary concrete. They will not damage the strength before being heated at 700℃.
The raw material ratio of aerated concrete blocks
Aerated concrete block is composed of several materials like other concrete. Therefore, there is a question of which materials are used and how much each material is used. The percentage of the number of various materials used in the ingredients is called the mix ratio.
For aerated concrete blocks, to determine an adequate mix ratio, the following requirements must be met:
(1) The product has good performance and meets the requirements of construction. Among the many properties, the first is the bulk density and compressive strength. At the same time, the durability of the product must also be considered.
(2) Products or blanks have good process performance and are compatible with factory production conditions. Such as pouring stability. The fluidity (consistency) of the slurry, hardening time and simple process flow, etc.
(3) The raw materials used are a few varieties, comprehensive sources, low prices, no pollution or low pollution, and use as much industrial waste as possible. The determination and use of the mixture ratio of aerated concrete generally require the research and experiment of the theoretical mixture ratio, the resolution of the primary mixture ratio for production, and the economy of the mixture ratio. Finally, calculate and determine the formula.
The construction method of aerated concrete blocks
Aerated concrete blocks are generally used in infill walls, and the strength grades of the used blocks are generally A3.5 for partition walls and A5 for external walls. The strength of the mortar is not less than M5.
Before aerated concrete blocks are laid, a block arrangement diagram should be drawn according to the plan and elevation of the building. Set the skin number bar at the corner of the wall, remove the block skin number and block height on the skin number bar, draw the alignment line between the upper edge lines, and build according to the alignment line.
The masonry surface of aerated concrete blocks should be watered appropriately. It is advisable to use particular tools for laying aerated concrete (ash-laying shovel, saw, drill, engraving, straight frame, etc.).
The mortar joints of the aerated concrete blocks wall should be horizontal and vertical, with full mortar. The mortar fullness of horizontal mortar joints should not be less than 90%; the mortar fullness of vertical mortar joints should not be less than 80%. The thickness of the horizontal mortar joint and the width of the vertical mortar joint shall not exceed 15mm.
At the corners of the aerated concrete blocks wall, the blocks of the vertical and horizontal walls should be laid on each other, and the end faces of the separated blocks should be exposed. At the T-shaped junction of aerated concrete block walls, the cross-wall blocks should be revealed on the sidewalls and sit in the middle of the vertical wall blocks.
Without adequate measures, aerated concrete blocks shall not be used in the following parts:
(1) The part below the moisture barrier of the building;
(2) Long-term immersion or chemical corrosion environment;
(3) Walls that have been in an environment with vibration sources for a long time;
(4) The surface of the block is often in a high-temperature environment above 80℃. No scaffold eyes shall be left on the walls of aerated concrete blocks. The block walls on each floor should be built continuously without leaving any connections. If it is necessary to leave the chase, it should be kept as an oblique chase or intermittently on the and window opening.
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