Foamed cement is a foam that has a certain tension after the cement foaming agent is pressurized by an air compressor, and then the foam and the cement slurry are simultaneously stirred, and the cement will continuously expand during the stirring process, when the expansion effect reaches a predetermined ratio. After that, foamed cement can be formed.
Commonly used fields are floor heating insulation, roof insulation, and filling of walls of frame structures.
In the material selection, the cement is generally made of 32.5R ordinary Portland cement. There are two kinds of foaming agents on the market. There are two kinds of animal and plant in the market. For the heat preservation industry, we advocate animal use because of the performance. The foaming agent has the characteristics of independent pores and high strength, and the foamed cement has the advantages of light bulk density, uniform pore distribution, good heat preservation, certain impermeability and good sound insulation; and vegetable foaming agent. Due to the characteristics of continuous bubbles, the foaming cement made with respect to the animal foaming agent has a high bulk density, a slightly poor heat preservation property, and is inferior to the animal foaming agent in impermeability and sound insulation, but the vegetable foaming The agent has the advantages of large foaming amount and good fluidity, and is easier to handle than the animal foaming agent in the floor heating construction. In addition, we recommend that the foaming agent manufacturer produce foaming agents with different characteristics according to the construction needs. For example, for inclined roofing, we recommend pure animal foaming agent, mainly using its poor fluidity and good strength. For flat roofing and floor heating construction, we recommend using a mixed foaming agent because the mixed foaming agent is in animal nature. Based on the addition of certain botanical ingredients, the foaming ratio is increased, the fluidity is enhanced, and it is easy to level, which is more suitable for floor heating construction.
Let's talk about the advantages of foamed cement for roofing and floor insulation projects.
1. Excellent thermal insulation performance: thermal conductivity is 0.080-0.125 W/(m?k), and thermal resistance is about 20-30 times that of ordinary concrete.
2. Sound insulation effect: Foam concrete contains a large number of independent bubbles, and the distribution is even, the sound absorption capacity is 0.09-0.19%, which is 5 times that of ordinary concrete, and has the function of effective sound insulation.
3. Good integrity: on-site pouring construction, combined with the main project, no need to leave the gap and vent pipe.
4. Low density: The dry bulk density is 250-600 kg / m3, which is 1/5-1/8 of the density of ordinary concrete, which can reduce the overall load of the building.
5. High compressive strength: compressive strength is 0.9-4.5Mpa.
6. Better water resistance: independent dense bubbles and good integrity, so that it has a certain waterproof performance.
7. Anti-cracking: low shrinkage and crack resistance 8 times that of ordinary concrete.
8. Long life: the same life as the main project.
9. The construction process is simple: there is no need to find another slope layer on the flat roof.
Some preparations before construction
It is recommended to use ordinary Portland cement with a thickness of 32.5 R or more, or slag Portland cement. When it has an aggressive medium, it should be selected according to the design requirements.
It is not recommended to add other substances such as sand.
The debris should be cleaned and wetted with water. The problem that should be paid attention to when sprinkling water is that the water needs to be evenly distributed, and there should be no water accumulation, which can effectively prevent precipitation and collapse in future construction.
Foams used in the preparation and use of foams should generally be made of special equipment. The foam should be controlled to a diameter of 0.5-2 mm and should be elastic and not easily broken. The concrete foam should be used with the preparation and the retention time should not exceed 20 minutes.
One problem that needs to be paid attention to during construction is that when the total thickness exceeds 10 cm, it is preferable to layer the construction.
The flat roof adopts the structure to find the slope, the slope should not be less than 3%; the material should be used to find the slope, the slope should be 2%; the gutter and the gully should be longitudinally sloped, the slope should not be less than 1%, and the water drop of the bottom should not exceed 150mm.
Due to the low consistency of the foam concrete and the high fluidity, the thickness of the inclined roof insulation is not easy to control. In order to ensure the quality, the inclined roof should be constructed by combining precast concrete slabs with on-site foamed concrete on-site casting. The specific methods are: (1) prefabricated foam concrete slabs; (2) pouring 10-20 mm foam concrete on the roof and laying prefabricated foam concrete slabs. (3) Leveling with low-lying concrete with foam concrete. Because the prefabricated foam concrete slab and the in-situ foamed concrete are produced by the same material and the same process, the thermal expansion coefficients of the two are identical and can be well combined, thus ensuring good insulation and integrity of the roof.
In addition, when the bulk density is less than 300kg / m3, it is advisable to add a coagulant during construction. The amount of coagulant is generally 4%---6% of the amount of cement, and the dosage is appropriately increased according to the type of coagulant, construction temperature and engineering requirements. Less. However, the problem to be noted is that less than 300kg / m3 can only be used as the insulation level, and it should never be used as the load-bearing part.
The temperature at the construction site should not be lower than 3 °C. At the same time, after the construction is completed, moisturizing should be carried out. The allowable deviation of the thickness of the foam concrete insulation layer is usually +10%, -5% in the design. The surface flatness is 5 mm.
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