Classification standard of Al powder

Jul 17, 2021

Three classification standards of aluminum powder

The characteristic index value of the aerated aluminum powder is the amount of air supplied to the aluminum powder first, which is self-evident. However, the production process of concrete aerated blocks is much more complicated than that of ordinary concrete, and the large amount of air supply alone does not necessarily produce ideal air vents. If the outgassing is too fast and too early, the radon gas will easily escape from the slurry, resulting in collapse or agglomeration of vent holes, and the aluminum powder will outgas too late or the outgassing will last too long (long tail). When the slurry gradually thickens and loses its circulation, the vapor will eventually be forced into the slurry, resulting in a connection between the vent hole and the air intake. This situation is called "suppression", which is very harmful to the crafts. Therefore, to identify the characteristics of aluminum powder, we must also consider its gas evolution characteristics.
Classification standard of Al powder(图1)
1. Covered water area
Covered water area is a physical index value for qualitatively analyzing the particle size and appearance of aluminum powder. The water cover area of aluminum powder refers to the area where 1 gram of aluminum powder is continuously sorted on the river surface according to the single side of the particles, and there is no visible gap between the particles. Under normal circumstances, the size of the aluminum powder matches the water cover area. The softer the aluminum powder, the larger the water covered area. In addition, it should also be seen that the thinner the aluminum powder particles, the broad-leaved shape, and the larger the water cover area. However, some powder spraying particles are not large, and air oxidation is more serious. Although the water covered area is large, the specificity deviation. Therefore, simply using the water cover area can not fully reflect the characteristics of aluminum powder.
2. Gas curve
Whether the physical properties of aluminum powder is necessary to consider the production of concrete aerated blocks is ultimately reflected in the entire process of gassing and swelling of the slurry. Therefore, measuring the whole process of aluminum powder in the slurry can make a comprehensive comment on its characteristics. People call the curve of the change of gas production and supply with time during the whole process of aluminum powder gas generation as aluminum. Pink's gas curve. Generally, the selected method is to use the standard gas curve test requirements of the German Cipollex company for aluminum powder: 70mg of aluminum powder, at a temperature of 45℃, composed of 50g concrete, 30ml water, and 30ml with a molar concentration of 0.1mol/l Gas generation is carried out in cement mortar composed of NaOH aqueous solution, and the correlation curve between the gas generation time and the gas generation and supply (calculated as the thermodynamic temperature of the gas generation and supply) is the gas generation curve. Generally, people stipulate that the gas curve of aluminum powder falls within a certain range.
3. Regulations on aluminum powder paste
Nowadays, most processing plants have already changed to aluminum powder paste. In addition to the general characteristics of gas-producing aluminum powder, aluminum powder paste is also not easy to dust, does not cause electrostatic induction, is not afraid of damp and cold, and has a certain foam stabilization effect. It is an excellent variety for safety and economic development. The quality specified by JC/T407 for aluminum powder paste.