The specific gravity of aluminum is only 2.7. In the standard state, 1.241 hydrogen is produced per 1g of aluminum, so the amount is small and the cost is low. Aluminum powder has a relatively large output and a wide range of sources. It is used in the production of aerated concrete and is well controlled in technology. It is the most commonly used material for gas generation.
The aerated aluminum powder or aluminum powder paste used for aerated concrete also has a big difference. Due to the differences in production technology and quality control, even different batches of products in the same chemical company will not be exactly the same. Therefore, the actual gas evolution characteristic curve of the aluminum powder in use will have a different shape and form a different corresponding relationship with the ultimate shear stress curve of the slurry.
Although there is a short period of concentrated gas generation in the early stage of aluminum powder gas evolution, it becomes slow afterwards, and more aluminum powder stays in the slurry when it is close to thickening. In this case, the later gassing process is blocked. Suffocation and bubbling may occur, and the pouring is not stable enough.
(1) The gas evolution of aluminum powder is not concentrated
The gas generation curve rises gently, and a large amount of gas is generated after the slurry thickens. In this case, the slurry swells slowly, and the later suffocation is serious, even the slurry cannot expand normally, the bubbles in the slurry are perforated and merged, bubbling or even sinking.
(2) Poor composition of aluminum powder particles
The above phenomenon is mainly caused by the poor composition of aluminum powder particles. Although there are some fine particles, there are more large particles or some particles with low activity are mixed. If the aluminum powder is too fine, the outgassing time will be greatly advanced, in this case, if the slurry is too thin. Poor air-holding capacity, severe bubbling or even boiling may occur. In some cases, a large amount of gas may occur in the mixer, and its pouring stability will be more affected.
Aluminum powder has many uses. Because of its silver-white metallic luster, aluminum powder is commonly called aluminum silver powder or silver powder. According to market research of aluminum powder, its chemical composition is actually "aluminum" not "silver". Application range: powder coating, ink, plastic masterbatch, printing, imitation gold paper, imitation gold card, gold film, textiles, but it will oxidize and turn black when used in water-based paints and acid-base paints. It is not recommended for requirements where it is resistant to acid and alkali and combined with rainwater.