Hello,
Aerated concrete is perforated using aluminum, it is more about residues (esoteric in my opinion nevertheless)
This is a typical example when I talk about "dangerous half-knowledge." Once published on the internet without further explanations, the game of "telephone" starts; from ear to ear, the true content is reduced, while imagination increasingly comes to the fore...
Aluminum has recently gotten a bad reputation because it is responsible for the formation of yellow stains in the underarm area of light-colored T-shirts, shirts, and blouses. Manufacturers have reacted to this and now offer deodorants without this additive; it is interesting in this context that it is also contained in cosmetics but is (so far) bought and used by women without major concern.
***The essential basic materials or raw materials are to be specified in mass-% separately for sand, cement, quicklime, anhydrite/gypsum, pore-forming agent, water, reinforcement steel for prefabricated parts, and others (to be specified).
Example:
Sand 60 – 70 wt-%
Cement 15 – 30 wt-%
Quicklime 10 – 20 wt-%
Anhydrite/Gypsum 2 – 5 wt-%
Aluminum 0.05 – 0.1 wt-%
Additionally, 50 – 75 wt-% water (based on the solids) are used.
Further explanation of the materials used:
Sand:
The sand used is a natural raw material that contains natural accessory and trace minerals alongside the main mineral quartz (SiO2). It is an essential basic material for the hydrothermal reaction during steam curing.
Cement:
According to DIN EN 197-1; cement serves as a binding agent and is mainly produced from limestone marl or a mixture of limestone and clay. The natural raw materials are calcined and then ground.
Quicklime:
According to DIN EN 459; quicklime serves as a binding agent and is produced by calcining natural limestone.
Anhydrite / Gypsum:
According to DIN 1168; the sulfate carrier used influences the setting time of the aerated concrete and originates from natural deposits or is technically produced.
Aluminum:
Aluminum powder or paste serves as a pore-forming agent. Metallic aluminum reacts in the alkaline environment, releasing hydrogen gas that forms the pores
and escapes after the foaming process is complete.
Water:
The presence of water is the basis for the hydraulic reaction of the binders. Water is also necessary to produce a homogeneous suspension.
Release oil:
Release oil is used as a separating agent between the form and the aerated concrete mass. Polycyclic aromatic hydrocarbon (PAH)-free mineral oils are used, with long-chain additives to increase viscosity. This prevents running off in the mold and enables economical use.
The manufacturing process must be described and possibly illustrated with a simple graphic:
The ground quartz sand is mixed with lime, cement, and crushed aerated concrete recycling material, along with water and aluminum powder or paste, in a mixer to form an aqueous suspension and poured into molds. The water dissolves the lime with heat development.
The aluminum reacts in the alkaline environment. This reaction forms gaseous hydrogen, which creates the pores in the mass and escapes without residues. The pores usually have a diameter of 0.5 – 1.5 mm and are filled exclusively with air. After initial setting, semi-solid raw blocks are produced, from which the aerated concrete components are cut mechanically and with high precision.
The development of the final properties of the components takes place during subsequent steam curing for 5 – 12 hours at about 190 °C and a pressure of around 12 bar in steam pressure boilers, so-called autoclaves. Here, calcium silicate hydrates are formed from the raw materials used, corresponding to the naturally occurring mineral tobermorite. The material reaction ends with the removal from the autoclave. Thus, unlike concrete curing, the reaction only takes a few hours. After the completion of the curing process, the steam is reused for further autoclave cycles. The condensate generated is used as process water. In this way, energy is saved and environmental pollution with hot steam and exhaust gases is avoided.
***Source: Institut Bauen und Umwelt e.V.; PCR Aerated Concrete (the document is made available for download by the institute for any interested builder)
It is true that aluminum is suspected of accelerating Alzheimer’s disease; some researchers also speak of the causation principle. Those who do not want to wait for the results of ongoing research in this field and fear aluminum should strictly banish any aluminum foil from their household, buy aluminum-free cosmetics, and avoid beverages from cans.
No one needs to fear aerated concrete, however, because after completion of the manufacturing process this blowing agent is
no longer present.
Rhenish regards