AAC Blocks Uses Fly Ash Concrete

AAC is a Recycled Building Material

cementandflyashAAC is a construction building material which makes buildings sustainable or greener.  Along with renewable energies it’s a busy area of investment. AAC blocks requires less energy to produce compared to existing
brick-making techniques. Brick building materials are very energy-intensive. For example, in order to make bricks, clay is melted at more than 2,000 degrees Fahrenheit for more than a day. Brick production creates 13 billion lbs of CO2 each year and the cement industry is the second largest emitter of pollutants after utility companies.

AAC blocks are a recycled building material since they are made from a mixture of sand, fly ash, mine tailings, slag or other sources of silica, portland cement; quick lime; anhydrite; water; and an chemical aerating agent such as aluminum powder or paste.  The autoclaved aerated concrete building blocks are larger than traditional bricks, and
are marketed as the best recycled materials for green buildings used to construct all types of buildings to home builders, developers, manufacturers, retailers and the government.  Entire residential homes and commercial properties are build using the AAC buiding system.

ACC construction projects qualify for LEED rating when using this innovative and recycled building material.

Clean Coal, Anyone?

You’ve heard the greenwashing term “clean coal”, haven’t you? Well, there’s no such thing as “clean coal”. There’s nothing clean, green or healthy about “clean coal”.

Coal isn’t cheap energy when the environmental destruction from mining methods and the leftover ash are included in the equation. For example, the human produced CO2 is directly affecting the acidity of the ocean; water contamination by a cocktail of highly toxic metals including arsenic, lead, mercury, cadmium, beryllium, chromium, cobalt – all known human health hazards.

Coal waste is so toxic that when questioned about fly ash dumps by Sen. Barbara Boxer (D-Calif.), the DHS stated that that her committee can’t publicly disclose the location of coal ash dumps across the country for national security reasons.

“The pollution is so toxic, so dangerous, that an enemy of the United States?or a storm or some other disrupting event?could easily cause them to spill out and lay waste to any area nearby.”

Source: Huffington Post: coal ash toxic waste  spills too dangerous to reveal to the public

Coal ash aka fly ash is more radioactive than nuclear waste and belongs in a hazardous waste dump somewhere in a outerspace but aac blocks contain no radioactive decay. When you think about the uses of coal, aac concrete is the only useful benefit.

Safety of Cement and Concrete Products Containing Fly Ash:

“The fly ash is safely encapsulated with portland cement and/or blast furnace slag which are known to react with the flyash and effectively bind toxic metals, hence the aac block products are known to be stable. In other words, the toxic ash is encased and cannot leach. Autoclaved aerated concrete blocks are safe and contain the best performance properties of any building materials. In other words, aac blocks have nothing in common with the sub-standard, highly toxic and green-washed, non-fired, non-portland-cement-mixed fly ash bricks.”

For example, while greenwashed brick manufacturers products will disintegrate in a 31% mutriatic acid (HCl), aac concrete blocks (and clay bricks) are inert,  thus no leaching of toxic fly ash waste material.

What is the safety of cement and concrete products containing fly ash?

“Fly ash is used worldwide throughout the Portland cement/concrete production chain for production of cement clinker, in blended cements and as a cement replacement in concrete, particularly in the EU, Canada, China and Asia and S. Africa.”

“The standards in these countries for blended cements and Portland cement-substituted concretes allow for usages from ~ 0% to 20% in the US, and from ~ 5% to 40% in the rest of the world. The actual usage rates are lower: ~ 0% to 15% in the US and ~ 0% to 25% in the rest of the world, with the overall averages being about ~ 3% to 5%.”

“When fly ash is used to manufacture cement clinker, it partially substitutes for clay, bauxite and iron ore, and the final product is indistinguishable from normal cement (the toxic metals present in the fly ash are vaporized ? and the emissions from the kiln are scrubbed).

When fly ash is used in blended cements or in concrete, it undergoes a series of reactions with calcium-containing phases in Portland cement, resulting in the etching of fly ash particles, precipitation of calcium silicates/aluminates, exchange of calcium and magnesium in silicate/aluminate minerals with toxic metals, release of calcium and further etching and formation of silicate/aluminate phases, etc. The net effect is that the Portland cement degrades, mobilizes and mineralizes fly ash and in doing so binds the toxics into stable silicate/aluminate minerals. Portland cement is unique in this respect. Its high calcium content and reactivity enable it to encapsulate and effectively immobilize fly ash and other hazardous wastes, including heavy-metal containing industrial sludges, low-level radioactive waste, etc.”

“A number of studies have shown that at low fly ash levels, fly ash is quite effectively encapsulated by Portland cement, and that cements, concretes and products made with Portland cement plus fly ash appear to be stable and have a low hazard. However, there is still a significant hazard of metals leaching from the fly ash under certain
conditions ? such as in salt water, acid rain, etc, and of metals exposure during recycling.”  Source: CNET.com: Facts  about fly ash in cement and concrete products.


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