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   Background:

    The coal combustion process produces one of the largest unregulated solid wastes in the United States . Although in recent years a growing percentage of the airborne particulates (‘fly ash') found uses as a filler in the cement industry, recent changes in EPA regulations aimed at reducing greenhouse gasses (GHG) emissions has resulted in most of the 70 million tons of fly ash produced annually in the US becoming unusable for current construction processes due to high levels of unburned carbon, ammonia and/or other impurities. Furthermore, the significant costs associated with transporting and land filling solids derived from coal combustion could be further increased due to liabilities associated with the eventual leaching of harmful levels of aluminum, chloride, iron, manganese and toxic levels of arsenic, nickel, lead, copper and zinc into subterranean water tables. Thus, the development of innovative technologies for converting tens of million tons of combustion bi-products annually into useful products is an urgent need.

   Pollution and global warming:

    Actual production of Portland cement contributes 13.5 billion tons of carbon dioxide per year (1 ton of carbon dioxide for each ton of produced cement) which is equivalent to 7% of the total global emission of carbon dioxide to the atmosphere. Geopolymer is made out of waste materials like fly ash, therefore does not have an industry of itself, and does not contribute to carbon dioxide emissions.

                    
                
   Energy Consumption :

    The Portland cement production process is one of the most energy consuming mass production proceses. A mixture of powdered raw materials requires heating to over 1400 C to obtain cement powder, with its corresponding high use of fuels. Geopolymer, on the other hand, can be produced out of waste products like fly ash, or out of calcined kaolin (meta-kaolin) which consumes significantly less energy.

 
 

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