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ML NEVADA CEMENT COMPANY April 22 , 2015 Mr . Fiomi O' Neill Director of Operations Kleen Industrial Services 50 Oak Court # Suite 210 Danville, CA 94526 Re : Recycling Spent Materials Dear Mr. O ' Neill : In response to your request concerning the recyclability of spent materials containing iron oxide (Fe203 ), silica oxide ( Si02), calcium oxide (CaO) , and alumina oxide (A1203 ) in the manufacture of Portland cement clinker, Nevada Cement has the capacity and desire to use these materials as they are produced . Spent materials such as those listed above, are used in the Portland cement manufacturing process as an ingredient for the high iron oxide (Fe203 ) , silica oxide ( Si02 ), calcium oxide (CaO) , and alumina oxide (A1203 ) content of spent materials . Since most spent materials have already been heated , there is no additional CO2 to liberate . Therefore, the CO2 produced per ton of cement will decrease . Replacing raw feed with spent abrasives also eliminates the need to quarry raw material , reducing additional CO2 emissions . Portland cement is made from raw materials rich in the oxides of calcium, alumina, iron , and silica content. These materials are proportioned and ground into a fine mixture called " 'raw mix" this mixture is then sintered in a kiln at temperatures in excess of 2700 ° F . In the kiln the " raw mix" melts and forms " clinker, " this clinker exits the kiln and is air cooled . The cooled clinker is then ground with gypsum to produce Portland cement. Due to the large number of oxide rich materials that may be available throughout the United States and the world there is no set of national standards or specifications that regulate the use of spent materials or any other ingredient(s) as raw materials in Portland cement kilns . This does not mean that Portland cement manufacturing is without standards or specifications . Cement manufactures often have a set of internal standards or specifications for the quality of the raw materials . The reason for this is that each Portland cement kiln uses raw materials from varying sources or deposits . Making the formula for each Portland cement kiln unique owing to the differences in oxide concentrations found in their raw material sources (quarry) . Portland cement product standards are set forth in ASTM C- 150 . This standard or specification has been around in its present form (more or less) since 1940 . Prior to C- 150 , ASTM had other specifications for Portland cement dating back to ASTMS founding in 1889 . ASTM C- 150 covers all types of portend cements with two types of specifications or standards, one being chemical composition the other physical properties . Both standards must be met in order for the cement manufactured to be considered Portland cement . ASTM C- 150 also contains 13 test methods for the testing of the chemical and physical properties . These test methods are very specialized with very few qualified laboratories able to do most or all the tests . Generally speaking there is only a hand frill of laboratories nationally (other than the quality control laboratories of the manufacturing plants) that have the equipment and expertise necessary to do the tests as specified by ASTM C450 . Nevada Cements Portland cement does meet ASTM C- 150 specifications . Pagel of 2