Cement, portland, chemicals (10C)
Portland cement is a mixture of chemical substances produced by burning or sintering at high temperatures (greater than 1200.degree.C (2192.degree.F)) raw materials which are predominantly calcium carbonate, aluminum oxide, silica, and iron oxide.  The chemical substances which are manufactured are confined in a crystalline mass.  This category includes all of the chemical substances specified below when they are intentionally manufactured in the production of Portland cement.  The primary members of the category are Ca2SiO4 and Ca3SiO5.  Other compounds listed below may also be included in combination with these primary substances.:  CaAl2O4; CaAl4O7; CaAl12O1; Ca3Al2O6; Ca12Al14O33; CaO; Ca2Fe2O5;  Ca2Al2SiO7; Ca4Al6SO16; Ca12Al14Cl2O32; Ca12Al14F2O32; Ca4Al2Fe2O10; Ca6A14Fe2O15