There were 119 operating cement plants in the U.S. in' 1997, spread across 37 states and in Puerto Rico, owned by 42 companies. Inthat year Portland cement was produced at 118 plants 1997, while clinker was produced at 108 plants. Clinker kiln capacity varies between 75 and 1550 kilotonnes peryear (Research Triangle Institute, 1996; van Oss 1998).
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