Ash Grove Cement Co is laying off two-thirds of 68 workers at an old, high-cost plant in eastern Idaho to save money amid an economic downturn that’s dented the construction industry.

Ash Grove, based in Overland Park, Kan, said its Inkom facility will halt clinker production January 1.

Only about 20 employees in Inkom will be needed to produce finished cement as well as operate grinding and other facilities that will get clinker from other Ash Grove plants in the region.

Ash Grove is shuttering clinker production in Inkom as U.S. cement consumption drops.

The Portland Cement Association said consumption fell 13% during 2008 and could slip additional 12% in 2009, a development that’s forced other cement makers including Holcim Inc. to shutter plants, too.