Avondale Shipyards, Inc., a subsidiary of Ogden Corporation, announced that it has signed a contract to build a self-discharging cement barge at a price of approximately $16 million for the Atlantic Cement Company, Inc. of Stamford, Conn. The barge, 420 feet long by 80 feet wide, will be used by Atlantic in the coastwise movement of bulk cement. Construction will begin in the third quarter of 1981, and the barge will be delivered during the third quarter of 1982. The price is subject to full escalation as to labor and materials cost.