Nation

Martin Marietta Corp. announced that Stephen P. Zelnak Jr., president of Martin Marietta Aggregates at Raleigh, N.C., has been elected a vice president of the corporation. Zelnak, 44, has been president of Martin Marietta Aggregates since 1982. The parent company, based in Bethesda, Md., is an aerospace and information technology company engaged in the design, manufacture and integration of systems and products in the fields of space, defense, electronics, communications, information management, energy and materials.