In a large heavy saucepan, combine the sugar, water and orange juice concentrate. Cook over medium-high heat, without stirring, until a candy thermometer reads 238° (soft-ball stage). Remove from the heat; stir in pecans and orange zest.
Beat until mixture thickens and loses its gloss, about 2 minutes. Drop by teaspoonfuls onto waxed paper to set. Store in an airtight container.