Engineers designed a superstructure that combines concrete columns with steel beams for the $1 billion North Terminal of Louis Armstrong New Orleans International Airport, due to be completed within six months. Crews also used 260,000 square yards of 7-inch lean concrete and 17-inch unreinforced concrete to pave the taxiway aprons at the nearly 1 million-square-foot, 35-gate terminal, which has a curved, T-shaped form.