The maximum lengths for simple-span pretensioned concrete composite girders using high strength lightweight concrete (HSLWC) were investigated analytically using concrete strengths of 8, 10, and 12 si (55, 69, and 83 MPa) and prestressing strands of 0.6 in. (15.2 mm) diameter. The use of HSLWC produced spans up to 4 percent longer than the same section made with high strength normal weight concrete (HSNWC). Based on the AASHTO I-girder and AASHTO PCI bulb-tee sections examined in this study, the reduced girder weight eliminated the need for special transportation “superload�? permits. Modified AASHTO-PCI bulb-tees with one extra row of strands in the bottom flange extended the girders�? maximum span length by at least 10 ft (3.1 m). In all cases, the use of lightweight concrete caused greater girder deflections, but all of these values were within the AASHTO specified limit of L/800. Overall, the advantages of lightweight concrete with compressive strengths up to 12 ksi (83 MPa) include lower girder weight, relief from special permitting requirements, and longer span lengths.
