The purpose of this research was to determine the time-dependent behavior of high performance lightweight concrete and to examine how long-term behavior affects the prestress losses in high strength precast, prestressed concrete bridge girders made using expanded slate lightweight aggregate. Two different high performance lightweight concretes (HPLC) with strengths of 8000 and 10,000 psi (55 and 69 MPa) were developed. They had air-dry unit weights of 116 and 118 lb/ft3 (1855 and 1890 kg/m3), respectively. Creep, shrinkage, and other prestress loss parameters were investigated on 36 cylinder specimens and 4 AASHTO Type II girders. Generally, prestress losses determined from the AASHTO Type II girders made with HPLC were less than those predicted using AASHTO, PCI, and ACI 209 methods. Based on the experimental data, the total final prestress losses were estimated to be 20 and 15 percent of the initial prestressing force for the 8000 and 10,000 psi (55 and 69 MPa) HPLC, respectively.
