Development of High Performance Lightweight Concrete Mixes for Prestressed Bridge Girders

High performance lightweight concrete allows new options in the use of prestressed bridge girders. Three iterations of concrete mix designs were performed to develop two concrete mixes for use, one with psi at 28 days and the other with fc' = 6000psi at 28 days and the other with fc' = 8000psi at 28 days. Compressive strengths, modulus of elasticity, tensile, strength and flexural strength tests were carried out on each of the mixes. Two mixes were chosen which satisfied the specifications. Creep and shrinkage tests were carried out on both. Also, two 40-foot pretensioned bridge girders were fabricated from the 6000 psi mix and three 40-foot pretensioned bridge girders were fabricated from the 8000 psi mix. The 6000 psi mix performed well in both strength and workability tests, allowing it to be specified as a 7000 psi mix. The 8000 psi mix performed marginally, not reaching strength and being difficult to work. It can be specified as a 7500 psi mix.