Comparative study of the flexural behavior of lightweight and normal weight prestressed concrete beams

摘要

The objective of this research was to evaluate the feasibility of producing structural lightweight concrete prestressed girders with load-bearing capacities similar to conventional concrete girders. The methodology consisted of comparing the results of the production and monitoring of scaled prestressed concrete beams at a precasting plant and the subsequent flexural testing. The beams were produced using two types of lightweight concrete and a conventional reference concrete with similar compressive strengths to allow for a comparison of the structural performance of the beams. The goal was to estimate an upper bound for the development length of fully developed prestressing strands with a diameter of 15.2 mm (0.6"). The load-bearing capacity and ductility of the beams were determined by flexural tests. All lightweight and conventional concrete beams exceeded their nominal flexural strengths, which were calculated without accounting for the splitting cracks that all manufactured lightweight concrete beams developed alter the prestress release on their lower side. Based on these tests, upper bounds were determined for the development length of the prestressed strands with a diameter of 15.2 mm for the three types of concrete tested. Subsequently, the ductility factors of the beams tested under flexure were determined. Despite all of the tested beams were able to develop the full strength of the prestressed strands and showed a remarkably ductile behavior, it was concluded that the use of these lightweight concretes is not recommended in the fabrication of prestressed concrete bridge girders because of the potential reduction in their durability and bearing capacity due to stress corrosion, which is a result of the splitting cracks detected in all of the produced prestressed lightweight concrete beams.