Practical Use of 60 MPa Cast-in-Placing High-Strength Concrete for PSC Bridges

Despite recent developments in high-performance and multi-functional concrete with a design strength of about 40 MPa is still being used on superstructures of prestressed concrete (PSC) bridges. Therefore, the overall objective of this paper is to obtain experiences and data for the practical construction of cast-in-place high-strength concrete, especially over 60 MPa design strength, in order to apply it to superstructures of PSC bridges. After carrying out laboratory experimental programs of basic properties for seven different mix proportions suited to 60 MPa design strength, three mixtures of ordinary Portland cement (OPC), OPC with 30% blast furnace slag (BS30), and low-heat cement (LHC) were chosen among seven mixtures. Simulations of pumping and adiabatic temperature rise tests were then carried out. For practical application in the field, mock-up tests were performed for pumping conveyance with 150 meters of passing pipes and heat of hydration with 1.2 meter cubic specimens. Then the test results of heat of hydrations were compared with HeatCon program’s results. In the field applications, a 35 meter single span PSC girder bridge with developed high-strength concrete was constructed in the expressway. During the casting of girder concretes, quality controls were carried out with continuing controls of surface moisture and corrections of the unit water using the air-meter method immediately after batching. It was confirmed that the compressive strengths of girder concretes ensure that the target strength and the heat of hydrations of girder concrete were measured.