Self-Consolidating Concrete for Cast-in-place Concrete Bridges and Tunnels

Self-consolidating concrete (SCC) is a specially proportioned cement concrete that enables the fresh concrete to flow easily into the forms and around the steel reinforcement without segregation. Use of this type of concrete has gained widespread application in precast, prestressed bridge elements. The benefits are increased rate of production and safety, reduced labor needs, and lower noise levels at manufacturing plants. The recently completed and reported NCHRP Project 18-12, "Self-Consolidating Concrete for Precast, Prestressed Concrete Bridge Elements," has provided a very good and sound understanding of the SCC mix designs, testing, and workability, and the properties of fresh and hardened SCC. Although NCHRP Project 18-12 focused on the applications of SCC to precast, prestressed bridge elements, most of the findings are also applicable to cast-in-place concrete (CIP) (ready mixed concrete). Additional effort may be devoted to, but not limited to: (1) QC/QA of CIP SCC production, (2) quality control of the delivered concrete, (3) handling and Transportation requirements, (4) form pressures for taller walls and columns (5) preparation of construction joints, (6) control of heat of hydration, (7) surface finishing and curing requirements, (8) control of cracking, (9) guidelines for developing an SCC mix for bridge decks with cross slope of up to 2% or more, (10) guidelines for SCC placement to optimize the flowability of SCC in the horizontal and vertical directions, (11) guidelines for pumpability of SCC with respect to time and distance, (12) illustration of the benefits of CIP SCC by documenting field experiences of CIP SCC projects in the United States and abroad, (13) recommendations for structural parameters (creep, shrinkage, modulus of elasticity) for use of SCC in post-tensioned CIP concrete superstructures, and (14) recommendations for changes in the AASHTO Bridge Design and Construction Specifications for CIP SCC. Research is needed to address the factors that significantly influence the design, constructability, and performance of cast-in-place concrete bridges and tunnels using SCC, and to develop guidelines for the use of SCC in cast-in-place concrete applications, including recommended changes to the AASHTO LRFD Bridge Design and Construction Specifications. These guidelines will provide highway agencies with the information necessary for considering SCC to expedite construction and yield economic and other benefits. In the past 10 years, research in the United States has been focusing on the use of SCC in precast, prestressed applications. The precast/prestress producers have successfully taken advantage of the research findings and economic benefits. The precast/prestress producers have implemented SCC into everyday production to improve consolidation around reinforcement without vibration, enhance surface finish, accelerate placement, produce less wear and tear on equipment, reduce or eliminate vibration, and reduce patching and rework. The use of SCC in the United States ready-mixed market is still in its infancy. The highway agencies and the industry are waiting for guidelines in design and construction specifications to take advantage of the applications of SCC in cast-in-place bridges. Research is needed to improve the understanding of the physical and mechanical properties and the economic benefits of SCC in ready-mixed cast-in-place applications. The main objectives of this research are to (1) develop guidelines for the use of self-consolidating concrete in ready-mixed cast-in-place concrete in highway bridges and related structures, and (2) recommend relevant changes to the AASHTO LRFD Bridge Design and Construction Specifications.