UHPC
Strength and Flexibility.
UHPC is a family of concretes offering a combination of material and performance characteristics that create products with:
– Ductility, which is the ability to support tensile loads even after initial cracking
– Ultra high compressive strength (up to 200 MPa/29,000 psi)
– Extreme durability; low water to cementitious material (w/cm) ratio
– Self-consolidating and highly moldable mixtures
– High-quality surfaces
– Flexural/tensile strength (up to 40 MPa/5,800 psi) through fiber reinforcement
– Thinner sections; longer spans; lighter weight
– New graceful product geometries
– Chloride impermeability
– Abrasion and fire resistance
– No steel reinforcing bar cages
– Minimal creep and shrinkage after curing
UHPC is one of the latest advances in concrete technology and it addresses the shortcomings of many concretes today: It provides high strength to weight ratio, high tensile strength, high ductility, and volume stability. It has a compressive strength 2 to 3 times greater than conventional concrete and a flexural strength 2 to 6 times greater. These mechanical properties of UHPC make it ideal for prestressing applications. In addition to achieving high compressive strengths in excess of 25,000 psi (sometimes greater than 30,000 psi), UHPC is also nearly impermeable.
The higher strengths afforded to UHPC allows increased girder spans while maintaining similar or smaller cross-sectional areas. Costs may be reduced as the lower span to depth ratio of UHPC bridges require less embankment fill while providing more aesthetically pleasing profiles.
Increased span lengths mean fewer support structures such as piers which lead to improved safety when traveling under overpasses and lower environmental impact in water crossings.
Additionally, beam spacing can be increased allowing for faster construction times, lower transportation costs, and increased material efficiency.
ADVANTAGES
Of UHPC:
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Freeze/Thaw Resistant
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GREEN INNOVATION AND THE FUTURE UHPC:
While the current LEED (Leadership in Energy and Environmental Design) rating system lacks credits for ranking the numerous green benefits of precast concrete, points can often be achieved through the “Innovation in Design” UHPC can further promote green benefits with CO2 emission reductions. In addition, UHPC presents the opportunity for potentially lower embodied energy due to significant material reduction (up to 40 percent less weight) in optimized members. Long-term service life and expected minimal maintenance are material characteristics that lend themselves to reduced life cycle costs for structures. This enhanced durability needs to be factored into sustainable solutions to offset the currently higher costs of UHPC.
UHPC has important advantages over conventional and high-performance concretes, especially in the production of smaller and lighter sections and the potential elimination of passive mild steel reinforcement.