Evaluation of Ultra-High-Performance Fiber-Reinforced Concrete

About the report:

Recently, a new ultra-high-performance fiber-reinforced concrete (UHPC) was introduced into construction.  The fibers in UHPC provide tensile capacity across cracks, resulting in high shear capacity in bending members.  Typically, additional reinforcement for shear is not required.

The Virginia Department of Transportation (VDOT) is experimenting with UHPC to determine the possibility of using it in transportation structures.  The first bridge in Virginia to use UHPC beams was the bridge on Route 624 over Cat Point Creek in Richmond County.  The specified minimum 28-day compressive strength was 23 ksi and the specified maximum water–cementitious material ratio was 0.2.  UHPC with high strength and very low permeability was used in five beams in one of the 10 spans of the bridge.

The purpose of this study was to evaluate the use of UHPC in the Route 624 Bridge.  This was achieved by (1) observing the casting of UHPC beams; (2) evaluating the material properties of the UHPC; (3) testing a test beam to failure; (4) measuring strains in beams; and (5) noting any deck cracking.

The results of the study indicated that the use of the UHPC led to very high strength and high durability attributable to a very low water-cementitious material ratio, low permeability, high resistance to cycles of freezing and thawing, and very tight cracks under load, all of which should provide for a much longer service life compared to the use of conventional concrete.  However, because of the high cost of UHPC, more efficient shapes, design requirements, and material and construction specifications need to be developed to make UHPC practical for beams and other uses.  The study recommends that UHPC be considered for use in closure pours and beams with optimized cross sections.

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