We can address infrastructure problems using better concrete materials

BEYOND HIGH-STRENGTH CONCRETE: ULTRA-HIGHPERFORMANCE CONCRETE Metna Co. (Email: metnaco@gmail.com)

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Concrete:

The Most Widely Used Construction Material

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Dams Canals Pipes Offshore Platforms Bridges Buildings Nuclear Power Plants Highway & Airfield Pavements Hazardous Waste Containment Tunnels Protective Structures/Shelters Water Tanks

Ultra-High-Performance Concrete: Key Attributes

• Distinctly high compressive strength (>20 ksi, 140 MPa), tensile strength (>2.6 ksi, 18 MPa), ductility, toughness, blast and fire resistance, impermeability and durability.

• Some key features include high packing density of particulate matter, very low water/cementitious ratio, and effective use of discrete fibers.

3 Compressive Stress-Strain Behavior

Ultra-High-Peformance Concrete Vs.

Normal- and High-Strength Concrete

Typical Performance Characteristics of Normal-Strength Concrete (NSC), HighStrength Concrete (HSC), and Ultra-High-Performance Concrete (UHPC)

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Structural Efficiency Benefits (quantified for existing UHPCs)

Conventional Design

UHPC Design

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Durability Benefits (quantified

for existing UHPCs)

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Applications Beyond Concrete-Based Infrastructure (benefits quantified for existing UHPCs)

Structural Frame: Steel Replacement

Abrasion-Resistant, Low-Cost Dies for Production of Metal & Polymer Parts

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Existing UHPC Mix Designs

• High Packing Density

• Removal of coarse aggregate

• Use of specially graded fine aggregates

• Optional use of relatively inert powder

• Use of fine pozzolans (silica fume)

• Low Water/Binder Ratio

• Use of Advanced Superplasticizers

• Effective Use of Fibers

• High-Temperature Curing

Typical Mix Designs of Normal-Strength Concrete (NSC), High-Strength Concrete (HSC), and Ultra-HighPerformance Concrete (UHPC)

8 NSC HSC UHPC Max. Aggregate Size, mm 25 15 0.5 Aggregate/Binder Ratio 5.5 3.5 0.5 Water/Binder Ratio 0.55 0.35 0.15 Packing Density 0.65 0.7 0.8 Fiber Volume Fraction, % 0 0 2

Drawbacks of Existing UHPCs

• Excess Cementitious Contents

• High Heat of Hydration

• Large (Autogenous) Shrinkage (correlated with temperature rise)

• Restrained (thermal/autogenous)

Shrinkage Cracking

• Large Creep Deformations

• Need for Thermal Curing

• Specialty Aggregates

• Excess Mixing Time/Effort

• Cost

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Temperature Gradient

Large, Temp.-Dependent Autogenous shrinkage Restrained Shrinkage Cracking

Future Needs & Benefits

•Future Needs: Develop mix design and production methods for reliable and costeffective construction of UHPC infrastructure systems using commonly available materials and equipment.

•Key Benefit: Enable effective use of UHPC towards enhancement of the safety, structural efficiency, durability, sustainability, and initial and life-cycle economy of concrete-based infrastructure systems.

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