Bond Interface Strength between Ultra
High Performance Concrete and
Normal Concrete
Presented by Mariah Safritt
July 30, 2015
Motivation
• Repairing infrastructure is expensive and uses a lot of
resources, not efficient or sustainable
• UHPC is stronger, so less can be used while obtaining
higher strengths
• Can UHPC be used as a repair material for existing
structures?
• Are UHPC and normal concrete (NC) compatible?
Introduction to UHPC
• Definition: “hydraulic cement-based concrete with a
compressive strength at least equal to 22 ksi” (1)
• Compare to normal strength concrete 4-8 ksi
• UHPC properties compared to NC
– Higher compressive strength
– Higher tensile strength with ductility (use of fibers)
– Increased durability
– Higher initial cost but longer life cycle
Properties of UHPC
• Strength, toughness, durability, energy absorption
• Impact and fire resistance, freeze-thaw and corrosion
resistance, shear and bending resistance
• Negligible permeability and conductivity, volume
stability (low shrinkage/expansion)
• Resistance to chloride penetration
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Properties of UHPC
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Experiment Design
• 2 tests run: Slant Shear Test
(compression) and Splitting Tensile
Test (indirect tension)
• 3 UHPC mixes
– Mix 1: steel fibers
– Mix 2: silica fume and fly ash
– Mix 3: fly ash
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Experiment Design
• 3 surface preparations
– Normal
– Sand blasted
– Etched with hydrochloric acid
• Digital Image Correlation (DIC)
performed on all specimens for
future work (strain and
deformation analysis)
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UHPC Mix Design
Material
Mix 1: Weight
(lbs)
Mix 2: Weight
(lbs)
Mix 3: Weight
(lbs)
Portland cement
21.85
16.18
13.82
Fly Ash
--
3.93
9.21
Silica Fume
5.57
4.05
--
Fine sand
10.69
24.27
21.48
Superplasticizer
12 mL
25 mL
12 mL
Steel Fibers
0.86
--
--
Water
8.20
7.25
6.90
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UHPC Mix Design
• Cement: Type I/II
• Sand fineness: 75 μm to 1.2 mm
• Sand moisture content: saturated surface dry (SSD)
sand for mixes 1 & 3, oven dry sand for mix 2
• Superplasticizer (HRWR) used: Glenium 7500
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UHPC Mix Procedure
• Mix all cementitious materials (cement, silica fume, fly ash)
dry until well mixed (1-2 min)
• Add sand and mix well (1-2 min)
• Add HRWR to water first, and then add half of water and mix
2-3 min
• Add rest of water and mix 3-4 min
• Add any fibers at the very end of mixing procedure and mix
until homogeneous
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Experiment Procedure
1) ASTM standard molds (C39, C882, & C496)
- Cylinders: 4x8 in. with dummy section half the size of cylinder, divided
along 30° line
- Prisms: 4x3x16 in. prisms, with each section 4x1.5x16 in.; use pieces of
wood to create dummy section
2) Design and mix normal concrete mix (ACI A4 standard mix)
3) Once cured, roughen surfaces of NC for contact with UHPC
- 3 cylinders & 3 prisms sandblasted, 3 cylinders & 3 prisms etched with HCl
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Experiment Procedure
4) Design UHPC mixes, mix and place UHPC in molds with NC sections
5) Cure in moist curing room; cut prisms into 3 inch long cubes before testing
6) Once fully cured, perform tests on specimens based on ASTM standards
- slant shear  direct compression and shear stress
- splitting tensile  indirect tension along bond interface
- DIC  deformation and strain
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Results
Table 1. UHPC Compressive Strengths
Batch
2 Day Strength 7 Day Strength 14 Day Strength
1
6800 psi
9251 psi
10992 psi
2
5238 psi
7179 psi
11289 psi
3
3948 psi
5908 psi
7354 psi
Table 2. Normal Concrete Compressive Strength
Batch
7 Day Strength
Normal A4 Concrete
4668 psi
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Results
Table 3. Slant Shear test results
Specimen
Surface Prep
Strength (psi)
Break Characterization
1A
Normal
4200
Bond interface
1B
Sand blasted
7635
Substrate failure
1C
HCl etched
4124
Bond interface
2A
Sand blasted
6973
Substrate failure
2B
Normal
3486
Bond interface
2C
HCl etched
2524
Bond interface
3A
Normal
3034
Bond interface
3B
Sand blasted
5183
Bond interface
3C
HCl etched
1386
Bond interface
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Results
Table 4. Splitting Tensile test results
Specimen
Surface Prep
Strength (psi)
Break Characterization
1J
HCl etched
2013
Bond interface
1K
Sand blasted
2490
Bond interface
1L
Normal
2153
Bond interface
2J
Normal
1975
UHPC failure
2K
HCl etched
1519
UHPC failure
2L
Sand blasted
2841
Bond interface
3J
Normal
1734
Bond interface
3K
HCl etched
1724
Bond interface
3L
Sand blasted
2129
Bond interface
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Results
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Discussion
• Strongest overall UHPC mix was Mix 2 with silica fume and
fly ash
•
Best surface preparation (resulted in highest bond strengths)
was sand blasting
• Most specimens (all but 4) broke along the bond interface; 2
broke in substrate material and 2 broke in the UHPC
• All specimens showed higher strengths in slant shear test than
splitting tensile test
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Conclusion
• Sand blasted surface preparation creates a stronger bond
between UHPC and normal concrete
• UHPC Mix 2 (with silica fume and fly ash) was the
strongest mix design used since it had the highest overall
compressive strength
• UHPC Mix 1 was strongest for the slant shear test and
UHPC Mix 2 was strongest for the splitting tensile test
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Questions?
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Sources
1) Naaman, Wille; 2012; The Path to Ultra-High Performance Fiber
Reinforced Concrete (UHP-FRC): Five Decades of Progress; UHPC
International Symposium
2) Sarkar; 2010; Characterization of the Bond Strength between Ultra High
Performance Concrete Bridge Deck Overlays and Concrete Substrates;
Michigan Tech thesis
3) Wille, Naaman, Parra-Montesinos; 2011; Ultra-High Performance
Concrete with Compressive Strength Exceeding 150 MPa (22 ksi): A
Simpler Way; ACI Materials Journal
4) Russell, Graybeal; 2013; Ultra-High Performance Concrete: A State-ofthe-Art Report for the Bridge Community; Federal Highway
Administration
5) Graybeal; 2013; TECHBRIEF Development of Non-Proprietary UltraHigh Performance Concrete for Use in the Highway Bridge Sector;
FHWA
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Acknowledgments
•
Professor Devin Harris, mentor
• Dr. Andrei Ramniceanu, Civil Engineering department lab manager at
UVA
• Mike Burton, concrete lab manager at VCTIR
• Evelina Khakimova, Muhammad Sherif, and Sherif Daghash, grad
students at UVA
• Ken and Sam and all the other VCTIR employees
• Dr. Emily Parkany
• Dr. Amir Gheitasi
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