Specialty Concrete - High End Value Materials

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Specialty Concrete - High End Value Materials
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High-Value Concrete

• All concrete is high value!
• Cost of material (small)
• Cost of placement (significant)
• Cost of Replacement (HIGH)

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High-Value Concrete

• High value generally associated with
  High-Performance
• What is High-Performance?
• High-Early Strength Concrete
• High-Strength Concrete
• High-Durability Concrete
• Self-Consolidating Concrete
• Reactive Powder Concrete

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Characteristics of High-Performance Concretes

• High early strength
• High strength
• High modulus of elasticity
• High abrasion resistance
• High durability and long life in severe
  environments
• Low permeability and diffusion
• Resistance to chemical attack

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Characteristics of High-Performance Concretes

• High resistance to frost and deicer scaling
  damage
• Toughness and impact resistance
• Volume stability
• Ease of placement
• Compaction without segregation
• Inhibition of bacterial and mold growth

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Materials Used in High- Performance
Concrete
Material Primary Contribution/Desired Property
Portland cement Cementing material / Durability
Blended cement Cementing material / Durability / High strength
Fly ash / Slag / Silica fume Cementing material / Durability / High strength
Calcined clay/ Metakaolin Cementing material / Durability / High strength
Calcined shale Cementing material / Durability / High strength
Superplasticizers Flowability
High-range water reducers Reduce water-cement ratio
Hydration control admix. Control setting
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Materials Used in High- Performance
Concrete
Material Primary contribution/Desired property
Retarders Control setting
Accelerators Accelerate setting
Corrosion inhibitors Control steel corrosion
Water reducers Reduce cement and water content
Shrinkage reducers Reduce shrinkage
ASR inhibitors Control alkali-silica activity
Improve workability/reduce paste
Polymer/latex modifiers
Optimally graded aggr.
Durability
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Selected Properties of High- Performance
Concrete
Property Test Method Criteria that may be specified
High Strength ASTM C 39 70-140 MPa _at_ 28 to 91 days
H-E Comp. Strength ASTM C 39 20-30 MPa _at_ 3-12 hrs or 1-3 days
H-E Flex. Strength ASTM C 78 2-4 MPa _at_ 3-12 hrs or 1-3 days
Abrasion Resistance ASTM C 944 0-1 mm depth of wear
Low Permeability ASTM C 1202 500 to 2000 coulombs
Chloride Penetration AASHTO T 259/260 Less than 0.07 Cl at 6 months


Low Absorption

• 2 to 5

ASTM C 642
ASTM C 469
High Mod.of Elast.
More than 40 GPa
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High-Early-Strength Concrete

• High-early compressive strength
• ASTM C 39 (AASHTO T 22)
• 20 to 28 MPa (3000 to 4000 psi)
• at 3 to 12 hours or 1 to 3 days
• High-early flexural strength
• ASTM C 78 (AASHTO T 97)
• 2 to 4 MPa (300 to 600 psi)
• at 3 to 12 hours or 1 to 3 days

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High-Early-Strength Concrete
May be achieved by

• Type III or HE high-early-strength cement
• High cement content 400 to 600 kg/m3
  (675 to 1000 lb/yd3)
• Low water-cementing materials ratio (0.20 to 0.45
  by mass)
• Higher freshly mixed concrete temperature
• Higher curing temperature

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High-Early-Strength Concrete
May be achieved by

• Chemical admixtures
• Silica fume (or other SCM)
• Steam or autoclave curing
• Insulation to retain heat of hydration
• Special rapid hardening cements

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High-Strength Concrete

• 90 of ready-mix concrete
• 20 MPa - 40 MPa (3000 6000 psi) _at_ 28-d (most
  30 MPa 35 MPa)
• High-strength concrete by definition
• 28 day compr. strength
• ? 70 MPa (10,000 psi)

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High-Strength Concrete Materials
Aggregates

• 9.5 - 12.5 mm (3/8 - 1/2 in.) nominal maximum
  size gives optimum strength
• Combining single sizes for required grading
  allows for closer control and reduced variability
  in concrete
• For 70 MPa and greater, the FM of the sand should
  be 2.8 3.2. (lower may give lower strengths and
  sticky mixes)

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High-Strength Concrete Materials
Supplementary Cementing Materials

• Fly ash, silica fume, or slag often mandatory
• Dosage rate 5 to 20 or higher by mass of
  cementing material.

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High-Strength Concrete Materials
Admixtures

• Use of water reducers, retarders, HRWRs, or
  superplasticizers mandatory in high-strength
  concrete
• Air-entraining admixtures not necessary or
  desirable in protected high-strength concrete.
• Air is mandatory, where durability in a
  freeze-thaw environment is required (i.e..
  bridges, piers, parking structures)
• Recent studies
• w/cm 0.30air required
• w/cm lt 0.25no air needed

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High-Strength Concrete
Placing, Consolidation, and Curing

• Delays in delivery and placing must be
  eliminated
• Consolidation very important to achieve strength
• Slump generally 180 to 220 mm (7 to 9 in.)
• Little if any bleedingfog or evaporation
  retarders have to be applied immediately after
  strike off to minimize plastic shrinkage and
  crusting
• 7 days moist curing

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High-Durability Concrete

• 1970s and 1980s focus on High-Strength HPC
• Today focus on concretes with high durability in
  severe environments resulting in structures with
  long life High-Durability HPC

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High-Durability Concrete
Durability Issues That HPC Can Address

• Abrasion Resistance
• Blast Resistance
• Permeability
• Carbonation
• Freeze-Thaw Resistance
• Chemical Attack
• Alkali-Silica Reactivity
• Corrosion rates of rebar

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High-Durability Concrete
Confederation Bridge, Northumberland Strait,
Prince Edward Island/New Brunswick, 1997

• Cement 398 kg/m3 (671 lb/yd3)
• Fly ash 45 kg/m3 (76 lb/yd3)
• Silica fume 32 kg/m3 (72 lb/yd3)
• w/c 0.30
• Water Red. 1.7 L/m3 (47 oz/yd3)
• HRWR 15.7 L/m3 (83 oz/yd3)
• Air 5-8
• 91d strength 60 MPa (8700 psi)

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Self-Consolidating Concrete
Self-consolidating concrete (SCC) also known as
self-compacting concrete flows and consolidates
on its own

• developed in 1980s Japan
• Increased amount of
• Fine material (i.e. fly ash or limestone filler)
  
• HRWR/Superplasticizers
• Strength and durability same as conventional
  concrete

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Self-Consolidating Concrete
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SCC for Power Plant in PennsylvaniaMix
Proportions
Portland cement (Type I) 297 kg/m3 (500
lb/yd3) Slag cement 128 kg/m3 (215
lb/yd3) Coarse aggregate 675 kg/m3 (1,137
lb/yd3) Fine aggregate 1,026 kg/m3 (1,729
lb/yd3) Water 170 kg/m3 (286
lb/yd3) Superplasticizer ASTM C 494, Type F
(Polycarboxylate-based) 1.3 L/m3 (35
oz/yd3) AE admixture as needed for 6 1.5 air
content
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Reactive-Powder Concrete (RPC)

• Properties
• High strength 200 MPa (can be produced to 810
  MPa)
• Very low porosity
• Properties are achieved by
• Max. particle size ? 300 ?m
• Optimized particle packing
• Low water content
• Steel fibers
• Heat-treatment

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Mechanical Properties of RPC
Property Unit 80 MPa RPC
Compressive strength MPa (psi) 80 (11,600) 200 (29,000)
Flexural strength MPa (psi) 7 (1000) 40 (5800)
Tensile strength MPa (psi) 8 (1160)
Modulus of Elasticity GPa (psi) 40 (5.8 x 106) 60 (8.7 x 106)
Fracture Toughness 103 J/m2 lt1 30
Freeze-thaw RDF 90 100
Carbonation mm 2 0
Abrasion 10-12 m2/s 275 1.2
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Reactive Powder Concrete
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Raw Material Components

• Cement
• Sand
• Silica quartz
• Silica fume
• Micro-Fibres - metallic or poly-vinyl acetate
• Mineral fillers - Nano-fibres
• Superplasticizer
• Water

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uctal
What is the typical Ductal mix ?
Cement
710 kg/m3
Silica fume
230 kg/m3
Crushed Quartz
210 kg/m3
Sand
1020 kg/m3
Fibres
Superplasticizer
40 - 160 kg/m3
13 kg/m3
Total water
140 kg/m3
No aggregates !
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uctal
What is the typical Ductal mix ?
Cement
28 - 30
Silica fume
9 10
Crushed Quartz
8.5 9
Sand
42 43
Fibres
Superplasticizer
1.7 6.5
Total water
0.6
5.5 6
No aggregates !
w/c 0.20