special concrete - high end out put value for materials
TRANSCRIPT
Engr.Arivusudar Nagarajan
Special Concrete - High End Out put Value for Materials
High-Value Concrete All concrete is high value!
Cost of material (small) Cost of placement (significant) Cost of Replacement (HIGH)
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
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
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
Materials Used in High-Performance Concrete
Material Primary Contribution/Desired Property
Portland cement Cementing material / DurabilityBlended cement
Cementing material / Durability /
High strength
Fly ash / Slag / Silica fumeCalcined clay/ MetakaolinCalcined shaleSuperplasticizers FlowabilityHigh-range water reducers Reduce water-cement ratioHydration control admix. Control setting
Materials Used in High-Performance Concrete
Material Primary contribution/Desired property
Retarders Control settingAccelerators Accelerate settingCorrosion inhibitors Control steel corrosionWater reducers Reduce cement and water contentShrinkage reducers Reduce shrinkageASR inhibitors Control alkali-silica activity
Improve workability/reduce pastePolymer/latex modifiers
Optimally graded aggr.Durability
Selected Properties of High-Performance Concrete
2% to 5%
Property Test Method
Criteria that may be specified
High Strength ASTM C 39 70-140 MPa @ 28 to 91 daysH-E Comp. Strength ASTM C 39 20-30 MPa @ 3-12 hrs or 1-3 daysH-E Flex. Strength ASTM C 78 2-4 MPa @ 3-12 hrs or 1-3 daysAbrasion Resistance ASTM C 944 0-1 mm depth of wearLow Permeability ASTM C 1202 500 to 2000 coulombs
Chloride Penetration AASHTO T 259/260 Less than 0.07% Cl at 6 months
Low Absorption ASTM C 642
High Mod.of Elast. ASTM C 469 More than 40 GPa
High-Early-Strength Concrete
High-early compressive strength ASTM C 39 (AASHTOT 22) 20 to 28 Mpa at 3 to 12 hours or 1 to 3 days
High-early flexural strength ASTM C 78 (AASHTOT 97)
2 to 4 Mpa at 3 to 12 hours or 1 to 3 days
High-Early-Strength Concrete
Type III or HE high-early-strength cement High cement content 400 to 600 kg/m3 Low water-cementing materials ratio (0.20 to 0.45 by
mass) Higher freshly mixed concrete temperature Higher curing temperature
May be achieved by —
High-Early-Strength Concrete
Chemical admixtures Silica fume (or other SCM) Steam or autoclave curing Insulation to retain heat of hydration Special rapid hardening cements
May be achieved by —
High-Strength Concrete 90% of ready-mix concrete
20 MPa - 40 Mpa @ 28-d (most 30 MPa – 35 MPa)
High-strength concrete by definition — 28 day – Compr. Strength 70 MPa
High-Strength Concrete Materials
9.5 - 12.5 mm 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)
Aggregates —
High-Strength Concrete Materials
Fly ash, silica fume, or slag often mandatory
Dosage rate 5% to 20% or higher by mass of cementing material.
Supplementary Cementing Materials —
High-Strength Concrete Materials
Use of water reducers, retarders, HRWRs, or super plasticizers — 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 ≥ 0.30—air required w/cm < 0.25—no air needed
Admixtures —
High-Strength Concrete
Delays in delivery and placing must be eliminated
Consolidation very important to achieve strength Slump generally 180 to 220 mm. Little if any bleeding—fog or evaporation retarders
have to be applied immediately after strike off to minimize plastic shrinkage and crusting
7 days moist curing
Placing, Consolidation, and Curing
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
High-Durability Concrete
Abrasion Resistance Blast Resistance Permeability Carbonation Freeze-Thaw Resistance Chemical Attack Alkali-Silica Reactivity Corrosion rates of rebar
Durability Issues That HPC Can Address
High-Durability Concrete
Cement: 398 kg/m3
Fly ash: 45 kg/m3
Silica fume: 32 kg/m3
w/c: 0.30 Water Red.: 1.7 L/m3
HRWR: 15.7 L/m3
Air: 5-8% 91d strength: 60 MPa
Case study : Confederation Bridge, Case study : Confederation Bridge, Northumberland Strait, Prince Edward Northumberland Strait, Prince Edward
Island/New Brunswick, 1997Island/New Brunswick, 1997
Self-Consolidating Concrete
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
Self-consolidating concrete (SCC) also known as self-compacting concrete — flows and consolidates on its own
Self-Consolidating Concrete
SCC for Power Plant in Arun excello —Mix Proportions
Portland cement (Type I) 297 kg/m3
Slag cement 128 kg/m3
Coarse aggregate 675 kg/m3
Fine aggregate 1,026 kg/m3
Water 170 kg/m3
Superplasticizer ASTM C 494, Type F (Polycarboxylate-based)
AE admixture as needed for 6% ± 1.5% air content
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
Mechanical Properties of RPC
Property Unit 80 MPa RPCCompressive strength MPa 80 200
Flexural strength MPa 7 40Tensile strength MPa 8Modulus of Elasticity GPa 40 (5.8 x 106) 60 (8.7 x 106)Fracture Toughness 103 J/m2 <1 30Freeze-thaw RDF 90 100Carbonation mm 2 0Abrasion 10-12 m2/s 275 1.2
Reactive Powder Concrete
What is the typical mix ?
230 kg/m3
710 kg/m3
210 kg/m3
40 - 160 kg/m313 kg/m3
140 kg/m3
1020 kg/m3
Cement
Silica fume
Crushed Quartz
Sand
FibresSuperplasticizer
Total water
No aggregates !
What is the typical mix ?
9 – 10%
28 - 30%
8.5 – 9%
1.7 – 6.5%0.6%
5.5 – 6%
42 –43%
Cement
Silica fume
Crushed Quartz
Sand
FibresSuperplasticizer
Total water
No aggregates !w/c = 0.20
