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hvalue.ppt
- 1. Specialty Concrete - HighEnd Value Materials
- 2. High-Value Concrete High-Value Concrete Allconcrete is high value! Cost of material (small) Cost of placement (significant) Cost of Replacement (HIGH)
- 3. High-Value Concrete High valuegenerally associated with High-Performance What is High-Performance? High-Early Strength Concrete High-Strength Concrete High-Durability Concrete Self-Consolidating Concrete Reactive Powder Concrete High-Value Concrete
- 4. High-Value Concrete Characteristics of High- PerformanceConcretes 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
- 5. High-Value Concrete Characteristics of High- PerformanceConcretes 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
- 6. High-Value Concrete Materials Used inHigh- Performance Concrete Material Primary Contribution/Desired Property Portland cement Cementing material / Durability Blended cement Cementing material / Durability / High strength Fly ash / Slag / Silica fume Calcined clay/ Metakaolin Calcined shale Superplasticizers Flowability High-range water reducers Reduce water-cement ratio Hydration control admix. Control setting
- 7. High-Value Concrete Materials Used inHigh- 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
- 8. High-Value Concrete Selected Properties ofHigh- Performance Concrete Property Test Method Criteria that may be specified High Strength ASTM C 39 70-140 MPa @ 28 to 91 days H-E Comp. Strength ASTM C 39 20-30 MPa @ 3-12 hrs or 1-3 days H-E Flex. Strength ASTM C 78 2-4 MPa @ 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 ASTM C 642 2% to 5% High Mod.of Elast. ASTM C 469 More than 40 GPa
- 9. High-Value Concrete High-Early-Strength Concrete High-early compressivestrength 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
- 10. High-Value Concrete High-Early-Strength Concrete Type IIIor 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 May be achieved by —
- 11. High-Value Concrete 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 —
- 12. High-Value Concrete High-Strength Concrete 90%of ready-mix concrete 20 MPa - 40 MPa (3000 – 6000 psi) @ 28-d (most 30 MPa – 35 MPa) High-strength concrete by definition — 28 day – compr. strength 70 MPa (10,000 psi)
- 13. High-Value Concrete High-Strength Concrete Materials 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) Aggregates —
- 14. High-Value Concrete 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 —
- 15. High-Value Concrete High-Strength Concrete Materials 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 ≥ 0.30—air required w/cm < 0.25—no air needed Admixtures —
- 16. High-Value Concrete High-Strength Concrete Delaysin 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 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
- 17. High-Value Concrete High-Durability Concrete 1970sand 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
- 18. High-Value Concrete High-Durability Concrete AbrasionResistance Blast Resistance Permeability Carbonation Freeze-Thaw Resistance Chemical Attack Alkali-Silica Reactivity Corrosion rates of rebar Durability Issues That HPC Can Address
- 19. High-Value Concrete Cement: 398kg/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) High-Durability Concrete Confederation Bridge, Northumberland Strait, Prince Edward Island/New Brunswick, 1997
- 20. High-Value Concrete Self-Consolidating Concrete developedin 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
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- 22. High-Value Concrete Portland cement (TypeI) 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 SCC for Power Plant in Pennsylvania—Mix Proportions
- 23. High-Value Concrete 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
- 24. High-Value Concrete Mechanical Properties ofRPC 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 <1 30 Freeze-thaw RDF 90 100 Carbonation mm 2 0 Abrasion 10-12 m2/s 275 1.2
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- 26. High-Value Concrete Cement Sand Silica quartz Silica fume Micro-Fibres - metallic or poly-vinyl acetate Mineral fillers - Nano-fibres Superplasticizer Water Raw Material Components uctal
- 27. High-Value Concrete What is thetypical Ductal® mix ? 230 kg/m3 710 kg/m3 210 kg/m3 40 - 160 kg/m3 13 kg/m3 140 kg/m3 1020 kg/m3 Cement Silica fume Crushed Quartz Sand Fibres Superplasticizer Total water No aggregates ! uctal
- 28. High-Value Concrete What is thetypical Ductal® 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 Fibres Superplasticizer Total water No aggregates ! uctal w/c = 0.20