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Group presentation 101 firefighting
This document discusses materials and properties for high-performance concrete used in a high-rise building project. It lists nine group members assigned to the preliminary design project aiming to create sustainable and durable concrete using synergistic effects of supplementary cementitious materials. The document then discusses characteristics, materials, properties and considerations for developing high-performance, high-strength, and high-early-strength concrete. Typical mix designs are provided as examples.
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Group presentation 101 firefighting
- 1. Group assignment Project: Preliminarydesign a sustainable and durable concrete using synergistic effects of SCMs for a high rise building. Group Members: L163330115, L163330118, L163330108, L163330113, L163330116, L163330119, L163330103, L163330114, L163330120
- 2. 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
- 3. 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
- 4. Material Primary Contribution/DesiredProperty 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 Materials Used in High-Performance Concrete
- 5. High-Value Concrete Materials Usedin 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
- 6. 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
- 7. High-Early-Strength Concrete • High-earlycompressive 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
- 8. High-Early-Strength Concrete • TypeIII 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 —
- 9. High-Early-Strength Concrete • Chemicaladmixtures • Silica fume (or other SCM) • Steam or autoclave curing • Insulation to retain heat of hydration • Special rapid hardening cements May be achieved by —
- 10. 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)
- 11. 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 —
- 12. 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 —
- 13. 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 —
- 14. 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
- 15. What is thebest 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 ! w/c = 0.20
- 16. What is thetypical 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 !