Published on March 6, 2014
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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 HighPerformance What is High-Performance? High-Early Strength Concrete High-Strength Concrete High-Durability Concrete Self-Consolidating Reactive Concrete Powder Concrete
Characteristics of HighPerformance 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 HighPerformance 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 HighPerformance Concrete Material Portland cement Primary Contribution/Desired Property Cementing material / Durability Blended cement Fly ash / Slag / Silica fume Calcined clay/ Metakaolin Calcined shale Superplasticizers High-range water reducers Hydration control admix. Cementing material / Durability / High strength Flowability Reduce water-cement ratio Control setting
Materials Used in HighPerformance Concrete Material Retarders Primary contribution/Desired property Control setting Accelerators Corrosion inhibitors Water reducers Shrinkage reducers ASR inhibitors Optimally graded aggr. Accelerate setting Control steel corrosion Reduce cement and water content Reduce shrinkage Control alkali-silica activity Improve workability/reduce paste Polymer/latex modifiers Durability
Selected Properties of HighPerformance 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
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
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
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
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)
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)
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. High-Value Concrete
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 freezethaw environment is required (i.e.. bridges, piers, parking structures) Recent studies: w/cm ≥ 0.30—air required w/cm < 0.25—no air needed
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 bleeding—fog or evaporation retarders have to be applied immediately after strike off to minimize plastic shrinkage and crusting 7 days moist 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 Durability Issues That HPC Can Address Abrasion Resistance Blast Resistance Permeability Carbonation Freeze-Thaw Resistance Chemical Attack Alkali-Silica Reactivity Corrosion rates of rebar
High-Durability Concrete 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)
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
SCC for Power Plant —Mix 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 (Polycarboxylatebased) 1.3 L/m3 (35 oz/yd3) 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 Compressive strength Flexural strength Tensile strength Unit 80 MPa RPC MPa (psi) 80 (11,600) 200 (29,000) MPa (psi) MPa (psi) 7 (1000) 40 (5800) 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
Reactive Powder Concrete
Raw Material Components Cement Sand Silica quartz Silica fume Micro-Fibres - metallic or poly-vinyl acetate Mineral fillers - Nano-fibres Superplasticizer Water
What is the typical mix ? Cement 710 kg/m3 230 kg/m3 210 kg/m3 1020 kg/m3 Silica fume Crushed Quartz Sand Fibres kg/m3 40 - 160 13 kg/m3 140 kg/m3 High-Value Concrete Superplasticizer Total water
What is the typical mix ? Cement 28 - 30% Silica fume 9 – 10% Crushed Quartz 8.5 – 9% Sand 42 –43% Fibres Superplasticizer 1.7 – 6.5% 0.6% 5.5 – 6% Total water w/c = 0.20 No aggregates !
Conclusion High Value concrete is a specialized series of concrete designed to provide several benefits in the construction of concrete structures that cannot always be achieved routinely using conventional ingredients, normal mixing and curing practices.
References http://www.mse.mtu.edu/ http://elearning.vtu.ac.in/12/enotes/Adv_Conc_Stru/Unit7-KK.pdf
Thank You High-Value Concrete
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