Modern Concrete Materials

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Modern Concrete Materials
NY Construction Materials Assoc Concrete
Technical Conference Troy, NY March 21, 2007
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Much is the Same
Much is Different
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Not So-Sustainable Environment
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Sustainable Environment
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CONCRETE IS UNIQUE

• Initially concrete has no structural properties
• Testing normally evaluates potential properties

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Concrete Is anEngineered Material
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Types of Concrete
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Raw Materials Heat (lots of heat)
Clinker
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Clinker Gypsum
Portland Cement
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ASTM C 150Standard Specification for Portland
Cement

• Specifies mandatory chemical requirements.
• Lists optional chemical requirements.
• References other documents pertaining to sampling
  and testing.

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ASTM C 150

• Specifies mandatory physical requirements.
• Lists optional physical requirements.
• Has provisions for packaging, storage,
  rejection.
• Requires certification upon purchasers request.
• Covers 8 types of portland cement.

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Types Of Portland Cement
I Normal IA Type I with
air-entrainment II Moderate sulfate/heat
generation IIA Type II with air-entrainment
III High early strength IIIA Type III with
air-entrainment IV Low heat of hydration V
High sulfate resistance

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More Recent Ideas

• Use of up to 5 limestone addition
• Use recycled fuels for manufacturing
• Use of synthetic gypsum
• Use of blended cements

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Blended Hydraulic Cements
ASTM C 595 - 05 (AASHTO M 240)
Type IS Portland blast-furnace slag cement Type
IP Portland-pozzolan cement Type
P Portland-pozzolan cement Type
I(PM) Pozzolan-modified portland cement Type
S Slag cement Type I(SM) Slag-modified portland
cement
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More Recent Ideas

• Classifications and nomenclature revisions
  currently under ballot at ASTM

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Hydraulic Cements ASTM C 1157

• First performance specification for hydraulic
  cements
• Cements meet physical performance test
  requirements rather than prescriptive
  restrictions on ingredients or cement chemistry
  as in other cement specifications.
• Provides for six types

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Hydraulic Cement
ASTM C 1157

• Type GU General use
• Type HE High early strength
• Type MS Moderate sulfate resistance
• Type HS High sulfate resistance
• Type MH Moderate heat of hydration
• Type LH Low heat of hydration

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Supplementary Cementing Materials

• Fly ash
• Slag Cement
• Silica Fume

• Metakaolin
• Natural Pozzolans
• Diatomaceous Earth

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Where do SCMs come from ?
Fly Ash
Coal Fired Power Plants
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Fly Ash Manufacture

• After ignition, volatile matter and carbon are
  burned off
• This now fused product is rapidly cooled after
  leaving the fire box and solidifies into
  spherical glassy particles
• The newly formed fly ash is now collected by
  electrostatic precipitators or bag filters

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ASTM C 618- Standard Specification for Fly Ash
Classifies Fly Ash into two groups based on coal
source
CLASS F FLY ASH

• Siliceous or alumina-silicate glass is most
  active constituent
• LOIs can be up to 10 (most less than 3)
• Class F fly ash are pozzolanic only, have no
  cementitious properties

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CLASS C FLY ASH
ASTM C 618- Standard Specification for Fly Ash
Classifies Fly Ash into two groups based on coal
source

• Calcium alumina-silicate glass is most active
  constituent
• LOIs usually less than 1
• Class C fly ash can react by themselves with
  water to harden

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Typical Oxides in Slag Fly Ash
 
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COLOR (function of carbon/Fe2O3content)

• Portland Cement Dark grey to light grey
• Fly Ash Black to pale yellow
• Bast Furnace Slag Nearly white

Relative Density (Specific Gravity)

• Portland Cement 3.05 - 3.25
• Fly Ash 2.20 - 2.90
• Blast Furnace Slag 2.85 - 2.95

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FINENESS

• Portland Cement 3000-5000 cm2/g
• Fly Ash 2000-6000 cm2/g
• Blast Furnace Slag 3000-6000 cm2/g

PARTICLE CHARACTERISTICS

• Portland Cement Rough texture,irregular shape
• Fly Ash Smooth, spherical
• Blast Furnace Slag Rough texture, irregular
  shape

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Fly Ash performance depends on....

• Chemical Variation
• SiO2 (silica) range from 25 to 60
• Al2O3 (alumina) range from 10 to 30
• Fe2O3 (iron oxide) range from 5 to 25
• Phase (glassy reactive, crystalline non-reactive)
• Physical Properties
• Shape, fineness, particle size distribution,
  density
• Finer ash typically better performance
• Carbon content

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Fly Ash Impact on Plastic Concrete Properties

• Workability usually improved
• volume of total cementitious increases due to
  S.G.
• spherical shape provides gt slump at same water
  content
• Bleeding reduced
• volume of fines increased-- blocks bleed channels
  
• Improved pumpability
• greater cohesiveness, minimizes segregation
• pump line friction decreases

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Fly Ash Impact on Hardened ConcreteProperties

• Rate of strength gain slowed at early ages
• Type F fly ash--early age strengths usually
  reduced
• Class Cs typically develop strength faster than
  Class Fs
• At later ages, pozzolanic activity will usually
  result in equivalent or higher strengths
• Lower peak heat of hydration (reduce thermal
  crack)
• Class C gt peak heat of hydration compared to
  Class F
• Long term durability significantly improved

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Where do SCMs come from ?
Slag Cement
Iron Steel Industry Blast Furnace
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Raw Material (Granules)
Slag Cement
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Specifications And GradesFor GGBFS

ASTM C 989 Standard Specification for Ground
Granulated Blast-Furnace Slag for Use in Concrete
Grade 80 Slags with a low activity index Grade
100 Slags with a moderate activity index Grade
120 Slags with a high activity index
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Typical Oxides in Slag Fly Ash
 
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Slag Performance Depends On

• Slag chemical composition
• Alkali content in the system
• Slag glass content
• Physical characteristics
• Fineness of the slag and cement
• Early hydration concrete temperature

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Slag Impact on Plastic Concrete Properties

• Overall workability improved
• Water absorption reduced in early stages of
  mixing
• Bleeding usually decreases
• dependent on slag fineness versus cement fineness
  
• Pumpability improved
• promotes cohesiveness, reduces segregation

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Slag Impact on Hardened Concrete Properties

• Compressive - Flexural strength
• Strength gain is usually slower early age
  strength is reduced
• Permeability reduction
• Permeability decreases as slag contents increase
• Overall heat of hydration reduced
• Long-term durability significantly improved

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COLOR

• Portland Cement Dark grey to light grey
• Fly Ash Black to pale yellow
• Blast Furnace Slag Nearly white

• Portland Cement 3.05 - 3.25
• Fly Ash 2.20 - 2.90
• Blast Furnace Slag 2.85 - 2.95

Relative Density (Specific Gravity)
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FINENESS

• Portland Cement 3000-5000 cm2/g
• Fly Ash 2000-6000 cm2/g
• Blast Furnace Slag 3000-6000 cm2/g

PARTICLE CHARACTERISTICS

• Portland Cement Rough texture,irregular shape
• Fly Ash Smooth, spherical
• Blast Furnace Slag Rough texture, irregular
  shape

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Silica Fume (Micro Silica)

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Silica Fume in ConcreteASTM C 1240
By-product of the Silicon Metal/Ferrosilicon
Alloy Industry
Silica Fumefinely divided residue resulting from
the production of silicon, ferro-silicon, or
other silicon-containing alloys that is carried
from the burning surface area of an electric-arc
furnace by exhaust gases.
ACI 234
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Silica Fume Manufacture

• By-product of the reduction of high-purity quartz
  with coal or coke and wood chips in electric arc
  furnaces
• Fume condenses from silica gases rising from the
  furnaces
• Gases rapidly cool, forming glassy, spherical
  particles
• A system for filtering the hot air and gases is
  used to collect the silica fume

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FINENESS

• Portland Cement 3000-5000 cm2/g
• Fly Ash 2000-6000 cm2/g
• Blast Furnace Slag 3000-4000 cm2/g
• Condensed Silica Fume 200,000-300,000 cm2/g

PARTICLE CHARACTERISTICS

• Portland Cement Rough texture,irregular shape
• Fly Ash Smooth, spherical
• Bast Furnace Slag Rough texture, irregular
  shape
• Condensed Silica Fume Smooth, spherical

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COLOR

• Portland Cement Dark grey to white
• Fly Ash Black to pale yellow
• Bast Furnace Slag Dark grey to light grey
• Condensed Silica Fume Light grey to bluish grey

SPECIFIC GRAVITY

• Portland Cement 3.12 - 3.17
• Fly Ash 2.20 - 2.90
• Blast Furnace Slag 2.85 - 2.90
• Condensed Silica Fume 2.10 - 2.30

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Physical effects of silica fume in concrete

• 15 dosage rate equates to 2 million silica fume
  particles for every one cement particle
• Improves paste strength in the critical
  transition zone between the cement paste and
  coarse aggregate
• Dramatic impact on concrete properties at low
  addition rates (5 to 10)

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Silica Fume Impact on Plastic ConcreteProperties

• Water demand will increase due to high silica
  fume surface area
• Superplasticizers are usually required
• Typically for every ten pounds of silica fume an
  additional gallon of water is required
• Silica fume concrete may feel a bit sticky...
• because it is

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Silica Fume Impact on Hardened Concrete Properties

• Compressive - Flexural strength
• Considerable increases in strength at all ages
• Permeability reduction
• Very low to negligible coulomb values achieved
• Long-term durability significantly improved

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More Recent Ideas

• Use of Blended SCMS for concrete going through
  the balloting process at ASTM
• Use of ternary (or other) systems
• Various combinations of OPC, FA, Slag, and SF
• Cementing systems containing high volumes of
  SCMs
• Various research on these types of concretes is
  underway

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Aggregates for Concrete
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More Recent Ideas

• Use of recycled aggregates

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Lightweight Aggregate
ASTM C 330

• Expanded
• Shale
• Clay
• Slate
• Slag

• Produce structural lightweight concrete
• Internal curing

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Mixing Water for Concrete
Use of Recycled Water becoming mandated in some
parts of the country
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Chemical Admixtures

• Fibers
• Corrosion inhibitors
• Shrinkage reducing
• Hydration control
• Extended slump life
• Finishing enhancements

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Concrete Color Systems

• Consistent
• Variety of color selection
• Ease of use
• Repeatable

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Thank You
Thomas M Greene Grace Construction
Products Regional Technical Services
Manager Houston, Texas