Why Use Blended Cements

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Why Use Blended Cements?
Midwest Concrete Consortium April 21, 2005

• Paul D. Tennis, Ph.D.
• Consulting Engineer
• Portland Cement Association

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Plan

• What are blended cements?
• Why use blended cements
• Environmental
• Performance
• Durability
• Strength
• Harmonization

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Hydraulic Cements

• Portland
• Blended (or composite)
• Performance

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Definition (ASTM C 219)

• A hydraulic cement
• consisting of two or more inorganic
  constituents (at least one of which is not
  portland cement or portland cement clinker) which
  separately or in combination contribute to the
  strength gaining properties of the cement . . .

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Blended Cements

• Materials
• fly ash
• calcined clay
• silica fume
• ggbf slag
• calcined shale
• others

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History

• First large-scale US production in 1910
• First US specs in 1950s
• ASTM C 595-67
• ASTM C 1157-92

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Portland Cement Types

• ASTM C 150 (AASHTO M 85)
• Type I
• Type II
• Type III
• Type IV
• Type V

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Blended Cement Types

• ASTM C 595 (AASHTO M 240)
• Type I(SM) slag-modified portland cement
• Type IS portland blast-furnace slag cement
• Type S slag cement
• Type I(PM) pozzolan-modified portland cement
• Type IP portland-pozzolan cement
• Type P portland-pozzolan cement

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Composition Limits

• I(SM) lt25 slag
• IS 25 to 70 slag
• S gt70 slag
• I(PM) lt15 pozzolan
• IP P 15 to 40 pozzolan

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C 595 Options

• 0.10 expansion at 180 days in C 1012
• 290 kJ/Kg at 7 days, 330 kJ/Kg at 28 days
• 250 kJ/Kg at 7 days, 290 kJ/Kg at 28 days
• 193 in standard mortar

• MS
• MH
• LH
• A

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Performance Cements

• ASTM C 1157
• Type GU
• Type HE
• Type MS
• Type HS
• Type MH
• Type LH

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C 1157 Options

• R
• Strength

• 0.020 at 14 days 0.060 at 56 days
• Minimums of table
• Minimum at an age
• Range
• Range at an age

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Applications
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Applications
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Requirements
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General Properties

• Compared to portland cements, blended cements are
  usually believed to have
• lower early strength
• higher ultimate strength
• lower heat of hydration
• Strength at 28 days comparable

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General Properties

• Improvements may occur in
• workability
• water demand
• durability

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Advantages

• Less CO2 emitted and energy used
• Reduced solid waste
• More durable concrete
• Consistency

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Energy Intensive
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Durability

• Permeability
• Corrosion
• ASR
• Sulfate resistance

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Disadvantages

• Limits on flexibility

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1-Day Strength
Source PCA 2001 Survey
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28-Day Strength
Source PCA 2001 Survey
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Availability
Source 2001 PCA Survey
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Why Use Blended Cements?

• Performance
• Environmental benefits

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For More Information

• Visit the PCA Website
• www.cement.org/tech
• Contact me
• ptennis_at_cement.org
• [phone]