Virginia Concrete Conference March 8, 2012 · March 8, 2012 . What Makes Durable Concrete? A...
Transcript of Virginia Concrete Conference March 8, 2012 · March 8, 2012 . What Makes Durable Concrete? A...
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Virginia Concrete Conference
March 8, 2012
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What Makes Durable
Concrete? A Cement/Admixture Perspective
Jeremy Betts
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• Limestone
• Iron
• Silica
• Aluminum
• Gypsum
•
Understanding “Lisa G”
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Cement Properties
Gypsum
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C3A
• Gypsum added to control flash set
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C3A Durability Concerns
• Subject to sulfate attack • Potential DEF with high
curing temperatures (above 158F)
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Alkali Durability Concerns
• Responsible for ASR and ACR • Water Soluable Alkalis are the culprit
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Calcium Hydroxide Carbonation (lowers steel corrosion resistance)
Easily reacts with acids
Sulfate Attack
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• •
What chemical is responsible directly or indirectly for the majority of concrete
durability issues, including: ASR, sulfate attack, corrosion, freeze/thaw?
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Chemical Admixtures
• Properties that decrease durability – Overdosing – High chloride content
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How Chemical Admixtures Increase Durability
Air Entrainers Lithium based Corrosion inhibitors Water reducers Water repellents Shrinkage Reducers
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Mineral Admixtures
• Class F Fly Ash • Slag • Silica Fume • Metakaolin • Other Pozzolans
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Benefits of SCM’s • Consume Alkalies and
Calcium Hydroxide • Decreases Permeability • Increases Strength • Increases Durability
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Use SCM’s and Admixtures whenever
possible
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