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Concrete: Fundamentals

Concrete: Fundamentals. Prepared by: Marcia C. Belcher Construction Engineering Technology. Common Uses. Slabs (roadways, bridges, airstrips) Beams & Columns Parapets (highways) Piers (structures, bridges) Pipe Foundations (large and small) Retaining Structures (dams).

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Concrete: Fundamentals

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  1. Concrete: Fundamentals Prepared by: Marcia C. Belcher Construction Engineering Technology

  2. Common Uses • Slabs (roadways, bridges, airstrips) • Beams & Columns • Parapets (highways) • Piers (structures, bridges) • Pipe • Foundations (large and small) • Retaining Structures (dams)

  3. Special Needs of Concrete • Exposure & use conditions require attention in mix design. • Marine environment • De-icing salt exposure • Freeze-thaw • Hi sulfate exposure • Early use of structure (bridge decks) • Very thick pours (homogenous pours like earth dams & parapets) • Very slender elements (pipe)

  4. What Can We Do To Modify Concrete Design • Add plasticizers to increase workability • Use larger aggregates to increase strength • Reduce W/C ratio to increase strength • Use air entrainment to improve durability • Use pozzolans to improve chloride resistance • Use “accelerators” increase cure rate for hi early strength • Use set retarders or fly ash to decrease internal temperature & reduce shrinkage cracking

  5. Portland Cement Types • The ingredients in the Portland cement can be modified to produce various properties. • These are called “Types”

  6. Portland Cement Types – Type I • General Purpose • Most commonly used • No special curing, setting or resistance characteristics • Suitable where no special properties are required

  7. Type II • Type II cement contains no more than 8% tricalcium aluminate (C3A) for moderate sulfate resistance. • Increases resistance to sulfate attack over Type I • Lower heat of hydration • Used for mass pours such as bridge piers • Used where ground water contains high sulfate levels

  8. Type III – High Early Strength • Similar to Type I cements except it is ground finer • This increased hydration rate. • Results in rapid curing & higher early strengths. • Results in higher heat of hydration • Used in cold weather concreting • Used when early strength is required

  9. Type IV • Hi levels of dicalcium silicate and tetracalcium aluminoferrite • Used in massive concrete structures where heat generated from hydration must be minimized. • Low heat of hydration = slow strength development • Used for mass pours such as dams where shrinkage problems may occur

  10. Type IA, IIA, IIIA, IVA • “A” implies that air entraining is added to the portland cement

  11. Cement Type Vs. Strength Gain

  12. Temperature Vs. Cement Type

  13. Effects of Moist Curing On Strength

  14. Effects of Environmental Temperature on Strength Gain

  15. W/C vs. Strength

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