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 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)
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)
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
Portland Cement Types • The ingredients in the Portland cement can be modified to produce various properties. • These are called “Types”
Portland Cement Types – Type I • General Purpose • Most commonly used • No special curing, setting or resistance characteristics • Suitable where no special properties are required
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
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
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
Type IA, IIA, IIIA, IVA • “A” implies that air entraining is added to the portland cement