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ECU CMGT 2210 - Lecture 5-Concrete I - Copy

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Slide 1In This Unit…Concrete is everywhereMaterials in TransportationBridgesNuclear Waste ContainmentIntroductionIntroductionComparison with Other Building MaterialsIntroductionConcrete Constituents (Proportions by Volume)Concrete Constituents (Proportions by Volume)Manufacture of Portland CementSlide 14How Cement is MadeTypes of Portland CementType IType IIType IIIType IVType VProperties of Fresh ConcreteHydration5648Slide 25Slide 26Slide 27Slide 28Slump TestSlide 30Slump TestLecture 5: Concrete IKamalesh Panthi, Ph.D.Department of Construction ManagementEast Carolina UniversityCMGT 2210 - Construction & Civil MaterialsIn This Unit…IntroductionCementTypes of CementImportant PropertiesConcrete is everywhereBy weight- One half to Two thirds of our Infrastructure is Concrete Roads and Bridges SidewalksHouses (Foundations) Skyscrapers PipesDams Canals Nuclear Waste ContainmentMaterials in TransportationA rural U.S. public road with portland cement concrete pavement MI, 1 mile 1909BridgesNuclear Waste ContainmentIntroductionAdvantages of Concrete as a Construction MaterialsCheapest and most readily available constituent materialsEasiness to give any structural shape and sizeExcellent resistance to water -water retaining structures like dam, pipe-lines etc.Excellent fire resistance properties.Less requirement of skilled labor.Energy saving and environment friendly.IntroductionLimitations Low tensile strength Low Ductility (elongation) Low strength to weight ratio Susceptible to cracking (Volume Instability)Slow material developmentFormed on siteComparison with Other Building MaterialsIntroductionConcrete Constituents (Proportions by Volume)Concrete Constituents (Proportions by Volume)Manufacture of Portland Cement1. Crushing and grinding of raw materialsCalcium Oxide (calcareous material)•limestone, chalk, or oyster shellsSilica & Alumina (argillaceous material)•clay, shale, blast furnace slag2. Heat and melt in a kiln at 1400-1650oC (2500-3000oF) which forms cement clinker3. Add gypsum (delays set time) to clinker and pulverize to fine powder7 x 1011 particles / lb•small particles produce a large surface area for more complete hydrationCement ProductionHow Cement is Madehttp://www.youtube.com/watch?v=n-Pr1KTVSXo&NR=1Types of Portland CementType I- Ordinary Portland CementType II- Modified or Blended Portland CementType III- Rapid Hardening Portland CementType IV- Low Heat Portland CementType V- Sulphate-Resisting Portland CementType IAn excellent general cement used in most construction where there is no exposure to sulphates on soil or groundwaterROADSFLOORSBRIDGESBUILDINGSType II In some applications, a very low early strength or high heat of hydration may be a disadvantage and for this reason, a modified cement was developed in the US.In this cement, a small quantity of mineral admixtures (Fly ash, slag) is blended with ordinary Portland cement to control the heat of hydration.Recommended for structures with low heat generation, moderate sulfate attack.PIPESSLABS ON GROUNDPOSTSType IIIRapid Hardening Portland Cement A higher content of C3S (70%) and higher fineness- higher strength at early stage early removal of formwork or sufficient strength for further constructionSuitable for construction at low temperatures- safeguard against early frost damageNot suitable for mass concrete construction- because of high rate of heat developmentCOLD WEATHERCONCRETINGFAST TRACK PAVINGRAPID FORM REMOVAL FOR PRECAST CONCRETEType IVLow Heat Portland Cement Contains low content of C3S (35%) and C3A (5%)Developed for use in mass concrete structures such as gravity damsSlower development of strength but ultimate strength is unaffectedLARGE BRIDGE PIERSHOOVER DAMType VSulphate Resisting Portland CementContains low content of C3A (3.5%) to avoid sulphate attackHighly suitable for off-shore structuresRelatively high costPIPESProperties of Fresh ConcreteSettingStiffening: change from plastic to solid (initial and final)•not the same as hardening, which is strength gain•handling, placing, & vibrating must be completed before initial set•finishing between initial and final•curing after final setFalse Set: premature stiffening within a few minutes•due to humidity in cement during storage•remix without adding waterQuick set /flash set are different – cannot be fixedHydration Chemical reaction of cement with water“Hardening” – is not setting or drying•Drying = evaporation = no water – stops reaction – stops strength gain5648Slump Test1234Slump Testhttp://www.youtube.com/watch?v=Hmo7tMsRD1g&feature=relatedSlump


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