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Slide 1In This Unit…Significance and ObjectivesConcrete in the USSlide 5The plan for describing the stepsStep 1: Assemble the informationSlide 8Slide 9Slide 10Slide 11Slide 12Slide 13Step 2: Choose SlumpStep 2: Choose Slump (ACI Table 6.3.1)Rule of Thumb On Ready-MixSlide 17Step 3 – Maximum Size of AggregateStep 3: Max. Size of AggregateSlide 20Step 4: Estimate the Water And Air ContentsStep 4 : Estimate Mixing Water and Air (ACI Table 6.3.3)Step 4 : Estimate Mixing Water and Air (ACI Table 6.3.3)Step 4 : Estimate Mixing Water and Air (ACI Table 6.3.3)Slide 25Step 4 : Estimate Mixing Water and Air (ACI Table 6.3.3)Summary Up to NowSlide 28Slide 29Slide 30Maximum W/C for SulfatesSlide 32Step 6: Compute the Cement ContentStep 6: Compute the Cement ContentSlide 35Slide 36Slide 37Step 7-Estimate Coarse Aggregate WeightSlide 39Slide 40Slide 41Slide 42Step 9 Adjust for Aggregate MoistureStep 9 Adjust for Aggregate MoistureSlide 45Lecture 7: Concrete IIKamalesh Panthi, Ph.D.Department of Construction ManagementEast Carolina UniversityCMGT 2210 - Construction & Civil Materials1In This Unit…Mixture Proportion Basics2Significance and Objectives3Concrete Mix Design•Selecting the correct proportions of cement, fine and coarse aggregates, and water•As economical as possible•Adequate workability•Specified strength•Suitable resistance against chemical attacksConcrete in the US•Estimating the required batch weights for concrete involves a sequence of ‘logical straightforward steps’ which in effect fit the characteristics of the available materials into a mixture suitable for the work•ACI is the authority on mixture proportioning (211)4We can convert the ACI process to ten steps for Mixture Proportioning 5The plan for describing the stepsWhat I would like to do is:– go through the 10 steps (I will show the same list over and over illustrating where we are at)– try to explain a little about where the steps come from– show a working example of how to use the information that we are providing•This will be done using slides with a yellow background6Step 1: Assemble the information7Step 1: Assemble Information from Specifications and Local Materials•Job specifications may tell usSpecified strength (f’c)Maximum water to cement ratioMinimum amount of cement (cement content)Required air contentSlump (workability)Member dimensions and/or aggregate sizeCover and spacing of reinforcementIf other cementitious materials are permitted and if so what the limits on using them may be8Step 1: Assemble Information from Specifications and Local Materials•Exposure conditions– Salt water– freeze-thaw– sulfate exposure•Production Facility Records– Test records for your facility9Step 1: Assemble Information from Specifications and Local Materials•Material Properties– Specific gravities of cementitious materials– Aggregates• Aggregate gradations•Fineness modulus•Maximum aggregate size•Dry rodded unit weight•Bulk specific gravities•Absorption•Moisture contents– Admixture information10Step 1: Assemble Information from Specifications and Local Materials•Exterior Slab-on-grade (non-reinforced)•Air Entrained• Exposure - Moderate• Max Aggregate Size - 1.5”• 28 Day Strength - 4000 psi• Material Properties:11We can Convert the ACI Process to Ten Steps for Mixture Proportioning1213Step 2: Choose Slump14Step 2: Choose Slump (ACI Table 6.3.1)151-3 inchesRule of Thumb On Ready-Mix•Estimate Slump of 6 in (150 mm) Unless Otherwise Stated (Residential) (You will have a better idea of what you need)•If You Don’t Get It Right – The Contractor Finisher Will•ROT - 1” of Slump is 10 lb/yd3 of water16We can Convert the ACI Process to Ten Steps for Mixture Proportioning17Step 3 – Maximum Size of Aggregate18Step 3: Max. Size of Aggregate19•Exterior Slab-on-grade (non-reinforced)• Exposure - Moderate• Max Aggregate Size - 1.5”• 28 Day Strength - 4000 psi• Material Properties:We can Convert the ACI Process to Ten Steps for Mixture Proportioning20Step 4: Estimate the Water And Air Contents21Step 4 : Estimate Mixing Water and Air (ACI Table 6.3.3)22Step 4 : Estimate Mixing Water and Air (ACI Table 6.3.3)23Step 4 : Estimate Mixing Water and Air (ACI Table 6.3.3)24•Approximately 275 lb/yd3•But wait a second before we move on•Durability is ImportantThe Majority of the Concrete Will Be Exposed To Freezing and Thawing25Step 4 : Estimate Mixing Water and Air (ACI Table 6.3.3)26Summary Up to Now27We can Convert the ACI Process to Ten Steps for Mixture Proportioning28Step 5 – Selection of the Least Water-Cement Ratio (ACI Table 6.3.4 a)29Step 5 – Selection of the Least Water-Cement Ratio (ACI Table 6.3.4 a)30Maximum W/C for Sulfates31We can Convert the ACI Process to Ten Steps for Mixture Proportioning32Step 6: Compute the Cement Content33Step 6: Compute the Cement ContentCement by Weight= Water Contentw/cCement by Weight= 275 0.48Cement by Weight = 572.92 lbs/yd334We can Convert the ACI Process to Ten Steps for Mixture Proportioning35Step 7 – Estimate Coarse-Aggregate Content (Bulk Volume- Table ACI 6.3.6)36Step 7 – Estimate Coarse-Aggregate Content (Bulk Volume- Table ACI 6.3.6)37Step 7-Estimate Coarse Aggregate WeightCoarse Aggregate Weight= 0.71 x 98 lbs/CF x 27 CF/CY=1878.66 lbs/CY38We can Convert the ACI Process to Ten Steps for Mixture Proportioning39a. Volume displaced by water =275/(62.4*1) =4.41 ft3 b. Volume displaced by air =27*(4.5/100)=1.22 ft3c. Volume displaced by cement =572.92/(62.4*3.15) =2.91 ft3 d. Volume displaced by gravel =1878.66/(62.4*2.71) =11.11 ft3 Total=27 ft340Water =4.41 ft3Cement =2.91 ft3 Gravel =11.11 ft3 Air =1.22 ft3 Remaining Space is Fine AggregateStep 8: Estimate Fine Aggregate Using the Absolute Volume MethodStep 8: Estimate Fine Aggregate Using the Absolute Volume MethodVolume displaced by water = 4.41 ft3Volume displaced by cement = 2.91 ft3Volume displaced by gravel = 11.11 ft3Volume displaced by air = 1.22 ft3______________________________________________________________________Total known volume = 19.65 ft3e. Volume displaced by sand =(27-19.65) = 7.35 ft3f. Weight of sand = 7.35*2.65*62.4 ft3= 1215.40 lb41We can Convert the ACI Process to Ten Steps for Mixture Proportioning42Step 9 Adjust for Aggregate Moisture43+0.9%+2.1%+0.4%+0.7%Sand GravelStep 9 Adjust for Aggregate

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