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CONCRETE MIX-DESIGN ACI Standard Practice for Selecting Proportions for Normal, Heavyweight, and Mass Concrete

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Principles of Mix-Proportioning Design STRENGTH PLACEABILITY DURABILITY ECONOMY

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WORKABILITY PLACEABILITY CONSISTENCY Table A Table A Recommened Slumps For Various Types of Construction

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Type of ConstructionSlump, mm Maximum*Minimum Reinforced foundation wall and footing 7525 Plain footings, caissons, and substructure walls 7525 Beam and reinforced walls10025 Building Columns10025 Pavement and slabs7525 Mass concrete7525 Table A Recommended Slumps For Various Types of Construction * May be increased 25 mm for methods of consolidation other than vibration

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STRENGTH & STIFFNESS Compressive Strength (f’c 28 day) Flexural/ Tensile Strength Elastic Modulus

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Concrete Durability “ Concrete must be able to endure those exposures that may deprive it of its serviceability ” Freezing and thawing Wetting and drying Heating and cooling Chemicals Deicing Agents

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Concrete Durability Spalling of concrete structure due to Freeze-Thaw Deterioration

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Concrete Durability Spalling of concrete structure due to Sulfate Attack Spalling of concrete structures due to Carbonation

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* Uniformly graded - Few points of contact - Poor interlock (shape dependent) - High permeability * Well graded - Good interlock - Low permeability * Gap graded - Only limited sizes - Good interlock - Low permeability Types of Gradations

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Aggregate Size Definitions Nominal Maximum Aggregate Size Nominal Maximum Aggregate Size –one size larger than the first sieve to retain more than 10% Maximum Aggregate Size Maximum Aggregate Size –one size larger than nominal maximum size % Passing

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1. Choice of Slump TableA Choice of max. size of aggregate 3. Estimation of mixing water TableA Selection of W/C ratio TableA Mix-Design Flowchart 9 No.

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5. Calculation cement content (5) = (3) / (4) 6. Estimation of coarse aggregate (6) = Volume of CA(TableA ) x dry-rodded unit mass 7. Estimation of fine aggregate Absolute volume Basis Vol. of sand= Vol. of concrete - (V w +V C +V CA +V air ) 7.1 Mass Basis Wt. of sand = wt. of conc.(A ) – total wt. of all materials 8

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8. Adjusted weight from moisture of sand and coarse aggregate Trial batch Check properties of fresh and Harden concrete Stop Yes No.

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Example 1. Concrete is required for portion of structure that will be below ground level in a location where it will not be exposed to severe weathering or sulfate attack. Structural considerations require it to have an average 28-day compressive strength of 24 MPa with slump of 75 to 100 mm. the materials properties are as follows nominal max. size of coarse aggregate = 37.5 mm. dry rodded mass of 1,600 kg/m 3 cement type I : S.G. = 3.15 bulk specific gravity of coarse aggregate = 2.68, absorption = 0.5% bulk specific gravity of sand = 2.64, absorption = 0.7%, F.M. = 2.8 Determine the quantities ingredients per m 3 of concrete.

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Example 1. Step 1 From A Slump = mm. Step 2 Given max size = 37.5 mm. Step 3 From A , estimate mixing water = 181 kg/m 3 Step 4 From A (a) W/C = 0.62 Step 5 Cement = 181/0.62 = 292 kg./m 3 Step 6. From A and fineness modulus (FM) of sand = 2.8 and max. size of coarse aggregate = 37.5 mm, Volume of CA = 0.71 dry mass of CA = 1600 x 0.71 = 1,136 kg. Step 7.1 Mass Basis From A the mass of cubic meter of concrete = 2410 kg Water = 181 kg Cement = 292 kg CA = 1136 kg Total = 1609 kg, hence mass of sand = = 801 kg.

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Example 1. Step 7.2 Absolute Volume Basis V of water = 181/1000 = m 3 V of cement = 292/(3.15*1000) = m 3 V of CA = 1136/(2.68 x 1000) = m 3 V of entrapped air = 0.01 x 1 = 0.01 m 3 Total solid volume of ingredients except fine aggregate = m 3 V of sand = 1.0 – = m 3 Required weight of dry sand = x 2.64 x 1000 = 771 kg

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Example 1. Step 8. Adjusted weight from moisture of sand and coarse aggregate SAND CA 0.5 % = 1.5 % 0.7 % = 5.3 % CA wet = 1.02 x 1136 = 1159 kg. Sand wet = 1.06 x 771 = 849 kg. Add water =181-(0.015 x 1136 ) – (0.053 x 771) = 122 kg. absorptionsurface water

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Example 1. The estimate batch masses for a cubic meter of concrete are : Added water = 122 kg Cement = 292 kg Wet coarse aggregate = 1159 kg Wet sand = 849 kg Total = 2422 kg

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