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**CONCRETE MIX-DESIGN ACI-211.1-91**

Standard Practice for Selecting Proportions for Normal, Heavyweight, and Mass Concrete

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**Principles of Mix-Proportioning Design**

PLACEABILITY STRENGTH DURABILITY ECONOMY

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**PLACEABILITY CONSISTENCY WORKABILITY**

Table A Recommened Slumps For Various Types of Construction WORKABILITY

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**Table A1.5.3.1 -Recommended Slumps For Various Types of Construction**

Type of Construction Slump, mm Maximum* Minimum Reinforced foundation wall and footing 75 25 Plain footings, caissons, and substructure walls Beam and reinforced walls 100 Building Columns Pavement and slabs Mass concrete * 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 structures due to Carbonation**

structure due to Sulfate Attack

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**Types of Gradations * 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

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**Aggregate Size Definitions**

% Passing % Passing 100 99 89 72 65 48 36 22 15 9 4 100 90 72 65 48 36 22 15 9 4 Nominal Maximum Aggregate Size one size larger than the first sieve to retain more than 10% Maximum Aggregate Size one size larger than nominal maximum size For HMA pavements these are the definitions for gradations.

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**3. Estimation of mixing water**

Mix-Design Flowchart 1. Choice of Slump TableA 2. Choice of max. size of aggregate 3. Estimation of mixing water TableA No. 4.Selection of W/C ratio TableA 9 5

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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 7.1 Mass Basis Wt. of sand = wt. of conc.(A ) – total wt. of all materials 7. Estimation of fine aggregate 7.2 Absolute volume Basis Vol. of sand= Vol. of concrete - (Vw+VC+VCA+Vair) 8

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**8. Adjusted weight from moisture of sand and coarse aggregate**

7 8. Adjusted weight from moisture of sand and coarse aggregate 9. Trial batch Check properties of fresh and Harden concrete No. 2 Yes Stop

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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/m3 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 m3 of concrete.

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**Example 1. Step 1 From A1.5.3.1 Slump = 75-100 mm.**

Step 2 Given max size = 37.5 mm. Step 3 From A , estimate mixing water = 181 kg/m3 Step 4 From A (a) W/C = 0.62 Step 5 Cement = 181/0.62 = 292 kg./m3 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 = m3 V of cement = 292/(3.15*1000) = m3 V of CA = 1136/(2.68 x 1000) = m3 V of entrapped air = 0.01 x 1 = m3 Total solid volume of ingredients except fine aggregate = m3 V of sand = 1.0 – = m3 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 = 5.3 % 0.7 % SAND absorption surface water CA 0.5 % = 1.5 % 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.

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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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PREPARED BY: MARCIA C. BELCHER CONSTRUCTION ENGINEERING TECHNOLOGY Concrete: Fundamentals.

PREPARED BY: MARCIA C. BELCHER CONSTRUCTION ENGINEERING TECHNOLOGY Concrete: Fundamentals.

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