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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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Presentation on theme: "CONCRETE MIX-DESIGN ACI-211.1-91 Standard Practice for Selecting Proportions for Normal, Heavyweight, and Mass Concrete."— Presentation transcript:

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

2 Principles of Mix-Proportioning Design STRENGTH PLACEABILITY DURABILITY ECONOMY

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

4 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

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

6 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

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

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

9 * 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

10 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

11 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.

12 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

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

14 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.

15 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.

16 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

17 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

18 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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