Presentation on theme: "CONCRETE MIX-DESIGN ACI"— Presentation transcript:
1 CONCRETE MIX-DESIGN ACI-211.1-91 Standard Practice for Selecting Proportions for Normal, Heavyweight, and Mass Concrete
2 Principles of Mix-Proportioning Design PLACEABILITYSTRENGTHDURABILITYECONOMY
3 PLACEABILITY CONSISTENCY WORKABILITY Table A Recommened Slumps For Various Types of ConstructionWORKABILITY
4 Table A188.8.131.52 -Recommended Slumps For Various Types of Construction Type of ConstructionSlump, mmMaximum*MinimumReinforced foundation wall and footing7525Plain footings, caissons, and substructure wallsBeam and reinforced walls100Building ColumnsPavement and slabsMass concrete* May be increased 25 mm for methods of consolidation other than vibration
6 Concrete Durability“ Concrete must be able to endure those exposures that may deprive it of its serviceability ”Freezing and thawingWetting and dryingHeating and coolingChemicalsDeicing Agents
7 Concrete Durability Spalling of concrete structure due to Freeze-Thaw Deterioration
8 Concrete Durability Spalling of concrete structures due to Carbonation structure due toSulfate Attack
9 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
10 Aggregate Size Definitions % Passing% Passing1009989726548362215941009072654836221594Nominal Maximum Aggregate Sizeone size larger than the first sieve to retain more than 10%Maximum Aggregate Sizeone size larger than nominal maximum sizeFor HMA pavements these are the definitions for gradations.
11 3. Estimation of mixing water Mix-Design Flowchart1. Choice of SlumpTableA2. Choice of max. sizeof aggregate3. Estimation of mixing waterTableANo.4.Selection of W/C ratioTableA95
12 5. Calculation cement content (5) = (3) / (4) 6. Estimation of coarse aggregate(6) = Volume of CA(TableA ) x dry-rodded unit mass7.1 Mass BasisWt. of sand = wt. of conc.(A ) –total wt. of all materials7. Estimation of fine aggregate7.2 Absolute volume BasisVol. of sand= Vol. of concrete - (Vw+VC+VCA+Vair)8
13 8. Adjusted weight from moisture of sand and coarse aggregate 78. Adjusted weight from moisture ofsand and coarse aggregate9. Trial batchCheck properties of fresh andHarden concreteNo.2YesStop
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 followsnominal max. size of coarse aggregate = 37.5 mm.dry rodded mass of 1,600 kg/m3cement type I : S.G. = 3.15bulk specific gravity of coarse aggregate = 2.68, absorption = 0.5%bulk specific gravity of sand = 2.64, absorption = 0.7%, F.M. = 2.8Determine the quantities ingredients per m3 of concrete.
15 Example 1. Step 1 From A184.108.40.206 Slump = 75-100 mm. Step 2 Given max size = 37.5 mm.Step 3 From A , estimate mixing water = 181 kg/m3Step 4 From A (a) W/C = 0.62Step 5 Cement = 181/0.62 = 292 kg./m3Step 6. From A and fineness modulus (FM) of sand = 2.8 and max. size of coarse aggregate = 37.5 mm, Volume of CA = 0.71dry mass of CA = 1600 x 0.71 = 1,136 kg.Step 7.1 Mass BasisFrom A the mass of cubic meter of concrete = 2410 kgWater = 181 kgCement = 292 kgCA = 1136 kgTotal = 1609 kg, hence mass of sand = = 801 kg.
16 Example 1. Step 7.2 Absolute Volume Basis V of water = 181/1000 = m3V of cement = 292/(3.15*1000) = m3V of CA = 1136/(2.68 x 1000) = m3V of entrapped air = 0.01 x 1 = m3Total solid volume of ingredients except fine aggregate = m3V of sand = 1.0 – = m3Required 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= 5.3 %0.7 %SANDabsorptionsurface waterCA0.5 %= 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.
18 Example 1.The estimate batch masses for a cubic meter of concrete are :Added water = 122 kgCement = 292 kgWet coarse aggregate = 1159 kgWet sand = 849 kgTotal = 2422 kg