Designing Concrete Mixture Proportions

Designing Concrete Mixture Proportions • Dr. Peter Taylor PE (IL) • Dr. Xuhao Wang • Dr. Ezgi Yurdakul

Outline Introduction Proportioning: Paste quality Aggregate system Paste quantity In reality‌

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Proportioning Approaches Past • Structural concrete • Other concrete • Waterproof concrete

1:2:4 1:3:6 Add salt

• No chemicals • No SCMs • Precision was ugly • Bulking made it worse 4

Proportioning Approaches Present • ACI 211 • Last revised in 1991 • Linear • Developed • Before water reducers • Before supplementary cementitious materials • Primarily focused on structural concrete • 100 mm (4”) slump • 30 MPa (~4000 psi)

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Workability

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Workability

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Preconceptions • More cement = more strength • Strength is everything • Slump indicates quality • Gradations of individual fractions are critical

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Design • Choosing what you need • Workability, setting time • Durability, strength, cracking risk

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Proportioning

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Proportioning Filler Gradation

Glue What sort How much

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Proposed Mixture Proportioning Procedure Aggregate system

Paste Quantity

Koehler

Paste Quality

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How do we proportion to achieve design goals?

Aggregate System Type, gradation

Workability

Transport

Strength

Cold weather

Shrinkage

Aggregate stability

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Paste quality

Air, w/cm, SCM type and dose

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Paste quantity

Vp/Vv

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Step 1 Paste Quality • Binder type • Cement type • SCM type and dosage • w/cm • ~0.38-0.42 • Air void system • <0.2 SAM • <0.008 in. spacing factor • >5% in place • Stable 14

Step 2 Aggregate system • Choices…

• 2 bins or 3?

• ASTM C33 • Or combined: • Haystack • Shilstone Plot • Power 45 • Tarantula

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Step 2 Aggregate system â&#x20AC;¢ ASTM C33

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Step 2 Aggregate system â&#x20AC;˘ Haystack

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Step 2 Aggregate system â&#x20AC;¢ Power 45

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Step 2 Aggregate system â&#x20AC;˘ Shilstone

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Step 2 Aggregate system â&#x20AC;˘ Tarantula Curve

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Step 2 Aggregate system â&#x20AC;¢ What if we got a perfect Power 45

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Step 2 Aggregate system â&#x20AC;˘ 3 Combinations of the same materials

Coarse Limestone 1" Fine river sand Int. Limestone 3/8"

Traditional 60.0 30.0 10.0

Power 45 47.5 35.3 17.2

Tarantula 44.9 45.7 9.5

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Step 2 Aggregate system â&#x20AC;˘ 3 Combinations of the same materials

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VKelly • Kelly ball test • Developed in the 1950s in US • Standardized in California DOT test • Comparable to slump test

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VKelly • Measure initial slump (initial penetration) • Start vibrator for 36 seconds at 8000 vpm • Record depth every 6 seconds • Plot on root time • Calculate slope = VKelly Index

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VKelly Index 0.80

1.1 in/â&#x2C6;&#x161;s

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VKelly Index 1.1 in/â&#x2C6;&#x161;s

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Step 2 Aggregate system â&#x20AC;˘ Choose an aggregate systemâ&#x20AC;Ś

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Step 2 Aggregate system â&#x20AC;˘ Tarantula Curve

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Step 3 Paste Content

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Step 3 Paste Content

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Step 3 Paste Content

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Workability

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Strength

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Air Permeability

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Rapid Chloride Penetration

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Shrinkage

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Step 3 Paste Content â&#x20AC;˘ Effect of aggregate gradation

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Step 3 Paste Content • Need a minimum paste for workability • Excess has a: • Small negative effect on strength • Negative effect on permeability, shrinkage, cost • “Optimum” depends on: • Aggregate type • Gradation • Binder type • Typically Vv ~125-200% 39

Proposed Mixture Proportioning Procedure Aggregate system

Paste Quantity

Koehler

Paste Quality

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Doing the Sums Aggregate System Project

Effect of gradation

9/29/2016

Materials

The wonders of a spreadsheet and a solver function…

Cementitious Coarse Agg Fine Agg Intermediate

Blue= Input Data Red = Calculation Yellow = Output Black = Working

472 1" Sand 3/8"

Don’t touch!

Don’t touch!

Don’t touch!

Sieve Analysis Data Max nominal aggregate size

Percent mass Sieve: 2" 1 1/2" 1" 3/4" 1/2" 3/8" #4 #8 # 16 # 30 # 50 # 100 # 200

1.00

inch (0.75, 1.0 or 1.5)

Coarse

1"

% Pass 100.0 100.0 99.0 73.9 37.5 19.7 3.5 0.8 0.4 0.4 0.3 0.3 0.3

44.9 % Mix 44.9 44.9 44.4 33.2 16.8 8.8 1.6 0.4 0.2 0.2 0.1 0.1 0.1

100.0

Fine

Sand

% Pass 100.0 100.0 100.0 100.0 100.0 100.0 98.6 88.3 68.9 37.0 9.7 0.8 0.2

45.7 % Mix 45.7 45.7 45.7 45.7 45.7 45.7 45.1 40.3 31.5 16.9 4.4 0.4 0.1

Intermediate

3/8"

% Pass 100.0 100.0 100.0 100.0 100.0 90.2 21.6 2.0 0.6 0.4 0.4 0.3 0.3

9.4 % Mix 9.4 9.4 9.4 9.4 9.4 8.5 2.0 0.2 0.1 0.0 0.0 0.0 0.0

Combined Cum. Retained % 0.0 0.0 0.4 11.7 28.1 37.0 51.3 59.1 68.3 82.9 95.4 99.5 99.7

Percent Passing % 100.0 100.0 99.6 88.3 71.9 63.0 48.7 40.9 31.7 17.1 4.6 0.5 0.3

Sieve Retained % 0.0 0.0 0.4 11.3 16.3 8.9 14.4 7.8 9.2 14.6 12.5 4.1 0.3

Fineness Modulus

0.0 1.4 11.7 31.1 63.0 90.3 99.2 2.97

Coarsness Factor Workability Factor Adjustments Adjusted Workability Factor

Power 45 least difference Power 45 error Fine Coarse

31.0 350.2

31.5 31.5

23.9 15

0.0

4.5 113.7

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Individual and Combined Gradations 100

Greater than 15% on the sum of #8, #16 and #30 24-34% of fine sand (#30-200)

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80 Percent Passing

Percent Retained

Tarantula error

24-34 >15

Tarantula 25

15 10 5

60 C33

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Sand 3/8"

20

1"

0

# 200

# 50

# 100

# 30

#8

# 16

#4

3/8"

1/2"

1"

3/4"

2"

1 1/2"

Combined

0

# 200 # 100 # 50 # 30 # 16

#8

#4

3/8" 1/2" 3/4"

1"

1 1/2"

2"

Sieve

Sieve

Power 45

Shilstone Chart

100

45

IV Sandy

80

60 Mixture

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Max Density Limits

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III Small Agg

II

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Workability Factor

% Passing

Measure Va

62.55 40.89 0.00 40.89

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I Gap 30

V Coarse 25

20

0 #200 #50

#16

#4

1/2"

Sieve (^0.45)

1"

2"

100

80

60

40

Coarseness Factor

20

0

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Doing the Sums The wonders of a spreadsheet…

Paste Quality Project

Effect of gradation

9/29/2016

Materials Targets Cement SCM 1 SCM 2 Coarse Agg Fine Agg Intermediate Water

R.D. 3.15 2.65 1.00 2.68 2.66 2.68 1.00

Type I C Ash Slag 1" Sand 3/8"

Cementitious w/cm Air % % SCM 1 % SCM 2

472 0.42 5.0 20 0

pcy

Voids in aggregate Required Vp/Vv

28.1 125

% %

Strength RCP Wenner

Blue= Input Data Red = Calculation Yellow = Output Black = Working

% % %

psi coulomb kΩ-cm

Don’t touch!

Don’t touch!

Don’t touch!

7 days 56 days 28 days

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Doing the Sums The wonders of a spreadsheet…

Mixture Proportions Project

Effect of gradation

9/29/2016

Mixture Proportions Targets Cement SCM 1 SCM 2 Coarse Agg Fine Agg Intermediate Water Air %

Cementitious Volume of paste Volume of aggs Volume of voids vp/vv w/cm % SCM 1 % SCM 2 Mass aggs

Actual R.D. 3.15 2.65 1.00 2.68 2.66 2.68 1.00

Pounds 378 94 0 1495 1522 314 198 5.0 4000

Type I C Ash Slag 1" Sand 3/8"

472

125 0.42 20 0 3330

472 26.0 74.0 20.8 125.0 0.42 20 0 3330

Volume 1.92 0.57 0.00 8.94 9.17 1.87 3.18 1.35 27.00

pcy % %

Blue= Input Data Red = Calculation Yellow = Output Black = Working

Don’t touch!

Don’t touch!

Don’t touch!

5.2 % % pcy

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Does it Work?

• Local project – as built

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Trial Batches • Workability / Admixture dosages / Void ratio • Air void system • Setting • Strength gain • Permeability

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Why bother?

• Save money • Improve Sustainability • Better product

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