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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-
-
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Paste quality
Air, w/cm, SCM type and dose
Paste quantity
Vp/Vv
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-
-
-
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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 • ASTM C33
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Step 2 Aggregate system • Haystack
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Step 2 Aggregate system • Power 45
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Step 2 Aggregate system • Shilstone
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Step 2 Aggregate system • Tarantula Curve
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Step 2 Aggregate system • What if we got a perfect Power 45
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Step 2 Aggregate system • 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 • 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/√s
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VKelly Index 1.1 in/√s
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Step 2 Aggregate system • Choose an aggregate system‌
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Step 2 Aggregate system • 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 • 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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