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Concrete Mix Design-The New Technology
Systech 2008 Customer Conference
Presented by James M. Shilstone, Jr.
Shilstone/Day Technologies, Inc. 1 http://www.shilstone.com
Concrete
Mixture
Optimization
2010 Concrete Optimization Technology Conference
Concrete mixtures fit a need
� Structural needs
� Service life conditions
� Aesthetics
� Construction requirements
� Locally available materials
� Cost effective
� Environmental considerations
Specs as a laundry list
� Low slump
� Low w/cm
� Low shrinkage
� High strength
� Low permeability
� Non-segregating
� Freeze-thaw resistant
√
√
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Concrete Mix Design-The New Technology
Systech 2008 Customer Conference
Presented by James M. Shilstone, Jr.
Shilstone/Day Technologies, Inc. 2 http://www.shilstone.com
Specs in balance
Low w/cm
Low permeablilty
No cracks
Higher cement
More heat
Greater shrinkage
Higher cost
Blind Men & the Elephant
Duff AbramsSelecting Mixture Proportions
� Select max agg
� (Choose air content)
� Determine best blend of coarse and fine agg for minimum water
� Determine water
� Determine cement
� Proportion pozzolans
� Determine combined aggregate
Concrete Mix Design-The New Technology
Systech 2008 Customer Conference
Presented by James M. Shilstone, Jr.
Shilstone/Day Technologies, Inc. 3 http://www.shilstone.com
Paste & Aggregate
� Paste
� Strength, durability
� Cost
� Aggregate
� Need for paste
� Concrete “infrastructure”
� Combined concrete
� All the parts work together
Optimizing Aggregate
� Grading approaches� Coarseness Factor, Mortar Factor
� Individual % retained, % passing, .45 Power
� Combined Fineness Modulus
� Mix Suitability Factor and Specific Surface
� Minimum voids� Particle packing / ternary diagram
� Dewar minimum voids
� Rheology� Viscosity and shear
� deLarrard
Optimum aggregate combination
2500
3000
3500
4000
4500
5000
Percent coarse aggregate
PS
I
0.45
0.5
0.55
0.6
0.65
0.7
W/C
Ra
tio
Concrete Mix Design-The New Technology
Systech 2008 Customer Conference
Presented by James M. Shilstone, Jr.
Shilstone/Day Technologies, Inc. 4 http://www.shilstone.com
Coarseness Factor Chart
Coarseness Factor
1990’s Aggregate Distribution
Concrete Mix Design-The New Technology
Systech 2008 Customer Conference
Presented by James M. Shilstone, Jr.
Shilstone/Day Technologies, Inc. 5 http://www.shilstone.com
WATER DEMAND
RESULTS OF GAP GRADING
HAYSTACK - “Optimum”
Concrete Mix Design-The New Technology
Systech 2008 Customer Conference
Presented by James M. Shilstone, Jr.
Shilstone/Day Technologies, Inc. 6 http://www.shilstone.com
C33 - 1923 Graded Mix
Colorado Bridge Deck
Wisconsin Univ/DOT ResearchOptimized Aggregate Conclusion
� Compressive strength - plus 10 to 20%
� Air entraining agent - minus 20 to 30%
� Potential water demand - minus 20 to 30%
� Potential high spacing factor for air voids
� Reduced segregation and higher densityfollowing extended vibration
Concrete Mix Design-The New Technology
Systech 2008 Customer Conference
Presented by James M. Shilstone, Jr.
Shilstone/Day Technologies, Inc. 7 http://www.shilstone.com
Wisconsin DOT/UnivEffects of particle distribution on segregation
8/18 Grading Spec
Air Force Findings
Concrete Mix Design-The New Technology
Systech 2008 Customer Conference
Presented by James M. Shilstone, Jr.
Shilstone/Day Technologies, Inc. 8 http://www.shilstone.com
Workability Zones
Mortar Requirements
MORTAR NEEDS(Approximate)
� 52.0 for a 5” diameter high pressure pump with a long stroke (gravel).
� 54.0 to 55.5% for 5” diameter high pressure pump with long stroke (cubical crushed).
� 55.5 to 57% for lighter, but good, pumps (crushed stone).
� 60% for 1/2” sharp edged crushed stone with a 2” line.
� 63.3 to 63.8% for topping mixes.
Concrete Mix Design-The New Technology
Systech 2008 Customer Conference
Presented by James M. Shilstone, Jr.
Shilstone/Day Technologies, Inc. 9 http://www.shilstone.com
.45 Power Chart
Specific Surface
33.5846SS
3.60153.431050.69#200
7.80039.63814.12#100
9.169815.815813.75#50
5.900715.133929.56#30
4.808717.812744.69#16
0.925.751662.5#8
0.66488.31868.25#4
0.22525.63476.563/8"
0.27486.87482.191/2"
0.210289.063/4"
0.01880.94299.061"
0011001-1/2"
SS value%rtdFactor% PassingSieve
Mix Suitability Factor
� MSF = f(SS, % air, cement)� MSF Targets
� < 16 – Too harsh� 16-20 – Harsh, zero slump mixes� 20-22 – Industrial slabs� 22-25 – Structural concrete� 25-27 – Pumpable concrete� 26-28 – Pumpable lightweight� 27-31 – Flowing concrete
Concrete Mix Design-The New Technology
Systech 2008 Customer Conference
Presented by James M. Shilstone, Jr.
Shilstone/Day Technologies, Inc. 10 http://www.shilstone.com
Use a variety of methods
The Problem
None of these methods address particle shape and texture.
Proportion coarse agg –ACI 211
Concrete Mix Design-The New Technology
Systech 2008 Customer Conference
Presented by James M. Shilstone, Jr.
Shilstone/Day Technologies, Inc. 11 http://www.shilstone.com
Proportion coarse agg –ACI 211
Proportion coarse agg –ACI 211
Developed in 1938 for concrete placed without vibrators
Particle packing
Concrete Mix Design-The New Technology
Systech 2008 Customer Conference
Presented by James M. Shilstone, Jr.
Shilstone/Day Technologies, Inc. 12 http://www.shilstone.com
Concrete Rheology
Optimizing paste
Minimize the paste, but make it high quality
Lower w/c = less permeable concrete?
3000
3500
4000
4500
5000
5500
6000
0.35 0.4 0.45 0.5 0.55 0.6 0.65
� Lower w/c means more cement
� More cement means more heat
� More heat causes thermal shrinkage
� More cement causes more autogenous shrinkage
� More shrinkage means more cracks
Concrete Mix Design-The New Technology
Systech 2008 Customer Conference
Presented by James M. Shilstone, Jr.
Shilstone/Day Technologies, Inc. 13 http://www.shilstone.com
High w/c Ratio
High w/c Ratio
Low w/c Ratio
Concrete Mix Design-The New Technology
Systech 2008 Customer Conference
Presented by James M. Shilstone, Jr.
Shilstone/Day Technologies, Inc. 14 http://www.shilstone.com
Low w/c Ratio
Very Low w/c Ratio
Concrete Mix Design-The New Technology
Systech 2008 Customer Conference
Presented by James M. Shilstone, Jr.
Shilstone/Day Technologies, Inc. 15 http://www.shilstone.com
Real-life concrete
0
0.5
1
1.5
2
2.5
0 0.2 0.4 0.6
w/c ratio
paste volume
Unhydrated Hydrated Cement
Cement efficiency
400 450 500 550 600 650 700
Plain cement Cement + AdmixCement + Ash Cement + Admix + Ash
Cementitious particle size
� Fly ash – 1–200 µm
� Cement – 10-50 µm
� GGBFS – 5-30 µm
� Silica Fume – 0.1-0.3 µm
� Particle size distribution matters
Concrete Mix Design-The New Technology
Systech 2008 Customer Conference
Presented by James M. Shilstone, Jr.
Shilstone/Day Technologies, Inc. 16 http://www.shilstone.com
Hydration of Portland Cement
Cement + Water
C-S-H + Ca(OH)2 + Other
C
C
C
C
C
C
C
Hydration of Portland Cement
Pozzolanic Reaction in Concrete
Ca(OH)2 + Pozzolan
more….. C-S-H
Concrete Mix Design-The New Technology
Systech 2008 Customer Conference
Presented by James M. Shilstone, Jr.
Shilstone/Day Technologies, Inc. 17 http://www.shilstone.com
C C
CC
C
Effect of Pozzolanic Reaction
Marin Airport - PR
500
1500
2500
3500
4500
5500
6500
7500
8500
5 sk 6 sk 7.5 sk
Cement Cem + ash
Determining cement-ACI 318
•Best – use historical test data and determine
appropriate overdesign,
then determine cement
content
•Alternate – produce lab
batches to develop w/c vs
strength curve and select
appropriate cement content
•If no data available, use
“expertise”
Concrete Mix Design-The New Technology
Systech 2008 Customer Conference
Presented by James M. Shilstone, Jr.
Shilstone/Day Technologies, Inc. 18 http://www.shilstone.com
ACI 318 Overdesign Criteria
�Moving average of 3fcr = (f’c + 2.33s)/√3 = f’c + 1.28s
� Individual <= 5000 psifcr = (f’c – 500 psi) + 2.33s
� Individual > 5000 psifcr = (0.90 *f’c) + 2.33s
Paste Content
Paste = everything passing the #200 sieve
Mortar = everything passing the #8 sieve
Air = 1.35 cftPaste = 9.2 cft%AirPaste= 14.7%
There is NO perfect way
Concrete Mix Design-The New Technology
Systech 2008 Customer Conference
Presented by James M. Shilstone, Jr.
Shilstone/Day Technologies, Inc. 19 http://www.shilstone.com
Admixtures
� Air entraining agents
� Water Reducers
� Retarders
� Superplasticizers
� Accelerators
� VMA, set inhibitors
� No way to predict effect of admix
� Admix performance depends on other materials
Heat signature of paste
“Developing a Simple and Rapid Test for Monitoring the
Heat Evolution of Concrete Mixtures for Both Laboratory and Field Applications” –
Center for Transportation Research and Education
Self-consolidating concrete
� Fluidity without segregation
� Ways to achieve
� Well-graded aggregate blend
� Viscosity modifiers
� Admixtures
� Finely divided powders
� Very difficult to achieve on a production basis
Concrete Mix Design-The New Technology
Systech 2008 Customer Conference
Presented by James M. Shilstone, Jr.
Shilstone/Day Technologies, Inc. 20 http://www.shilstone.com
High fines manufactured sand
� Proposed revision to ASTM C-33
� Allow up to 18% passing #200
� Dust of fracture only
� Can increase strength, decrease permeability
� Requires increased Super-P dosage
� Particle shape critical
Challenges to mix design
� Impact of particle shape and texture on water demand and rheology
� Interaction between cement, mineral additives, admixtures and water
� Effect of ambient conditions on concrete performance
� Effect of processing variables on concrete performance
� Tests that reflect performance