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Performance Engineered Mixtures
1
Dr Peter Taylor, PE (IL)
WCPA Annual Concrete Pavement Workshop
Peter Taylor Presentation February 13, 2015 1 of 47
Design is more than copy/paste
• The mix• The test• The spec
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What Do We Want?
• The Owner wants:Strong enoughCrack freeAbility to resist the environmentSafetyCost effective
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What Do We Want?
• The Contractor wants:The right workability for his machine
(water content, agg gradation)Control of the setting time (SCM type)Cost effective
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What is concrete?• Aggregates• Cement• Supplementary cementitious materials• Water• Admixtures
5
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But I have been doing it this way for 30 years…
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Proportioning ApproachesPast
• Structural concrete 1:2:4 • Other concrete 1:3:6• Waterproof concrete Add salt
• No chemicals• No SCMs• Precision was ugly• Bulking made it worse
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• Developed Before water reducersBefore supplementary cementitious
materials• Primarily focused on structural concrete100 mm (4”) slump30 MPa (~4000 psi)
• ACI 211 last revised in 1991Linear
Proportioning ApproachesPresent
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Absolute Volume Approach
• Paste volume based on coarse aggregate size
• Coarse aggregate volume based on subtracting the fineness modulus (FM) of sand from a fudge factor
• Fill the remaining volumewith sand
• Linear process
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Koehler
Proportioning ApproachesFuture
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Proposed Mixture Proportioning Procedure
Choose the Aggregate System• Combined gradation• Determine void ratio
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Aggregate System• Tarantula Curve (Ley)
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Aggregate System• 50/50 – void ratio 27.1%• Tarantula – void ratio 25.3%
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Proposed Mixture Proportioning Procedure
Choose a Paste System for Performance
• Cementitious blend• W/Cm• Air content
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Proposed Mixture Proportioning Procedure
Choose Paste Volume• All voids must be filled with paste• And a bit more to coat the particles
for workability
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Proposed Mixture Proportioning Procedure
Choose Paste Volume• Need enough paste for base workability
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Proposed Mixture Proportioning Procedure
Choose Paste Volume• Need enough paste for mechanical
properties ~125 - 175% of voids
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Proposed Mixture Proportioning Procedure
Put it all together
• Measuring workability
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Proposed Mixture Proportioning Procedure
Put it all togetherTarantula 50/50
Void ratio 125 150 125 150 175Cementitious 427 505 424 500 543
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Proposed Mixture Proportioning Procedure
Input aggregates
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Proposed Mixture Proportioning Procedure
Check aggregates
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Proposed Mixture Proportioning Procedure
Input paste parameters
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Proposed Mixture Proportioning Procedure
Calculate proportions
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Proposed Mixture Proportioning Procedure
Check proportions• Check workability• Check air
• Adjust paste volume
• Check hardened properties
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Test Methods
• Tests• Do we know what’s in there?
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What do we need to measure?
• What is the potential distress?Tougher environmentsNew materialsNew practices
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Test Methods
• Tests• VKelly – workability response to vibration
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Test Methods
• Tests• The Box – workability response to vibration
• Edge slump vs honeycomb
Ley
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Test Methods
• Tests• Calorimetry tells us about the chemistry of
the system (Uniformity)
Hydration Profile
0.00
3.00
6.00
9.00
12.00
15.00
0:00:00 6:00:00 12:00:00 18:00:00 24:00:00
Time of Hydration (hrs)
J/gh
Sample "5P"Sample "5C"Sample "5F"Sample "5S"
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Test Methods
• Tests• Unit weight – something is wrong
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Test Methods
• Tests• Super Air Meter (SAM)• Air void system in fresh
concrete
Ley
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Test Methods
• Tests• Ultrasonic Pulse Velocity (UPV)• Setting and therefore sawing time
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Test Methods
• Tests• Ultrasonic Pulse Velocity (UPV)• Setting and therefore sawing time
y = 0.9891x + 219.01R² = 0.8997
y = 1.0227x + 299.05R² = 0.8114
0
200
400
600
800
1000
1200
0 50 100 150 200 250 300 350 400 450
Saw
tim
e, m
inut
es
UPV Initial Set, minutes
IA Early EntrySawConventional Saw
LATE
MN Early
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Test Methods
• Tests• Maturity – strength development up to 24
hours
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Test Methods
• Tests• Resistivity – Potential Durability
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Test Methods
• Sensors• Movement• Temperature• Moisture• Chemicals
Ceylan
Slowik
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What do we want to measure?
• Critical Properties at design / proportioning stage
• Uniformity at deliveryTesting3’rd party records
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AASHTO Guide Specification
• Based on existing specs• Add new thinking• Take out some stuff
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Materials
• Cement – M85, M240• Slag cement – M302• Fly ash – M295 (ASTM C 1709)• Admixtures – M154, M194 (others?)
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Materials• AggregatesM80 for contaminantsPP65 for ASR Local practice For d-cracking
Continue with current individual fraction gradation
Address combined gradation in proportioning
ASTM C 1761 for IC
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PrescriptiveProperty Value AASHTO Test
Method When Test Must be Conducted*
Combined Aggregate Gradation
Within Tarantula Curve T27 All
#8 - #30 >15% 24% < #30 - #200 < 34% Cementitious content 400 lb/yd3, minimum Batch records Mixture design
658 lb/yd3, maximum Batch records Mixture design Portland cement content 50% of cementitious,
minimum Batch records Mixture design
Class C Fly Ash** 30% maximum cement replacement
Batch records Mixture design
Class F Fly Ash** 25% maximum cement replacement
Batch records Mixture design
GGBFS** 50% maximum cement replacement
Batch records Mixture design
w/cm ratio [0.42] […] maximum Batch records All
Entrained air 4% after placement, and T 152, T 196M/T 196,or T 199
All
0.2 SAM number Super-air-meter All
2% maximum loss during placement
T 152, T 196M/T 196,or T 199
All
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Performance
Property Value AASHTO Test Method
When Test Must be Conducted
Electrical Resistivity [27] […] kΩ-cm minimum at [28] […] days
TP 95 All
Compressive strength [4000] [3500] […] psi minimum at [28] [90] days
T 22 All
Freeze thaw resistance RDM > [80] […] % C666 Mixture design
Shrinkage Crack free at [14] […] days
ASTM C 1581 Ring
Mixture design
<0.06 % ASTM C 157 mod**
Mixture design
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ReportProperty AASHTO Test Method Modulus of elasticity at 28 days
ASTM C 469
Drying shrinkage ASTM C 157 Coefficient of thermal expansion
T 336
Rate of strength development to 90 days
T 22
Rate of development of electrical resistivity
TP 95
Unit weight T 121
Slump T119
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QCProperty AASHTO Test Method When Test Must be Conduc
Air void system Foam Drainage Mixture design
Slump Within 1” of design mix T 119M/T 119
Unit weight Within 3 pcf of design mix
T 121
Calorimetry Adiacal Construction
Maturity ASTM C 1074 Construction
Strength development T 22 Construction
Resistivity Development TP 95 Construction
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Quality
• Saves money and heartburn• Defines risk and responsibility• Needs “good” tests
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Closing• Did you get what you thought you paid for?
• Did you measure what you really want?
• Concrete can last a long time…
Chicago Sun Times
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Discussion…
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