Optimized Mixtures Will Save
You Headaches and Money
The DFW Connector Experience
4 December 2015
ACPA Annual Meeting
J. Mauricio Ruiz, P.E. (TX)
The Transtec Group, Inc.
David Santin
NorthGate Constructors
OUTLINE
• The Concept
• The DFW Connector Experience
• Impact of Optimized Aggregate Gradation on PCCP
Performance
• Final Thoughts
Optimized Aggregate Gradation (OAG)
Concept
• Reduce paste content by use of an intermediate aggregate
• Sufficient paste volume to fill voids and provide workability
• Many states now allow/encourage optimized aggregate blending
• Benefits reported:
• Reduced shrinkage
• Lower cost
• Greater strengths
• Improved workability
OAG Tools
• Workability-Coarseness Factor Chart
• 8-18 Chart
• Power 0.45
• TARANTULA Curve
OAG is not a fix-all
Coarse Sand
Fine Sand
Aggregate Texture Matters!
OAG for ND paving
Improved uniformity
and workability
How to Achieve Concrete Uniformity?
1. Eliminate gap graded concrete mixtures
2. Control gradation
3. Avoid poor quality aggregate
4. Ensure sufficient pre-blending and mixing
5. Focus on good process control and
stockpile management
DFW Connector
• Owner: TxDOT
• D-B Firm: NorthGate
Constructors
• Lead Design: PB Americas
• Pavement Design: Transtec
• Cost: Over $1.0 billion
• Construction Schedule: 4 years (2010-2014)
• 226 lane miles of CRCP (600,000 yd3)
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www.dfwconnector.com
Logistics of 3rd Aggregate
• Find intermediate aggregate source
• Material cost and haul cost
• Plant set up to handle a 3rd aggregate
• Extra room at the plant site
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DFWC Gradation
TEX-470-A
Sieve analysis before each production day
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DFWC Gradation
TEX-470-A
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DFWC Gradation
TEX-470-A
12
Mixture Optimization
with COMPASS
COMPASS
(Concrete Mixture Performance Analysis System)
1. A system that guides the user through the mix design
process
2. Considers job-specific conditions and materials
3. Assists in optimizing mix gradations and proportions
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Mix Optimization
Paste Vol.
30
Optimal mixture
20
0.45
0.38
w/c
Optimization Criteria
• Strength
• Workability
• Cost
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DFWC Mix Optimization
Top Ten Optimum Mixtures
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Mixture Proportioning Process
• Materials
• Round intermediate and natural
• Manufactured sand discarded
• Seasonal changes – 20% and 35% Fly ash replacement
• Mixture proportioning
• Computer proportioning : COMPASS and TEX-470-A
• Lab trial batches – small quantity
• Batch plant adjustments
Mix Proportions (4.8 sack)
• Cement
293 lb/cy
• Fly Ash
159 lb/cy
• #57 Stone
• 3/8” Pea Gravel
• Natural Sand
• Water
1,620 lb/cy
337 lb/cy
1,477 lb/cy
191 lb/cy
Uniform Concrete Mixture
Uniform Concrete Surface Requiring
Minimum Finishing
DFW Connector Realized Benefits
• Strength
• Avg. 7-day breaks – 4,748 psi (specified 3,500 psi)
• Avg. 28-day breaks – 6,731 psi (specified 4,400 psi)
• Cost savings
• $500k to $600k in savings for every 20 lbs cement content reduction per
cu. yd.
• Average IRI numbers in the low 60’s ( spec is 75 in/mi for PCCP)
• Low end of cementitious content with good workability
• Mix remained very consistent compared to other concrete mixtures
in the past (consistent air and slump)
HIPERPAV Analysis of Aggregate Blending
• HIgh PERformance Concrete PAVing
– Systems Approach simulation
• Environment,
• Materials,
• Pavement Design, and
• Construction Factors
Stress / Strength
– FHWA-sponsored software
Cracking
Time since Construction
HIPERPAV Early-Age Cracking Analysis
(6 sack Mix) – Cold Front
Stress-Strength ratio: 100%
Higher
heat of
hydration
and
shrinkage
HIPERPAV Early-Age Cracking Analysis
(5 sack Mix) – Cold Front
Stress-Strength ratio: 97%
Sensitivity of Cement Paste Volume
on Cracking Risk
Final Thoughts
• Optimized Aggregate Blending Benefits:
• Reduced cement paste – Lower shrinkage/Cost
• More consistent mixture: Less edge slump and
segregation
• Less Rework
• Savings in production time, labor, and materials
• Increased performance
END
Q&A