how many tons of concrete were recycled across the entire
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Specifications Have Different Risk Profiles
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Owner/Designers
Contractor
0
100
Method QC/QA End-Result Performance/
Warranty
Type of Specification
Construction Specifications Have Evolved
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PRS
Warranties
1960 1970 1980 1990 2000
1950
1940
1930
1920
1910
2000
QA Specifications
Method Specifications
Warranties
1970
1935
1915
Prescriptive PCC Patching Mixtures Replaced With Performance Based Mixes in 2008
Strength is significantly overdesigned with prescriptive specs
Not enough emphasis on durability with prescriptive specs
High cracking potential with prescriptive specs
Needs for performance- based specification: Adequate strength, maturity
based
Good durability
Eliminated cracking
Revised Performance Requirements For Patch Mixes
Compressive Strength (ASTM C 39)
Opening to traffic: 2850 psi @ 20 hrs or 4000 psi @ 48 hrs.
Acceptance and payment: 3500 or 4000 psi @ 14 days
Time to cracking (ASTM C 1581) : 10 days
Freeze-thaw (ASTM C 666 Proc. A): 300 cycles, RDM ≥ 80%
Drying shrinkage: 0.05% @ 28 days
Chloride permeability: 2000 Coulombs @ 28 days (accelerated)
Alkali-Silica Reactivity (ASTM C1293): <0.04% ONLY if alkali > 5.0 lb/yd3
Air void system (ASTM C 457): 0.008-in, 600 in2/in3, 4.0%
Condition of Tollway Crack Resistant High Performance Concrete Bridge Decks
In 2012, CTL Group Laboratories researched and developed Tollway performance related specifications for crack resistant high performance concrete (HPC) bridge deck concrete using local materials in plant produced and lab produced mixes
Enhances sustainability
Minimizes cracking of the decks
Improves the resistance to chloride penetration
Provides adequate freeze thaw resistance
Test Method Performance Requirement Time, days
AASHTO T 22-10 4000 ≤ f’cr ≤ [f’cr + 1500] psi at 14 days 14
AASHTO T 119 Slump greater than 3" for 45 minutes
after water added to cement 1
ASTM C1581-09a
(Ring Test)
Minimum 28 days with no cracking
Exempt when less than 600 lb/yd3 cementitious
and a minimum of 1.5 gal/yd3 SRA is used
28 (0)
AASHTO T 160-09
(Length Change)
Maximum 0.03 percent after
7 days curing and 21 days drying, zeroed at the start of drying 28
AASHTO T 161(A)-08
(Freeze/Thaw Mod.)
Minimum RDM of 80 percent after 300 cycles
Exempt if ASTM C457 requirements are met and
aggregate is IDOT Class A+
74 (7)
AASHTO T 303
(Alkali Reactivity)
Expansion less than 0.10% at 16 days
Exempt if total alkali content from cement is less than 4
lb/yd3
16 (7)
ASTM C457-11
(Hardened Air)
Spacing factor not exceeding 0.008-in
Specific surface not less than 600 in2/in3
Total air content not less than 4.0%
7
AASHTO T 277-07
(Cl Penetration) Max 1250 C after 28 day accelerated curing 28
Performance Requirements for HPC Deck Mixes
Success of Tollway Crack Resistant HPC Mixes Developed Through Research
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Not a single shrinkage crack to be found in the 28 I-90 bridge decks constructed in 2013 and 2014 with Tollway HPC concrete
Can we further improve it to produce 75 year life bridge decks without the need for stainless steel?
All Future Pavement Construction to Use Only Peformance Related Optimized Ternary Mixes
Between 2014 and 2026, more than a million cu. yds. of performance related ternary pavement mixes (Class TL) to be produced for new Chicagoland expressways
Mixes will require a minimum of 35% SCM’s
Blended cements allowed to optimize gradation
Feed of washed chips is mandatory
More than 500,000 cu yds to be placed on I-90 in 2015 & 2016
Performance Requirements For Pavement Mixes
Compressive Strength (ASTM C 39)
Opening to traffic: 2500 psi @ 3 days (425 psi flexural)
Ultimate: 3500 psi @ 14 days (650 psi flexural)
Target: 5500 @ 28 days age
Maximum: 6500 @ 28 days age
Plastic air: 5.5% - 8.0% for slip form; 5.0% - 8.0% for manual
Hardened air: (ASTM C457): 0.008-in., 630 in2/in3, 4.0%
Slump: Contractor’s choice for slip form, 2”– 4” for manual
Alkali-Silica Reactivity (AASHTO T 105): not to exceed 5.0 lb/yd3 in portland cement
Air void system (ASTM C 457): 0.008-in, 600 in2/in3, 4.0%
PRS Applied to Larger Concrete Paving Projects Starting in 2015
Project would have at least 10 sublots
Will be evaluated and determined by Tollway
Pay factors will be different by corridor
Pavement Type Selection Report (LCCA) is the Construction PRS Basis
Traffic
Design
Reliability and Performance Criteria
Support conditions
M & R strategies
Costs and other miscellaneous data
13
First Define Acceptance Quality Characteristics (AQC’s)
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Measureable
More rapid the better
Correlate with performance
Prediction models
Are under contractor’s control
Can be varied on the project x
Acceptance Quality Characteristics (AQCs)
Five AQCs
Compressive strength
Air
Thickness
Smoothness
Dowel Alignment
Each has
Target
Rejectable level
Maximum level
All AQC tests MUST be tested with random sampling
Levels of Pavement Quality
Target Quality Level (TQL)
At target 100% pay
Near target pay adjustment (incentive/disincentive)
Rejectable Quality Level (RQL)
Corrective measures required
Maximum Quality Level (MQL)
No further incentive
Example of How a Pay Factor is Measured
Slab Thickness
Test with MIT-Scan T2 meter as described by user manual
Random pre-determined locations
Computed from average of four measurements per sublot
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Slab Thickness Pay Factor Curve
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85
90
95
100
105
12.50 12.75 13.00 13.25 13.50 13.75 14.00
Pay F
acto
r, %
PCC Thickness, in
Std. Dev. = 0.25 in
Std. Dev. = 0.50 in
Std. Dev. = 0 in
PRS Evaluation on 2013 I-90 Projects
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Using Example PRS
Maximum pay – 105.3%
Minimum pay – 93.3%
Average pay – 99%
We are achieving this quality level with current practice!
Lot Composite Pay Factors
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100100100100100100
dowelsmththkairstr
lot
PFPFPFPFPFPF
Maximum Composite PF: 105%
Minimum Composite PF: 85%*
*Provided AQCs meet the RQL standards
Spreadsheet to Track PRS Data
Will calculate pay factors even with partial data
Data distributed to all through e-Builder
Benefits to Performance Specifications
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Improved design-to-construction communication
Develop more rational pay factors
Improved and focused testing by all parties
Improved tradeoff analyses
Improved understanding of performance by all
Improved quality focus
Clearer distinction in roles and responsibilities
Creates a more innovative environment