Transcript Prescription to Performance

The P2P Initiative –
Focus on Innovation
and Quality
© National Ready Mixed Concrete Association
All rights reserved
Announcement
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This program is registered with the AIA/CES for
continuing professional education. As such, it does
not include content that may be deemed or construed
to be an approval or endorsement by the AIA of any
material of construction or any method or manner of
handling, using, distributing, or dealing in any material
or product.
Introduction
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Continuing education for engineers and architects
Length of Presentation: 1 Hours
Architects Earn 1 LUs
Engineers Earn 1 PDHs
NRMCA is an AIA/CES Registered Provider
Records kept on file with NRMCA and AIA/CES Records
What is the P2P Initiative?
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Prescription-to-Performance
 An alternative to current prescriptive specifications
 An initiative of the concrete industry
 Spearheaded by the NRMCA
P2P GOALS
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Allow performance specifications as an alternative to current
prescriptive specifications
Leverage expertise of all parties to improve quality and reliability of
concrete construction
Assist architects/engineers to address concrete specifications in
terms of functional requirements
Allow flexibility on the details of concrete mixtures and construction
means and methods
Better establish roles and responsibilities based on expertise
Elevate the performance level and quality of ready mixed concrete
Foster innovation and advance new technology at a faster pace
What is a prescriptive Specification?
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Do not always cover intended performance
May conflict with intended performance
Limits competitive bidding
No incentive for quality control
Not in the owner’s best interest
Prescriptive Specification
Intended Performance
Typical Criteria
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Placing/Finishing
 Slump
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Strength
 Max
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Max Shrinkage
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Resistance To:
•
Freeze-Thaw
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Deicer scaling
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Corrosion
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Sulfate attack
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ASR
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Cracking
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Abrasion
 Min
w/cm ratio
cement content
 Min/max
air
 Min/Max
pozzolans/slag
 Blended
cements
 Aggregate
 Source
grading
Limitations
 Chloride
Limits
Water-cement Ratio
Air
Air
Water
Paste
Water
Cement
Cement
Compressive Strength, psi
Does w/c alone control strength?
8000
Mix 1
7000
Mix 2
6000
Mix 3
5000
4000
3000
2000
1000
0
0.40
0.45
0.5
0.55
0.6
Water-Cement Ratio (w/c)
0.70
Charge Passed, Coulombs
Does w/c alone control permeability?
8000
Portland cement
7000
SCM1
SCM2
6000
Ternary Blend
5000
4000
3000
2000
1000
0
0.70
0.55
0.45
Water-Cement Ratio (w/c)
What is a Performance Specification?
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Focus on performance and function
Flexibility to adjust mixture ingredients and proportions to
achieve consistent performance
Measurable and enforceable
Benefits to the Owner
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Improved quality
Improved performance
Reduced construction time
Reduced cost
Higher confidence in concrete construction
Benefits to the Engineer/Architect
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Focus on function rather than composition
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Strength, Durability, Shrinkage, etc.
Simplified submittal review
Improved product consistency
Reduced conflict with contractor/producer
Reduced risk – contractor and producer are
responsible for performance
Benefits to the Contractor
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Improved
communication/coordination
Constructability requirements
addressed
Predictable performance
Innovate on construction means and
methods
Benefits to the Producer
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Eliminates conflicts and improves clarity in
specifications
Encourages innovation and rewards
investment in quality control
Allows optimization of mixtures for
performance
Allows adjustment of materials/proportions
to compensate for material or ambient
conditions variations
What are the Challenges?
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Acceptance of Change
Trust / Credibility
Knowledge Level (training)
Reference Codes and Specifications
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Prescriptive limitations
Measurement and Testing
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Reliability of existing tests
Reliability of jobsite tests
What Activities are Underway?
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Communication
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Engineers, Architects, Contractors, and Producers
 Articles and presentations
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Developing Producer Quality System / Qualifications
Developing Model Spec / Code Revisions
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Documenting Case Studies
Conducting Research
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Look at model codes from other countries (Canada, Europe, Australia)
Look at similar initiatives in the US (FHWA and DOTs)
Test Methods for Performance
Quantifying differences between prescriptive and performance mixes
Delivering Training Programs
Lab Study Demonstrating Advantages of
Performance Specification
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Case 1: Real Floor Specification from a Major Owner
Case 2: Typical HPC Bridge Deck Specification
Case 3: ACI 318 Chapter 4 Code – prescriptive durability
provisions
Fresh Concrete Tests
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Fresh Concrete Properties
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Slump: ASTM 143
Air Content: ASTM C 231
Density: ASTM C 138
Temperature: ASTM C 1064
Initial Setting Time (Case 1): ASTM C 403
Finishability (Case 1): Subjective rating (5=Excellent to 1=Poor)
Segregation (Case 1): Cylinders vibrated, density of top and
bottom half compared
Hardened Concrete Tests
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Compressive Strength, ASTM C 39
Length Change, ASTM C 157
Durability Tests
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Rapid Chloride Permeability Test (RCPT), ASTM C 1202
Rapid Migration Test (RMT), AASHTO TP 64
Sorptivity, ASTM C 1585
Bulk Diffusion, ASTM C 1556
Case 1 - Concrete Floor Specification
Prescriptive
Performance
Specified = 4000 psi;
Average = 5200 psi
Specified = 4000 psi;
Average past records
Max w/c = 0.52, penalties, rejected
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No fly ash or slag
SCMs may be used
Slump (max) = 4”, Non AE
Slump = 4” – 6”, Non AE
Combined aggregate gradation
8% - 18%
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No HRWR
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Shrinkage < 0.04% at 28 days
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Setting Time = 5 ± ½ hours
Specified by Contractor
Experimental Program (5 concrete mixtures)
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One control (prescriptive) and 4 performance mixtures
FS-1: CM = 611, w/cm = 0.49, 8-18% aggregate
FS-2: CM = 517, w/cm = 0.57, 8-18% aggregate
FS-3: CM = 530, 20% FA, w/cm = 0.57, 8-18% aggregate
FS-4: CM = 530, 20% FA with binary aggregates, w/cm = 0.53,
#467 stone aggregate
FS-5: CM = 530, 20% SL, 15% FA with binary aggregates, w/cm =
0.54, #467 stone aggregate
Combined Aggregate Grading of FS Mixtures
Combined Aggregate Grading for FS Mixtures Relative to 8-18
criteria
Individual Percent Retained
25
FS-1
FS-2
20
FS-3
FS-4
15
FS-5
10
5
0
2
1-1/2
1
3/4
1/2
3/8 #4 #8
Sieve Size
#16 #30 #50 #100 #200
Compressive Strength and Setting Time
Floor Slab Mixes
12:00
5,870
6,000
Initial Set time
10:00
5,050
4,860
4,980
4,720
5,000
8:00
5:30
6:00
4:12
4:45
5:59
4,000
5:17
3,000
4:00
2,000
2:00
1,000
0:00
0
FS-1
FS-2
FS-3
FS-4
FS-5
28 day Compressive Strength, psi
7,000
Segregation & Shrinkage
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Segregation Index: Difference in the coarse aggregate
content was consistently about 20% except for Mixture
FS-5 which was about 15%
Shrinkage: All mixtures except FS-5 had 28 day
shrinkage < 0.020%
Slab Finishability Test
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All 5 concrete mixtures had a rating above 4.5 indicating
excellent finishability
Durability
3500
3050
3067
RCPT, Coulombs
3000
2500
2000
1500
1000
538
635
584
FS-4
FS-5
500
0
FS-1
FS-2
FS-3
Mixture ID
Summary – Floor Slab Mixtures
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All performance mixtures met performance requirements
except Mixture FS-5
Strength over-design factor, limiting w/cm increased
cement contents
Use of SCMs was beneficial
Continuous aggregate grading mixtures did not impact
performance
Performance mixtures had substantial material costs
savings
Case 2 - HPC Bridge Deck Specification
Prescriptive
Performance
Specified 28 d strength=4000 psi;
Average past records
Specified 28 d strength=4000 psi;
Average past records
Max w/cm = 0.39
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Total CM = 705.
15% FA plus 7% to 8% SF
SCM required. Maximum amounts per
ACI 318 for deicer scaling
Air = 4% to 8%
Air = 4% to 8%
RCPT < 1500 coulombs
RCPT < 1500 coulombs
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Shrinkage < 0.04% at 28 days
Slump = 4” – 6”
Slump = 4” – 6”
Specified by Contractor
Experimental Program (4 mixtures)
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One control (prescriptive) and 3 performance mixtures
BR-1: C = 550, Class F FA = 105, SF = 50; Total = 705
BR-2: C = 426, Class F FA = 150, SF = 24; Total = 600
BR-3: C = 300, SL = 300; Total = 600
BR-4: C = 426, Class F FA = 150, UFFA = 34; Total = 612
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w/cm=0.39 for all mixtures except 0.36 for Mix 4
Strength
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Compressive Strength: 28 day strengths were much
higher than specified (6800 to 8970 psi)
2000
1800
RCPT, Coulombs
1600
RCPT@45D
RCPT@180D
0.028
RMT@60D
RMT@180D
0.024
0.020
1400
1200
0.016
1000
0.012
800
600
0.008
400
0.004
200
0
0.000
BR-1
BR-2
BR-3
BR-4
RMT, mm/(V-hr)
RCPT (ASTM C 1202), RMT (AASHTO TP 64)
Rapid Migration Test
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FHWA Performance Grade (AASHTO TP 64)
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Grade 1: RCPT = 2000 to 3000; RMT = 0.024 to 0.034
Grade 2: RCPT = 800 to 2000; RMT = 0.012 to 0.024
Grade 3: RCPT < 800; RMT < 0.012
Drying Shrinkage (ASTM C 157)
Drying Shrinkage
0.050%
0.043%
Length Change, %
0.040%
0.030%
0.024%
0.025%
0.024%
BR-2
BR-3
BR-4
0.020%
0.010%
0.000%
BR-1
Summary – HPC Bridge Deck Mixtures
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All performance mixtures met performance requirements
Performance mixtures had similar or better performance
than Prescriptive mixtures
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Drying shrinkage, workability (stickiness), HRWR dosage,
strength, RCPT, RMT
Performance mixtures had substantial material cost
savings
Case 3 - ACI 318 Chapter 4
Prescriptive durability provisions
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Objective: Determine if w/cm is the best measure for
durability (permeability).
Experimental Program (4 mixtures)
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One control (prescriptive) and 3 performance mixtures
318-1: 750 lbs Portland cement mixture
318-2: CM = 700; 25% FA (1.16% less paste)
318-3: CM = 564; 25% FA (7.24% less paste)
318-4: Same as #3 but yield adjusted largely by coarse aggregate
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w/cm = 0.42
Slump = 3.75” – 6.5”; Air = 4.1% to 7.4%
Results
At same w/cm=0.42
Mix
318-1
318-2
318-3
318-4
Compressive Strength – 5,440
28 days, psi
5,950
5,670
5,600
Length Change – 180
days, %
0.064%
0.048%
0.037%
0.032%
RCPT – 180 days,
coulombs
2772
608
533
457
RMT – 180 days,
mm/V-hr
0.030
0.0077
0.015
0.0082
Summary – ACI 318 Mixtures
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Code limitations on w/cm are no guarantee for high
durability concrete
Considerable advances in the use of SCMs and
chemical admixtures
Code durability provisions should be performance based
Conclusions
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Prescriptive specs do not assure performance
Performance mixtures achieved equal or better
performance
Great opportunity for mixture optimization
Producers compete on their knowledge, resources
ACI 318 durability provisions needs to change
ACI 318 Chapter 4 Restructuring
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Exposure Category F – Exposure to freezing and
thawing cycles
Exposure Category S – Exposure to water-soluble
sulfates
Exposure Category P – Conditions that require low
permeability concrete
Exposure Category C – Conditions that require
additional corrosion protection of reinforcement
Exposure to freezing and thawing cycles
Exposure Category F – Exposure to freezing and thawing cycles
Class
F0
Description
Condition
Concrete not exposed to freezing and thawing cycles
F1
Moderate
Occasional exposure to moisture
F2
Severe
Continuous contact with moisture
F3
Very Severe
Continuous contact with moisture and exposed to
deicing chemicals
Exposed to water-soluble sulfates
Exposure Category S – Exposure to water-soluble sulfates
Class
Description
Water-soluble sulfate
(SO4) in Soil,
percent by weight
S0
Negligible
SO4 <0.10
SO4 <150 ppm
S1
Moderate
0.10≤ SO4 <0.20
150≤ SO4 <1500 ppm
Seawater
S2
Severe
0.20≤ SO4 <2.00
1500≤ SO4 <10,000 ppm
S3
Very
Severe
SO4 >2.00
SO4 >10,000 ppm
Sulfate (SO4) in
Water, ppm
Conditions that require low permeability concrete
Exposure Category P – Conditions that require low permeability concrete
Class
Condition
P0
Low permeability to water not applicable
P1
Concrete intended to have low permeability to water
Conditions that require additional corrosion
protection of reinforcement
Exposure Category C
Conditions that require additional corrosion protection of reinforcement
Class
Condition
C0
Additional corrosion protection not a concern – for concrete that will
be dry or protected from moisture in service
C1
Exposure to moisture but will not be exposed to external source of
chlorides in service
C2
Exposure to moisture and an external source of chlorides in service
– from deicing chemicals, salt, brackish water, seawater, or
spray from these sources
Requirements for Concrete - Exposure Class F
Exposure
Class
Max
w/cm
Min f’c
psi
Additional Minimum Requirements
F0
-
-
-
F1
0.45
4500
Table 4.4.1
-
F2
0.45
4500
Table 4.4.1
-
F3
0.45
4500
Table 4.4.1
Table 4.4.2
Table 4.4.1—Total Air Content for Concrete Exposed to
Cycles of Freezing and Thawing
Air content, percent
Nominal maximum
aggregate size, in.*
Class F2 and F3
Class F1
3/8
7.5
6
1/2
7
5.5
3/4
6
5
1
6
4.5
1-1/2
5.5
4.5
2†
5
4
3†
4.5
3.5
Table 4.4.2—Requirements for Concrete Subject to Deicing
Exposure Class F3
Cementitious materials
Maximum percent of total
cementitious materials by
weight*
Fly ash or other pozzolans
conforming to ASTM C 618
25
Slag conforming to ASTM C 989
50
Silica fume conforming to
ASTM C 1240
10
Total of fly ash or other pozzolans,
slag, and silica fume
50†
Total of fly ash or other pozzolans
and silica fume
35†
Requirements for Concrete - Exposure Class S
Exposure
Class
Max
w/cm
Min f’c
psi
Additional Minimum Requirements
S0
-
-
-
S1
0.50
4000
Cement Types II, IP(MS), IS(MS),
P(MS), I(PM)(MS), I(SM)(MS)
S2
0.45
4500
Cement Type V
No calcium chloride admixtures
4500
Cement Type V + pozzolan‡
No calcium chloride admixtures
S3
0.45
Requirements for Concrete - Exposure Class P
Exposure
Class
Max
w/cm
Min f’c
psi
Additional Minimum Requirements
P0
-
-
-
P1
0.50
4000
-
Requirements for Concrete - Exposure Class C
Exposure
Class
Max
w/cm
Min f’c
psi
Max
water-soluble chloride
ion (Cl−) content in concrete,
percent by weight of cement
Additional
Requirement
Reinforced Concrete
C0
-
-
1.00
-
C1
-
-
0.30
-
C2
0.40
5000
0.15
Min.
Cover
Prestressed Concrete
C0
-
-
0.06
-
C1
-
-
0.06
-
C2
0.40
5000
0.06
Min.
Cover
Future Specification for Concrete
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Concrete for parking garage slabs and beams shall meet
the following requirements:
Specified compressive strength, f’c = 5,000 psi
Exposure class F3, S0, P1, C2
Resources
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Visit www.nrmca.org/P2P
Download Example Specifications
Download P2P Articles
Download Research Studies
The P2P Initiative –
Focus on Innovation
and Quality
Questions?