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Performance Engineered: Mixtures and AASHTO PP 84: It's Time for a Change
1. Image Here
Office of Infrastructure
MICHAEL F. PRAUL, PE
SENIOR CONCRETE ENGINEER
FHWA, OFFICE OF INFRASTRUCTURE
Performance Engineered
Mixtures and AASHTO PP 84:
It’s Time for a Change
All images FHWA unless otherwise noted.
2019 NCPA Concrete Paving Workshop
2. Timeframe for widespread use of SCMs
28-day strength testing
Slump test
We Are Horrible With Change
Image Pixabay
3. 1920 198019601940 2000
ASTM C231ASTM C143
Evolution of Concrete Testing
Slump Cone Pressure Meter
1981
Rapid Chloride Permeability Test
1922 1949
FHWA/PCA
4. Performance Engineered Mixture Concept
Understand what makes concrete last and
what failure mechanisms we see
Specify critical properties to address those
failure mechanisms and test for them
Starting point for a performance-driven
QA specification and acceptance program
for owner agencies
5. PEM/PP 84 Specification Development
The Team
o Dr. Peter Taylor, Director, CP Tech Center/Iowa State
o Dr. Jason Weiss, Oregon State University
o Dr. Tyler Ley, Oklahoma State University
o Dr. Tom Van Dam, NCE
o Cecil Jones, Diversified Engineering
o Tom Cackler/Gordon Smith, CP Tech Center
o Mike Praul, FHWA
ETG Participants/Reviewers
o Champion States
o ACPA National, ACPA Chapter Execs
o PCA
o NRMCA
6. AASHTO PP 84: A Better Specification
Strength
Shrinkage
Freeze-thaw resistance
Transport properties
(Permeability)
Aggregate stability
Workability*
Require the things that matter
7. AASHTO PP 84
A guide specification with tests completed either
during mixture design or at placement or both that
focus on concrete performance.
Allows DOTs to take what they like from the
document and make it their own.
DOTs should not give up what they already know is
important for them.
8. AASHTO PP 84
A commentary is included that gives the technical
background behind the tests and limits.
A tool to help you improve your concrete.
The document is not designed to be used without
modifying for local practice and experience.
9. PEM/PP 84: It’s our Superpave
Most significant field-level
advancement in decades
Answers the question “With our
loss of staff and resources, how are
we going to be able to get the job
done in the future?”
Collaboration with industry (It’s
more than just the tests!)
Why We’re Excited
Concrete Evolution
Image Pixabay
10. Jerry Voigt, ACPA
“It’s the agency’s
responsibility to
allow for
innovation. It’s
the contractor’s
responsibility to
deliver.”
Image ACPA
11. How Do Contractors Deliver
in a Performance Specification?
Image Pixabay
13. Standard procedures (AASHTO, ASTM, state)
Laboratory accreditation/qualification program
Technician training and certification programs
State Independent Assurance Program
Calibrated equipment schedules
Controlling Sampling and Testing Variability
16. Prescriptive vs. Performance Specifications
Prescriptive
Agency dictates how the
material or product is
formulated and constructed
Based on past experience
Minimal/uncertain ability
to innovate
Requires agency to have
proper manpower and skill
set to provide oversight
Performance
Agency identifies
desired characteristics
of the material or
product
Contractor controls how
to provide those
characteristics
Maximum ability to
innovate
Reduced oversight
burden on the agency
17. Agency Acceptance
Contractor Quality Control
Qualified (certified) Personnel
Qualified Laboratories
Independent Assurance
Dispute Resolution for Test Results
Quality Assurance Defined: 23 CFR 637
}
State
processes,
independent
of material
18. Quality Control
PP 84 acknowledges the key role of QC in a
performance specification
Requires an approved QC Plan
Testing targets, frequency, and action limits
Equipment and construction inspection
Mirror design-build experience
Requires QC testing and control charts
Unit weight
Air content/SAM
Water content
Formation Factor (via Surface Resistivity)
Strength
Image Pixabay
19.
20.
21.
22. Change State mind set that QC is not its business
Gordon Smith example
Change (some) industry mind set that QC is not its
business
Provide guidance on developing State specification
language
QC Testing Guide (very similar to guidance for the
acceptance program but slanted to industry)
QC test tech briefs and videos
Frequency
Control charts and usage
QC Plan template and guidance
Quality Control Evolution
23. 3%
4%
5%
6%
7%
8%
9%
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
AirContent,%
Test #
Air content and Unit Weight
Air Content Unit Weight
Dual Axis Plot Example
Air content plotted on the left vertical axis
Unit weight plotted on the right vertical axis
136
137
138
139
140
141
142
143
144
145
1463%
4%
5%
6%
7%
8%
9%
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
UnitWeight,pcf
AirContent,%
Test #
Air content and Unit Weight
Air Content Unit Weight
24. 0
5
10
15
20
25
2-2 3-1 3-2 3-3 5-1 5-2 6-1 6-2
SurfaceResistivity,KOhm-cm
56 Days
Low
Moderate
High
0
5
10
15
20
25
2-2 3-1 3-2 3-3 5-1 5-2 6-1 6-2
SurfaceResistivity,KOhm-cm
28 Days
Low
Moderate
High
Unit Weight/Heat Signature/Permeability
Unit Weight – Real Time
Surface Resistivity – 56 DaysHeat Signature – Info in a day
Field Data from an MCT project
Real Time 28 / 56 days
Surface Resistivity – 28 Days
25. Cements
Widespread use of SCMs
Advancements in chemical admixture technology
De-icers
Agency personnel and experience levels
Industry knowledge base
“But Mike, You’re Asking for a Lot of Change”
Change has already happened!
27. PEM Pooled Fund Partners
FHWA
State Departments of Transportation
(DOTs)
Industry (American Concrete Pavement
Association, Portland Cement Association,
National Ready Mixed Concrete
Association, others)
Image Pixabay
29. Pooled Fund Emphasis
Implementation
Education and training
Adjustments in specifications based on
field performance
Continued development of a knowledge
base relating early age properties to
performance
Introduction and Key Points
There are four main sources of inherent variability.
Variability exists in all construction materials. It is one of the key factors that is integral to Quality Assurance and must be clearly understood. Variability is defined as “differences in measured test values for a given Quality Characteristic within a stable pattern due to chance, or outside this normal pattern due to an assignable cause.” Variation can be controlled, but cannot be eliminated. The level of Quality of any material or product is associated with the level of Variability. There are four primary sources of Inherent Variability; Material Variability, Process (or Production/Construction) Variability, Sampling Variability and Testing Variability. Sampling and Testing Variability, combined, have been stated as comprising up to 50 percent of the total overall composite variation in test results from independent random samples.
Instruction
Review information on the slide.
Engagement
N/A
This table illustrates the variation associated with standard test procedures typically encountered in paving projects. Note that we are only interested in the actual materials variability and are constantly trying to improve the testing procedure to minimize all other sources of error.
Precision and Bias considerations Established test procedures (ASTM, AASHTO) have accounted for test variability through precision and bias statements
All physical tests have built in variability that must be accounted for in some manner
Performance based specifications for the following:
Materials:
Cementitious materials
Aggregates
Admixture
Water
Reinforcing Steel
Dowel Bars
Fibers
Subbase materials
Joint materials
Designs and Systems:
Pavement Life without major reconstruction
Pavement Life with limited maintenance
Pavement Life with cars only loads
Pavement Life with heavy loads
Prefabricated Pavement Systems
Welcome the audience
Same air content data that the class just plotted
Note that the unit weight axis is in reverse order (heavier to lighter) – why would we do this? How are air content and unit weight related?
What should the unit weight do as the air content increases? Unit weight should decrease
