achieving better quality roads through better specifications
TRANSCRIPT
Achieving Better Quality Roads through Better Specifications
APWA Florida Chapter Annual
Tradeshow
Presented by
Matthew J. LaChance
Vanasse Hangen Brustlin, Inc.
Project Name Goes HereAchieving Better Quality Roads through Better Specifications
Do I really need my own paving specifications?
Specifications are a tool to help insure you get the product that is right for your job.
But you also have to test for conformance to make sure you’re getting what you asked for!
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Issues with Use of Typical Specifications
Insufficient material properties specified Don’t handle multiple roads in one day well Difficult to enforce May be outdated “Method Based” Specifications Little or no testing to determine conformance
Project Name Goes HereAchieving Better Quality Roads through Better Specifications
Issues with Use of Typical Specifications
Insufficient material properties specified• FDOT Standard Specification 331 – Marshall Mix Design
o Limited aggregate testingo Allows excessive use of RAPo Cannot adapt to today’s traffic levelso Viscosity graded asphalt cementso Potential for unstable mixes
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Unstable mix examples
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Issues with Use of Typical Specifications
Don’t handle multiple roads in one lot well• State specs based on long runs on state highways• One “sample lot” = up to 4000 tons of production• When applied across several roads, a single road may fail,
even though lot average passes
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Issues with Use of Typical Specifications
Difficult to enforce• When material is just slightly off spec – what do you do?
Accept? Reject and remove?
May be outdated• Existing municipal specifications may refer to older State
specs that refer to liquid asphalt grades that aren’t produced today
Project Name Goes HereAchieving Better Quality Roads through Better Specifications
Issues with Use of Typical Specifications
“Method Based” Specifications• Specify how work must be done – what tools to use, etc.
• When desired end results are not met – who is responsible?
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Issues with Use of Typical Specifications
Difficult to Read or Interpret
• Many municipalities “piggy back” or reference state or county specifications
• Often amendments to state or county specifications are made in separate documents
• Requires Inspectors to have multiple specifications in order to reference
• More difficult to interpret and enforce than the Federal Tax Code
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Issues with Use of Typical Specifications
Little or no testing to determine conformance• “No need to test – they do QC testing at the plant”
• Many municipalities don’t do density testing for conformance
• The mat looked good…
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Which pavement met the density spec?
This one?
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or this one?
Project Name Goes HereAchieving Better Quality Roads through Better Specifications
So what can I do differently?
Standalone, All-inclusive Document Quality Based Specifications Joint Density Superpave Test for Conformance
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Standalone, All-inclusive Document
Based on State specifications Includes standard specifications and alterations for
the “special needs” of the municipality Easier for contractors to provide a quality product
when all information in one place Easier to enforce with all requirements in one
place
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Quality Based Specifications
Contractor assumes primary responsibility for quality of material and construction
Owner responsible for sampling to verify accuracy of contractor’s tests
Sampling based on estimated volume of material to be placed
Control strips to establish achievable process control (dress rehearsal)
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Quality Based Specifications
Normally Includes pay factors• Provides penalties to handle material or work that is slightly
out of spec (to offset lower than average quality)• Provides understood procedure for when material is “out of
control”• Provides incentive for tighter control of material and work
(to reward better than average quality)• Reduces disputes after job is done
Project Name Goes HereAchieving Better Quality Roads through Better Specifications
Joint Density
Recognized fact that density at joint is more difficult to achieve
Rather than simply ignore density at joint, require slightly lower density – verify with control strip
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Joint Density
Joint construction methods• Conventional (confined edge)• Cutting Wheel (FAA)• Notch wedge joint• Hot poured rubber “tack”
• No “casting” of material
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Confined Edge JointConfines the outside edge of the mat as much as possible to create a
“nearly vertical” edge with end gates or other attachments
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Cutting Wheel
Cutting a 1 to 2 in. (25-50 mm) of the unconfined edge after compaction of the initial pull
10 in. (250 mm) cutting wheel
Vertical face tacked Rolled from hot side with 6
in. (150 mm) overlap on cold side
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Notched Wedge JointVariation of wedge joint
NOTCH ±12.5mm(1/2 in)
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Hot rubberized joint compound may improve the bond between lanes, but figure on an extra dollar a foot cost
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No “Casting”
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SuperpaveThere is nothing super about it…
No new aggregate or liquid asphalt Not just for highways & heavy vehicles It is a new way of specifying the materials and
quality of construction that is required Better ability to match materials and construction
to expected use of the pavement
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What is Superpave?
Superpave is an acronym for
Superior Performing Asphalt Pavements
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What is Superpave?
Improved System for Specifying:
• Asphalt Binders• Mineral Aggregates• Mixture Designs• Performance Prediction
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What makes Superpave so great?
Aggregate Property Tests• Coarse aggregate angularity• Fine aggregate angularity• Flat or elongated particles• Clay content• Toughness• Soundness• Deleterious materials
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What makes Superpave so great?
Improved Mix Design
•Gyratory Compaction is more realistic and provides flexibility
•Moisture susceptibility tests have been added
Photo goes here
Gyratory Compactor
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Performance Graded Asphalt Binder (PGAB)
Represents hot temperature design criteria in ˚C
Represents cold temperature design criteria in ˚C
76 -22
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Performance Grades Average 7-day Maximum Pavement Temperatures, °C
46 52 58 64 70 76 82 ?
Average 1-day Minimum Pavement Temperature, °C
+2 -4 -10 -16 -22 -28 -34 ?
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Typical Cross Section
Bituminous Surface CourseBituminous Binder Course
Base Course
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New Cross Section
HMA Superpave 9.5mm Level ?HMA Superpave 12.5mm Level ?
Base Course
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Comparison of Mix Names
MassDOT Superpave Course
Type S III 9.5mm Surface
Type S I 12.5mm Intermediate or Surface
ABC 25mm or 37.5mm
Base
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ESAL = Equivalent Single Axle Load
Level Design ESALs (million)
A < 0.3 B 0.3 - < 3.0 C 3.0 - < 30.0 D > 30.0
Where do Superpave Levels come from?
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Will Superpave cost more?
Most of the time, no. In fact, because they are already approved for state use and the inconvenience of producing several types of mixes, many producers are charging less for Superpave mixes.
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Do I have to use Superpave mixes?
No, Type S mixes are still available Using state mixes makes design and
approval process easier and faster Superpave gives designers more flexibility
with lift thickness and loading characteristics
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Summary
Ability to pay per mix type per street Control Strip (Dress Rehearsal) Joint Density Requirement Incentive/Disincentive Test material at the plant Density testing in field
Project Name Goes HereAchieving Better Quality Roads through Better Specifications
Test for Conformance
Achieving Better Quality Roads through Better Specifications
Questions & Answers
APWA Florida Chapter Annual
Tradeshow
Presented by
Matthew J. LaChance
Vanasse Hangen Brustlin, Inc.