Asphalt Pavement Ispection Basics ctt.pdf

Asphalt mixtures

1. Ask the Expert:
Asphalt Pavement Inspection Basics
Chuck Mills, PE
Director of Engineering
[email protected]

2. 2
HMA Construction Inspection
•Sound inspection practices during
construction are vital to obtain quality
•Both Agency and Contractor are
responsible
•Process control and acceptance procedures
alone will not ensure quality
•Key components of Inspection are:
–Enforcement of specifications
–Ensure good practices are being used
–Observation of materials and workmanship

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•How do we define Quality?
–Meets Agency mixture specifications
–Meets Agency density specifications
–Smooth riding surface
–Uniform texture and appearance
–Obtains expected service life
–Long Lasting asphalt pavement
What is Quality?

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•Responsibilities
–Represent the owner’s interests
–Keep daily construction diary
–Monitor ambient air and mat temperatures
–Track tonnage with truck tickets
–Calculate yield
–Monitor compaction with nuclear or non-nuclear
gauge
–Observe materials and workmanship
–Make sure that good practices are being used
HMA Construction Inspection

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MDOT Temperature and Weather Limitations
–Min temp 35 deg. F, min. 200 lbs/syd
–Min temp 40 deg. F, min. 120 lbs/syd
–Min temp 50 deg. F, any course
Temperature and Weather Limitations

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Min. and Max. Mix Temperatures

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Why does it matter if the mix is too cold?
–Because the mix stiffens as it cools. This makes it difficult to
obtain proper roadway compaction.
–Proper roadway compaction is probably THE most
important factor in determining the logevity of the roadway.
Every effort must be made to obtain the target density
during the compaction process.
Temperature and Weather Limitations

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Why does it matter if the mix is too hot?
–Because the lighter fractions of the asphalt
binder evaporate at higher temperatures.
–This makes the remaining binder stiffer,
and causes early aging of the binder. Aged
binder tends to be more brittle, and more
suseptable to cracking.
Temperature and Weather Limitations

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Importance of Tack Coat
•What is it?
•Why is it applied?
Courtesy of Pavement Design Materials, Analysis, and Highways
(2020)
Courtesy of NCAT

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Importance of Tack Coat

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Importance of Tack Coat
GOOD
Even uniform coverage
No puddles
No stripes
BAD
Uneven coverage
Clogged nozzles /
improper orientation
Stripes are clearly visible

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Is There Segregation??
• Is the paver causing segregation?
• If we are segregated in the trucks
and the hopper what can we do?
• Segregation is created. The compaction
process cannot undo segregation

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We need to pay attention at every step from the plant to
the paver to avoid segregation

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Blemish
<<<<< Direction of Paving
Screed adjustment and set up can play a very important role in
compaction
Screed Set up and Laydown

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No Segregation: Temperature or Material
Best practices and consistency will lead to full
pay and a quality project

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Questions
www.apa-mi.org
when smoothness matters!
Chuck Mills, PE
Director of Engineering
[email protected]

17. 17
CTT –
Asphalt
Series