Transcript 20070207A - Oklahoma Department of Transportation

2007 ANNUAL CONFERENCE
WHEN TO
WORRY ABOUT
TEST RESULTS
Danny Gierhart, P.E. ODOT
Bituminous Engineer
ANSWER:
(However, you need to worry
about some more than others)
•
What is the test designed to tell you?
•
What are the potential ramifications of
a failing test result?
•
Are the potential ramifications minor
or major?
•
For this test, how much could the
degree out of specification affect
pavement performance?
Test results are often used to
document the degree out of
specification so that a corresponding
financial penalty can be assessed.
The very best use of test results is to
track the ongoing quality of a project
and make corrections as necessary to
ensure a quality pavement.
•
LIQUID ASPHALT
•
AGGREGATE
•
HOT MIX ASPHALT
ASPHALT BINDER TEST –
DYNAMIC SHEAR RHEOMETER (DSR)
1.15
ASPHALT BINDER TEST –
DYNAMIC SHEAR RHEOMETER (DSR)
•
What is the test designed to tell you?
The purpose of the test is to address potential
rutting due to binder stiffness.
•
What are the potential ramifications of
a failing test result?
Typical failing DSR tests reveal increased rutting
and/or cracking potential. from negligible up to
an average of 1/4”. They can also indicate
whether or not the binder has sufficient polymer.
ASPHALT BINDER TEST –
DYNAMIC SHEAR RHEOMETER (DSR)
•
Are the potential ramifications minor
or major?
A typical failing DSR test indicates relatively
minor problems. Large deviations can
indicate significant problems.
•
How much does the degree out of
spec affect pavement performance?
DSR tests that are slightly low (running 0.90
to 0.99) are minor. Tests that are ½ the target
indicate a lower grade of binder was sampled.
ASPHALT EMULSION TEST –
SAYBOLT-FUROL VISCOSITY
1.15
77
20 - 100
22
ASPHALT EMULSION TEST –
SAYBOLT-FUROL VISCOSITY
• What is the test designed to tell you?
The purpose of the test is to show the as-delivered
viscosity, or fluidity of the material.
• What are the potential ramifications of
a failing test result?
Failing tack coat results will often be on the low
side, indicating a deficiency of residual asphalt.
This could cause slippage between lifts. For chip
seal emulsions, a low value could mean that
aggregate particles will not stick well. Results on
the high side may be caused by an old sample.
Slippage between lifts as a result of insufficient
adhesion.
ASPHALT EMULSION TEST –
SAYBOLT-FUROL VISCOSITY
•
Are the potential ramifications minor
or major?
Failing viscosity tests that are an accurate indicator
of low residual asphalt content can, under the right
circumstances, have serious ramifications.
•
How much does the degree out of
spec affect pavement performance?
Field application has a significant effect on
performance. It is very difficult to establish how big
the problem is based on test results alone.
RED FLAG ALERT!
Emulsion test results are only as good as
the sample quality. Emulsion samples are
particularly susceptible to compromise.
• Samples obtained after the emulsion
is diluted onsite.
• Samples obtained, but not submitted
for weeks.
• Samples allowed to sit in sun or roll
around in truck.
• Samples placed in a contaminated
container.
ASPHALT CUTBACK TEST –
KINEMATIC VISCOSITY
30 - 60
45
ASPHALT CUTBACK TEST –
KINEMATIC VISCOSITY
• What is the test designed to tell you?
This test also shows the as-delivered viscosity, or
fluidity of the material. It tells the supplier about
the uniformity of shipments.
•
What are the potential ramifications of
a failing test result?
Low test results indicate a higher ratio of diluent
to asphalt cement. The prime may not provide
the moisture barrier intended. High test results
indicate a lower ratio of diluent to asphalt cement.
ASPHALT CUTBACK TEST –
KINEMATIC VISCOSITY
•
Are the potential ramifications minor
or major?
Failing viscosity tests have a minimal effect on the
quality of prime. For example, both MC-30 and MC70 are acceptable for use as prime coat. An out-ofspec high MC-30 may meet or be low for MC-70.
•
How much does the degree out of
spec affect pavement performance?
Out-of-spec on the high side should not have a major
effect. Tests for MC-30 that are significantly low will
likely result in an ineffective moisture barrier.
AGGREGATE TEST GRADATION
Comparison
Comparison
Comparison
AGGREGATE TEST –
GRADATION (Max. Agg. Size)
• What is the test designed to tell you?
The maximum aggregate size influences allowable
pavement thickness, susceptibility to segregation,
asphalt content, and volumetric requirements.
•
What are the potential ramifications of
a failing test result?
A gradation on the maximum sieve size that is
less than 100% indicates the presence of oversized particles. This could result in compaction
difficulties, segregation, and asphalt content
problems.
AGGREGATE TEST –
GRADATION (Max. Agg. Size)
•
Are the potential ramifications minor
or major?
Gradations results showing less that 100% passing
the maximum sieve size are rare and usually only
slightly less than 100%. Potential ramifications are
minimal.
•
How much does the degree out of
spec affect pavement performance?
Results deviating by 10% or more indicate that a
different type of HMA was sampled than expected.
Comparison
AGGREGATE TEST –
GRADATION (% Passing # 200)
• What is the test designed to tell you?
The % passing the # 200 sieve influences
compaction, asphalt content, and volumetric
requirements.
•
What are the potential ramifications of
a failing test result?
A low % passing the # 200 may result in high air
voids, permeability, and a lower AC demand. A
high value may result in low air voids and VMA, a
higher AC demand, and a tender mix.
Check cracking as a result of a high % passing the
#200 sieve combined with a low binder content
High % passing the #200 gives the HMA a lighter appearance,
indicating a lower film thickness and lower durability.
AGGREGATE TEST –
GRADATION (% Passing # 200)
•
Are the potential ramifications minor
or major?
High dust portions can have major ramifications
on the longevity of a roadway. They are typically
accompanied by lower than necessary binder
contents which reduce pavement durability.
•
How much does the degree out of
spec affect pavement performance?
Deviations inside the tolerance of 2% typically don’t
have too much of an effect. Deviations greater than
2% should be addressed immediately.
Comparison
AGGREGATE TEST –
GRADATION (% Passing # 8)
• What is the test designed to tell you?
The % passing the # 8 sieve has a major influence
on voids and permeability.
•
What are the potential ramifications of
a failing test result?
A low % passing the # 8 sieve may result in a
permeable mix. A high value is not as worrisome
as a low value.
Low % passing the # 8 indicates a mix that is subject to
permeability, which in turn can lead to stripping.
AGGREGATE TEST –
GRADATION (% Passing # 8)
•
Are the potential ramifications minor
or major?
A low % passing the # 8 sieve can have major
ramifications on the longevity of a roadway. They
are often accompanied by permeability issues
which can lead to stripping.
•
How much does the degree out of
spec affect pavement performance?
Gradations near the lower broad band are especially
of concern when accompanied by a low % passing
the # 200 sieve.
AGGREGATE TEST –
SAND EQUIVALENT
AGGREGATE TEST –
SAND EQUIVALENT
• What is the test designed to tell you?
The test is intended to show the relative
proportions of fine dust or clay-like material in
the aggregate.
•
What are the potential ramifications of
a failing test result?
A low sand equivalent result indicates a high
percentage by volume of clay-like fines. These
fines may cause the asphalt binder to debond
from the aggregate in the presence of moisture.
Low sand equivalents indicate a high percentage of clay-like
fines, which can cause a poor bond with the asphalt binder.
AGGREGATE TEST –
SAND EQUIVALENT
•
Are the potential ramifications minor
or major?
Although extremely rare, a failing sand equivalent
test indicates a very poor aggregate quality, which
can have major ramifications to the longevity of the
pavement.
•
How much does the degree out of
spec affect pavement performance?
Sand equivalent results do not have to be much out
of spec to be a cause for concern.
HOT MIX ASPHALT TEST –
TENSILE STRENGTH RATIO
HOT MIX ASPHALT TEST –
TENSILE STRENGTH RATIO
• What is the test designed to tell you?
The test is intended to show the susceptibility of
the HMA to moisture damage.
•
What are the potential ramifications of
a failing test result?
A failing TSR indicates the mix is inherently
susceptible to stripping and raveling.
Tensile Strength Ratio
AASHTO T 283
• Moisture Sensitivity
– Prepare set of 6 specimens
• 6.5 to 7.5% voids
– Represents anticipated in-service voids
– Use 3 specimens as controls
– Remaining 3 specimens are vacuum saturated 70
to 80%
– Min. 16 hour freezing at 0oF
– 24 Hours in 140oF water bath
– Bring all specimens to test temperature (77oF)
and determine indirect tensile strength
Tensile Strength Ratio
AASHTO T 283
Saturating Specimens
Freezing Specimens
Specimens in Hot Water Bath
Moisture Sensitivity
AASHTO T 283
Determine the indirect
tensile strengths of both
sets of 3 specimens
Calculate the
Tensile Strength
Ratio (TSR)
Avg. wet tensile strength
TSR =
Avg. dry tensile strength
Minimum of 75% required for field tests
HOT MIX ASPHALT TEST –
TENSILE STRENGTH RATIO
•
Are the potential ramifications minor
or major?
The ramifications of a failing TSR can be severe.
•
How much does the degree out of
spec affect pavement performance?
Because the test procedure is not one of the most
repeatable, results down to around 70% should be
confirmed by further testing. TSR results less than
65% would be just cause for immediate work
stoppage to investigate and fix the problem.
HOT MIX ASPHALT TEST –
ASPHALT BINDER CONTENT
Result
JMF
Comparison
HOT MIX ASPHALT TEST –
ASPHALT BINDER CONTENT
• What is the test designed to tell you?
The test shows the percent of asphalt binder by
weight of the total mix.
•
What are the potential ramifications of
a failing test result?
A low binder content can lead to premature aging
of the pavement, stripping, or raveling. A high
binder content can lead to flushing or bleeding in
the pavement.
Low binder contents can lead to raveling, stripping, and
premature aging.
High binder contents can lead to flushing or bleeding.
HOT MIX ASPHALT TEST –
ASPHALT BINDER CONTENT
•
Are the potential ramifications minor
or major?
The ramifications would likely be different
depending on the degree out of spec. Whether any
of the potential pavement distresses occur also
depend on other factors.
•
How much does the degree out of
spec affect pavement performance?
Binder content is one of several parameters that
affect each other. However, binder contents very far
out of spec should be a major cause for concern.
HOT MIX ASPHALT TEST –
AIR VOID CONTENT
Specimen 1
Specimen 2
Average
HOT MIX ASPHALT TEST –
AIR VOID CONTENT
• What is the test designed to tell you?
The test shows the percent air voids in labmolded specimens. This test indicates a mix
property, not in-place air voids.
•
What are the potential ramifications of
a failing test result?
With a low air void content, the pavement is
susceptible to rutting, flushing, and bleeding. For
high air void contents, the pavement is susceptible
to premature aging, raveling, and stripping.
HOT MIX ASPHALT TEST –
AIR VOID CONTENT
•
Are the potential ramifications minor
or major?
The ramifications can be severe depending on the
degree out of specification. Whether any of the
potential pavement distresses occur also depend
on other factors.
•
How much does the degree out of
spec affect pavement performance?
All failing void contents need some type of action.
Mixes that are 1% or more out of spec indicate a
need for immediate shutdown for more trials.
HOT MIX ASPHALT TEST – VOIDS
IN MINERAL AGGREGATE (VMA)
Specimen 1
Specimen 2
Average
HOT MIX ASPHALT TEST – VOIDS
IN MINERAL AGGREGATE (VMA)
• What is the test designed to tell you?
VMA is calculated from the binder content test and
lab-molded specimens. It tells about the total
volume of the voids created by aggregates.
•
What are the potential ramifications of
a failing test result?
Samples with low VMA do not have enough void
space to provide the proper amount of binder and
the proper amount of air. Low VMA, depending on
the reason, could result in many distress types.
HOT MIX ASPHALT TEST – VOIDS
IN MINERAL AGGREGATE (VMA)
•
Are the potential ramifications minor
or major?
The ramifications can be severe depending on the
degree out of specification. Whether any of the
potential pavement distresses occur also depend
on other factors.
•
How much does the degree out of
spec affect pavement performance?
Mixes that are 1% or more out of spec indicate a
need for immediate shutdown for more trials.
HOT MIX ASPHALT TEST –
ROADWAY DENSITY
Core 1
Core 2
Core 3
HOT MIX ASPHALT TEST –
ROADWAY DENSITY
• What is the test designed to tell you?
The test indicates the in-place density achieved by
the compactive effort of the rolling operation.
•
What are the potential ramifications of
a failing test result?
Low density may result in permeability, stripping,
raveling, cracking, premature aging, and
premature failure. High density may result in
rutting, flushing, or bleeding.
HOT MIX ASPHALT TEST –
ROADWAY DENSITY
•
Are the potential ramifications minor
or major?
The ramifications of failure to achieve proper
density are major. Proper density can in part make
up for other shortcomings. Improper density can
cause failure even if other parameters are good.
• How much does the degree out of
spec affect pavement performance?
Any failing density report should cause the
agency to closely examine the rolling operation.
The further out of spec, the shorter the anticipated
pavement life.
In summary, all failing test results
should be followed up on.
Some test results may be received after
all of the material is already in place.
Some test results will be received in
time for corrective action, which should
be immediate.
Remember that a few hours time
addressing a problem may prolong the
pavement life by several years.
QUESTIONS?