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Testing Turnaround and HMA QC/QA Subtask Group Joint Meeting DENNIS DVORAK, PAVEMENT AND MATERIALS ENGINEER RESOURCE CENTER 9/29/2015
Testing Turnaround
and HMA QC/QA
Subtask Group
Joint Meeting
DENNIS DVORAK, PAVEMENT AND
MATERIALS ENGINEER
RESOURCE CENTER
9/29/2015
2007 Section 39 Peer Review
2
QC/QA
Stability values
Dispute Resolution
Penalties
NDI vs Cores
Moisture Content
2007 Peer Review
3
QC/QA recommendations:
Sublot size of 750 Ton
Maximum lot size of 20 sublots
Use t-test for validating contractor test results
Volumetric properties should be used for acceptance
Testing turnaround of 1-3 days
Maine
Use State Tests for Acceptance
3 business days testing turnaround
Contractor transports samples to lab next
day
Maine DOT tests within 2 business days
Contractor and RE are provided results via
E-mail within 24 hours of test completion
4
Maine
Contractor transports samples to lab next
business day
Sample security?
5
Recommendation DEVELOP AND IMPLEMENT UPDATED
TTECHNICIAN CERTIFICATION PROGRAM FOR ALL TESTERS (5 YEAR)
Training
Written Test
Proficiency Test
Passing IA checks (witness and split sample testing as appropriate) during previous 2 years can serve as proficiency test for recertification
6
Recommendation
Independent Assurance
Continue system approach where at least
90% of active testers are checked annually
7
Recommendations Caltrans should not provide results of acceptance
tests until comparison lot (t-test) is complete and all QC test results provided by contractor
Specification should allow new pay lot to start when the a specific mix design has not been placed on project for 30 days (minimum of 3 QC tests).
Multiple pay lots can be combined into one comparison lot (minimum of 4 and maximum of 7 Caltrans acceptance tests)
8
Recommendation
Caltrans should provide contractors
opportunity to conduct split sample or
proficiency sample testing once or twice
a month to ensure that both labs can get
similar results
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Quality Characteristics used
for Acceptance
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Quality Characteristic Number of States
Va (Laboratory Air Voids) 43
Density 52
Smoothness 50
%Asphalt Content 45
VMA 32
*2014 FHWA Quality Assurance Assessment Update
PWL
Used in 30 states
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Ignition oven and post-
production gradations
Ignition oven
Used in majority of states
Aggregate from burn-off used for
gradation acceptance
12
Recommendations
Va, Density, Smoothness as Pay factors
Could add %AC, VMA and one or two
critical sieves as Pay Factors
Use ignition oven and post-production
gradation
PWL to calculate pay factors
Shut-down criteria for tests without pay
factors
13
Recommendation
Eliminate Maximum Aggregate
Temperature
Use post-production gradation from ignition
oven (or extraction if aggregate has
excessive break down)
Ensure that PG binder grade is not effected
14
Variability in RHMA-G mix
designs
Caltrans allows contractor to vary
number of gyrations and pressure during
mix design
No other state allows number of gyrations
and pressure to change
Recommendation
Standardize number of gyrations and
pressure within three years
Caltrans should not allow contractor to
change number of gyrations and pressure
after mix design approval (unless new mix
design approved)
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