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AASHTO Subcommittee on Materials Haleh Azari, Ph.D.
August 4, 2009
Status of Research at AMRL
Outline Accomplished work Ongoing research Future projects
Accomplished work
NCHRP 9-26 Under NCHRP 9-26, AMRL has been conducting a
multi-phase research project to improve estimates of precision in AASHTO test methods for various pavement materials
NCHRP Reports available online from previous phases of the study: Phase 1, http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_w54.pdf
Phase 2, http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_w66.pdf
Phase 3, http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_w71.pdf
Phase 4, http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_w109.pdf
Phase 5, http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_w114.pdf
Ongoing Projects
NCHRP 9-26 (A) “Interlaboratory Studies and Data Mining to Collect Data for the Preparation of Precision Statements”
Develop, verify, or update precision estimates for several AASHTO test methods selected by AASHTO Highway Subcommittee on Materials (HSOM) on broad range of highway materials including soil, aggregate, asphalt binder, asphalt mixture, hydraulic cement, and hydraulic cement concrete
NCHRP 9-26A- 2007 to Present
Prepared precision statements for 11 test methods:
Divided into 7 tasks
Combination of interlaboratory studies and data mining
Tasks 1: Prepare precision statements using AMRL and CCRL Proficiency Data Prepared precision statements for: T104 (sulfate soundness) T22 (compressive strength), T154 (time of
setting), and T186 (early stiffening) T105
Three reports including the proposed precision statements for the 5 test methods are completed and will soon be available online
Task 2: P & B for AASHTO T148, “Measuring the Length of Drilled Concrete Cores”
A round robin study was conducted Six cores, 4” and 6” in diameter and 6” to
12” in height were obtained from LTTP Data collected from the cores carried to 7
state and private laboratories in East coast (MD, PA, DE, NJ,VA and NC
Precision estimates were developed and report is being prepared
Task 3: P & B for AASHTO T180, Moisture-Density Relations of Soil
Conducted an ILS and examined PSP data 4 fine and coarse blends suitable for base
and subbase were prepared and shipped to 35 participating labs
Each lab received 12 boxes 3 replicates * 4 blends
Data received from 28 laboratories Determined precision estimates for
methods B and D of T180 The report is being reviewed by the panel
Task 4: P & B for AASHTO T 265, “Laboratory Determination of Moisture Content of Soils”
Conducted an ILS using the same 4 soil-aggregate blends as in T180 ILS
AASHTO T 265 ILS
A total of 1440 samples were prepared and shipped to 40 laboratories.
Each laboratory received 36 samples 3 replicates * 4 blends * 3 moisture contents =36
Samples were prepared at optimum, 2% below, and 2% above the optimum moisture content of blends.
P &B were determined from the results obtained from 32 labs A report of the study is being prepared
Task 5: P & B for AASHTO T267, “Determination of Organic Content in Soils by Loss on Ignition”
Conducted an ILS involving 12 organic-soil blends: 3 types of soil (clay, silt, sand) 4 different % of fine grits of walnut shells (0%, 2%, 5%, 8%)
A total of 1080 samples were prepared and shipped to 30 labs
Each lab received thirsty-six 500-g samples :
3 soil * 3 replicates * 4 levels of organic content =36
Precision estimates prepared based on data from 25 laboratories
A report of the study is being prepared
Task 6: P & B for AASHTO T 283, “Resistance of Compacted Asphalt Mixtures to Moisture-Induced Damage”
Conducted an ILS Two mixtures with known low and high
levels of moisture susceptibility were selected Sandstone aggregate from MD as moisture
susceptible Limestone mixture from PA as moisture
resistant
AASHTO T 283 ILS 60 labs received materials and instructions to compact,
condition, and test TSR specimens 30 labs received materials for 4” Marshall 30 labs received materials for 6” Superpave Gyratory
Two sets of materials were distributed to each lab: Limestone aggregate from PA and PG 64-22 asphalt Sandstone aggregate from MD and PG 64-22 asphalt
For both limestone and sandstone mixtures 20 out of 30 laboratories sent gyratory results 15 out of 30 laboratories sent Marshall results
Conclusions of T283 ILS Precision estimates developed Report is being prepared Very large within- and between-
laboratory standard deviations (acceptable difference between results of 2 laboratories is 27%)
Very laborious test; not many laboratories commit the time
Not enough control over the parameters of the test
Task 7: P & B for AASHTO T242 “Frictional Properties of Paved Surfaces Using a Full-Scale Tire”
Precision estimates for T242 were prepared based on Texas Transportation Institute (TTI) and Transportation Research Center (TRC) friction data
Data included 7 years of arrival and departure friction values from Visiting Friction Measuring units of 24 state DOTs
Report of the study is being reviewed by the panel
AMRL Research Laboratory
“Special Projects Building” at NIST, 1963
Laboratory Equipment With the support of NCHRP 9-26 panel, AMRL purchased a
complete set of equipment specific for asphalt mixture performance testing
NCHRP equipment were installed in laboratory spaces in March 09 Asphalt Mixture Performance Tester (AMPT), Environmental
Chamber, Servopac gyratory compactor, circular saw & core drill Supplies: ovens, mixer, scales, sieve shaker, Bulk and max specific
gravity equipment, Coredry …
A research technician was hired in March 4 years of experience working in asphalt lab at VTRC
Environmental Chamber and AMPT
Shelby Oven and Servopac Gyratory Compactor
Aggregate Processing Lab
Mixture Processing Lab
NCHRP 9-26A- Appropriate Conditioning Time for Performance Testing of Asphalt Mixtures with Absorptive Aggregate During conditioning period, two processes occur: 1) absorption of asphalt into pores of aggregates 2) stiffening of asphalt
In Phase 4 of the study, the effect of absorption on volumetric properties of mixtures with absorptive aggregate examined
More absorption into pores of aggregate leaves smaller film of asphalt, which might be more vulnerable to stiffening
Effect of conditioning time on stiffening of mastic and mechanical properties of mixtures with absorptive aggregate is being investigated
Tests Utilized in the Study
X-ray microtomography to determine the change in asphalt (mastic) thickness with conditioning duration
X-ray diffraction (XRD) to investigate the change in crystalline structure of asphaltenes in mixtures conditioned for various durations
Nono-indentation to determine and compare hardness and elastic modulus of mastic in mixture conditioned for various durations
Dynamic modulus and flow number test using AMPT
X-Ray Microtomography
Allows determination of mastic thickness after conditioning for different durations
Resolution of 3 micron/pixel Can monitor thickness above voxel size
Evaluating Change in Mastic Film Thickness using X-ray microtomography
Absorptive Aggregate Non-Absorptive Aggregate
0.00
20.00
40.00
60.00
80.00
100.00
120.00
140.00
160.00
180.00
0hr 2hr 4hr
Film
Thi
ckne
ss (
Pixe
ls)
Average Film Thickness: Non-Absorptive
Measured
Calculated
Nano-Indentation
Elastic modulus and hardness of asphalt mastic can be compared after various conditioning periods
One testing cycle consists of loading segment, dwell time (30 s), and unloading segment
Several peak loads and loading rates can be examined Load and displacement resolution of the indenter are 1nN
(NanoNewton) and 0.01 nm (nanometer)
X-Ray Diffraction (XRD)
Change in X-ray pattern and peaks indicate the deterioration of crystalline structure of asphaltene due to aging
Can determine how fast the crystalline structure deteriorate Change in crystalline parameters relates to change in unit weight
of asphaltene
Performance Testing using AMPT
Conducting dynamic modulus and flow number test using AMPT
Change in fatigue and permanent deformation resistance of the mixture with change in short-term conditioning time is being explored
Dynamic Modulus Results at 20° C, Non-Absorptive Aggregate
NCHRP 20-7- Hydraulic Cement Composition Analysis and Performance Prediction A joint AMRL and NIST Project
Using advanced statistical data exploration methods, Performance prediction models (heat of hydration, sulfate resistance, setting times, strength gain…) are being developed by comparison of CCRL performance data to XRD determined phase compositions
NCHRP 20-7- Hydraulic Cement Composition Analysis and Performance Prediction Bogue bias is being determined using Bogue compositions
calculated using CCRL oxide test data and XRD-determined compositions
Developed models will be proposed to be incorporated into related AASHTO standards
CaOSiO2
Al2O3
Fe2O3
SO3
CO2
=
0.7369 0.6512 0.6226 0.4616 0.4119 0.56030.2631 0.3488 0.0000 0.0000 0.0000 0.00000.0000 0.0000 0.3774 0.2098 0.0000 0.00000.0000 0.0000 0.0000 0.3286 0.0000 0.00000.0000 0.0000 0.0000 0.0000 0.5881 0.00000.0000 0.0000 0.0000 0.0000 0.0000 0.4397
∗
C3SC2SC3A
C4 AFCSCC
NCHRP 20-7- Development of a Test Method for Optical Sizing and Roundness Determination of Glass Beads Utilized in Traffic Markings A joint AMRL and NIST Project Designed and conducted an ILS Prepared standard samples of three types of glass beads Sent 9 samples (3 types* 3 replicates) to each of 30 participating
laboratories to measure size distribution and roundness of the glass beads
15 laboratories conducted measurements using traditional sieve and roundometer (ASTM C1155 and C1218)
10 laboratories utilized computerized optical methods Accuracy and precision of the methods were evaluated
NCHRP 20-7- Characterization of the Beads by NIST NIST evaluated the parameters of the computerized optical
methods via analysis of X-ray images of glass bead samples One sample- sprinkled glass beads on contact paper then rolled
into a tube
Non-round
Round
107
0
0.05
0.1
0.15
0.2
0.25
0.3
0.4 0.5 0.6 0.7 0.8 0.9 1
III (P)
W/L3DT/L3DT/W3DW/L2DXcmin / L(2D)SPHT2DSPHT3D20 % line
Rou
ndne
ss p
aram
eter
s
Cutoff value
Roundness Fraction of Glass Beads as a Function of the Cutoff Value
Future Research Projects
NCHRP 4-35- Improved Test Methods for Specific Gravity and Absorption of Coarse and Fine Aggregate
A joint NCAT, AMRL, and NIST project NCAT has evaluated the available tests 1 test method for each fine and coarse
aggregate will be selected in Sept.
AMRL will prepare the experimental plan for the ruggedness study of the selected tests
AMRL, NIST, and NCAT will each conduct ruggedness testing in their own labs
Impacts of changes to test methods on HMA mix design and PCC proportioning will be determined
NCHRP 20-7 (272) Rheological Characterization of Flow Table Reference Material A joint AMRL and NIST Project awarded in
June 09 Production of flow table reference material
(mixture of silica powder and oil) is empirical and is based on trial and error
Flow values provided by the table are different from one batch to another
Objectives are to characterize the reference material using fundamental measurement techniques and to suggest a more efficient method for its production
NCHRP 20-7 (272) Rheological Characterization of Flow Table Reference Material
viscosity of oil, PSD of powder, and rheological properties (yield stress and plastic viscosity) of the mixture will be characterized using modern methods of measurements
Impact on the rheological properties from changes in the oil viscosity and the PSD of the powder is being determined
A methodology to produce the reference material more efficiently and measuring the properties without using the flow table is being developed
Precision and Bias Studies The precision and bias studies of the following
test methods requested by 9-26 panel: Multiple Stress Creep and Recovery (MSCR) test
(AASHTO TP 70, ASTM D7405) Hamburg test (AASHTO T 324) for permanent
deformation and moisture damage
The next set of requirements for precision and bias statements by SCOM
Studies Requested by 9-26 Panel Substitution of mercury devices with the alternative devises
in AASHTO test methods Investigate the effect of using alternative temperature and
pressure measuring devices on the precision and accuracy of the methods using mercury devices.
Investigate the calibration methods for the alternative devices.
Conduct a ruggedness study of AASHTO T 312 Development of a database for long-term storage of and
access to field data from projects built with WMA, high RAP content mixes, modified mixes, etc.
Research in Support of Mix and Aggregate FHWA ETG Initiatives
Establish specification criterion for permanent deformation using the Flow Number (Fn) Test Conducted with the AMPT equipment Prior to conduct of FHWA Pool fund study for implementation
of AMPT, test criteria and values of test parameters need to be established
Conduct of ruggedness study for measurement of E* with the indirect tensile test in support of Dr. Richard Kim work in NCSU.