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.