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February 2012
NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM
Responsible Senior Program Officer: E. T. Harrigan
Research Results Digest 369
AASHTO T 209: EFFECT OF AGITATION EQUIPMENT TYPE
ON THEORETICAL MAXIMUM SPECIFIC GRAVITY VALUES
This digest summarizes key findings of research conducted in NCHRP
Project 10-87(01), "Precision Statements for AASHTO Standard Methods
of Test," by the AASHTO Asphalt Materials Reference Laboratory (AMRL)
under the direction of the principal investigator, Dr. Haleh Azari. The digest
is an abridgement of the full final report, which is available for download
at http://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=3049.
BACKGROUND or mechanical agitation, removes entrapped
air in order to accurately determine the Gmm.
AASHTO T 209, Theoretical Maximum
The Gmm is then used to determine both the
Specific Gravity and Density of Bituminous
air void content and the in-place density of
Paving Mixtures, describes a test method
the HMA. In-place density is commonly
for determination of the theoretical maxi-
used in the acceptance and pay-factor de-
mum specific gravity (Gmm) and density of
termination of HMA.
uncompacted hot mix asphalt (HMA).1 The
Analysis of the AMRL Proficiency
Gmm and the density of HMA are fundamen-
Sample Program data has demonstrated that
tal properties whose values are influenced
mechanical agitation provides less variation
by the composition of the HMA mixtures
in test results when compared to manual ag-
in terms of types and amounts of aggre-
itation. However, several types of mechan-
gates and asphalt materials. Gmm is used
ical vibratory shakers are commonly used to
to calculate percent air voids in compacted
apply agitation. It was not known if these
HMA and to provide target values for the
different devices provide significantly dif-
compaction of HMA. Gmm also is essen-
ferent results when compared to one another.
tial when calculating the amount of asphalt
In addition, the effects on Gmm values of
binder absorbed by the internal porosity of
changes in vibration intensity from various
the individual aggregate particles in HMA.
settings of the vibrating devices had not
AASHTO T 209 requires application
been explored.
of a vacuum to a sample of HMA loose mix.
The vacuum, combined with either manual
C O N T E N T S OBJECTIVES AND SCOPE
Background, 1 The goal of this research was to eval-
1AASHTO T 209-10, Theoretical Maximum Spe-
Objectives and Scope, 1
cific Gravity and Density of Hot Mix Asphalt uate the effect of using various devices
Survey of State DOT
(HMA). In Standard Specifications for Transpor- and methods on measured values of Gmm.
Laboratories, 2
tation Materials and Methods of Sampling and The specific objectives were to (1) compare
Experiment Design, 2 the Gmm between manual and mechanical
Testing, 30th ed. American Association of State
Results and Analysis, 7 Highway and Transportation Officials, Washington, agitation; (2) investigate the relationship
Findings and Conclusions, 23 D.C., 2010. between the measured Gmm and the vibratory
