Page 36 - MODELING OF ASPHALT CONCRETE

14 Cha pte r T w o

Standard Purpose of Test and Applicability for Modified Asphalt
Test Protocol Binders (MABs)
Tensile (Extensional) Properties
Forced Ductility @ Not a An index of tensile strength and energy required for
4°C standard complete failure. Specifically developed for polymer
modified asphalts and used widely in North America.
Response usually includes an initial and a secondary
peak of the stress which is used to calculate a ratio
showing effect of the modifier. Test taken from joint
sealant testing field.
Elastic Recovery @ D8084 An index of the capability of modified asphalt for elastic
25°C recovery. Measured using the conventional ductility set up
but sample is stretched and then cut to measure recovery
of cut ends. One of the most widely used to determine if
modified binder includes elastomers. Used in North America,
Australia and Europe. Method has been modified several
times and is run using sliding plate rheometer, ARRB
Elastometer, Consistometer, and torsional loading setup.
Toughness and Not a An index of energy to failure used to detect modifiers and
Tenacity @ 25°C standard assess their contribution to toughness. A hemispherical
test head is inserted in an asphalt container and then pulled
out. The area under the load deformation curve is divided
into an initial peak area and a terminal tenacity area.
The sum is the toughness. Elastomeric modifiers could
have a significant effect on tenacity and on toughness
particularly if they are cross-linked.

TABLE 2-1 List of Asphalt Traditional Tests (Continued)

these measures has been recognized by several researchers, and many attempts have
been made to correlate them with more fundamental rheological properties. For
example, formulas were proposed to calculate the coefficient of viscosity from
penetration (Saal and Labout 1958; Van der Poel 1954; Heukelom 1973; Davies 1981).
Ductility was considered by some researchers as an indicator of internal structure
(Halstead and Zenewitz 1961; Barth 1962), while others showed that it may be correlated
with certain shear susceptibility parameters (Traxler 1961; Traxler et al. 1944; Kandhal
and Wenger 1975). Other researchers tried to combine the two measures (penetration
and ductility) and relate them directly to pavement performance (Halstead 1961; Serafin
et al. 1967). The softening point was also correlated with more fundamental measures;
Van der Poel (1954) indicated that it can be considered as equipenetration temperature,
while Jongepier and Kuilman (1969) indicated that softening point is an equimodulus
temperature rather than an equiviscous temperature. These correlation studies have
relied on some general correlations that suffer in many instances from exceptions, low
statistical significance, and limited sampling of asphalts.
Viscosity, also a single point measure, is a fundamental material property expressed
in absolute units. However, the coefficient of viscosity is only a fundamental absolute
measure for Newtonian fluids. Newtonian fluids are those whose properties are