ASPHALT BINDERS AND ASPHALT MIXTURES - Materials for Civil and Construction Engineers - page 367

Te r tiary

Secondary

Primary

N FN (Flow Number)

Loading Cycles

FIGURE 9.31 Typical relationship between total cumulative
plastic strain and loading cycles.

major zones: primary zone, secondary zone, and tertiary flow zone. The time
at which tertiary flow starts is referred to as the Flow Time . The flow time is
a significant parameter in evaluating the rutting resistance of HMA.

Triaxial Repeated Load Permanent Deformation Test Another approach to
measuring the permanent deformation characteristics of HMA is to use a re-
peated load test for several thousand repetitions and to record the cumula-
tive permanent deformation as a function of the number of load repetitions.
In this test, a haversine pulse load consisting of a 0.1 second and 0.9 second
dwell (rest) time is applied for the test duration, typically about three hours
or 10,000 loading cycles.
Results from the repeated load tests typically are presented in terms of
the cumulative permanent strain versus the number of loading cycles.
Figure 9.31 illustrates a typical relationship between the cumulative plastic
strain and number of load cycles. In a manner similar to the triaxial static
creep test, the cumulative permanent strain curve can be divided into three
zones: primary, secondary, and tertiary. The cycle number at which tertiary
flow starts is referred to as the Flow Number . In addition to the flow num-
ber, the test can provide the resilient strain and modulus, all of which are
correlated to the rutting resistance of HMA.

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9.9.5 Marshall Method of Mix Design

The basic steps required for performing Marshall mix design are as follows
(The Asphalt Institute 1995):

1. aggregate evaluation
2. asphalt cement evaluation