ETL 1110-l-139

22 Jun 90

Analysis and Asphalt Selection

The climatological data allow classification of the site by temperature

region and allow an estimate of pavement temperature. According to Table 4 of

Enclosure 1, the pavement temperature index classifies the site as a cold

region where the PVN method should be used to select the grade of asphalt

cement, The DFI allows the use of Figure 2 (Enclosure 1) to estimate a mini-

mum pavement temperature at a 2-in. (5 cm) depth. From Figure 2, a minimum

anticipated pavement temperature is about -22" F (-30" C).

Table 5 of Enclosure 1 shows that this cold region can be further classi-

fied as a moderately cold region since its DFI is less than 3,000

Fahrenheit-days. Table 5 also indicates that the required PVN of the asphalt

selected must be greater than -0.5 for a design index of 10. This will mini-

mize low temperature pavement cracking.

Now, PVN values must be determined for the available asphalt cements.

This can be done by either plotting penetration and viscosity at 275" F

in Figure 1 of Enclosure 1 or by using PVN equations. If the details

(135"

of Figure 1 are not sufficient to accurately determine PVN values, equations

should be used.

The general PVN equation1 is as follows:

X)(-1.5)

PVN

where

L

logarithm of viscosity in centistokes at 275" F

C) for a PVN

of 0.0 at the given penetration

logarithm of viscosity in centistokes at 275" F

C) of a given

X

asphalt

logarithm of viscosity in centistokes at

F

C) for a PVN

of -1.5 at the given penetration

Values of X can be determined directly from asphalt cement viscosity data as

provided in this example, but values of L and M are a function of the

penetration values of each asphalt. Equations for the values of L and M

are:

0.79674

(PEN)

L

4.25800

LOG

1

N. W., "Using Paving Asphalt Rheology to Impair or Improve Asphalt

Pavement Design and Performance", Asphalt Rheology: Relationship to Mixture,

ASTM STP 941, 0. E. Briscoe, Ed., American Society for Testing and Materials,

Philadelphia, 1987.

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