Lesson 5/Learning Event 1
Percent Voids Total Mix. Checking back into this curve at 4.7 percent, the value of OAC is
about 4.2 percent, which is within the allowable range of 3 to 5 percent.
Percent Voids Filled with AC. Checking back into this curve at 4.7 percent, it is found that the
value is about 72 percent, which is within the limits of 70 to 80 percent.
Step 4, Flow
In the example, using the value of 4.7 percent asphalt, as OAC, the curve shows an expected
flow of approximately 11. This is below the maximum criterion of 16 for surface course for high
pressure tires as given in column 3 of Table 9.
Since all1 criteria have been met, the asphalt content of the mix being used as an example is
considered to be 4.7 percent asphalt based on the weight of the total mix (Figure 18).
FIGURE 18
JOB MIX FORMULA
Once the optimum asphalt value has been selected, it is necessary to set up the "Job-mix
Formula," This is nothing more than a statement of the percentages of the total mix weight of
each of the ingredients in the mix.
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