15 May 2001
c. Step 3. Determine the percentage of each aggregate to be used so that the gradation
requirements for the blend are satisfied. The gradation requirements for this example job are outlined in
table B-3. The gradation requirements for recycled hot mix are the same as those for new mixtures.
Through trial and error, it was determined that a blend using 50 percent reclaimed asphalt materials,
24 percent coarse aggregate, 19 percent fine aggregate, and 7 percent natural sand would satisfy the
gradation requirements (table B-3).
Gradation of Recycled Mixture
19 mm (3/4 inch)
12.7 mm (1/2 inch)
82 - 96
9.5 mm (3/8 inch)
75 - 89
4.75 mm (No. 4)
59 - 73
2.36 mm (No. 8)
46 - 60
1.18 mm (No. 16)
34 - 48
600 Fm (No. 30)
24 - 38
300 Fm (No. 50)
15 - 27
150 Fm (No. 10)
8 - 18
75 Fm (No. 200)
d. Step 4. Conduct a penetration test on the recovered asphalt cement. A penetration test on the
asphalt recovered from the in-place asphalt mixture indicated an asphalt penetration of 10. The target
penetration for this example (mild climate) is about 50. Because of the low penetration, it will be
necessary to use a low-viscosity asphalt cement, AC-2.5, and possibly an asphalt recycling agent.
e. Step 5. Prepare three samples at each selected asphalt content with no recycling agent and
three samples at each selected asphalt content, including an additional 0.5 percent recycling agent. The
added asphalt content should be varied from 2.5 to 4.0 percent for the samples with no recycling agent
and from 1.5 to 3.0 percent for the samples with 0.5 percent recycling agent. Figure B-3 shows the
properties of the mixtures with various added asphalt contents and 0.5 percent recycling agent.
Figure B-4 shows the properties of the mixtures at various asphalt contents with no recycling agent.
f. Step 6. Select the optimum asphalt content for the mixture with no recycling agent and for the
mixture with 0.5 percent recycling agent. The optimum asphalt content and mixture properties for the
two mixtures, as well as the penetration of the asphalt cement recovered from these two mixtures, are
listed in table B-4.
g. Step 7. Select a preliminary mix design to provide penetration of recovered asphalt cement to
be approximately 50 by interpolating between penetration values of 40 and 90 as determined in step 6.
The change in penetration with a change in recycling agent is not linear, but for the preliminary mixture
design a linear interpretation is sufficient. The properties at optimum asphalt and recycling agent
contents are presented in table B-5.