Asphalt Mix Basics

Report
Tanya Nash
State Materials Office
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


Asphalt Overview
Asphalt CQC (Specs 334 and 337)
Miscellaneous Information, Specification
Changes, and Research
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3
1” Friction Course
4” Structural Course
8” Base (Limerock or Asphalt)
12” Stabilized Subgrade
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
Blend of:
 Asphalt binder (6%)
 Aggregate (94%)

Method of Design
 Hubbard Field (…1960’s)
 Marshall (1960’s – 1998)
 Superpave (1998 ….)

Produced through an
asphalt plant
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

“Binds” the aggregate together.
Provides…..
 the “glue.”
 lubrication for compaction.
 durability (resistance to cracking).

The most expensive part of an asphalt mix.
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Where does asphalt come from?
Crude Oil
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How does crude get here?
Pipeline
Ship
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Oil Refinery
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CRUDE OIL DISTILLATION
(TYPICAL)
1000
ASPHALT
TEMPERATURE oF
800
GAS OIL
600
DIESEL
KEROSINE
400
GASOLINE
200
GAS
0
0
20
40
60
PERCENT DISTILLED
80
100
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
Grading system based on climate
PG 67-22
Performance
Grade
Average 7-day
max pavement
design temp
Min pavement
design temp
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
Florida:
PG 67-22 (153°F to -8°F)
 Old AC-30 / 60 pen
 Actually PG 67-10
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
Minnesota:
Arizona:
PG 58-34 (136°F to -29°F)
PG 70-10 (158°F to 14°F)
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
PG 67-22 – Standard Grade
 <20% Reclaimed Asphalt Pavement (RAP)

PG 64-22
 20 – 29% RAP

Recycling Agent (RA)
 ≥ 30% RAP

PG 76-22
 PG 67-22 base asphalt + SB or SBS Polymer
 ≤ 20% RAP
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
Asphalt Rubber Binders
 ARB-5 - Dense graded friction course (≤ 20% RAP).
 ARB-12 - Open graded friction course (no RAP).
 ARB-20 - Asphalt Rubber Membrane Interlayer
(ARMI). No Rap allowed.
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
Structural Courses (334) Superpave
 SP-9.5, SP-12.5, SP-19.0

Friction Courses (337)
 FC-9.5, FC-12.5, FC-5 (OGFC)
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Base Courses (234)
 B-12.5
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Other
 Asphalt Treated Permeable Base (ATPB)
▪ Used under PCC pavements
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
Purpose: Load carrying portion of pavement
 Superpave Mix Design

Three mixes based on max aggregate sizes
 9.5 mm (SP-9.5)
 12.5 mm (SP-12.5)
 19.0 mm (SP-19.0)

Five Traffic Levels (A-E)
 Based on 18,000 lb. Equivalent Single Axle Loads (ESAL’s)
 Low traffic = A, High traffic = E

Concept: Put the right mix on the right road
 Higher traffic level is not necessarily better
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15,000 lb
6,000 lb
0.48 ESAL + 0.01 ESAL
34,000 lb
1.10
+
=
34,000 lb 12,000lb
1.10 + 0.20
0.49 ESALs
=
2.40 ESALs
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ESALS come
from
planning
Traffic Levels
are found in
the Contract
Traffic Level
ESAL’s
A
< 300,000 ESAL’s
B
300,000 < 3 million ESAL’s
C
3 million < 10 million ESAL’s
D
10 million < 30 million ESAL’s
E
≥ 30 million ESAL’s
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3%
1%
19%
D
B
C
40%
TL-A
TL-B
TL-C
TL-D
TL-E
37%
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
Coarse mixes – More coarse aggregate than fine
 Higher density requirement
 Greater likelihood of being permeable
 Placed thicker
 Tough workability

Fine mixes – More fine aggregate than coarse
 Similar to old FDOT Type S mixes

Shown on the mix design
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Fine graded SP-12.5 mix
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Coarse graded SP-19.0 mix
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Purpose: Provide a pavement surface with good
tire/pavement friction.

Required on all jobs with:
 Design Speed ≥35 mph, except rural 2-lane roads with
5-yr projected AADT of ≤3,000.

Use polish resistant aggregate
 Oolitic limestone (Dade & Broward Counties)
 Granite (Georgia & Canada)
 Siliceous Wackestone (Canada)
 Shell rock (Palm Beach Co.)

Use asphalt rubber binder (ARB) or PG76-22.
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 Good microtexture
▪ Function of the aggregate
 Superpave mixes:
▪ FC-9.5 (1” thick)
▪ FC-12.5 (1 ½” thick)
▪ Formerly called FC-6
 100% oolite or 60% granite
▪ If granite, then can contain 20% RAP, otherwise no RAP.
 ARB-5 or PG 76-22 depending on traffic level.
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 Required on high speed multi-lane facilities.
▪ Design Speed ≥ 50 mph
 Good macrotexture.
▪ Minimize hydroplaning.
 FC-5 (3/4” to 7/8” thick)
 100% friction approved aggregate (No RAP).
 ARB-12 or PG76-22.
 Stabilizing fibers (more asphalt, less draindown).
 Granite aggregate requires hydrated lime.
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FC-5 Nassau County
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Close-up FC-5 Macrotexture
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
B-12.5
Superpave Mix
 Traffic Level B

May substitute an SP-12.5
 It’s basically the same mix!
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Questions/ Comments?
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