Transcript Asphalt Mix Basics
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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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 10
Oil Refinery
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CRUDE OIL DISTILLATION (TYPICAL) 1000 ASPHALT 800 GAS OIL 600 DIESEL KEROSINE 400 GASOLINE 200 0 0 GAS 20 40 60 PERCENT DISTILLED 80 100 13
Grading system based on climate
PG 67-22
Performance Grade Average 7-day max pavement design temp Min pavement design temp 14
Florida: PG 67-22 (153°F to -8°F) Old AC-30 / 60 pen Actually PG 67-10 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) Base Courses (234) B-12.5
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 0.48 ESAL
+
6,000 lb 0.01 ESAL
=
0.49 ESALs
34,000 lb 1.10
+
34,000 lb 1.10
+
12,000lb 0.20
=
2.40 ESALs
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Traffic Level
A B C D E
Traffic Levels are found in the Contract ESALS come from planning ESAL’s
< 300,000 ESAL’s 300,000 < 3 million ESAL’s 3 million < 10 million ESAL’s 10 million < 30 million ESAL’s ≥ 30 million ESAL’s
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19% D 3% 1% B C 40% TL-A TL-B TL-C TL-D TL-E 37% 22
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 33
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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