Asphalt Mix Basics

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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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