Asphalt Mix Basics

Transcript Asphalt Mix Basics

Tanya Nash State Materials Office

 Asphalt Overview  Asphalt CQC (Specs 334 and 337)  Miscellaneous Information, Specification Changes, and Research

1” Friction Course 4” Structural Course 8” Base (Limerock or Asphalt) 12” Stabilized Subgrade

 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

 “Binds” the aggregate together.

 Provides…..

 the “glue.”  lubrication for compaction.

 durability (resistance to cracking).

 The most expensive part of an asphalt mix.

Where does asphalt come from?

Crude Oil

How does crude get here?

Pipeline Ship 10

Oil Refinery

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)

 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

 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.

 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

    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

15,000 lb 0.48 ESAL

6,000 lb 0.01 ESAL

0.49 ESALs

34,000 lb 1.10

12,000lb 0.20

2.40 ESALs

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

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

Fine graded SP-12.5 mix

Coarse graded SP-19.0 mix

 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.

 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.

       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.

FC-5 Nassau County

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!