Superpave – Low VolumePaul CURREN, P.E.Curren Consulting

Purpose of Low Volume Specification

Caltrans recognizes that new Section 39 Superpave specification may not be applicable to many local agency projects

Desire by Industry and Agency partners to allow for mixes generally accepted based on past specifications i.e. maximum medium (2006) and HMA (2010)

Allowance for lower cost aggregates (Type B) which perform well on low volume roadways

Reduced QC and QA requirements for lower volume roads due to less performance risk

What is Low Volume?

Mix Design Level Selection CriteriaTraffic Index Mix Design Level> 8.0 Level I6.0 to 8.0 Level II≤ 5.5 Level III

Applications of Levels

Level I is for arterials which have considerable truck traffic. Aggregate and mix requirements consistent with new 2015 Superpave Specifications with QC and QA modifications

Level II is for collectors which have medium levels of truck traffic. Aggregate and mix requirements reflect 2010 HMA requirements for aggregates and mix requirements

Level III is for residential streets, parking lots, pathways and miscellaneous areas. Aggregate and mix requirements more consistent with 2006 maximum, medium type mixes

HMA Mix Design RequirementsQuality characteristic Test method Level I Level II Level III

Air voids content (%)AASHTO T 269a

Ninitial > 8.0Ndesign = 4.0Nmax > 2.0

Ndesign = 4.0 Ndesign = 3.5

Gyration compaction (no. of gyrations)AASHTO T 312

Ninitial = 8Ndesign = 85Nmax = 130

Ndesign = 65 Ndesign = 65

Voids in mineral aggregate (min, %)b

Gradation:No. 43/8-inch1/2-inch3/4-inch

SP-2Asphalt Mixture

Volumetrics

  

16.5–19.515.5–18.514.5–17.513.5–16.5

  

16.0–19.015.0–18.014.-0–17.013.0–16.0

  

15.5–18.514.5–17.513.5–16.512.5–15.5

Dust proportion SP-2 0.6–1.3 0.5–1.4 NAHamburg wheel trackd (min number of passes at 0.5-inch rut depth)

Binder grade:PG 58PG 64PG 70PG 76 or higher

AASHTO T 324 (Modified)c

   

10,00015,00020,00025,000

   

10,00015,00020,00025,000

   

8,00012,00015,00020,000

Hamburg wheel trackd (min number of passes at the inflection point)

Binder grade:PG 58PG 64PG 70PG 76 or higher

AASHTO T 324 (Modified)c

   

10,00010,00012,50015,000

   

10,00010,00012,50015,000

   

8,0008,00010,00012,000

Aggregate Quality Requirements

Quality characteristic  Requirement

Test method Level I Level II Level IIIAggregate gradationa AASHTO T 27 JMF ± TolerancePercent of crushed particlesCoarse aggregate (min, %)

One-fractured faceTwo-fractured faces

Fine aggregate (min, %)(Passing No. 4 sieveand retained on No. 8 sieve.)One fractured face

AASHTO T 335

  

9590   

70

  

5050   

20

  

25    

20Los Angeles Rattler (max, %)

Loss at 100 Rev.Loss at 500 Rev.

AASHTO T 96 

1240

  

45

  

50Sand equivalent (min.)b, c AASHTO T 176 47 45 42Flat and elongated particles (max, % by weight at 5:1) ASTM D4791 10 NA NA

Nonmanufactured sand, (max, %)   10 10 20e

Acceptance Criteria    Level I Level II Level III

Quality characteristic Test method RequirementAsphalt binder content (%) AASHTO T 308

Method A JMF -0.3, +0.5 JMF ± 0.50 JMF ± 0.50HMA moisture content (max, %) AASHTO T 329 1Air voids content at Ndesign (%)a, b AASHTO T 269 4.0 ± 1.5 4.0 ± 1.5 3.5 ± 2.0Voids in mineral aggregate on plant-produced HMA (min, %)a

Gradation:No. 43/8-inch1/2-inch3/4-inch

SP-2 Asphalt Mixture

Volumetricsc

   

15.5–18.514.5–17.513.5–16.512.5–15.5

   

15.0–18.014.0–17.013.0–16.012.0–15.0

   

NA

Dust proportion SP-2 0.6–1.3 0.5–1.4 NADensity of HMA by non-destructive density device correlated to cores or (if specified) by core (% of max theoretical density)e, f

California Test 375 91–97 Method Process

of ConstructionHamburg wheel track(min number of passes at 0.5-inch rut depth)

Binder grade:PG 58PG 64PG 70PG 76 or higher

AASHTO T 324 (Modified)

   

10,00015,00020,00025,000

   

7,500**12,50017,50020,000

NA

Hamburg wheel track(min number of passes at inflection point)

Binder grade:PG 58PG 64PG 70PG 76 or higher

AASHTO T 324 (Modified)

   

10,00010,00012,50015,000

NA NA

Aggregate Size by Lift Thickness

Type A HMA pavement lift thickness Gradation0.10 foot ⅜ inch

Greater than 0.10 to less than 0.20 foot

½ inch

0.20 foot or greater ½ or ¾ inch

Density Requirements

QC Requirements Requires only 5 locations with 1 core per location for gauge

correlation (not the 20 cores per CT 375). Must also correlated QA gauge at same time.

Allows non-nuclear correlated gauges Maximum lots of 500 tons 1 gauge test per 50 tons, 3 minimum If cores required, 1 per 250 tons, contractor takes cores 

QA Requirements Allows acceptance by correlated gauge density or cores

Smoothness

Eliminates Inertial Profiler 12 Foot Straight Edge Standard Measurement

Excludes:

INTERLAYERS

REPLACE ASPHALT CONCRETE SURFACING (DIGOUTS)

MIX VERIFICATION (Production Startup Only)

Other:

Provides default binder of PG64-10 ro PG 64-16

Requires any agreed upon changes to Method Compaction to be in writing

Changes QC and QA testing requirements and frequencies Example: Binder Content, Gradation and Sand Equivalent are

1,500 ton intervals and carry over day to day.

Status:

Draft Specification sent out to Industry and Agency partners for review and comment in spring.

Caltrans has requested work to cease until other 2015 Section 39 issues resolved

Acknowledgements:

HMA-LV Co-chairman: Tim Denlay and Kee Foo

CalAPA: Russ Snyder and Rita Leahy

Questions?