Caltrans HMA Type C

CalAPA Fall Conference24 October 2013

Skip BrownAsphalt Consulting Services

Sacramento, CA

Presentation Overview

What? Why? Where? How? Local Successes

Caltrans HMA Type C – What’s in a name? AKA

…

High Stability

IntersectionDesert

What?

Type A … on steroids Rut resistant mix made with

similar components as Type A, BUT with minor changes in the aggregate structure and stiffer binder

What?

Type Chigher stability than conventional Type A

3 Mix choices: 1-inch, ¾-inch, ½ -inch

Mix choice CRITICAL as it determines minimum lift thickness

What?

Modified Compaction with CA Kneading Compactor150 tamps at 230ºF500 additional tamps at 140ºF

Stability Initial – ≥ 37Modified – ≥ 35

What? Type A vs Type C(½-inch Mix)

Sieve Size Type A Type C

¾-inch 100 100

½-inch 95-99 90-98

⅜-inch 75-95 64-86

No. 4 55-66 42-57

No. 8 38-49 29-39

No. 30 15-27 13-19

No. 200 2-8 3-7

What? Type A vs Type C

Mix Design Data - Example

Property Type A Type C Spec

OBC (% dwa) 5.5 4.9

Air Void Content (%)

4.0 4.0 4.0

Initial Stability 37 39≥37≥37

Modified Stability 41 ≥35

VFA (%) 72 6865 – 7560 – 70

Note – Caltrans recommends selecting binder content at 5% air voids for Central Valley and Desert.

Bradshaw Rd off-ramp Highway 50 (WB)¾-inch, Type A, AR-80008-years after placement

More than 1-inch of rutting!

Why?

Where? Intersections Bus Stops Toll Facilities Haul Roads Landfills Airports High Traffic Roadways

Ticket Booths Ready-Mix

Plants HMA Plants Quarries Recycle Yards

Slow moving or Standing Loads

How? – Mix Design Mix Designation

1-inch ¾-inch ½-inch

Aggregate Crushed Particles

Aggregate Size Type A Type C

Coarse(2 Fractured Faces)

≥ 75% ≥ 95%

Fine(1 Fractured Face)

≥ 70% ≥ 90%

How? Mix Design

Binder Recommend “harder” binder, ie,

Grade “bump” Central Valley – PG 70-10 (rather PG

64-10) Binder Content

5% air voids or 4% air voids? Caltrans recommendation

5% for Valley and Desert 4% for Coast and Mountain

Impact of Aggregate Sizeon Lift Thickness

½-inch Type CTolerance

TV ±

¾-inch 100 ─

½-inch 90-98 6

⅜-inch 64-86 6

No. 4 42-57 7

No. 8 29-39 5

No. 30 13-19 4

No. 200 3-7 2

Nominal Maximum Aggregate Size (NMAS)

(one size larger than the first sieve to retain more than 10%)

1001009072654836221594

100998972654836221594

¾-inch

½-inch

⅜-inch

No. 4

No. 8

No. 30

No. 200

⅜-inchmix

½-inchmix

What? Type A vs Type C(½-inch Mix)

Sieve Size Type A Type C

¾-inch 100 100

½-inch 95-99 90-98

⅜-inch 75-95 64-86

No. 4 55-66 42-57

No. 8 38-49 29-39

No. 30 15-27 13-19

No. 200 2-8 3-7

Construction Considerations

Ratio of Lift Thickness (LT) to NMAS Maintain LT/NMAS of 4:1

Segregation ** – doesn’t like to be “handled”

Compaction – It’s difficult to compact! Need high amplitude, low roller speed to achieve density.

** Pick-up machineMTVRaking

Improper handling and/or placement can cause segregation resulting in raveling.

Paver with Slides inserted over Wings

The WRONG way

The RIGHT way

Effective Way to “Pinch” and Roll a Cold Joint

Local Successes

Highway 50 Ramps I-80 at Yolo Causeway Local Agencies

Sac County (Watt Ave) Roseville (Sierra College Blvd) Elk Grove (Bradshaw Rd) West Sac (I-80 Off Ramp to West El

Camino )

Watt Ave & Folsom Blvd

Traffic – Very Heavy w/ High Truck Volume

Teichert Mix Design - ½-inch Type C

Watt Ave ½-inch Type C

Watt Ave Number 2 Lane½-inch Type C Mix

After 4 Years

< ¼-inch rutting

No rutting in any other lanes!

Review - HMA Type C AKA High Stability, Intersection,

Desert Rut Resistant Mix Slow Moving & Standing Loads 3 Choices: 1-inch, ¾-inch, ½ -inch** Coarser Aggregate Gradation &

Stiffer Binder OBC at 5% Air Voids** Maintain LT/NMAS of 4:1 High Amplitude, Low Roller Speed Local Success!

** Skip’s Recommendations

QUESTIONS?

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