Basics of Hot-Mix Asphalt

Dr. R. Buzz Powell, P.E.

NCAT Pavement Test Track

3

Content

• Specifications

• Materials

• Mix Design

• Production

• Hauling

• Placement

• Compaction

Specifications

• Development of proper standards

• Agency adoption & enforcement

• Level playing field for bidding

• Design via economy of materials

• Compliance at lowest possible cost.

Specifications

Materials

• Virgin aggregate cost

• Distance of hauls

• PG binder grade(s)

• Mix additives

• Reclaimed/recycled

• Bulk specific gravities.

Virgin Aggregates

• Specified gradation(s)

• Sufficient stockpiles

• Geology/availability

• Friction history

• Surface chemistry

• Absorption/gravity

• Microtexture/macrotexture

• LA Abrasion Loss.

Materials

Materials

11

Mix Design

• Cost of liquid asphalt

• Total vs aged binder content

• Voids in mineral aggregate

• Design compactive effort

• Shape of gradation curve

• Nominal maximum aggregate size

• Rutting vs cracking/durability.

Mix Design

Mix Design

Balance

15

Mix Production

• Plant limitations

• Stockpile characterization

• Virgin cold feed(s)

• Reclaimed/recycled bins

• Computer settings

• Cold vs hot starts

• Storage silo practices

• Truck loading/weighing.

Mix Production

Hauling

• Release agents

• Lab sampling

• Tarping practices

• Distance to job

• Front/back hauls.

Hauling

Paving

• Safety !!!

• Milling operation

• Brooming/cleaning

• Tack practices

• Transfer/remixing

• Paver speed

• Cross slope

• Smoothness.

Paving

Paving

Paving

Paving

Compaction

• Roller availability

• Rolling pattern

• Mat temperature

• Stopping/parking

• Cold joint overlap

• Distance from paver.

Compaction

Summary

• Specifications

• Materials

• Design

• Production

• Hauling

• Placement

• Compaction

28 http://www.omnicrete.com.au/road-safety-surfacing/

High Friction Surface Treatments

Dr. R. Buzz Powell, PEAssistant Director & Test Track Manager

277 Technology Parkway

Auburn, AL 36830

Phone: (334) 844-6857

Cell: (334) 750-6293

Email: buzz@auburn.edu

Web: www.pavetrack.com

Twitter: www.twitter.com/pavetrack