1

AAPA training Bitumen Emulsion Binders

What is an emulsion?

A suspension of two immiscible liquids e.g. salad dressing

Australian  Asphalt  Pavement  Associa�on  

What is a Bitumen Emulsion ?

  Bitumen emulsions –  two-phase mixture –  bitumen droplets suspended in water

  Can be based on –  Unmodified bitumen –  Cutback bitumen –  Polymer modified bitumen

Droplet  Size      10  –  20  Microns  

Australian  Asphalt  Pavement  Associa�on  

n  Emulsions  are  manufactured  in  a  colloid  mill  with  simultaneous  addi�on  of  bitumen,  water  and  emulsifier  (Soap).  

n  Small  globules  are  created  which  are  coated  with  emulsifier      

 Australian  Asphalt  Pavement  Associa�on  

Bitumen Emulsions   Emulsifier imparts

and electrostatic charge   Stops the bitumen

from coalescing.

2

Australian  Asphalt  Pavement  Associa�on  

Bitumen Emulsions Grades

Anionic – Negatively charged   Anionic Rapid Setting (ARS) - surface sealing,

patching work or as a tack coat for asphalt work.

  Anionic Medium Setting (AMS) - specialised enrichment, patching and sealing work.

  Anionic Slow Setting (ASS) - surface enrichment, soil stabilisation and dust laying.

Australian  Asphalt  Pavement  Associa�on  

Bitumen Emulsions Grades

  Cationic – positive charge

  Cationic Rapid Setting (CRS) - can be used with damp aggregate. Preferred general purpose sealing and patching emulsion.

  Cationic Medium Setting (CMS) - enrichment, patching and sealing work.

  Cationic Slow Setting (CSS) - particularly suited to soil stabilisation.

Australian  Asphalt  Pavement  Associa�on  

Bitumen Emulsions Grades

  Cationic Aggregate Mixing (CAM). –  Contains a cutter or flux oil to permit

stockpiling of cold mix. –  CAM patching mix has superior

performance over fluxed bitumen mixes (no bleeding)

Australian  Asphalt  Pavement  Associa�on  

Breaking of Emulsions

  Once in contact with air/aggregate the Emulsion will break. –  Bitumen begins to coalesce and the water

evaporates.

  Emulsion is cured once all water had evaporated

  Rate of setting can be adjusted control of emulsifier chemistry.

Emulsion has started to “break”

3

Breaking almost complete

Australian  Asphalt  Pavement  Associa�on  

Bitumen Emulsions - Cationic

  Most aggregates have a negative net surface charge.   Cationic emulsion break due to

–  evaporation –  coalescence due to chemical reaction when exposed to

air and or aggregate.   Cationic emulsions break and cure at a faster rate

than anionic.   Suited to sealing and patching applications

Australian  Asphalt  Pavement  Associa�on  

Bitumen Emulsions - Anionic

  Anionic emulsions have little or no natural affinity for the aggregate.   Coalesence is (slower) by natural evaporation of

the water.   Anionics are more suited for

–  Soil stabilisation –  Dust suppression

4

Australian  Asphalt  Pavement  Associa�on  

Why use Bitumen Emulsion ?

Compared to bitumen –  Lower handling temperatures –  Applied at lower pavement temperatures without

need for cutter –  Cures more quickly than cutbacks –  Can be used for thin surfacing applications in remote

locations (slurry & microsurfacing) Consequence of sealing over a cutback too early

Emulsion - Maintenance

  CRS170 / 60 – 60% of class 170   Maintenance operations

–  Skin patching

–  Crack sealing

–  Edge repairs

–  Dust Suppressants

–  Cold Mix (CAM)

  Properties specified in Australian Standard 1160

Emulsion - Maintenance

  Applied at ambient temperature –  may be heated to 40°C

  Can run –  application rates > 1.6 l/m2

  Susceptible to damage whilst

‘green’ or ‘cheesy’ –  Achieves full binder cohesive

strength once cured

Skin patching - first layer of double/double 10/7 seal

Australian  Asphalt  Pavement  Associa�on  

Emulsion - Sealing

  High Bitumen Content Emulsion (HBCE) –  Bitumen content 70-75%

  Higher viscosity, applied at 75-85°C   Modified (SBR Latex) and Unmodified   Cures more quickly than 60% emulsion

–  More suitable for heavily trafficked roads   Less risk of binder run off than 60%   Lower transport costs per litre of

residual binder

5

High binder content emulsions must be heated to achieve uniform distribution

Otherwise this can happen

Australian  Asphalt  Pavement  Associa�on  

Surface Enrichment rejuvenation agents replace lost binder hungry spray seals and oxidized asphalt surface.

Emulsions – other uses

Australian  Asphalt  Pavement  Associa�on  

Tack Coat used to bond fresh asphalt to existing old bituminous surface

Emulsions – other uses

Emulsion Primes   Cure more quickly than cutback   Apply next treatment sooner   Proprietary products not watered down sealing/

patching grades  

Emulsions – other uses

Australian  Asphalt  Pavement  Associa�on  

Emulsion Storage Storage Typically 3 months   Droplets will settle over time   Circulate regularly   Constant temperature (20-25C)   Inspect tanks annually

6

Australian  Asphalt  Pavement  Associa�on  

Emulsion Handling

  Never mix anionic and cationic types   Never load emulsion on top of hot bitumen   Always ensure Tanker is flushed between loading different emulsions. – Flush with water (hot/cold) & kerosene. Never

diesel/petrol

Bitumen Emulsions for Spray Sealing

The following factors also help determine the grade of bitumen emulsion to be used:

§  Traffic including volume, type and speed; §  Existing road surface; §  Size and type of aggregate to be used; §  Environmental factors including weather

factors, pavement temperature, pavement moisture content.

§  Timing of next treatment

Australian  Asphalt  Pavement  Associa�on  

AUSTROADS GUIDE TO THE SELECTION AND USE OF BITUMEN EMULSIONS