High Float Emulsions For Chipseals

What, Why, How

A h lt l i i t fAsphalt emulsions consist of...

• Asphalt• WaterWater• Chemical emulsifying agents

k AC d d i t– keep AC suspended in water

Ch i l l if i tChemical emulsifying agents

• Usually have no effect on cured AC• Exception - high float agentsException high float agents

– form networked gel structure

Hi h Fl t Ch i lHigh Float Chemicals

• Are called “tall oils”– derived from pine treesderived from pine trees

• Form gel structure similar to “Jello” in AC residueAC residue

Wh t d thi l t t d ?What does this gel structure do?

• Prevents flowing at high temperatures and low shear rates

• Is less temperature-susceptible than the base ACbase AC

• Allows thicker films of asphalt on aggregatesaggregates

• Allows the use of softer AC’s, which ’t b ittl t l taren’t as brittle at low temps.

Wh t d thi l t t d ?What does this gel structure do?

• Doesn’t flow at pavement surface temperaturesp

Emulsion Grade AC High Float Residue

What does “High Float” mean?What does High Float mean?

• Emulsion residue passes the “float” test• Emulsion residue passes the float test– ASTM D139; AASHTO T-50

PassPass

Fail

Advantages for emulsion chip and g psand seals• Asphalt doesn’t bleed at high temps.• Use of softer base AC’sUse of softer base AC s

– less brittleness at low temps.less shelling of aggregates– less shelling of aggregates

• Gives more time for chips to be embeddedembedded.

Typical High Float Emulsions for yp gChipseals• HFRS-2 High Float Rapid Set• HFMS-2 High Float Medium SetHFMS 2 High Float Medium Set• HF-90 High Float 90 Pen

HF 150 Hi h Fl t 150 P (M t• HF-150 High Float 150 Pen (Most commonly used HF chipseal emulsion in E t W hi t )Eastern Washington)

High Float 150 g

• Slower setting than Cationic emulsions– Will allow traffic to seat rock in cooler climates and

over longer periods than Cationicsover longer periods than Cationics• Easier to handle

– More stable than CationicsM f i i• More forgiving– Emulsion can be left open longer than Cat’s– Works with dirtier aggregate and will still grab theWorks with dirtier aggregate and will still grab the

stone• Crushed Cover stone is generally the preferred

aggregateaggregate.

Hi h Fl t W ’t!High Float Won’t!

• It isn’t meant for high traffic seals, for those use clean chip and CRS-2P ppolymer modified cationic emulsion

• Not meant for immediate sweeping leaveNot meant for immediate sweeping, leave the excess rock on and let traffic push the large stone inthe large stone in.

WSDOT “crushed Cover Stone” 9-03.4(2)

• ¾” square 100 % passing• 5/8” square 95-100• U.S. No. 4 20-45• U.S. No. 200 0-7.5• % fracture by wt., min. 75• Sand Equivalent min. 40

S i S i i P• Static Stripping test Pass• Much dirtier than chips used with cationic emulsions• Cats generally require less than 2% passing No 200• Cats generally require less than 2% passing No. 200

WSDOT Crushed Cover Stone

• Prep just like any other chipseal.Apply approx. .40 to .46 Gal / yd2 (When using CrushedApply approx. .40 to .46 Gal / yd When using Crushed Cover Stone.Does not need to be covered immediately unlike cationicscationics.

Note the distance of chip spreader b hi d f h l i Thi h ldbehind fresh emulsion. This should not be done with cationics.

Apply 30 to 35 lbs. of Aggregate. Small aggregate will drop first, but High Float gg g p , g150 will allow time for rolling and traffic to push larger stone into the sealto push larger stone into the seal.

R ll llRoll normally

Stagger your trucks, they do a gg y , ygreat job of seating aggregate.

The fresh seal will look like this after rolling. T ffi ill t th l tTraffic will seat the large stone

Let traffic do your rolling for a few y gdays before sweeping Th fi l d tThe final product

In summaryIn summary• Use HF-150

• If you can’t get clean aggregatef C S• If your used to Cutback Seals

• Low traffic roadsIf ki i diti t d i t• If your working in conditions not conducive to Cationic seals– Cooler weather, late seasonCooler weather, late season– Over granular bases– Low traffic that won’t be enough to seat rock soon.

Th kThank you.

• Any Questions?