Asphalt Emulsions - A Green Technology Coming of Age

8/13/2019 Asphalt Emulsions - A Green Technology Coming of Age

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A Green Technology Comes of Age

Prepared by

Delmar SalomonPavement Preservation Systems, LLC

LTRC Emulsion: Design, Construction, and Performance ConferenceBaton Rouge, Louisiana

July 1, 2008


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1. What are asphalt emulsions2. What are the types of asphalt emulsions

3. Manufacturer of emulsions

4. Setting and breaking of emulsions

Presentation


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First asphalt emulsion use 1900-1910 in U.S.10 million ton of asphalt emulsion worldwide

2-3 million ton of asphalt emulsion in USA

Some Figures

10% of asphalt used as emulsion25% in France, 5-10% in U.S.A.

Spain, France, Brazil are important


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Emulsion Basics

Emulsions are MIXTURES of two immiscible liquids,such as oil and water, STABILIZED by an EMULSIFIER

Emulsifier PROTECTS the droplet

How?


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Why Use Emulsions?

Cold processes saveenergy

easier handling andStorage (Low viscosity)

safe and environmentallyfriendly

low-cost on-site andin-place techniques

easily mixed with latex

water dilutable


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The emulsion is a chemically stabilized system;all components contribute to the stability of the

system

Necessary Components Continuous phase - Water

Non-continuous phase - Asphalt (dispersed phase)

Surfactant - Emulsifying Agent

Mechanical Energy Shear (colloid mill)


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solvent 0-10%

asphalt 40-70%

water 30-50%

chemicals 0.2-2.5%

Asphalt Emulsion composition


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Surface

Fog seal

Chip seal

Cold mix

Slurry Seal

Microsurfacing

Cape seal

Scrub seal

Structure

Cold in place recycling

(CIR)

Full depth reclamation(FDR)

Emulsion Applications


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= Balance of attractive and repulsive interactions

Attractive >> Van der Waals ForcesRepulsive >>> Electrostatic forces


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DLVO = Derjaguin-Landau-Verwey-OverbeekTHEORY developed in 1930

Primary minimum: irreversible flocculation

Vsec

Secondary min

Weak flocculation

d

VT (d) = VA (d) + VR (d)

VT

Vmax

Vmax

Emulsion breaking

Sievedevelopment


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Effect of constant shear at 50 RPM and 50oC on emulsion viscosity

0.00

50.00

100.00

150.00

200.00

250.00

300.00

350.00

400.00

0 10 20 30 40 50 60 70 80 90 100 110 120

Time (minutes)

Viscos

ity

(m

Pa

s)

microstructure breakdown

steady-state viscosity

breaking of emulsion


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Water-air or water-oil interface is hightension (energy)

Surface Active Agent adsorbs at interface

Lowers the tension (energy) at the interface

Lowers the work needed to make new

interface

Emulsifiers lowers energyat the interface


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Func t ions of the Emu ls i fier

Determ ines type of emuls ion fo rmed. i.e. O/W or W/O

Reduces energy needed to emu lsi fy asphalt

Determ ines charge on emu lsion droplets

Stabi l izes emuls ion droplets as they are form ed in the

col lo id m i ll

Stabi l izes the droplets du ring sto rage of the emuls ion

Provides the r ight set t ing behavior

Inf luences the phys ical propert ies of the emulsionInf luences p ropert ies o f cu red road mater ial .


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Stab i lizat ion o f Asphal t Drop lets

+ + +++ +

Cationic emulsi f ier-electros tat ic repuls ion prevents close app roach of d rops

No emuls i f ier-droplets can com e into con tact and coalesce

- - --- -

An ionic emulsi f ier-electros tat ic repu ls ion p revents clo se app roach of d rops


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Surfactants

Oil Loving Tail Water Loving ead

Lipophilic Part ydrophilic Part

Hydrophobic Part Hydrophobe


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If an asphalt d roplet were the size o f the earth, then

the emulsi f ier head wou ld occupy an area of 4 squarem i les and the hydro carbon tai l would penetrate 5 m iles

deep

asphalt droplet

d iameter 3/1000 mm

emu lsi f ier length

3/1 000 000 mm


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Surfactants at Water-Oil

interfaceThere is anequilibrium

betweensurfactants at theinterface andthose in the water.

Water hatingtails point outin the oil or air

Water lovingheads immersed

in the water

When theconcentration ofsurfactants in the

water reach theCMC thenmicelles start toform

Surfactant molecule

ifi i i i


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Emulsifiers stabilize particles

-cationic example:

Asphalt particle

Positively charged emulsifier


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Cationic Anionic


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Hydrocarbon Chain Oil Loving)Head Group Water

Loving)

Counter ion WaterLoving)

HC

Cl

NH3

Cationic Emulsifier


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Hydrocarbon Chain Oil Loving)Head Group Water

Loving)

Counter ion WaterLoving)

HC

Na

SO3

Anionic Emulsifier


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Typ ical Emulsi f ier Struc tu res

Hydro carbon tai l with 12-20 carbons hyd roph i l ic head

groupcounter ion

R(tall ow ) --------------------------------- +N (CH ) 3 Cl-

R(tall ow ) ---------------------------------NH2+CH CH 2 2CH2NH+3 2Cl-

R(no ny lpheny l) ------------------------O----CH

R(tall o il )----------------------------------

R(lignin)-----------------------------------

COO-

SO-3

Na+

+Na

noneCH2 2OCH2CH2O---H

R = long chain hydrocarbon


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RNH3

+ + Cl -RNH2

+ HCl =

inso lub le neutral form + acid = so lub le cat ion ic 'soap'

Cationic Soaps are prepared from am ines

and acid

2RNH3 +HPO32-RNH + H3PO4 =

inso lub le neutral form + acid = so lub le cat ion ic 'soap'

2

+

R = Hydrocarbon chain


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Some charged emulsifiers do not needpH adjustment

N(CH)3+R Cl -

soluble quaternary amine

SO3- Na+R

soluble olefin sulphonate


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rapid-sett ing:react ive emulsion sets qu ickly even w ith un react ive

aggregates

medium-set t ing:

medium react ive emuls ion which can be mixed wi th

open g raded agg regates w ith low f ines content

slow-set t ing:

low react ive emuls ion which can be m ixed w i th

react ive agg regates w ith high f ines con tent


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Naming of Emulsions(ASTM)

CRS - 2

cationic rapid-setting

High viscosity

(65% asphalt)

CSS - 1h

cationic slow-setting

hard asphalt

Low viscosity(57% asphalt)

HFMS - 2s

high-float

with solvent

medium-setting(anionic)

RSAnionic rapid setting

-2PPolymer modified


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Emuls ions are class i f ied accord ing to

Sett ing Rate and Part ic le Charge

rapid-sett ing

medium-set t ingslow-sett ing

+ve

CRS

CMS

CSS

CMS

CRS

CSS

RS

MS

SS

-ve

chip-seal

open-graded m ixdense-g raded m ix

Application


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Manufactu re of Asphalt Emuls ions


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Emulsifiers in EmulsionManufacture

Emulsifiers stabilize the asphalt droplets

Di h l i &


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Disperse asphalt in water &

chemical under high energy


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An Emulsion Process Diagram

AC Tank

Emulsion

Sales Tank

Cooling TowerColloid Mill

Soap Concentrate

Tank

Soap ProcessTank

Heat

Exchanger

Hot water

Cooling water

Centrifugal pump

Gear Pump

Gear Pump

Fuel

TankLatex

Tank

DieselNaphtha

NX-1118

Emulsifier

Process Water

HCl

Additives (i.e. salt)

HCl


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Cost Contributions per Ton of Emulsion

Asphalt 66%Emulsifier 20%

Other raw materials

and energy 6%

Fixed costs 4% Investment cost 4%

Accurate flow control minimizes excess asphalt

Inline water heating saves energy

Innovative chemical dosage system reduces

chemical waste


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Setting and Cur ing of Asphal t Emuls ions


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Breaking and Cur ing

Breaking/Sett ing : Emu lsion is destabi l ized and

no longer can be di luted in water

Cur ing : Water and so lvent is lost from the

system and the f inal propert ies of the residualasphalt are reached


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Breakdown of the Emuls ion

Evaporat ion o f Water

Evapo rat ion o f water forces d rop letstogether and eventual coalescence


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Agg regate react iv i ty

su rface area, su rface charge, su rface chem istry

f i l ler chemis try e.g. cement, l ime

Temperature, hum idi ty, w ind speed

Emu lsion react iv i tyemuls i f ier chem istry, concentrat ion

other addit ives

asphalt visco si tyMechanical treatment e.g. compact ion

Facto rs Affect ing Breaking and Curing


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Poss ible Stages in the Sett ing o f a Cation ic

Asphalt Emuls ion

contact of emulsioncontact of emulsion

with aggregatewith aggregate

adsorption of 'free'adsorption of 'free'

Emulsifier, pH risesEmulsifier, pH rises

Rise in pHRise in pH

leads toleads to

flocculationflocculation

coagulation/spreadingcoagulation/spreading

over surfaceover surface

contact of emulsioncontact of emulsion

with aggregatewith aggregate

adsorption of 'free'adsorption of 'free'

Emulsifier, pH risesEmulsifier, pH rises

Rise in pHRise in pH

leads toleads to

flocculationflocculation

coagulation/spreadingcoagulation/spreading

over surfaceover surface

Interaction of Cationic


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+

+

+

+

++

+

+

+

+

+

+

+

++

+

+

+

+

+

+

+

++

+

+

+

+

- - - - - -+

+

+

-+

+

AGGREGATE SURFACE

+

+

+

+++

+

+

+

+

+

+

++

+

+

+

+- - - - - -+ ++

-+ + +

AGGREGATE SURFACE

+ +

Increasing

Mixing Time

Equilibrium between

interfacial and bulk

emulsifier concentrations

upset by introduction ofcharged aggregate.

Adhesion of emulsifier to

aggregate surface causes a

decrease in bulk and interfacial

concentrations. Droplets beginhomo- and hetero-flocculation.

Interaction of Cationic

Emulsion with Aggregate


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Breakdown of the Emuls ionFlocculat ion and Coalescence

Emulsion Droplets

Charge on droplets

prevents close

approach

Flocculation

Close approach ofdroplets leads to

adhesion between

droplets. Water is

squeezed out

Coalescence

Water drainsbetween droplets

and surfactant film

breaks down,

Droplets fuse,

trapping some water

Coalescence

Trapped waterdiffuses out.

Setting Curing


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Breakdown of the Emuls ionFlocculat ion and Coalescence

Floccu lat ion and coalescence in contactw i th agg regate


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Whats on the horizon for asphalt

emulsion technology?

Application of rheological type tests

Faster curing spray seals

Cold-pour crack sealant

Use of emulsions for warm mix

High residue emulsion

Solvent free emulsions-penetrating prime coat


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Studies and Resources Manual for Emulsion-Based Chip Seals for Pavement Preservation-

NCHRP #14-7 (end:2-13-2009) Good Roads Cost Less: UTAH DOT Office of Research (2007)

Asphalt Emulsion Technology, TRB Circular, EC102,August,2006

Asphalt Emulsion Technology, TRB Circular , EC-122Review of Asphalt Emulsion Residue Procedures, October, 2007

Basic Asphalt Emulsion Manual, AEMA & Asphalt Institute (seewww.aema.org)

Putting Fog and Rejuvenator Seals to the Test:Helen King, in BETTER ROADS , January,2008
http://www.aema.org/http://www.aema.org/

Documents

Asphalt Emulsions - A Green Technology Coming of Age