Asphalt Emulsions - A Green Technology Coming of Age
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Transcript of 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/