Slurry Systems Analysis
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Transcript of Slurry Systems Analysis
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Definition of an emulsion
An emulsion is a homogeneous mixture of twoimmiscible liquids.
Immiscible liquids: qu s t at norma y on t m x
Oil (or, in this case, asphalt) and water
Homogeneous:
No layering
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Example: Salad dressing
Not an emulsion Unst able emulsion
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Roles of the emulsifier
Imparts stability Prevents layers from forming
Imparts charge Cationic vs. Anionic (Positive vs. Negative)
Imparts mixing and curing characteristics Slow Set vs. Quick Set
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Cationic emulsifier structure
CH3 CH2 CH2 CH2
CH2 CH2 CH2 CH2
CH2 CH2 CH2 CH2
CH2 CH2 CH2 C
O
CH2 CH2NH2
CH2 CH2NH2
NH
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Cationic emulsifier structure
CH3 CH2 CH2 CH2
CH2 CH2 CH2 CH2
CH2 CH2 CH2 CH2
CH2 CH2 CH2 C
O
CH2 CH2NH2
CH2 CH2NH2
NH
Head group: Polar, w ater loving (or hydrophilic)
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Cationic emulsifier structure
CH3 CH2 CH2 CH2
CH2 CH2 CH2 CH2
CH2 CH2 CH2 CH2
CH2 CH2 CH2 C
O
CH2 CH2NH2
CH2 CH2NH2
NH
Head group: Polar, w ater loving (or hydrophilic)
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Cationic emulsifier structure
Tail group: Hydrocarbon, oil loving (or lipophilic)
CH3 CH2 CH2 CH2
CH2 CH2 CH2 CH2
CH2 CH2 CH2 CH2
CH2 CH2 CH2 C
O
CH2 CH2NH2
CH2 CH2NH2
NH
Head group: Polar, w ater loving (or hydrophilic)
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Cationic emulsifier structure
Tail group: Hydrocarbon, oil loving (or lipophilic)
Head group: Polar, w ater loving (or hydrophilic)
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Emulsion production
Asphalt
Emulsion
Soap
SolutionColloid Mi ll
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Inside the colloid mill
(.)
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Stabilized asphalt droplets
+ + WaterWater
++
+
++
+Repulsion
Water
+
Water
+
++
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Aggregate charge
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The chemistry of mix time
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Water Water
+
--
-+
+ +
-
-
-
+ + +
-
+
+ + +
Water Water
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The chemistry of mix time
WaterWater
Water
-
+
++
+
-
-
+ +Water
+
+ ++
Water Water
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Chemical break
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Increasing mix time
++ +
+ --
Water Water
+
+ +
++
--
--Water
+ +
+
+ ---
-
-
Water
WaterWater
Increase emulsifier dosage in the emulsion
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Mineral filler chemistry
Tw o Compet ing React ions
3 2 2 2
Cement (or lime) react s w it h acidic emulsion
2
More st able system mixes longer
e t er eact on = em ca reaCement (or lime) has high pH - When combined w ith
ac c emu s on av ng a ow p - ys em s es a ze
Destabil ized systems break
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Aluminum sulfate
Aluminum Ions
Leads to longer mix time
Low pH
No shift in system pH because alum pH is
similar to emulsion pH No destabilizing effect
Also leads to longer mix time
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Factors that affect curing
Water content
Mix time More stable emulsion More mix time
Longer cure time
Emulsion pH
Particle size of the emulsion
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Emulsion pH and curing
Siliceous aggregate systems
Negatively charged aggregates
, ,
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Siliceous a re ates:Lower emulsion pH Faster cure rate
+Water
++
+++
+
+
-
--
Water
+ +
++ + -
--
-
+ + +++ -
-
-
Water
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Siliceous a re ates:Lower emulsion pH Faster cure rate
WaterWater Water
++
+
+
+ ---
-
+ + --
-
Water
++
+++
-
-
-
Water
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Emulsion pH and curing
Calcareous aggregate systems
Limestone, dolomite
CaCO3+ 2HCl CaCl2 + CO2+ H2O
Limestone react s w it h acidic emulsionCaCl2 is formed Calcium ions st abilize t he system
e uc ng e ac , re uces e s a z ng e ec
Speeds the cure rate
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Emulsion particle size and curing
Smaller particle size emulsions Faster cure time
Target particle sizes ~ - 90% less than 7-8 microns
Tight particle size distribution Narrow bell-shaped curve
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Particle size distributions
Very small Larger t han target
mv = 2.8 mv = 8.1
90% < 4 .0 90% < 17.7Size (microns)
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Practical summary
Mix time application onto the road
Increase emulsifier content in the system by
adding retarder Change mineral filler amount
Increase aluminum sulfate amount
F exi i ity - wit in parameters o t e esign Emulsion manufacturer
ncrease emu s er con en n e emu s on
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Practical summary
Curing - traffic time Contractor
Eliminate retarder
Change the mineral filler amount ecrease a um num su a e amoun
Emulsion manufacturer
Check particle size
Adjust soap solution pH
