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Surfactant additives to improve the sustainability of asphaltDavid Needham and Mark SmithAkzo Nobel Surface Chemistry ABAsphalt Applications
CIHT – IAT SeminarBelfast 21st January 2013
Surface Chemistry | Asphalt Applications 2
Agenda
Overview of fatty amine surfactant chemistry
Bitumen emulsion applications overview
Adhesion improvement in asphalt
Aggregate – bitumen – water interaction
Symptoms of stripping
Wetfix® Additives to improve adhesion
Warm mix technology – Mark Smith
Bitumen emulsion applications
Road Applications•Surface dressing
•Tack/Bond coat
•Slurry and micro surfacing
•Cold mix
•Cold recycling
•Stabilisation
Industrial applications•Waterproofing and roofing
•Many more…
Type of emulsionCRS
CRS
CQS
CSS
CSS
CSS
SS
Amine ChemistryDiamine (EO)
Quat amine
Imidazoline/amidoamine/Quat
EO-Diamine/Quat/ Others
“
“
Alkyl sulphonate
Amphoterics
Fatty acids
Resins…
Surface Chemistry | Asphalt Applications 5
Adhesion in AsphaltBitumen – Aggregate chemical interaction
•Many high PSV aggregates have a silicate content
• e.g. Basalts, Sandstones, Granites
•Silicates have a net negative charge due to SiO2 -
•Acid groups in bitumens result in a net negative charge
•Overall effect is no chemical affinity between aggregate and bitumen
Surface Chemistry | Additives to improve Performance 6
0 20 40 60 80 100
Quartzite
Granite
Sandstone
Diorite
Basalt
Limestone
Marble
Silicate Content (%)
Adhesion in asphaltBitumen – Aggregate surface interaction•Aggregate surfaces are hydrophilic
•Bitumen is a non aqueous or “oily” substance
Aggregate surfaces energetically prefer to be in contact with water rather than bitumen, which means…
1. Bitumen cannot displace moisture from a surface and so will not coat or adhere properly to moist aggregates
Requires Active Adhesion
2. Bitumen will be displaced from aggregate by water over time
Requires Passive Adhesion
Surface Chemistry | Asphalt Applications 7
Surface Chemistry | Additives to improve Performance 8
Moisture in Asphalt leads to stripping
Asphalt may seem like a waterproof material…
…but water can enter most mix types through various means and attack
the bitumen-aggregate bond by osmosis through the binder
Percolation, PermeationSurface water can penetrate asphaltvia the voids
Capillary actionWater from sub-grade can riseup through asphalt via the voids
Water vapourMoisture in the air can enter voidsin asphalt and condense
Pumping action of traffic accelerates the passage of water
Surface Chemistry | Asphalt Applications 9
Evidence of early stripping effects on asphalt surface
4 months 6 months 12 months
Surface Chemistry | Asphalt Applications 12
The consequences of stripping
Visible
•Loss of chippings from surface – ravelling
•Crack development and Potholing
Underlying
• Deterioration of running surface
• Loss of stiffness in pavement layers
• Rutting in wheel tracks
Surface Chemistry | Asphalt Applications 13
Drivers for improving durability in general
•Increased focus on durability of Asphalt Pavements
More value for money for client
Less interventions – cost and congestion
•Increasing raw material costs – particularly bitumen!
•Environmental impact
Paving operations use a lot of energy and create emissions
•Optimized use of non renewable resources
Surface Chemistry | Asphalt Applications 14
Cationic adhesion promoters
Cationic adhesion promoters are fatty amine, amidoamine or imidazoline surfactants (surface active agents)
Fatty alkyl carbon chain Cationic head group
++
Surface Chemistry | Asphalt Applications 15
Adhesion promoter effect
Active adhesionAggregates are normally hydrophilic
Under normal circumstances, aggregates have a higher affinity for water than on oily substance such as bitumen
Active adhesion promoters increase the SL interfacial energy SL), decreasing the contact angle ( ) between bitumen and
aggregate allowing the bitumen to coat the aggregate – even in the presence of water
Movie…
L
S
V
Surface Chemistry | Asphalt Applications 17
Adhesion promoter effect
Passive adhesion
Over time, water can displace bitumen from an aggregate surface – this is called stripping
Passive Adhesion Promoters create a chemical bond between bitumen and aggregate preventing stripping throughout the service life of the asphalt
Surface Chemistry | Asphalt Applications 18
Wetfix® Adhesion Promoters
AkzoNobel Wetfix® and Diamine® products are a range of nitrogen (amine) and phosphorus based surfactant adhesion promoters that are added to the bitumen at levels of 0.3 to 0.5% w/w
For Hot Mixed Asphalt (Passive Adhesion with some active)
Wetfix® BE
Wetfix® AP17
Wetfix ® AP55
For colder* applications (Active and passive adhesion)
Wetfix® N422
Diamine® OLBS* Foam mix, patching mixtures, spray applications
Adhesion Promoter performance
Performance test examples
•German studies from 2009 using RBT
• Range of aggregate and bitumen types
• Comparison with PMB
• TSR results
• NTEC – ICL study
• Long term effectiveness study
• US situation
Surface Chemistry | Asphalt Applications 19
Stripping of 3 different aggregate types with 5 bitumens, A to E
Surface Chemistry | Asphalt Applications 20
0
5
10
15
20
25
30
35
40
45
A B C D E
Coa
ting
reta
ined
afte
r 24
hr ro
lling
(%) [
Quarzit Granit Diabas
A D
ausgewählt
•Rolling Bottle Test•Aggregates performed as expected - Diabas best, Quartzite worst•Binder A performed best overall - However, B better with Granite•Binder D performed worst overall - However, B and E worse with quartzite•Binders A and D carried forward for further tests…
Effect of AP’s, H1 to H5 on Granite with two bitumens, A and D
Surface Chemistry | Asphalt Applications 21
0
10
20
30
40
50
60
70
80
90
100
Bit H1 H2 H3 H4
Bit A Bit D
•Both untreated binders had <20% resistance to stripping
•All Wetfixes increased coverage to ~80% with either binder
Effect of AP’s, H1 to H4 over rolling timeGranite aggregate with “good bitumen” A
Surface Chemistry | Asphalt Applications 22
0
10
20
30
40
50
60
70
80
90
100
6h 24h 48h 72h
Bit A H1 H2 H3 H4
•Without AP, aggregate is mostly stripped after 24hrs rolling
•AP’s maintain coating well beyond the 24hrs
•Illustrates even “good bitumen and aggregate” will strip eventually
and AP can prevent this
Effect of AP compared to PMB
Surface Chemistry | Asphalt Applications 23
0
10
20
30
40
50
60
70
80
90
100
6 hrs 24hrs 96hrs
Rolling time
Ret
aine
d bi
nder
cov
erag
e (%
)
50/70 G none
PMB 45 A none
50/70 G N422, 0.8%
50/70 G BE, 0.8%
50/70 G AP17, 0.3%
50/70 P N422, 0.8%
50/70 P BE, 0.8%
50/70 P AP17, 0.3%
•Greywacke aggregate
•PMB does not do much to prevent stripping
•AP retains binder even after 96hrs rolling
Outcome from German studies
•A need and the possibility to reduce stripping and improve durability was identified
•Two Bundeslands (Saxony and Th ringen) with severe stripping problems were very quick to specify the addition of AP
•Hamburg region is implementing AP requirements in 2013
•New national document requesting measures to improve durability in asphalt – raise binder content, decrease voids and check binder affinity by RBT
Surface Chemistry | Asphalt Applications 24
Surface Chemistry | Asphalt Applications 25
TSR test results
0102030405060708090
100
TSR
(%)
1 Week 1 Month
Storage Time in Water at 40°C
No Adhesion Promoter 0.3% Wetfix AP17
Long term effectStudy at Jönköping airport•AP was used in asphalt runway construction in 1992
• ITSR improved from <85 to 95%
•Core taken in 2008 showed same resistance to water
Surface Chemistry | Asphalt Applications 27
75 80 85 90 95
Initial no Wetfix
Initial with Wetfix
16 years with Wetfix
ITSR values
US test methods and specs
• Boiling water test
• >95% retained coating
• Tensile Strength Ratio (Wet/Dry) (TSR)
• >0.75 and some specify >0.85
• Some also specify a minimum wet strength
• Hamburg Wheel Tracking Test
• <12.5mm rutting
• 10,000 passes for PG 64-22
• 15,000 passes for PG 70-22
• 20,000 passes for PG 76-22.
Surface Chemistry | Asphalt Applications 30
Surface Chemistry | Asphalt Applications 31
Small initial cost of addition of AP is soon paid offTypical road section or airport project…• 15,000 tonnes paved hot mix 750t bitumen• Est. investment costs of approx €1.4 M• ~15 yrs life expectancy
• 3.75t Wetfix® @ 0.5% on the bitumen• one time cost ~€12 k• 0.8 % of the total investment cost
• If the road lasts only two months longer, Wetfix® has already paid for itself!
• In reality…• The road will last many years longer resulting in massive
whole life cost savings• …..and reduction in Carbon Footprint
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