Surfactant additives to improve the sustainability of asphalt · •Bitumen is a non aqueous or...

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


Key Fatty Amine Production Technology

Fatty Amine Derivatives


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…


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



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


Evidence of early stripping effects on asphalt surface

4 months 6 months 12 months


Symptoms of StrippingDrilled Cores…


Symptoms of strippingRavelling or chipping loss…


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


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


Cationic adhesion promoters

Cationic adhesion promoters are fatty amine, amidoamine or imidazoline surfactants (surface active agents)

Fatty alkyl carbon chain Cationic head group

++


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


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


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


Stripping of 3 different aggregate types with 5 bitumens, A to E


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5

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30

35

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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


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10

20

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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


0

10

20

30

40

50

60

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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


0

10

20

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60

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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



TSR test results

0102030405060708090

100

TSR

(%)

1 Week 1 Month

Storage Time in Water at 40°C

No Adhesion Promoter 0.3% Wetfix AP17

NTEC – ICL Moisture damage studyPeel force and energy


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


75 80 85 90 95

Initial no Wetfix

Initial with Wetfix

16 years with Wetfix

ITSR values

US situation with the use of AP


US Best practice forum 2004Main conclusions


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.



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

Warm mix asphalt

Surfactant additives to improve the sustainability of asphalt · •Bitumen is a non aqueous or...

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