aditivos04b
TRANSCRIPT
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Additives for
Warm Mix Asphalt
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Content :
Warm Mix Asphalt technologies
CecabaseRT technology
Advantages of CecabaseRT
Examples of field jobs
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Warm Mix Asphalt technologies
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4
To remove liquid waterin theaggregates
To reduce the bitumen viscosityenough to fully coat the aggregates in
a time scale compatible with theprocess
4
Working at high temperature isnot artificial, it is necessary:
0
1
2
3
4
110 120 130 140 150 160 170 180
Temperature (C)
P
en35/50BitumenViscosity(Pa.s
)
Why we use hotmixes?
T
AGGREGATE
1. The bitumen temperature is fixedby the refinery vacuum distillation processpractically, difficult reduce bitumen T.
2. The aggregates represent ~95% of an asphalt mixture.
Buthow to reduce the asphalt mixture fabrication temperature?
Decreasing the process temperaturetranslates into decreasing the aggregates
temperature.
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Water Foam based processes
Consists in adding waterto form a foamwhen the water evaporatesdue tothe mix temperature. The water may be added directly (nozzles) or indirectly usingzeolites, wet fine mineral aggregates, emulsion, etc..
Improves aggregates coating thanks to an apparent volume enhancementof binder bythe foam. Probably improves workability of the mix thanks to lubricating effect of the foam.
m m m m
Grampr, L, Gonzalez-Lon, J,A. and Barreto, G. (2008) Enrobs tides par additivation chimique Revue Gnrale des Routes, No866,2008, pp 44-50.
http://www.astecinc.com
Zeolite
Compaction can become an issue as thefoam disappearsshortly after production
These techniques usually require amodificationof the mixing plant
Precautions should be taken due to the
addition of water(cohesion of theasphalt mix, water susceptibility of the mix)
http://upload.wikimedia.org/wikipedia/commons/5/58/Zeolite-ZSM-5-3D-vdW.pnghttp://upload.wikimedia.org/wikipedia/commons/5/58/Zeolite-ZSM-5-3D-vdW.png -
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Allows for a coverage of the mineral
aggregate at reduced temperatures
Below the crystallizationtemperatureof the wax (~100C)workability of the mixture becomespoor and compaction cant beachieved.
The addition of waxes change thebitumencharacteristics (Penetrationgrade, viscosity, low temperatureproperties, etc)
Wax based chemicals additives
Additives (used at 2-3 wt% in asphalt binder) that reduce the viscosity of the
asphalt binder at processing conditions
Improved aggregates coating at lower temperature thanks to viscosity reductionof binder by the liquid (melted) productwhich acts as a solvent. An improvedworkability of the mix is possible to the lower viscosity of binder
Hurley, G.C.; Prowell, B. D. Evaluation of SASOBIT for us in Warm mix asphalt.
NCAT Report 05-06. June 2005
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Surfactant additives
Addition of a chemical surfactantadditive (0.3-0.5 wt% in the binder) thatchanges interfacial propertiesof the binder without changing asphalt binderrheology
Improved coatingat lower temperature thanks to surface tension reduction at thebinder/aggregate interface
Improved workability of the mix thanks the control the interface structurebetweenbitumen and aggregates, thus reducing the internal frictionsthat increase theworkabilityof an asphalt mixture.
Improved striping resistance of the mix thanks to surfactant action at binder/aggregateinterface
Chemical additive
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9
SurfactantAdditives
Wax Additives
Foaming
techniques
Zeolites
TC reduction Cost per ton of mix Pros and Cons
- 40C ~ 1/T
Cheapest and easiest additive technique
Robust, compaction aid
Anti-stripping effectkeep HMA mechanical prop.
Effective for long hauling
Consumption of Additive for each ton produced
- 30 to - 40C 2 - 3/T
Increase rut resistanceEffective for long haulingComplex to incorporate (solid pellets)Compaction issues below crystallization ~100CModification of binder (low T properties, cracking)
- 15 to - 30C0 but several
10,000investment
Cheap Process after initial investmentShort lifetime of foam
Average aggregate coating at WMA temperatureMix sensitive (binder, aggregate, lime)
- 30C 2 - 3/T
Increased lifetime of the foamPlant modification, complex introduction kit
Anti-strip often necessaryModification of mix design
WMA techniques in a nutshell
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CecabaseRT technology
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Typical properties of the additive :
LiquidViscosity < 1000 cPo at 20C Density :~ 1.00
Flash point : > 200C
Readily soluble in asphalt binder
Packaging: bulk, ~1000kg IBC,~200kg drums (1 drum eq. to 1000T of mix)
How to use CecabaseRT :
In line orbatchaddition to the asphalt binder
0.3 to 0.5%dosage based on total binder weight
Compatiblewith all kinds of bindersno curing time
Stablein stored asphalt binder over 7 days
Mix production temperature is reduced to120-140C depending on mix type : Heating of aggregates is typically ~ 40C less than
the corresponding HMA
Binder temperature remains the same as HMA
Good compaction is ensured down to 90-110C
How to use CecabaseRT
Asphalt (usual T)
Aggregates
(reduced T)
WMA
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Effect of Cecabase RT on binderproperties
Dynamic viscositymeasured at constantshear rate : 100 s-1
0.1
1
10
100
80 100 120 140 160
Temperature (C)
Viscosity(Pas)
Neat 35/50 bitumen
+ 0.3% additive
+ 0.5% additive
Since the additive interact at
the aggregate surfaceand
only small amountsare
required to have the improved
workability on the mix thereis no effect on the properties
on the binder
Viscosity unchanged bythe additive atconcentrations used
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Effects of CecabaseRT
50/70Asphalt
50/70 Asphalt+ 0.5% CB RT
30/45Asphalt
30/45 Asphalt+0.5% CB RT
SBS modifiedAsphalt
SBS modifiedAsphalt +0.5% RT
Penetration(1/10mm)
51 50 33 37 52 56
Ring andBall (C)
51.2 50.8 54.2 53.6 57.8 57.2
No change in Asphalt penetration grade or R&B temperature
Electron microscopy shows no difference of mix with HMA :
mm
25 m
Good distribution ofaggregates
Good coverage ofaggregates (even fines)
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Effect of additive on the mix
160C 120C
Reference mix Mix +0.5%Cecabase RT
Reference mix Mix +0.5%Cecabase RT
Void % 2.0 1.9 3.2 2.8
Marshall Stability
(kN)
11.0 10.5 8.8 10.0
Usually only small differencesare observed through standard compactionmethods (ex. Marshall)
The effect of the additive is seen on the workabilityof the asphalt mix.
However, the evaluationof workability in the laboratory can be quitechallenging
Bennert, T.; Reinke, G.; Mogawer, W.; Mooney, K. (2010) Assessment of Workability / Compactability of Warm Mix Asphalt.
2010 TRB Meeting Proceedings, paper 10-2223
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Workability effect of Cecabase RT
Evaluation of the workability of WMA in the lab is challenging
Test based on the recommendations onreport 691 from NCHRP (US)
Comparison of the number of gyrationsrequired to achieve a given void % with agyratory compactor :
Evaluation by laboratory BaustofflaborHamburg, following standard German testfor workability
Torque recording of a screw type rotationaldevice introduced in the mix :
Mixing at 120C, measurement at 90C, 8% void240
250
260
270
280
290
300
310
320
330
Reference asphalt mix Asphalt mix with 0,5%
Cecabase RT
Reference asphalt mix Asphalt mix with 0,5%
Cecabase RT
160C 120C
Torque(N.cm)
0
50
100
150
200
250
300
Control HMA 160C Control WMA (no add it ive) 120C WMA 120C - Cecabase RT - 0 ,4%
Gyration#
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Improvements of adhesion are achieved with CecabaseRT
ITSR :
Mechanical characterization
Open-graded friction course with modified binder, PG 76-28Compaction PCG 600kPa, 40 gyrations
Conditioning 1 day in water at 60C0
2
4
6
8
10
12
14
Void % ITS (kN)
conditioned
ITS (kN)
Void%
orITS(kN)
Reference HMA 160C
Reference WMA 120C without additive
WMA 120C with 0,4% Cecabase RT
TSR
Hot Mix Asphalt 0.58
WMA without
Additive 0.31
WMA with
Cecabase RT 0.84
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Hamburg Test
The hamburg test is a mix between a rutting test and a anti-stripping test.
Gmm (Maxtheoretical
specific gravity)
Air voids (%) Max. rut depth(mm)
HMA (160C) 2.425 6.95 -13.3
WMA (130C,
0.4% CB RT)2.445 7.2 -9.1
AASHTO T324
0/25mm mix, compacted in SGC
20,000 wheel passes
In water at 50C
http://www.fhwa.dot.gov/pavement/asphalt/labs/mixtures/hamburg.cfm
Hajj, E.; Cortez, E. Evaluation of the Cecabase RT warm mix additive, final report. Septembre 2001 University of
Nevada, Reno US
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Rutting resistance
NF P 98-253-1 Hot mixasphalt
Warmmix
asphalt
Limits inthe std.
Rutting (%)after 30,000cycles
4.11 4.19
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Fatigue
Oliveira, J.; Silva, H.; Abreu, L.; Gonzalez-Leon, J. The role of a surfactant based additive on the production of
recycled warm mix asphaltsLess is more. Construction and Building Materials 35 2012 693-700
Evaluated by the University of Minho (Portugal) on a regular 0/10 mix and a 0/10 mix with50% RAP, following the EN 12697-24.
4 point bending test
T 20C, 10 Hz
Mix A 0/10
Mix B 0/10 + 50% RAP
Similar Fatiguebehaviorbetween HMAand WMA with
additive
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Advantages of CecabaseRT
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2121
Compaction aid
Fast opening to traffic
Less heat & fumes
Environment Comfort Flexibility
Advantages of WMA with CecabaseRT
Less emissions
Energy savings
Increase use of RAP
Increased capacity
Night or winter work
Longer hauling
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Reduction of gas emissions
CO2
(Nm3/ton)
Eq. NO2
(g/ton)
TVOC
(g/ton)
PAH
(g/ton)
HMA 14.6 6.8 80.6 78.6
WMA 9.0 5.0 14.3 35.5
-38% -26% -83% -55%
Measurements taken on job site, on a worker, a paver driver anda compactor driver :
Typical values measured at the plantstack (production of very thinasphalt cement) :
Worker Paver Compactor
HMA 0.01549 0.0097 *
WMA 0.0053 0.0045 0.0019
-66% -54% *
Both HMA and WMA are well below exposure limits
(close to detection limits)
More than 20 different polyaromatics (PAH)
measuredexample :
Naphthalene(mg/m3)
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Increased use of recycled material
120
160
200
240
280
320
360
400
440
480
0 10 20 30 40 50
% RAP
AggregateT(C)
Tmix 120C
Tmix 160C
Calculated temperatures
+ 10-15% RAP
RAP
Virgin aggregates
CecabaseRT increase the amount
of RAP that can be introduced inthe mix by 10 - 15% :
Easier mix compaction
Less overheating of virginaggregates
Working for plants with and withoutheating systems for RAP
Significant reductions of the asphaltmix cost
Also possible with shingles (RAS)and crumb rubber (CRA)
Cold RAP
systems
Pre-heated
RAP systems
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Use as Compaction Aid
The workability effectof CecabaseRT can be used
to achieve the desired compaction target at Hot Mixtemperatures in various cases :
Fasterprogression : typically fewer compaction passesare required compared to HMA without additive
Gives more securityfor difficult mixes (high-end void%)
Increase chance of getting compaction bonus
Improve workability of stiff mixes(high RAP ) Ability to work at
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Dust
(mg/m3)
Fumes
(mg/m3)
Mix ofPollutants
(mg/m3)
HMA 12 11.4 12
WMA 3.5 3 2.9
-71% -74% -76%
Similar reductions are measuredat the plant:
Reduction of dust and fumes
Typical reductions measured on the paver(SMA job) :
HMA WMA
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Increase of Production rate
In some cases, residence time of aggregates in the barrel can bedecreased (lower heating T) without changing the burner settings
Case study : an increase from 210 to 280 tons of mix/hr (~ 30%
increase) was possible when switching from HMA to WMA
Useful during peak seasonor for debottlenecking
Flexible technology : easy to switch from HMA to WMA and back
Asphalt (usual T)
Aggregates
WMA120C
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Longer hauling
80
90
100
110
120
130
140
150
160
170
0 50 100 150 200Time (min)
Tem
perature(C)
WMA HMA
Limitfor WMA paving
HMA production
WMA production
+ 200%+25%
Limitfor HMA paving
A WMA with CecabaseRTmay be paved up to 25% later than standard HMA
A HMA with CecabaseRTmay be paved after a hauling time up to 3 timeslonger
t0
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Examples of field jobs
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Examples of field jobs - France
Bordeaux 2008High traffic road
High modulus asphalt cement (EME)
10/20 [1/10mm] asphalt
Produced at 130C (normally 170C). Laid down at 125C
Average density 95,6%
Gaillac 2011BBSGStandard 0/10 mm wearing course (BBSG), 6 cm layer
0,4% Cecabase RT Bio10
Cecabase RT945 used at 0.4%, added in tank 5 days before
500 tons paved at 120CHigh volume road : AADT > 15000
St Flour 2009Highway A75
Open graded friction course (BBTM) Thin layer 2,5 cm
5,6% binder, polymer modified Styrelf 13-600,4% Cecabase RT945
4000 tons produced at 135C, paved at 120C, compacted at 110C
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Examples of field jobs - Europe
Poland 2007Stone Mastic Asphalt (SMA)
0-8 mm aggregates - 0.4% fibers in the mix
Asphalt binder Pen. 50 + 3% SBS0,4% CecabaseRT945
3000 tons produced at 130C, paved at 120C, compacted at 100C
Italy (Padova) 2012
Fine gradation D8 type15% RAP added cold at the plant
Asphalt 70/100 penetration0,4% CecabaseRT Bio10
Mix produced at 150C, paved at 130C, compacted at
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Examples of field jobs - AmericaNew York State 20082 different jobs
1300T dense-graded mix with 30% RAP (Road 31 along Seneca River)
1000T dense-graded mix without RAP (Road 18 near Utica)Production at 120-130C, paved at 120C with good workability
Tennessee (Sevierville) 2012
Mix with difficult limestone aggregate15% RAPhigh traffic road
Asphalt PG64-22CecabaseRT945 and antistrip
Night work, light rain - Mix produced at 130C, compacted at 113C
Canada (Alberta) 200925,000 tons job
Dense graded mix without RAP (gravel pit aggregates)Interstate 35
Asphalt binder 200-300 Pen. with antistrip + 0.2% CecabaseRT945
Produced at 120C (vs 150C for control HMA)
California 2010Caltrans project with crumb rubber
12.5mm gap graded mixAsphalt PG 64-16 with 18% scrap tire
0.4% CecabaseRT - Produced at 130C (vs 165C for control HMA)
Tested on Heavy Vehicle Simulator (HVS) Cecabase RT WMA ismore rut resistant than control HMA
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Examples of field jobs Asia & LatAm
Australia 2008High %RAP mix
Base and Wearing Courses Type H-10mm30 and 40% RAPrespectively
Paving temperatures : 108-115C
Average compaction around 95%
Japan 2009Open graded type
-30C to -50C temperature decrease - Rainy conditions3000 tons produced at 130C, paved at 120C, compacted at 100C
China 20110-8 mm aggregates - 0.4% fibers in the mix
Asphalt binder Pen. 50 + 3% SBS0,4% Cecabase RT
3000 tons produced at 130C, paved at 120C,compacted at 100C
Argentina 2010
Open graded type mixAsphalt grade CA-30 (pen 50/60) with0,4% Cecabase RT945
Temperature decreased to 130CCore sampling
l l b l
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A real global coverage
Today Cecabase RT is present in more than 50 countries
More than 150 different customershave chosen Cecabase RT additives
Several millions tonsof Warm Mix Asphalt are produced each year withCecabase RT technology
Field jobs
Lab trials
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A simple way to reduce temperature of asphalt mixes by~ 40C by the addition of a liquid additive :
Patentedtechnology used since 2004on the field
Robust, work with all binders and asphalt mixes
No plant modification or high maintenance costs
Most cost-competitivesolution among additives
Systematic back-upof CECA technical experts
Mechanical properties of WMA are similar to thoseobtained with a control HMA
Benefit from immediate advantages :
Environment: reduction of emissions, gas savings,use of RAP
Comfort: compaction aid, less heat & fumes, quickopening to traffic
Flexibility: increased plant capacity, longer hauling,night or off-season work
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Th k !