Rutting and Moisture Resistance of Asphalt Mixtures Containing Polymer and Polyphosphoric Acid Modified Bitumen

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Rutting and Moisture Resistance of Asphalt MixturesContaining Polymer and Polyphosphoric AcidModified BitumenGilles Orange a , Jean-Valery Martin a , A. Menapace b , M. Hemsley b & G. L.Baumgardner ba Rhodia Recherches Aubervilliers Research Center, 52, rue de la Haie Coq, F-93308,Aubervilliers, Cedex E-mail:b Paragon Technical Services, Inc., P.O. Box 1639, Jackson, MS, 39218-1639, USA E-mail:Published online: 19 Sep 2011.

To cite this article: Gilles Orange , Jean-Valery Martin , A. Menapace , M. Hemsley & G. L. Baumgardner (2004) Ruttingand Moisture Resistance of Asphalt Mixtures Containing Polymer and Polyphosphoric Acid Modified Bitumen, Road Materialsand Pavement Design, 5:3, 323-354, DOI: 10.1080/14680629.2004.9689975

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Road Materials and Pavement Design. Volume 5 – No. 3/2004, page 323 to 354

Rutting and Moisture Resistance of AsphaltMixtures Containing Polymerand Polyphosphoric Acid Modified Bitumen

Gilles Orange* — Jean-Valery Martin* — A. Menapace**M. Hemsley** — G.L. Baumgardner**

* Rhodia RecherchesAubervilliers Research Center52, rue de la Haie CoqF-93308 Aubervilliers, Cedexgilles.orange; [email protected]

** Paragon Technical Services, Inc.P.O. Box 1639Jackson, MS 39218-1639, USA{a.menapace; m.hemsley; g.baumgardner}@paratechlab.com

ABSTRACT. Initial engineering properties of materials as well as mechanical andenvironmental conditions governs the behaviour of asphalt pavements in service. To enablepavements to accommodate increasing traffic intensity and axle loads in varying climateenvironments, high quality bitumen is required. Special binders are also needed for otherapplications, such as bridges and airport runways. These examples suggest the necessity ofbitumen modification. While modification of bitumen may be carried out via other methods,the most promising has been polymer modification. This paper discusses the performance ofhigh grade bituminous binders modified via synthetic polymers, polyphosphoric acid andcombinations thereof, and their performance in asphalt mixtures in subsequent laboratoryevaluation of moisture and mechanical damage (rutting). The effect of polyamine antistripaddition to asphalt mixtures modified with polymer and polyphosphoric acid is discussed.KEYWORDS: Permanent Deformation, Stripping, Superpave™, Polyphosphoric Acid, Polymer,Polyamine, Asphalt mixture, Tensile Stress Ratio, Hamburg Wheel Tracking Device.

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324 Road Materials and Pavement Design. Volume 5 – No. 3/2004

1. Introduction

Asphalt mixtures behaviour is dependent on the binder and aggregatecharacteristics, as well as bituminous binder content, temperature, binder ageing,and air void content of the mixture. Pure bitumen characteristics can be estimatedfrom room temperature consistency (penetration value), softening point (ring andball temperature), and cracking temperature (Fraas point). In case of modifiedbitumen, and especially with polymer addition, the rheological behaviour (thatmeans the time properties dependency) must be considered. The Superpave“binder” specification, developed in USA through SHRP program, establishes theperformance grade from criteria based on rheological approach. A unique feature ofthe Superpave specification is that the specified criteria remain constant, but thetemperature at which these criteria must be achieved changes for various grades.Performance based bituminous binders are used to improve mixtures performancesuch as controlled rutting, low temperature cracking and fatigue cracking (Bahia andAnderson, 1994; Asphalt Institute, 1998; Roberts et al., 2002).

The characteristics and performance of bitumen are temperature dependent, dueto the fact that bitumen may go through changes in state and may exist as a liquid(viscous), a semi solid (visco-elasto-plastic), or a solid (elastic) depending ontemperature (Figure 1).

0 2 0 4 0 6 0 8 0 1 0 0

Figure 1. Bitumen performance with temperature with the useful temperatureinterval (UTI)

The region between the two changes in state can be defined as the “usefultemperature interval” UTI. Superpave defines this UTI as the performance grade(PG) of the asphalt binder as shown in Figure 2.

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Asphalt Mixtures and Polyphosphoric Acid Modified Bitumen 325

The useful temperature interval UTI is limited for high temperature performanceby the average seven day maximum pavement design temperature in degrees Celsiusand limited for low temperature performance by the minimum pavement designtemperature in degrees Celsius.

Figure 2. SHRP Performance grades of asphalt binder: P.G. grades

So, it becomes possible to select a PG-binder grade for climatic conditions, butalso allows binder selection based on loading conditions. The specification allowsfor the assumption that an increase in the performance requirement due to theincreases in the expected loads is the same as an increase in the expectedtemperature performance or UTI. As an example we can use the standard grade ofPG64-22 for normal high speed traffic, which would be shifted to the PG70-22grade for slower heavy traffic and PG76-22 for heavy standing or interstate typetraffic. As one can see these PG-grades have 86, 92 and 98 Celsius degreetemperature performance ranges respectively (UTI). It has been determined that aPG-grade performance temperature range of greater than 90 degrees will requiresome form of modification, polymer modification has been the most utilised methodof modification (Lewandowski, 1994).

It should be noted that limitations of the Superpave binder specification havebeen identified with respect to performance grading of modified binders. The criteriaconcerning the PG definition seems to be insufficient, in some cases, to predict therutting behaviour of asphalt mixture from rheological laboratory tests on thebituminous binder. Due to these limitations, the high critical temperature(Tc: G*/sinδ criteria) has typically been supplemented by specification parameterssuch as minimum high temperature phase angle (δ) and elastic recovery. Otherproperties, such as zero shear viscosity (ZSV) and the repeated creep test have

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received attention as a predictors of the rutting potential of bituminous binders (LeHir, 2003). New criterion must be developed combining small deformation tests(rheology) and large deformation tests (plasticity). Similar problems occur withrespect to the low temperature specification (Eckmann et al., 2004).

Use of polymer modified bitumen to improve performance of asphalt pavementhas been required for several reasons to include: increased traffic (higher trucktraffic with heavier loads), delayed maintenance (maintenance funding shortages),and use of thinner pavements (costs control, but reduced service life).

Polymer modification has been the most widely accepted method of: styrene-butadiene polymers account for sixty-five percent of the polymers used in bitumenfor paving in Europe and over eighty percent of the polymers used in bitumen forpaving in the United States. The primary reason these polymers have achievedsuccess is that their elastomeric characteristics give bitumen the best blend ofproperties to address all three of the distresses mentioned above at economical uselevels. The polymer additives stiffen the bitumen at higher temperatures to resistpermanent deformation (rutting), and can, in some cases, make the material lessbrittle at low temperatures to reduce fatigue and thermal cracking: this is measuredas an increase of the high critical temperature measured by rheology (DSR) and aconstant or in some case a decrease of the low critical cracking temperaturemeasured by BBR/DDT test (Brule et al., 1998).

Other methods can be used to improve bitumen performances: for instance airblowing which was used in the past, and more recently specific chemicalmodification (Jain et al., 1998; Lee, 1975). Polyphosphoric acid (PPA) is a commonmethod of chemical modification, used in the U.S. since the early 1970s (PATENT,1973). Similar to polymer modification, modification with polyphosphoric acidstiffens the bitumen at high temperature improving resistance to permanentdeformation, without detrimental effects to low temperature properties (Orangeet al., 2004). PPA modification is different than air blowing in that there is nobitumen oxidation and PPA modified bitumen has better low temperature propertiesas compared to air blown bitumen (Orange et al., 2005). Polyphosphoric acidmodification can be considered as a new economical way to modify bitumen insteadof, or in conjunction with, polymer modification depending on performancerequirements. Since the early 1975’s, polyphosphoric acid has been used withsuccess as a modifier alone or in combination with polymers (PATENT, 1997).

Polyphosphoric acid reacts with the asphaltenes, leading to chemically modifiedbitumen. Polymer additives (SBS, EVA) are physical additives. There is an interestto improve bitumen properties through the use of a combination of chemical andphysical additives to improvement of high temperature viscosity, high and lowtemperature stiffness and crack resistance. So it is possible to obtain modifiedbitumen with high performance level at a reduced polymer content.

A study of modified bitumen binders using the combination of polyphosphoricacid and polymers will be presented herein. Laboratory tests have been done on

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asphalt mixtures: moisture resistance, and wheel tracking tests. The addition ofpolyamine antistrip and/or lime filler is discussed.

2. Experimental description

Bitumen chemistry and physical characteristics are important factors affectingbitumen modification. With this consideration, three bitumen sources with markedlydifferent characteristics were selected for this work. Bitumen sources were Saudifrom Saudi light crude, Venezuelan from Bachaquero crude, and California Valleyfrom a blend of California Valley crude sources (Table 1). In addition to varyingcrude sources polymer modification was performed with Styrene-Butadiene-Styrene(SBS) block copolymers and Ethylene Vinyl Acetate (EVA) from commerciallyavailable sources. Polymers used were radial SBS and a 50/50%wt blend of twoEVA polymers. Polyphosphoric acid modification was made using a 105%wtcondensed acid. (see details in Annex).

Antistrip additives were used in some experiments : polyamine antisitrip, andhydrated lime filler.

2.1. Preparation of polymer modified bitumen blends

All binders modified with polymer (either SBS or EVA) and polyphosphoricacid (PPA) were prepared in two stages: first, concentrate blend in a soft bitumen(140-160dmm), followed by dilution with a harder bitumen (50-60dmm).

The SBS samples were prepared by blending a concentrate of 15 wt% SBS(Dexco 2411) and 85 wt% soft asphalt using a laboratory high shear mixer(Silverson L4RT-W). Common processing temperatures for concentrate and dilutionrange from 190-200°C. Batch weights for concentrates were 2500 grams in a 3.8litre vessel. Concentrates were diluted to varying percentages and cured. Dilutiontime and curing varied from 5-24 hours with low shear agitation at approximately200 rpm.

The EVA samples were prepared by blending a concentrate of 15 wt% EVA(a blend of 50% Polybilt 103C, 50% Polybilt 502) and 85 wt% soft asphalt using alaboratory high shear mixer (Silverson L4RT-W). Common processing temperaturesfor concentrate and dilution range from 190-200°C. Batch weights for concentrateswere 2500 grams in a 3.8 litre vessel. Concentrates were diluted to varyingpercentages and cured. Dilution and curing time varied from 2-16 hours with lowshear agitation at approximately 200 rpm.

UV fluorescence microscopy was used to evaluate production of concentrate andcuring of diluted formulations. This process, commonly used in production ofpolymer modified bitumen, is purely qualitative and somewhat subjective.

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2.2. Bitumen and modified bitumen descriptions

The Saudi bitumen blends were prepared using a soft grade PG52-28 (140-1601/10mm) for the concentrate and a PG64-22 (50-60 1/10mm) as the dilutionbitumen. Typical performance grade properties are listed in Table 4-6 (seeAppendix). This bitumen is considered to be an even balance of compatibility andperformance with a low acid value (0.1 mg KOH/g bitumen) and moderateasphaltene content. Compositional analysis of the PG64-22 bitumen yields 10.4%asphaltenes (n-heptane insolubles) and 9.3% resins, 78.1% aromatics and 2.2%saturates. Composition of the PG58-28 has slightly lower asphaltenes and similardistribution of maltene components.

The Venezuelan bitumen blends were prepared using a soft PG52-28 (140-1601/10mm) for the concentrate and a PG67-22 (50-60 1/10mm) as the dilutionbitumen. Typical performance grade properties are listed in Table 7-9 (seeAppendix). This bitumen is considered to be slightly incompatible with SBS, butstrong for Performance Grading. This bitumen has a high acid value (3.5 mg KOH/gbitumen) and moderately high asphaltene content. Compositional analysis of thePG67-22 bitumen yields 11.0% asphaltenes (n-heptane insolubles) and 25.4% resins,58.9% aromatics and 4.7% saturates.

Composition of the PG58-28 has slightly lower asphaltenes and similardistribution of maltene components. An additional Venezuelan bitumen (B) wasused for adhesion experiments

Table 1. Neat bitumen physical properties (bitumen used for dilution)

Bitumen Description Saudi Light Venezuela California Valley

Performance Grade PG 64-22 PG 67-22 PG 64-10

Pene 1/10mm 56 60 50

R & B temp. (°C) 50 49 47

BrookfieldViscosity.(135°C) cps 468 478 250

Fresh: G*/sinδ (kPa) 1.424 1.163 1.232

Phase Angle (°) 87.4 88.1

Wt. loss (g) -0.13 0.027 0.32

RTFOT: G*/sinδ (kPa) 2.685 2.438 2.543

PAV: G*.sinδ (kPa) 4427 4526 3690

BBR - S (MPa) 205 241 132

BBR - m 0.321 0.32 0.477

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The California Valley bitumen blends were prepared using an AR2000 (PG58-16) in the concentrate and an AR4000 (PG64-10) as the dilution bitumen (except forblend 36 which used AR4000 in both concentrate and dilution). Typicalperformance grade properties are listed in Table 10-12 (Appendix). This bitumen isconsidered to be highly compatible with SBS, but poor for performance grading.This bitumen has a relatively high acid value at 1.6 mg KOH/g bitumen and a lowasphaltene content. Compositional analysis of the AR4000 bitumen yields 3.6 %asphaltenes (n-heptane insolubles) and 33.6% resins, 66.8% aromatics and 6.0%saturates. Composition of the AR2000 has slightly lower asphaltenes and similardistribution of maltene components.

2.3. Addition of polyphosphoric acid

Dispersion and cure of all polymer bitumen blends was evaluated via UVfluorescence microscopy. After achieving total fluorescence, the polymer modifiedbitumen was further modified with polyphosphoric acid.

With SBS, the PG grades achieved with Venezuelan and Saudi bitumens were76-22 and 82-22, depending on the polymer content (up to 6.6%).

0 0,2 0,4 0,6

0

1

2

3

4

5

6

SBS

%

PPA %

Venezuelan Saudi

Californian

Figure 3a. PG76-22. Partial substitution of SBS by Polyphosphoric acid at isograde (PG76-16 with California Valley)

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Polyphosphoric acid was used from 0.2% to 0.6%, in partial replacement of SBS,to obtain the same PG grade at a lower polymer content: see Figures 3a and 3b.

0 0,2 0,4 0,6

0

12

3

4

5

6

7

SBS

%

PPA %

Venezuelan SaudiCalifornian

Figure 3b. PG82-22. Partial substitution of SBS by Polyphosphoric acid at iso-grade (PG82-16 with California Valley)

The exact amount of SBS polymer and PPA is on Tables 4-5 (Saudi bitumen),Tables 7-8 (Venezuelan bitumen) and Tables 10-11 (California valley bitumen): SeeAppendix.

With EVA, the PG grades achieved with Venezuelan and Saudi bitumens were76-22 and 82-22, depending on the polymer content (up to 9%). Polyphosphoric acidwas used from 0.2% to 0.6%, in partial replacement of EVA, to obtain the same PGgrade at a lower polymer content : see Figure 4.

The exact amount of EVA polymer and PPA is on Table 6 (Saudi bitumen),Table 9 (Venezuelan bitumen) and Table 12 (California valley bitumen). SeeAppendix.

By the use of polyphosphoric acid, it is possible to reduce the polymer contentrequired to obtain the PG grade: for instance (see Figure 3a), it is possible to replace1.65% of SBS polymer by 0.6% of Polyphosphoric acid while maintaining thePG76-22 requirements (DSR and BBR values). This is possible because thecomplimentary effect on modification of the two additives. Such modification leadsto improved processing conditions, high temperature viscosity, and storage stability.

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0 0,2 0,4 0,6

02468

10121416

EVA

%

PPA %

Venezuelan SaudiCalifornian

Figure 4. PG76-22. Partial substitution of EVA by Polyphosphoric acid at iso grade(PG76-16 with California Valley)

3. Polymer/Polyphosphoric acid modified bitumen properties

3.1. Modified binder properties

The different characteristics of polymer and polyphosphoric acid modifiedbitumen are listed in the Appendix (Table 4 to Table 12/Appendix): Brookfieldviscosity, DSR (G*/sinδ) in the unaged state and after short term ageing (RTFOT)and BBR (S, m).values after long term ageing (PAV).

The PG grades achieved were PG76-22 and PG82-22 for the SBS and SBS/PPAmodified bitumens, and PG76-22 for the EVA and EVA/PPA modified bitumen.

All blends were performance graded in accordance with AASHTO M 320-03:DSR (after RTFO) and BBR (after PAV) test. Except for the Venezuelan with 5.1%SBS, all the criteria are satisfied.

Elastic Recovery for all modified binders was tested at 25°C, in accordance withAASTO T 301.

3.2. Discussion

As described previously in section 2.3. all binders were designed to achievesame PG: 76-22 and 82-22 for Venezuelan and Saudi, 76-16 and 82-16 forCalifornia Valley bitumen.

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The reduced level of polymer by substitution of a part of polymer (SBS, or EVA)by polyphosphoric acid (PPA) leads to a lower Brookfield viscosity (135°C) whencompared to the higher polymer content (100% polymer modification) at same PGgrade. The elastic recovery ER level remains quite constant whereas the amount ofSBS polymer is reduced. In the case of EVA the amount of polymer is to high toobtain in fact lower elastic recovery values.

PPA works well in combination with polymer, both SBS and EVA. It allows forreduction of polymer content while maintaining a given Performance Grade. Thismakes the product much easier to handle (mixing, compaction, workability). PPA isefficient for increasing the high temperature properties (G*, and phase angle), andallow to maintain good low temperature behaviour. PPA is compatible with polymermodified bitumen.

4. Asphalt Mixtures

Preparation of asphalt mixtures

Asphalt mixtures were prepared from polymer/polyphosphoric acid modifiedbitumen, with different aggregates. The specifics on the mix designs are defined bythe type of aggregates and the final gradations.

The limestone aggregate was from North East Texas (USA) and the graniteaggregate was from the Atlanta Georgia area (USA). The gradation for each mix isreported in Table 2 (% passing).

Table 2. Percent passing for limestone and granite aggregates

Sieve Size (mm) Limestone: % passing Granite: % passing12.7 100 96.1

9.525 97.7 87.94.75 60.2 54.32.36 - 38.2

2 38.3 -1.18 - 30.00.6 - 23.7

0.425 18.6 -0.3 - 16.6

0.18 7.7 -0.15 - 10.1

0.075 1.7 5.4

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The Venezuelan bitumen, neat and polymer/polyphosphoric acid modified, wasused for the mix ; some tests were also done with the California Valley bitumen.

Mixing temperatures used for each bitumen and modified bitumen were specificto each composition; compaction temperature was typically 10 °C below mixingtemperature.

A mixing temperature of 154 °C and compaction temperature of 145 °C wasused for the neat 76-22 bitumen with limestone or granite aggregates. The differentcompositions are listed in Table 3. Compositions 1 to 3 were made with limestoneaggregate; all other compositions (4 to 17) were made with granite aggregate.

Table 3. Mixes composition, and mixing- compaction temperature

N° Composition Additives AggregateMixingTemp.(°C)

1 Ven - PG67-22 (neat) - Limestone 154

2 Ven - PG76-22 (4.25% SBS) - Limestone 162

3 Ven - PG76-22 (2.6% SBS/0.6% PPA) - Limestone 162

4 Ven - PG67-22 (neat) - Granite 154

5 Ven - PG76-22 (4.25% SBS) - Granite 162

6 Ven - PG76-22 (2.6% SBS/0.6% PPA) - Granite 162

7 Ven - PG82-22 (5.1% SBS) - Granite 170

8 Ven - PG82-22 (3.5% SBS/0.6% PPA) - Granite 170

9 Ven - PG76-22 (3.8% EVA/0.6% PPA) - Granite 165

10 Ven - PG67-22 Polyamine Granite 154

11 Ven - PG76-22 (4.25% SBS) Polyamine Granite 162

12 Ven - PG76-22 (2.6% SBS/0.6% PPA) Polyamine Granite 162

13 Ven - PG76-22 (2.6% SBS/0.6% PPA) Lime Granite 162

14 Ven - PG76-22 (2.6% SBS/0.6% PPA) Polyamine+ Lime

Granite 162

15 Calif -PG64-10 (neat) - Granite 157

16 Calif - PG76-22 (5.5% SBS) - Granite 165

17 Calif - PG76-22 (3.75% SBS/0.6% PPA) - Granite 165

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Antistrip additives were used in some compositions:– Polyamine E-6 (0.5%wt in binder) in composition 10 to 12 ;– Hydrated Lime (17.5%wt in binder) in composition 13 ;– Polyamine E-6 (0.5%wt in binder) + Hydrated Lime (17.5%wt in binder) in

composition 14.

Polyamine was added to the hot binder while hydrated lime was incorporatedinto the aggregate. Compositions 10 to 14 can be compared to compositions 4 to 6(same PG and modification/no antistrip).

Moisture resistance, tensile stress ratio (TSR), and Hamburg wheel-tracking(HWTD) specimens were prepared, to observe the stripping and rutting resistance ofthe different compositions. One set of mix specimens, six each 150 X 65mm, wasprepared in accordance with the Marshall method with the specific gravitymaintained between 2.3 and 2.4. These specimens were used for moisture resistancetest (TSR). A second set of mix specimens was prepared with the SuperpaveGyratory Compactor in specific condition to obtain specific gravity of 2.4. Thesespecimens were used for rutting tests (Hamburg wheel-tracking test). Targeted airvoids for all specimens were 7%. Actual values were within 7 to 8% for TSRspecimens, and 5 to 7% for HWTD specimens.

TSR tests were performed according to the AASHTO T-283 (Texas TestMethod): after 24h curing, 3 specimens as dry state reference, and 3 specimenswater-saturated under vacuum (24h) followed with 1 freeze thaw cycle andstabilised in a room temperature water bath for 24h. 7% (±1%) air voids wastargeted along with 68% ±12% water saturation (AASHTO, 1998). Results consistof the ratio (TSR) between the strength at dry state and the strength at conditionedstate.

The Hamburg wheel-tracking tests were made following the Texas Test MethodTex-242. Tests are conducted under water, at temperature of 50°C. Loading of thesample is accomplished by applying a 705 N load onto a 47 mm wide steel wheel.The steel wheel is then tracked back and forth over the slab sample. The travel speedof the wheel is about 340 mm/sec (Aschenbrener, 1995). Test samples are loaded for20,000 cycles or until > 12 mm of deformation (rut) occurs. Results consist of rutdepth, creep slope, stripping inflection point, and stripping slopes: permanentdeformation versus wheel passes curves are recorded.

5. Pavement rutting and moisture resistance: results and discussion

5.1. Adhesion

The stripping phenomena could be quantified through the “boiling water test”developed by Belgium Road Research Center (BRR, 1992). The stripping rate isdetermined by residual acid titration (HF, or HCl) of coated granulates after ten

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minutes boiling water treatment, relative to acidic consumption of ref uncoatedaggregate. The effect of 1% polyphosphoric acid was observed on differentaggregates to include granite, porphyry and limestone, with non polymer modifiedVenezuelan bitumen: results are shown on Figure 5. The measured anti-strip valuesindicated a high level of moisture resistance with polyphosphoric acid modifiedbitumen in case of siliceous aggregate, and in less extent with limestone aggregate.

Venezuelan Bitumen

0

10

20

30

40

50

60

70

80

90

Porphyry Limestone Granite

Strip

ping

Rat

e (%

)

NeatPPA (1%)

Figure 5. Stripping rate (BRRC method) of Venezuelan bitumen (neat, and PPAmodified)

These results underline the antistrip properties of Polyphosphoric acid (PPA)with granite and porphyry aggregates.

Complementary experiments were done on stripping properties of coatedaggregates with Saudi bitumen modified by polyphosphoric (without polymer) aloneor in presence of polyamine (200P) anti-strip additive. Results are shown onFigure 6.

In case of siliceous aggregates, the positive effect of polyphosphoric acid isconfirmed, and even improved as the acid content is increased (up to 2%). Thepresence of anti-strip polyamine 200P (0.5%wt) doesn’t affect the antistrip effect ofpolyphosphoric acid as is demonstrated from these laboratory tests, according to theBRRC standard.

With limestone aggregate, the addition of polyphosphoric acid – even at 2% –has no antistrip effect. The use of polyamine 200P (0.5%) leads to an improvementof the stripping rate. This effect of polyamine on bitumen-aggregate adhesion ismaintained even improved in case of the bitumen modified with polyphosphoricacid.

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0

10

20

30

40

50

60

70

80

90

100

Neat Neat+1,2% PPA Neat+ 2%PPA Neat+ 0,5%200P

Neat+1,2% PPA+0,5% 200P

Neat+ 2%PPA+0,5%

200P

Dec

aotin

g ra

te (%

)

Silicious

Limestone

With Polyphosphoric acid alone Polyphosphoric acid + polyamine 200P

Figure 6. Stripping rate (BRRC method) of Saudi bitumen (neat, PPA and PPA +antistrip 200P modified) with limestone and siliceous aggregates

These results are not in accordance with the hypothesis of S.W. Bischarra et al.(2001), which suggest that possible reactivity between polyamine antistrip andpolyphosphoric acid can reduce the antistrip affect of polyamine.

5.2. Moisture resistance (TSR)

Tests were performed on asphalt mixes with granite and limestone aggregates,based on Venezuelan bitumen. The effect of some antistrip additives (polyamineadditive, and lime filler) were also observed.

Two effects can control the asphalt mixture moisture resistance: the bindercohesion at the test temperature (binder strength, and stiffness), and the binderadhesion to the aggregate.

5.2.1. Mixes with granite aggregates

With granite aggregates, the mixes corresponding to neat bitumen PG67-22(Venezuelan) and SBS/PPA modified PG76-22 and PG82-22 were measured.Results are shown on Figure 7: strength (dry, and conditioned state) and strengthratio (TSR).

The Tensile Strength Ratio (TSR) is quite constant between neat bitumen (PG67-22) and polymer SBS modified bitumen (PG76-22), even with the gradeimprovement. The polymer has no effect on moisture resistance in these tests. Bysubstitution of a part of SBS or EVA polymer with polyphosphoric acid, at iso-

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grade, we observe a large improvement of the Tensile Strength Ratio (TSR) from40% to 72%. This results is consistent with the stripping experiments on aggregates(cf. Figure 5): polyphosphoric acid acts as an antistrip additive with graniteaggregate in addition to an asphalt modifier.

0

10

20

30

40

50

60

70

80

Neat 67

-22

SBS 76-22

SBS/PPA 76-22

EVA/PPA 76-22

SBS 82-22

SBS/PPA 82-22

Asphalt

TSR

(%

)

0

24

6

8

10

12

14

1618

20

Strength (MPa)

Dry strength (MPa) Wet strength (MPa) TSR (%)

Figure 7. Moisture resistance (TSR) of mixes made from Venezuelan bitumen andgranite aggregate

There is no difference between SBS and EVA : therefore, the polyphosphoricacid effect is not believed to be dependant on the polymer type. This effect is not solarge in case of high SBS content, i.e. 5.1% (PG82-22), but in this case bindermicrostructure is very different.

5.2.2. Mixes with limestone aggregates

With limestone aggregate, the asphalt mixes corresponding to neat bitumenPG67-22 (Venezuelan) and SBS/PPA modified PG76-22 were measured.

Results are shown on Figure 8: strength (dry and conditioned state), and TSR.

The Tensile Strength Ratio (TSR) is quite constant between neat bitumen(PG67-22) and polymer SBS modified bitumen (PG76-22), as shown previously.We can notice that with limestone aggregate, the TSR is greater than with granitegranulates: that means better moisture resistance of these mixes. Polymer appears tohave no effect on moisture resistance. By substitution of a part of SBS polymer byPolyphosphoric acid, we observe a slight decrease of the Tensile Strength Ratio

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(TSR) from 70% to 60%. However the dry strength is higher than SBS alone, andthe decrease of TSR is only due to this high strength value. Again, this results isconsistent with the stripping experiments (cf. Figure 5): polyphosphoric acid has nostripping resistance effect with limestone aggregate.

20

30

40

50

60

70

80

Neat 67-22 SBS 76-22 SBS/PPA 76-22

Asphalt

TSR

(%)

0

2

4

6

8

10

12

14

16

18

20

Strength (MPa)

Dry strength (MPa) Wet strength (MPa) TSR (%)

Figure 8 Moisture resistance (TSR) of mixes made fromVenezuelan bitumen andlimestone aggregate

5.2.3. Effect of antistrip additives (Granite aggregate)

The TSR required specification limit is in generally greater than 70%. In case ofgranite aggregate, the measured value is about 40% (neat 67-22, and polymermodified 76-22): so, anti-strip additive has to be added. Polyamine E6 additive andhydrated lime filler has been used with the the mixes corresponding to PG67-22 neatbitumen (Venezuelan), and SBS/PPA modified PG76-22. Polyamine E-6 was usedat 0.5%, and hydrated lime at 1.0% of the aggregate, 17.5% in the binder. A testwas also made with a combination of 0.5% polyamine E-6 and 1.0% of lime inaggregate, 17.5% in the binder. Results are shown on Figure 9.

The Tensile Strength Ratio (TSR) is improved between neat bitumen (PG67-22)and antistrip treated bitumen (PG 67-22): the dry strength is reduced, but the wetstrength is increased from 7 MPa to 11 MPa. The mix specimen are evaluated at25°C: TSR tests clearly show the effect of binder/aggregate interface, but doesn’ttake into account the PG grade. Whereas with SBS polymer modified bitumen, thegrade is increased from 67-22 to 76-22, similar TSR value was observed withpolyamine (E6) and neat bitumen, and also with SBS/PPA. Lime, alone or incombination with polyamine E-6, leads to a slight improvement of the TSR valueswith SBS/PPA modification.

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0102030405060708090

100

Neat 67-22

Neat 67-22 + E6

SBS 76-22 + E6

SBS/PPA 76-22 + E6

SBS/PPA 76-22 + Lim

e

SBS/PPA 76-22 + Lim

e + E6

Asphalt

TSR

(%

)

02468101214161820

Strength (MP

a)Dry strength (MPa) Wet s trength (MPa) TSR (%)

Figure 9. Moisture resistance (TSR) of mixes made from Venezuelan bitumenand granite aggregate, with polyamine and/or lime additions

5.3. Rutting resistance (Hamburg wheel tracking test)

The Hamburg wheel tracking device (HWTD) is used as a specificationrequirement in some countries to evaluate both rutting and stripping in the same test.Tests are conducted under water, at high temperature (typically 50°C). Resultsobtained from the HWTD consist of rut depth, creep slope, stripping inflection point(SIP), and stripping slopes. The creep slope is the inverse of the deformation ratewithin the linear region of the deformation curve after post compaction and prior tostripping (if stripping occurs). The stripping slope is the inverse of the deformationrate within the linear region of the deformation curve, after the onset of stripping.

Figure 10 represents the measured deformation curves with HWTD on asphaltmix slab made from not modified and modified bitumen with granite aggregate.

The stripping inflection point (SIP) is the number of wheel passes correspondingto the intersection of the creep slope and the stripping slope. This value is used toestimate the relative resistance of the asphalt mixture slab to moisture-induceddamage. The test is stopped when one of the pre-defined values is attained: a rutdepth > 12 mm, or a number of cycles = 20,000.

Two effects can control the asphalt mixture rutting resistance as measuredthrough HWTD test: the binder cohesion at high temperature (binder strength andstiffness), and the adhesion to aggregates.

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Hamburg Wheel Tracking TestTest Method Tex-242-F

0

2

4

6

8

10

12

14

0 5000 10000 15000 20000

No. of Passes

Rut

Dep

th, m

m

Set 4

Set 5

Set 4

Set 4 : PG67-22Set 5 : PG76-22 (PG67-22+4,25%SBS)Set 6 : PG76-22 (PG67-22+2,6%SBS+0,6%PPA)

Set 5

Set 6

SIP

SIP

Figure 10. Typical Hamburg Wheel tracking Test curve (Venezualian bitume, withgranite aggregate). SIP : Stripping Inflection Point

5.3.1. Mixes with granite aggregate

With granite aggregate, the mixes corresponding to neat bitumen PG67-22(Venezuelan) and SBS/PPA modified PG76-22 and PG82-22 were measured.

Results are shown on Figure 11: rut depth and the corresponding number ofpasses (cycle number) for the different mixes.The rut depth (permanentdeformation) is at about 12 mm for 10,000 cycles in case of neat bitumen (PG67-22); the SBS polymer modified bitumen (PG76-22) presents similar permanentdeformation (11 mm), but for a greater number of cycles (20,000). This effect isonly due to the PG improvement, the SBS polymer having no effect on aggregateadhesion.

By substitution of a part of SBS polymer with polyphosphoric acid – at same PGgrade (PG76-22), we observe a large improvement of the rut depth (permanentdeformation) down to 3.5 mm for a larger number of cycles (20,000). A lower rutdepth is obtained with EVA/PPA system, compare to SBS/PPA. These results areconsistent with both the level of critical high temperature measured on binder (PGgrade) and the moisture resistance (TSR experiments) (cf. Figure 7). The SBS/PPAmodified bitumen were both better than the 100% SBS modified bitumen when

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compared on the Hamburg Wheel Tracking Test. The SBS/PPA modified bitumenactually passed this test, with a rutting value of 3.5 mm and 1.3 mm. The SBS/PPAshowed no stripping inflection point, while the SBS did and the SBS/PPA had 3times and 25 times the creep slope of the other asphalts.

02468

101214

Neat 67-22

SBS 76-22

SBS/PPA 76-22

EVA/PPA 76-22

SBS 82-22

SBS/PPA 82-22

Asphalt

Rut

dep

th (m

m)

0

5000

10000

15000

20000

25000

Cycles

Rut depth (mm) Cycles

Figure 11. Rutting resistance (HWTD - 50°C) of mixes made from Venezuelanbitumen and granite aggregate

At the same PG grade obtained with SBS alone or SBS/PPA combination, therutting resistance is very different. The antistrip effect of polyphosphoric acid withgranite aggregate may explain this higher resistance to permanent deformation inboth temperature and humidity conditions.

The antistrip effect due to PPA is clearly shown on Hamburg Wheel trackingcurves: Figure 10. The stripping inflection point appears at 8,500 passes for neat mixPG 67-22 and shift to 12,000 passes for SBS polymer modified mix PG 76-22.WithSBS/PPA combination the stripping inflection point is higher than 20,000 passes.Moreover, it seems that PPA also has a positive effect on the creep slope at samebinder PG.

The antistrip effect of polyphosphoric acid with granite aggregate leads to anincreased mixture resistance to permanent deformation at both high temperature andhumidity conditions. This effect is not so large in case of higher SBS content (PG82-22). At the same temperature condition the moisture sensitivity of mix is balancedby the upgrading of PG.

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5.3.2. Mixes with limestone aggregate

With limestone aggregate, the mixes corresponding to neat bitumen PG67-22(Venezuelan) and SBS/PPA modified PG76-22 were measured. Results are shownon Figure 12.

0

2

4

6

8

10

12

14

Neat 67-22 SBS 76-22 SBS/PPA 76-22

Asphalt

Rut

dep

th (m

m)

0

1000

2000

3000

4000

5000

6000

Cycles


Figure 12. Rutting resistance (HWTD) of mixes made from Venezuelan bitumenand limestone aggregate

With limestone aggregate, the 12 mm rut depth (permanent deformation) isobtained after only 2,000 cycles with neat bitumen (PG67-22): failure of specimen.This is considerably lower than with granite aggregate. The SBS polymer modifiedbitumen (PG76-22) presents similar permanent deformation (11 mm), but for alarger number of cycles (>5,000). This effect is due to the PG improvement with theSBS polymer modification.

The SBS/PPA and SBS modified bitumen have both better resistance than theneat bitumen when compared with the Hamburg Wheel Tracking Test; they bothdoubled the cycles to failure. By substitution of a part of SBS polymer bypolyphosphoric acid – at same PG (PG76-22), we observe a slight decrease of theasphalt mixture resistance: at same rut depth (12 mm), the corresponding number ofcycles is reduced from 5,250 to 4,000. These results are consistent with the TSRexperiments (cf. Figure 8). The adhesion with limestone aggregate is not improvedwith polyphosphoric acid.

While the SBS/PPA modified bitumen “doubled” the cycles to failure, the SBSmodified bitumen actually performed the best, adding another 1,000 cycles tofailure. All samples failed this test and the SBS did show a stripping inflection point,the other samples actually rutted too quickly to determine this inflection point.

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5.3.3. Effect of antistrip additives (Granite aggregate)

In case of granite aggregates, some problems have been observed concerning thebinder/aggregate interface: stripping rate, and low TSR values. A beneficial effect ofPPA, compared to polymer, is to both improve the binder grade and act as anantristrip agent. Antistrips (polyamine additives, or/and lime filler) have been usedin some mixe compositions.

The mixes composition with 1.0% lime in aggregate 17.5% in the binder and1.0% lime in the aggregate 17.5% in the binder + 0.5% E-6 were tested on theHamburg Wheel Tracking Test. The PPA/hydrated lime and E-6 combinationsactually passed this test. The PPA showed no stripping inflection point, while theothers did and the PPA had three times the creep slope of the other bitumen.

From these results, the use of hydrated lime with SBS/PPA modification increasethe rut depth (at 20,000 cycles) to 8 mm, but to a lesser extent than for the SBSpolymer alone (11.5 mm). By adding polyamine E-6 (SBS/PPA + lime), the rutdepth is slightly reduced to 6mm (at 20,000 cycles).

The relative negative effect observed with hydrated lime in association with SBSand PPA (Figure 13) could be linked with the natural reactivity of lime versus PPAwhich will probably reduce part of the large positive contribution of polyphosphoricacid to the adhesion phenomena previously observed (cf. Figures 5 and 6). Theassociation of a polyamine antistrip then brought some improvement to aggregateadhesion, but to a lesser extent than polyphosphoric acid.

02468

101214

Neat

67-

22

SBS

76-2

2

SBS/

PPA

76-

22

SBS/

PPA+

lime

SBS/

PPA+

lime+

E-6

Asphalt

Rut

dep

th (m

m)

0

5000

10000

15000

20000

25000

Cycles


Figure 13. Rutting resistance (HWTD) of mixes (Venezuelan bitumen/graniteaggregate) with antistrip additves

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HWTD deformation curves (Figure 14) clearly show the effect of lime inpresence of SBS+PPA on a shift of the Stripping Inflection Point. In combinationwith polyamine E6, so the stripping inflection point can be detected even after20,000 cycles, but the rut depth is higher than SBS+PPA.

Hamburg Wheel Tracking Test

0

1

2

3

4

5

6

7

8

9

0 5000 10000 15000 20000

No. of Passes

Rut

Dep

th, m

m

Set 14 Set 13

Set 6

Set 6 : PG76-22 (PG67-22+2,6%SBS+0,6%PPA) Set 13 : Set 6 + 17%wt (in binder) hydrated limeSet 14 : Set 13 + 0,5%wt (in binder) polyamine E6

Figure 14. Set 6: 76-22 ; 13 and 14 Typical Hamburg Wheel tracking Test curve(Venezuelan bitumen, with granite aggregates). SIP: Stripping Inflection Point

5.4. Discussion

The effect of the polyphosphoric acid (PPA) as well as the two antistrip additives(polyamine, lime) on the Tensile Strength Ratio (TSR) and the Hamburg WheelTracking data has been observed as a function of bitumen – aggregate – additivecombinations. In mixes PPA was used at 0.6%, by weight of the bitumen in all casesfor this testing, and in all cases the PPA was added to the neat or polymer modifiedbitumen prior to mixing the asphalt with the aggregate. Results indicated thatalthough same PG binder are achieved, the asphalt mix TSR and HWTD resultsindicated different behaviour of mixes from SBS and SBS/PPA modified bitumen.

Bitumen is generally described as a colloidal substance in which the dispersedphase, consisting of asphaltenes, is covered by a protective layer of polar resins;these complexes (micelles) are dispersed in a continuous maltenes phase whichconsists of a mixture of aromatic and saturate oils. The presence of resins andaromatics of adequate solvating power controls the peptisation of the micelles, and

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therefore has a strong influence on the bitumen rheology. If the aromatic resinfraction is not present in sufficient quantities, or has insufficient solvating power, anirregular open packed structure of linked micelles is obtained. The polarity of theasphaltene is quite important in reactions such as hydrogen-bonding of the acid-baseor the donor-acceptor nature of a given type of asphaltene: these hydrogen bondingcontribute to the viscosity behaviour. Association through polar groups may formthe basis for the lamellar structure, so that the order of a large micelle (asphaltenesagglomerated) may be established.

One of the effects of polyphosphoric acid is to modify the asphaltene + resinscontent which is increased by 5 to10% by addition of polyphosphoric acid accordingto the nature of the bitumen. This is coherent with a de-agglomerating effect of thePPA on the stacked asphaltenes molecules. As a consequence, stabilised, de-agglomerated asphaltenes are distributed over a larger fraction of resin. The originof this de-agglomeration comes in part from the neutralisation of polar interactionsbetween the stacked asphaltene molecules, either by protonation of basic sites(destruction of pre-existing hydrogen bonding networks) or by esterification. Theorgano-mineral system modifies the structuring of the bitumen. The main visibleconsequence is an increased dispersion and stabilisation of the asphaltenic micelles.A possible mechanism has been proposed (Orange et al., 2004).

TSR value is a good indicator of the asphalt mix moisture resistance, at roomtemperature. The moisture resistance can be correlated to the cohesion of bitumen(at room temp.) and to the bitumen-aggregate interface characteristics. The moistureresistance of mixes is better in case of limestone aggregate than granite aggregate.The difference could be explained by a more hydrophobicity of limestone surfacethan siliceous one (Domka, 1981). Bitumen acidity is favourable to some reactivitywith the basicity of limestone which modifies the binder-aggregate interface.

At same PG bitumen obtained either by polymer modification or by acombination of polymer and polyphosphoric acid, the moisture resistance isdifferent and mainly with granite aggregates. In case of polymer these results areconsistent with the work of Wegan et al. (1999) who have shown that SBS has noeffect on binder-aggregate interface, the effect of polymer is mainly due to the PGgrade improvement. Chemical modification of bitumen through polyphosphoric acidleads to not only an improvement of the PG grade but also contributes to developnew bitumen-aggregate interface interactions. Asphalt mixture moisture resistancemeasured values are consistent with decoating experiment (BRRC test) on neat andpolyphosphoric acid modified bitumen, in case of limestone and granite aggregates(Figure 5).

The adhesion of bitumen to aggregate is probably due to the interaction ofasphaltene functionalities. As Plancher et al. has demonstrated, these are at theorigin of the bitumen adhesion on aggregate (carboxylic acids, dicarbocylicanhydrides, 2-quinolone types, sulfoxides, nitrogen and ketones) (Plancher et al.,1977).

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The contribution of polyphosphoric acid to adhesion is probably due to twodistinct origin:

– asphaltene modification due to polyphosphoric acid as described by Orange etal. (2004);

– direct reactivity between the aggregate surface and a part of polyphosphoricacid added to the bitumen.

In case of antistrip addition (polyamine, lime) in polyphosphoric acid modifiedbitumen the same TSR value obtained indicates that the reaction proposed byBishara et al. (2001) has no consequence on the adhesion.

G. King has obtained different TSR results on mix with acid modification (Kinget al., 2002), but it was done with orthophosphoric acid and with atypical aggregate(sand containing clay) very sensitive to moisture damage. G. King observed thatmoisture damage may occur if acid is used at high concentration: this is differentfrom our results which show that, with polyphosphoric acid and granite aggregate,the antisitrip effect of polyphosphoric acid is higher as the acid content is increased(Figure 6).

The HWTD (Hamburg) test conditions are different from TSR conditions: theasphalt mixture behaviour is controlled by both the moisture resistance (at hightemperature) and binder permanent deformation. The PG improvement with polymermodification leads a slightly improved rutting resistance and the stripping point isshifted to a higher cycle number. With polymer and polyphosphoric acidcombination, at same PG than with polymer alone, the stripping inflection point isshifted to extremely high number of passes and so doesn’t occur under the testconditions. This is clearly shown on HWTD curves (Figure 10): polyphosphoric acidmodification has a positive effect on both the stripping point and the creep slope atsame binder PG.

The rutting resistance of mixes is better in case of granite aggregate thanlimestones aggregate. This could be explained by the difference of structure andmechanical characteristics between granite and limestone aggregates.

Bishara et al. have shown that combination of orthophosphoric acid andpolyamine antistrip additives affected the PG grade of acid modified bitumen(Bishara et al., 2001). This effect may decrease the rutting resistance of the mix. Tocheck this point, some complementary tests have been done on binder (Saudibitumen): in the case of polyphosphoric acid modified bitumen the PG improvementis slightly reduce with polyamine addition (cf. Figure 15).

Moreover high content with polyphosphoric acid in presence of polyamineadditive (0.5%) doesn’t affect the antistrip value (cf. Figure 6). With 1.2%polyphosphoric acid, the high temperature (G*/sinδ) is increased by +8°C. This PGgrade improvement is reduced with polyamine addition (0.5%); but this can becounterbalanced by the use of a higher content of polyphosphoric acid (i.e. 2%).

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54

58

62

66

70

74

78

Neat

(64-

22)

Neat

+ 1

.2%

PPA

Neat

+1.

2%PP

A +

0.5%

200P

Neat

+ 2

% P

PA +

0.5

%20

0P

Crit

ical

Tem

pera

ture

Tc

(°C

)

Figure 15. PG grade variation with PPA modification and Polyamine 200Pantistrip additive, from 64-22 to 72-22 (Saudi bitumen)

The effect of polyphosphoric acid and polyamine combination can becounterbalanced by formulation:

– using polyphosphoric acid, instead of orthophosphoric acid;– increase the polyphosphoric acid content to balance the polyamine effect.

Ho et al. (2002) have shown that the combination of polyphosphoric acid inbitumen with few percent lime reduce also the PG grade. In our case, we have useda larger amount of lime (1.0% in the aggregate, 17%wt in binder). This large amountof hydrated lime with respect to bitumen can affect the binder stiffness which couldpartially balance the loss of PG grade due to polyphosphoric acid contribution.Nevertheless, this improved stiffness is not enough to have a similar stripping binderresistance than with polyphosphoric acid.

6. Conclusion

Different asphalt mixtures were prepared from polymer andpolymer/polyphosphoric acid modified bitumen, with limestone or graniteaggregates. Moisture and rutting resistance have been measured on asphalt mixsamples by laboratory tests.

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The partial substitution of polymer (SBS, or EVA) by polyphosphoric acid(PPA) leads to equivalent PG grade modified bitumen, with a lower polymercontent, and by the way an improvement of properties as the viscosity and storagestability.

The bitumen-aggregate adhesion, measured by the boiling water test (BRRC),show that polyphosphoric acid has an antistrip effect with porphyry and graniteaggregate. No or limited effect is measured with limestone aggregate.

The use of polyphosphoric acid in association with polymer in order to modifythe bitumen leads to asphalt pavement with improved performances compared topolymer alone, at the same PG grade. Specifically, the moisture resistance (TSR)and the rutting resistance (HWTD) are considerably enhanced. The reactivity ofpolyphosphoric acid regarding basic additives as polyamine or lime is not an issue inrespect to formulation adjustment.

In case of limestone, the adhesion of neat bitumen is strong enough to avoid theuse of any antistrip additives: polymer or PPA/polymer are used to improve the PGgrade. With siliceous aggregates the interactions are weaker and so the use ofantistrip additives is necessary. Polyphosphoric acid provides this functionality,therefore, addition of antistrip polyamine is useless. PPA/polymer modificationleads to better properties than polymer alone, and high performance asphalt mixescan be easily developed.

7. Bibliography

AASHTO T-283, “American Association of State Highway and Transportation Officials”,June 1998.

Aschenbrener T., “Evaluation of Hamburg Wheel-Tracking Devices”, TransportationResearch Board, Transportation Research Record 1492, 1995.

Asphalt Institute, “SuperPave Level 1, Mix Design”, Superpave series, Maryland, No. 2(SP-2), 1998.

Bahia H.U., Anderson D.A., “The New Proposed Rheological Properties of Asphalt Binders”,ASTM Spec. Techn. Publ., Vol. 1241, 1994, p. 1-27.

Bishara S.W., King G.N., Mahoney D., McReynolds R.L., “Modifcation of binder with acid.Advantages and Disadvantages”, Transportation Research Board, TRB 2001,Washington (USA), 2001.

BRR 92, “Test de Désenrobage à l’Eau Bouillante de Pierres Enrobées par un LiantHydrocarboné”, BRRC Experimental procedure, MF 65/91, Bruxelles, 1991.

Brule B., Largeaud S., Maze M., Revue Générale des Routes et Aérodromes, Vol. 761, 1998,p. 36-50.

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Domka L., “Evaluation of the degree of Hydrophobicity of Precipitated Calcium Carbonatebased on the Measurement of the Heat of Wetting”, Przemysl Chemiczny, Vol. 60, No. 1,1981, p. 22-24.

Eckmann B., Maze M., Le Hir Y., Harders O., Gauthier G., “Checking Low TemperatureProperties of Polymer modified Bitumen”, 3rd Eurasphalt Eurobitume Congress, Vienna,Book II, May 2004, p 1195-1211.

Ho S.M.S., Zanzotto L., Macleod D., “Impact of Different Types of Modification on Low-Temperature Tensile Strength and Tcritical of Asphalt Binders”, Transportation ResearchRecord, No. 1810, 2002.

Jain P.K., Saxena A.K., Singh H., Studies in Surface Science and Catalysis, 113, 1998,p. 547-556.

King G., Bishara S.W., Fager G., “Acid/Base Chemistry for Asphalt Modification”, AAPT2002, Colorado Springs, USA, 2002.

Lee D.Y., “Modification of Asphalt and Asphalt Paving Mixtures by Sulphur Additives”, Ind.Eng. Chem. Proc. Res. Develop., Vol. 14, 1975, p. 171-177.

Le Hir Y., Anderson D.A., Planche J.P., Martin D., “Rheological Characterization ofBituminous Binder to Predict Pavement Rutting”, 6th RILEM Symposium PTEBM’03,Zurich 2003, p. 117-123.

Lewandowski L.H., “Polymer Modification of Paving Asphalt Binders”, Rubber Chemistryand Technology, Vol. 67, No. 3, 1994, p. 447-480.

Orange G., Dupuis D., Martin J.V., Farcas F., Such C., Marcant B., “Chemical Modificationof Bitumen through Polyphosphoric Acid”, 3rd Eurasphalt Eurobitume Congress, Vienna,May 2004, Book I, 2004, p. 733-745.

Orange G., Goubard M., Verhasselt A., Martin J.V., “Ageing Behaviour of Chemicalmodified Bitumen with Polyphosphoric Acid”, to be published 2005.

PATENT US 375278 (Tosco Lion), August 7, 1973.

PATENT WO 98/44047 (Ergon Inc.), May 31, 1997.

Plancher H., Dorrence S.M., Petersen J.C., “Identification of Chemical Types in AsphaltStrongly Adsorbed at the Asphalt-Aggregate Interfaces and their relative Displacement byWater”, Proceedings Assoc. of Asphalt Paving Technologists, Techn. Session 46, 1997,p. 151-175.

Roberts F.L., Mohammad L.N., WANG L.B., “History of Hot Asphalt Mixture Design in theUSA”, J. of Mater. Civil Eng., No. 7-8, 2002, p. 279-293.

Wegan V., Brule B., “Comparaison entre la Microstructure des Bitumes-Polymère tel quel etdans les Enrobés spéciaux”, Bulletin des Laboratoires des Ponts et Chaussée, 219,janvier-fevrier 1999, p. 3-16.

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8. Appendix

8.1. Origin of used additives

Bitumen sources were Saudi from Saudi light crude, Venezuelan fromBachaquero crude and California Valley from a blend of California Valley crudesources.

Styrene-Butadiene-Styrene (SBS) block copolymers: Dexco 2411 radial SBSfrom a Dow/ExxonMobil venture

Ethylene Vinyl Acetate (EVA): a 50/50 blend of Polybilt 103C/ Polybilt 502EVA from Exxon/Mobil.

Polyphosphoric acid was supplied by Rhodia.

Anti-strip additives used are: Polyamine E-6 (AKZO), Polyamine Cecabase200P (CECA).

8.2. Saudi neat and polymer modified bitumen

Table 4. Performance grade properties for the SBS and SBS/PPA modified Saudibitumen - PG achieved after modification: 76-22, Concentrated bitumen 150 pen,Dilution bitumen PG64-22

Blend Number 1 2 3 4

PPA % 0 0.2 0.4 0.6

Polymer % 4.75 4.10 3.75 3.40

Brookfield Visc. @ 135° 2950 3870 3290 2230

Fresh: G*/sinδ (kPa) 1.606 1.532 1.561 1.534

Phase Angle 67.1 64.5 66.2 69.2

Wt. Loss -0.105 0.21 -0.053 -0.034

RTFOT: G*/sinδ (kPa) 2.378 2.613 2.569 3.03

PAV: G*.sinδ 1198 1126 1422 1276

BBR: S (MPa) 125 142 148 143

BBR: m 0.325 0.335 0.332 0.327

Elastic Recovery (%) 87.50 86.70 85.00 85.00

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Table 5. PG achieved after modification: 82-22, Concentrated bitumen 150 pen,Dilution bitumen PG64-22. Polymer type SBS


PPA % 0 0.2 0.4 0.6

Polymer % 6.60 6.00 5.60 4.50

Brookfield Visc. @ 135° 8900 8750 8550 6300

Fresh: G*/sinδ (kPa) 1.863 1.697 1.843 1.533

Phase Angle 50.5 52.6 54.3 58.3

Wt. Loss -0.092 -0.073 -0.113

RTFOT: G*/sinδ (kPa) 2.311 2.412 2.536 2.446

PAV: G*.sinδ 413 516 536 672

BBR: S (MPa) 100 108 111 112

BBR: m 0.349 0.345 0.336 0.353


Table 6. Performance grade properties for the EVA and EVA/PPA modified Saudibitumen - PG achieved after modification: 76-22, Concentrated bitumen 150 pen,Dilution bitumen PG64-22


PPA % 0 0.2 0.4 0.6

Polymer % 9.60 7.50 5.50 4.70

Brookfield Visc. @ 135° 2440 1950 1590 1490

Fresh: G*/sinδ (kPa) 1.243 1.289 1.137 1.182

Phase Angle 80.1 80.9 81.8 82.1

Wt. Loss -0.103 -0.084 -0.058 -0.064

RTFOT: G*/sinδ (kPa) 2.445 2.348 2.462 2.881

PAV: G*.sinδ 602 730 822 982

BBR: S (MPa) 120 152 157 165

BBR: m 0.31 0.3 0.319 0.316


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8.3. Venezuelan neat and polymer modified bitumen

Table 7. Performance grade properties for the SBS and SBS/PPA modifiedVenezuelan bitumen - PG achieved after modification: 76-22, Concentrated bitumen150 pen, Dilution bitumen PG64-22


PPA % 0 0.2 0.4 0.6

Polymer % 4.25 3.75 2.9 2.6

Brookfield Visc. @ 135° 2350 2030 1510 1360

Fresh: G*/sinδ (kPa) 1.557 1.524 1.366 1.42

Phase Angle 68.7 68.6 78.3 79.4

Wt. Loss 0.012 -0.024 0.23 0.008

RTFOT: G*/sinδ (kPa) 2.472 2.802 2.281 2.58

PAV: G*.sinδ 1424 2038 1804 1934

BBR: S (MPa) 138 150 163 172

BBR: m 0.32 0.31 0.311 0.306


Table 8. Performance grade properties for the SBS and SBS/PPA modifiedVenezuelan bitumen. PG achieved after modification: 82-22, Concentrated bitumen150 pen, Dilution bitumen PG67-22


PPA % 0 0.2 0.4 0.6

Polymer % 5.1 4.5 4 3.5

Brookfield Visc. @ 135° 5850 4350 2900 3370

Fresh: G*/sinδ (kPa) 1.498 1.607 1.332 1.428

Phase Angle 57.7 63 66.8 66.1

Wt. Loss 0.011 0.047 0.032 0.016

RTFOT: G*/sinδ (kPa) 1.839* 2.362 2.765 3.359

PAV: G*.sinδ 854 962 1012 926

BBR: S (MPa) 105 127 146 127

BBR: m 0.342 0.336 0.318 0.334


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Table 9. Performance grade properties for the EVA and EVA/PPA modifiedVenezuelan bitumen. PG achieved after modification: 76-22, Concentrated bitumen150 pen, Dilution bitumen PG67-22


PPA % 0 0.2 0.4 0.6

Polymer % 6 5 4.4 3.8

Brookfield Visc. @ 135° 1670 1480 1550 1450

Fresh : G*/sinδ (kPa) 1.063 1.042 1.167 1.046

Phase Angle 82.6 82 81 81.5

Wt. Loss -0.073 0.017 -0.078 0.03

RTFOT: G*/sinδ (kPa) 2.431 2.288 3.731 3.542

PAV: G*.sinδ 1012 1320 783 2338

BBR: S (MPa) 138 164 168 174

BBR: m 0.327 0.313 0.301 0.31


8.4. California Valley neat and polymer modified bitumen

Table 10. Performance grade properties for the SBS and SBS/PPA modifiedCalifornia Valley bitumen - Concentrated bitumen AR2000, Dilution bitumenAR4000


PG Grade Achieve 76-16 76-16 76-16 76-10

PPA % 0 0.2 0.4 0.6

Polymer % 5.5 4.4 3.8 3.25

Brookfield Visc.@135° 2060 1450 1310 1140

Fresh: G*/sinδ (kPa) 2.092 1.595 1.414 1.253

Phase Angle 55.8 61.5 67.3 72.2

Wt. Loss 0.11 0.24 0.127 0.049

RTFOT: G*/sinδ (kPa) 2.327 2.521 2.335 2.296

PAV: G*.sinδ 1959 2203 2782 1719

BBR: S (MPa) 211 286 291 115

BBR: m 0.337 0.317 0.312 0.425


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Table 11. Performance grade properties for the SBS and SBS/PPA modifiedCalifornia Valley bitumen - PG achieved 82-16. Concentrated bitumen AR2000,Dilution bitumen AR4000


PPA % 0 0.2 0.4 0.6

Polymer % 7 5.9 5 4.65

Brookfield Visc. @ 135° 3320 2690 1970 2200

Fresh : G*/sinδ (kPa) 3.621 2.271 1.667 1.542

Phase Angle 31.4 43.2 52.8 58.7

Wt. Loss 0.133 0.136 0.156 0.078

RTFOT: G*/sinδ (kPa) 1.982 * 2.26 2.25 2.333

PAV: G*.sinδ 971 836 1376 1809

BBR: S (MPa) 248 258 255 290

BBR: m 0.317 0.311 0.325 0.31


Table 12. Performance grade properties for the EVA and EVA/PPA modifiedVenezuelan bitumen - Concentrated bitumen AR2000, Dilution bitumen AR4000


PG Grade Achieved 76-16 76-22 76-22 76-22

Concentrate Bitumen AR 4000 AR 2000 AR 2000 AR 2000

PPA % 0 0.2 0.4 0.6

Dilution Bitumen AR 4000 AR 4000 AR 4000 AR 4000

Polymer % 15.5 15 14 12.5

Polymer Type EVA EVA EVA EVA

Brookfield Visc. @ 135° 4590 5100 5100 4690

Fresh : G*/sinδ (kPa) 1.834 1.725 1.798 1.781

Phase Angle 73.2 74.9 75.1 76.1

Wt. Loss 0.145 0.2 0.216 0.19

RTFOT: G*/sinδ (kPa) 2.492 2.455 2.468 2.244

PAV: G*.sinδ 816 603 555 619

BBR: S (MPa) 151 252 264 285

BBR: m 0.313 0.357 0.369 0.355


Received: 1 December 2003Accepted: 18 June 2004

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Documents

Rutting and Moisture Resistance of Asphalt Mixtures Containing Polymer and Polyphosphoric Acid Modified Bitumen