effectivity and performance of rejuvenators

Effectivity and Performance of Rejuvenators

Author: Dr.-Ing. Daniel Gogolin

Laboratory studies

Recycling of reclaimed asphalt is one of the majorstrengths of asphalt as a construction material and eventoday is a decisive factor in asphalt road construction.Within the sense of the Statute for Promoting Recyclingand Ensuring Environmentally Compatible WasteManagement [1] (abbreviated to: "Recycling Mana-gement Legislation") and based on economic feasibilitystudies, large to very large quantities of reclaimedasphalt are frequently already being added to all asphaltlayers today.

The trend to increasing percentages of asphaltreclaimedbeing added to all asphalt courses and layers today hasalso increased the significance of the subject of aging(bitumen and asphalt mixtures). In this case, agingprocesses lead to a loss of the decisive properties inbitumen. For example: Loss of viscous characteristics(embrittlement) or loss of adhesive force.

In future, progressive aging of asphalt pavementsresulting from repeated recycling of asphaltreclaimed(second/third generation of asphalt) couldreclaimedlead to long term problems. The solution to these prob-lems could include rejuvenation of the old bitumen, i.e.far-reaching restoration of the original properties of thebitumen by adding so-called rejuvenators.

This three-part article describes possibilities such as• How the effectivity of using a rejuvenator can be

verified in the laboratory (Part 1),

• How verifications provided in the laboratory can bevalidated within the scope of a test trial (Part 2) and

• How various rejuvenators compare in a laboratorycomparison test (Part 3).

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rape seed oil, soften bitumen according to this definitionas a matter of principle. , these substancesHowevercannot be called rejuvenators - particularly with regard tothe modification to the rheological properties of thebitumen. In this context it is necessary to differentiatebetween so-called softeners and rejuvenators:

Rejuvenators reduce the viscosity while simultaneouslyrestoring the visco-elastic (rheological) properties of theaged bitumen. The aging process of the rejuvenatedbitumen is not negatively affected and correspondsessentially to the aging process of a fresh bitumen.

Softeners which reduce the viscosity, cannot, however,restore the visco-elastic (rheological) properties of abitumen. Softeners only soften or plasticize the bitumen.Under certain circumstances adding a softener to abitumen can result in accelerated aging due to the highlyvolatile constituents.

The position paper "Rejuvenators" published by theEuropean Asphalt Pavement Association [6] alsorecommended that, as a matter of principle, reju-venators should be used only when

• Environmental impacts and health and safetyhazards cannot occur during storage, processing,production or use.

• Future reuse and recyclability of the asphaltareconstituents not jeopardized.

• There won‘t be any negative technical to theeffectsfinal quality of the asphalt mixture.

Limitations for using asphaltreclaimed

The technical guidelines for use of asphalt (TLreclaimedAG-StB 09 [2] and M WA [3]) specify the limits for thesoftening point ring and ball (SP R&B) of recycledbitumen recovered from asphalt using the SPreclaimedR&B method as follows: individual value: 70 °C andmean value: 77 °C. Bitumen which exceed these SPsR&B should, as a rule, be considered to be critical and - ifthey are to be used - their suitability must be verifiedthenin a separate analysis within the scope of initial testing.According to present knowledge, nearly 30 % of thereclaimed asphalt occurring, is within a range, alreadycritical for recycling and, in some cases, can no longer berecycled at all.

At this point it is necessary to note that due to in-thecreased use of additives in asphalt mixtures, for exam-(ple use of viscosity-modifying additives, rubberizedasphalt or bitumen highly modified withmixturespolymers , purely physical tests, such as SP R&B or)needle penetration (NP) tests, do not always allowconclusions regarding the actual quality of the bitumen.One possibility for classifying such types of bitumen is todetermine the rheological values - for example by using adynamic shear rheometer (DSR). etailed informationDabout the components inside the reclaimed asphalt to beused provided by the principal in a construction project,can significantly facilitate evaluation/assessment of thespecific values for the bitumen.

Possibilities for rejuvenation

Rejuvenation mean : to restore to a former state; makesfresh or new again. According to the definition offered byS [4] additives are called rejuvenators when they arehenintended to restore the characteristics of aged andhardened reclaimedbitumen contained in the asphalt toits original state.

In Germany rejuvenators have played a role in asphaltroad construction for only a few years. In the meantime,numerous products as rejuvenators exist onreferred tothe and international market .German s

Physically a rejuvenator is usually understood to be asubstance which reduces the viscosity of hardenedbitumen by decreasing the SP R&B [5] or increasing theNP. that flux oils or natural oils such asIt should be noted

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• DSR(-10 bis +150 °C)

• BBR(-10 °C, 16 °C,-25 °C)

Rolling-Bottle-Test(6h, 24h)

Diabase filler

Limestone filler • SP ring and ball

Step 4

Step 1 Step 2 Step 3

Figure 1: Flowchart of Investigative Programm

• DSR(-10 bis +150 °C)

• BBR(-10 °C, 16 °C,-25 °C)

• DSR(-10 bis +150 °C)

• BBR(-10 °C, 16 °C,-25 °C)

• DSR(-10 bis +150 °C)

• BBR(-10 °C, 16 °C,-25 °C)

• DSR(-10 bis +150 °C)

• BBR(-10 °C, 16 °C,-25 °C)

• DSR(-10 bis +150 °C)

• BBR(-10 °C, 16 °C,-25 °C)




Diabase filler

Limestone filler

• SP ring and ball



50/70Basic bitumen

RTFOT+

PAV

RTFOT

RTFOT+

PAV

RTFOT

RTFOT+

PAV

Aged basic bitumen50/70 (RTFOT + PAV)

+Additive 2.0

• Needle penetration

• Softening point

ring and ball

Add

ition

of .

..


• Softening point

ring and ball


• Softening point

ring and ball


• Softening point

ring and ball


• Softening point

ring and ball


• Softening point

ring and ball


+Additive 2.0


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The additive should not have any negative effect on theadhesion between the aggregates and bitumen. In thethird step the adhesion was tested on the basic bitumenusing the rolling bottle test as described in the GermanAsphalt-StB, Part 11, and in direct comparison afteradding the two additives following long term aging for 6,24 and 72 hours in each case.

The last step in the process examined the influence ofvarious fillers (limestone filler and diabase filler) on theeffect of the additives. At this point the delta ring and ballprocedure as specified in DIN EN 13179-1 was used asan indicator for any possible limitation to the effect of arejuvenator resulting from interactions between thebitumen and, among others, highly reactive fillers.

Results of Studies

Both of the additives tested within the scope of theproject provided compatible results in terms of theirphysical and rheological effectivity. However, the studiesin Step 4 showed that addition of limestone fillerthe avirtually negated the effect of Additive 1.0. Since it is notpossible in practical situations - particularly when addingreclaimed aasphalt - that limestone filler or other highlyreactive mineral components are not contained in theasphalt mixture use of Additive 1.0 was not pursued. Thefor this application at this point.

Laboratory Research Program

The research program used is shown in Figure 1 in theform of a flow chart is subdivided into a total of fourandresearch steps.

Road construction bitumen pen 50/70 acc. to theGerman TL Bitumen 07/13 was chosen as the basicbitumen for all studies.

Two different products were used as rejuvenators (here:Additive 1.0 and Additive 2.0) which were not yetavailable on the market at the time of the study.

In the first step the basic bitumen used wascharacterized physically by the NP and the SP R&B tests.A sufficient quantity of the basic bitumen for allsubsequent tests was then subjected to short term andlong term aging (RTFOT acc. to DIN EN 12607-1 and PAVacc. to DIN EN 14769). The effectivity of the two additiveson the aged basic bitumenboth (RTFOT and PAV) andafter the addition of each additive at a rate of 3 % byweight .was then studied using the NP and SP R&B testsThe rejuvenated bitumen was then subjected to shortand long term aging again before analyzing.

In the second step, the rheological effectivity of therejuvenators was examined using a dynamic shearrheometer (DSR) based on DIN EN 14770 (cf. testparameters in Table 1) and bending beam rheometer(BBR) acc. to DIN EN 14771 analog to the aging stage inStep 1.

Figure 2: Needle penetration investigation results

50

40

30

20

10

0Nee

dle

pene

trat

ion

[1/1

0 m

m]

„original“ afterRTFOT

afterRTFOT + PAV


afterRTFOT + PAV

Basic bitumen 50/70 Aged basic bitumen 50/70 + 3% Additive 2.0

2227

41

50

32

19

Δ = 18

Δ = 31 Δ = 14Δ = 19

Δ = 22

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Based on the studies performed, it was possible to clearlyelaborate the effect of Additive 2.0 at the physical asonwell as rheological level. Figures 2 and 3 show thetheeffect of the additive on the aged basic bitumen with regardto NP and the SP R&B in the states before and afterrejuvenation andaftereach of thevariousaging stages.

In conclusion, the results of the NP as well as the SP R&Btests demonstrated that the long term aging effect (PAV)was completely negated by addition of 3 % ofalmostAdditive 2.0. Adding 3 % of Additive 2.0 reduced the SPR&B 11.6 °C (≈ 3.8 °C per 1 %) and increased the NPbyby 22 mm (≈ 7.3 mm per 1 %).1/10 /1

10

When using rejuvenators, immediate observation of theaging process after rejuvenation is of particularsignificance. In this process, repeated aging of therejuvenated bitumen should not result in any significantdeviation in the aging properties of the basic bitumenused. However previous experience shows that mercurialand significant increases in aging can occur, particularlywith products containing highly volatile constituents.

Based on the experience gained from laboratory testing, itis possible to confirm a comparable aging process to thebasic bitumen for Additive 2.0 following the two additionalaging stages.

Figure shows the test results from DSR analysis as a4phase angle in relation to the equivalent temperature T .eq

This form of representation makes it possible tographically demonstrate the effectivity of the rejuvenatoron a rheological basis.

The results of the physical studies were also confirmed bythis rheological approach. After rejuvenation withAdditive 2.0, the phase angle was increased by 2.8 ° andthe equivalent temperature reduced by -9.0 °C.Considered in rheological terms, the rejuvenatedbitumen is at virtually the same level as the original basicbitumen after short term aging (RTFOT). Therefore, longterm aging was approximately negated in terms of therheological values determined. Repeated aging of therejuvenated bitumen also leads to an aging processcomparable to the initial base bitumen.

Other possibilities for representation and evaluation ofthe rheological effectivity of a rejuvenator anddifferentiation between rejuvenators and softeners isfacilitated by the BLACK diagram. According to thepresent state of knowledge, it is possible to visualize thefollowing conclusions with the aid of this type of diagram(cf. Fig. 5):

Figure3: Investigation results for softening point ring and ball

70

60

50

40

30

20

10

0

Sof

teni

ng p

oint

rin

g an

d ba

ll [°

C]


afterRTFOT + PAV


afterRTFOT + PAV

Basic bitumen 50/70 Aged basic bitumen 50/70 + 3 % Additive 2.0

52.0

57.4

68.8

57.2

63.8

70.8

Δ = 5.4

Δ = 16.8 Δ = 6.6

Δ = 13.6Δ = 11.6

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• stiffnessAging of bitumen leads to an increase in theor viscosity (increase of complex shear modulus) andto a decrease in the viscosity or increase in theelastic constituents in bitumen (reduction of phaseangle)

• Addition of a softener (flux effect) leads to reductionastiffnessof the /viscosity, whereby the visco-elastic

constituents in the bitumen are affected onlymarginally, if at all.

• Addition of a rejuvenator (rejuvenation effect) leadssti f fnessto reduction of the /viscosity with

esimultaneous increase in the viscosity of thconstituents

Therefore, upon addition of a rheologically effectiverejuvenator, the BLACK diagram indicates a shift in thecurve back in the direction of the original curve for thebase bitumen before aging. By contrast, addition of asoftener does not result in shifting the curve in thedirection of the original position.

Fig. 6 shows the test results from DSR analysis in a BL ACKdiagram.

The diagram allows clear recognition of the shift in thecurve for road construction bitumen pen 50/70 in thedirection of the original curve for the fresh basic bitumenafter aging according to RTFOT and PAV and addition ofAdditive 2.0.

From a rheological point of view, the rejuvenated bitumenis at a level comparable to that of road constructionbitumen pen 50/70 after short term aging (acc. toRTFOT).

Measuring system Plate/Plate

Test type path-controlled/oscillating

Specified deformation 0.5 to 1.0 %

Test temperature range -10 to 60 °C / 60 to 150 °C

Test intervals 10 °C

Test frequencies 1.59 Hz

Tempering time betweentest intervals 15 min

Specimen diameter 8 mm / 25 mm

Gap width 1 mmTable 1: Test parameters for determination of the rheological binder

characteristics with DSR

Figure 4: Phase angle as dependent on equivalent temperature (Teq)

90.0

85.0

80.0

75.0

70.0

65.0

60.0

Pha

se a

ngle

[°]

T [°C]eq

30.0 40.035.0 45.0 50.0 55.0 60.0 65.0 70.0 75.0

-9.0 °C

+2.8 °

30/4550/70

70/100160/220

Basic bitumen 50/70after RTFOTBasic bitumen 50/70

Basic bitumen 50/70 after RTFOT and PAVAged basic bitumen 50/70 + 3 % Additive 2.0

+ 3 % Additive 2.0 after RTFOTAged basic bitumen 50/70Aged basic bitumen 50/70 + 3 % Additive 2.0 after RTFOT and PAV

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Figure 5: Exemplary presentation of bitumen aging and rejuvenation in a Black diagram

1.0E +08

1.0E +07

1.0E +06

1.0E +05

1.0E +04

1.0E +03

1.0E +02

1.0E +01

1.0E +00

Com

plex

she

ar m

odul

us[P

a]

Phase angle [°]

0 30 40 5020 60 7010 80 90 100

Basic bitumen

Rejuvenated bitumen

Aged basic bitumen

Rejuvenating effect

Ageing effect

Fluxing effect

Figure 6: Black diagram as proof of rheologically effective rejuvenation

1.0E +09

1.0E +08

1.0E +07

1.0E +06

1.0E +05

1.0E +04

1.0E +03

1.0E +02

1.0E +01

1.0E +00

Com

plex

she

ar m

odul

us[P

a]

Phase angle [°]

0 30 40 5020 60 7010 80 90 100

Basic bitumen 50/70

Basic bitumen 50/70 after RTFOT

Basic bitumen 50/70 after RTFOT and PAV

Aged basic bitumen 50/70 + 3 % Additive 2.0

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The behavior of bitumen at low temperature is of decisiveimportance, particularly when dealing with aged bitu-men. Studies using a BBR indicated that, at a limit of 300MPa for the flexural and 0.3 for the m-value,stiffnessrejuvenation of the aged bitumen led to a significantimprovement in the properties at low temperature.

Excerpts of the results of the low temperature tests areshown in Fig. 7 (flexural ). This clearly shows thatstiffnessafter rejuvenation the flexural is even better forstiffnessthe temperature characteristics than that of fresh basicbitumen. The increases to the level of freshstiffnessbitumen only after short and long term aging. In terms ofthe relaxation capability of the bitumen (m-value) theeffect is not quite as high in comparison to the flexural

stiffness - however, after rejuvenation, it was possible toachieve the level of bitumen aged according to RTFOT.

In addition to the actual bitumen studies, the interactionwith various mineral substances is also of particularsignificance for evaluation of a rejuvenator.the

The rolling bottle tests indicated that the affinity of thebinding agent to the after addition of theaggregatesadditive and further aging acc. to RTFOT and PAVincreased to a common level in each case after 6 h, 24 hand 72 h. Any negative influence on the adhesionproperties was excluded at this point.

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800

700

600

500

400

300

200

100

0

Ben

ding

stif

fnes

s [M

Pa]

Test temperature [°C]

-30 -25 -20 -15 -10 -5

Bending stiffness = 300 MPa:Basic bitumen 50/70= -17.9 °C

Basic bitumen 50/70 after RTFOT= -17.1 °CBasic bitumen 50/70 after RTFOT and PVA= -16.0 °C

Aged basic bitumen 50/70 + 3 % Additive 2.0 = -18.6 °CAged basic bitumen 50/70 + 3 % Additive 2.0 after RTFOT= -18.1 °C

Aged basic bitumen 50/70 + 3 % Additive 2.0 after RTFOT and PAV= -17.9 °C

Basic bitumen 50/7050/70 + 3 % Additive 2.0Aged basic bitumen

Basic bitumen 50/70 after RTFOT50/70 + 3 % Additive 2.0 after RTFOTAged basic bitumen

Basic bitumen 50/70 after RTFOT and PAV50/70 + 3 % Additive 2.0 after RTFOT and PAVAged basic bitumen

Limit value = 300 MPa

Figure 7: Results for bending stiffness in BBR

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Figure 8 clearly shows the results of the delta ring andball test performed. Within the scope of the studies theaged road construction bitumen pen 50/70 (acc. toRTFOT+PAV) and the rejuvenated bitumen were mixedand tested with limestone filler as well as with diabasefiller.

The increase in the SP R&B in direct comparison betweeneach of the variants "aged bitumen and aged bitumen +filler" and "rejuvenated bitumen and rejuvenated

bitumen + filler" was used as an indicator for anyinteraction with the two fillers. If any interaction orinfluence on the effectivity were present, addition of athefiller should increase the significantly up to thestiffnesslevel of the aged bitumen.

From the results obtained (Fig. 8) it can be ed thatconcludthe rejuvenating effect is not influenced by the mineralconstituents according to the present state of knowledgewith regard to Additive 2.0.

Figure 8: Investigation results for stiffening effect of filler

100

90

80

70

60

50

40

30

20

10

0

Sof

teni

ng p

oint

rin

g an

d ba

ll [°

C]

purewithout filler

withlimestone filler

withdiabase filler

purewithout filler

withlimestone filler

withdiabase filler

Aged basic bitumen 50/70 Aged basic bitumen 50/70 + 3 % Additive 2.0

Δ = 17.4

Δ = 27.0

Δ = 15.6

Δ = 29.4

68.2

85.6

95.2

57.2

72.8

86.6

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Conclusion

The test program clearly showed that, in terms of labora-tory technology, it is possible to adequately describerejuvenators with regard to their effect. In addition to theclassic physical parameters (e.g. SP R&B, NP), which arestill important for legal contracts, corresponding rheolog-ical studies should also be performed on a priority basis.According to present knowledge, rheological testscertain(e.g. DSR) offer the possibility of classifying variousproducts according to a purely plasticizing/softeningeffect or rheologically effective rejuvenation.

Using the studies on Additive 1.0, it was, as a matter ofprinciple, possible to deduce that considerationsregarding the effect of a rejuvenator alone are insuffi-cient and that to a much greater extent it is essential toinclude any possible interactions with the mineralconstituents in the asphalt mixture.

The aging process following rejuvenation also plays adecisive role in terms of the sustainability of the rejuve-nated asphalt mixture. At this point it is necessary toexclude accelerated aging processes during the expo-sure period/life cycle.

To summarize the study it can be concluded that the testsperformed to support the results allow the followingconclusions to be drawn for the effect of fillers onrejuvenators:

• It must be possible for a rejuvenator to restore thephysical as well as the rheological properties ofbitumen.

• Repeated aging should not lead to accelerated aging.

• The use of a rejuvenator should not lead to anyaggregatesnegative interactions between the and

bitumen.

• The effect of a rejuvenator should not be negativelyinfluenced by the mineral constituents of the asphaltmixture.

Prospect

Based on the consistently positive laboratory results forthe rejuvenator tested Additive 2.0 used two test, was forsections in the City of Münster. art of this publicationP 2will deal with preliminary laboratory tests, production ofthe mixed asphalt in an asphalt mixing plant, laying of theasphalt mixtures and the control tests and extendedstudies for validation of the previous laboratory results.

AUTHORDr. Daniel Gogolin, Certified EngineerIngenieurgesellschaft PTM Dortmund mbHFrische Luft 155 44B19 Dortmund-Wickedewww.ptm.net [email protected]

Bibliography[1] Gesetz zur Förderung der Kreislaufwirtschaft und Sicherung der

umweltverträglichen Bewirtschaftung von Abfällen

(Kreislaufwirtschaftsgesetz-KrWG) dated 24 February 2012 (BGBl. IS. 212)

[2] Technische Lieferbedingungen für Asphaltgranulat, TL AG-

StB, Ausgabe 2009, Forschungsgesellschaft für Straßen-

und Verkehrswesen (FGSV), Cologne

[3] Merkblatt für die Wiederverwendung von Asphalt, M WA,

Ausgabe 2009, Forschungsgesellschaft für Straßen- und

Verkehrswesen (FGSV), Cologne

[4] SHEN,J.; AMIRKHANIAN, S.; MILLER,J.: Effects of Rejuvenating Agents on

Superpave Mixtures Containing Reclaimed Asphalt Pavement.

In: Journal of Materials in Civil Engineering (2007), S. 376-384

[5] Deutscher Asphaltverband e.V., 2014. Wiederverwenden von Asphalt,

Bonn.

[6] EAPA Position Paper Rejuvenators - August 2018

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