Resources, Conservation and Recycling 54 (2010) 337347

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Resources, Conservation and Recycling

journa l homepage: www.e lsev ier .com/ locate / resconrec

Produc erfofor roa

Clara CelDipartimento d ienze,

a r t i c l

Article history:Received 4 MaReceived in reAccepted 18 A

Keywords:Recycled asphHigh-performFlexible pavem

ratorand sine inasphtabilietter

d micled ary stual chw bit

obtain paving mixtures with high content of recycled materials that, in relation to their intended use(surface, binder or base layer), can be considered as high-performance mixtures.

2009 Elsevier B.V. All rights reserved.

1. Introdu

Every yeimply a connatural resof bituminogate. Furthethe producfrom degramental consite.

For sustsumption oreusing toinvolved inseveral recyers of road1986).

The aimsome innovmechanical

CorresponE-mail add

0921-3449/$ doi:10.1016/j.ction

ar, construction and reconstruction of road pavementssiderable consumption of valuable and non-renewableources and, in particular, the component materialsus mixtures: bitumen and, above all, mineral aggre-rmore, maintenance work on road networks involves

tion of high quantities of discarded materials comingded bituminous pavements, with severe environ-sequences related to their transport to the landll

ainable development, the objectives of reducing con-f valuable natural resources and, at the same time,the maximum those natural resources, in any case,road works have urged road technologists to considercling techniques for new surface and/or structural lay-bituminous pavement (SETRA, 1997; Huet and Poirier,

of the research was to perfect in a laboratory studyative recycled asphalt mixtures, having physical andpropertiesnot lower than those speciedby the current

ding author. Tel.: +39 091 488062; fax: +39 091 487068.ress: clara.celauro@unipa.it (C. Celauro).

Italian Specication (MIT, 2002; ANAS, 2003; Autostrade, 2004) forasphalt, characterized byhigh content of recycled asphalt (30%, 40%and 50%) and designed for all layers (surface, binder and base). Onaccount of this, knowledge and know-how on traditional asphaltmix design (Roberts et al., 1996; Cominsky et al., 1994) was usedand it was aimed at striking a balance between the propertiesneeded for laying and assuring durability of recycled mixtures andtheir functional and structural properties (Pereira et al., 2004).

2. Material studied and experimental plan

In considerationof the typeofmixture tobe tested, as detailed inthe following paragraphs, the experimental study was specicallyplanned in order to determine the effect of the bitumen content aswell as of the maximum aggregate size in the mixture, besides theeffect of the content in recycled material.

The plan was focused on the characterization of each materialused for producing themixtures, both recycled andvirgin, aswell ason experimental tests for physical andmechanical characterizationof the nal product, in order to guarantee high quality and perfor-mance even though using high percentages of RA (Widyatmoko,2008), detailed as follows:

for each mixture studied, at each selected binder content and ateach studied RA percentage:

see front matter 2009 Elsevier B.V. All rights reserved.resconrec.2009.08.009tion of innovative, recycled and high-pd pavements

auro , Celauro Bernardo, Boscaino Gabrielei Ingegneria delle Infrastrutture Viarie, Universit degli Studi di Palermo, Viale delle Sc

e i n f o

rch 2009vised form 18 August 2009ugust 2009

altance mixtureents

a b s t r a c t

The paper deals with a specic labomechanical performance, for surface

Theaimof the researchwas to combasphalt (RA), coming from degradedrecycled mixtures obtained (mainly sthat should not be lower, or possibly bvirgin binder and aggregate.

For this purpose, innovative recyclecharacterized by high content of recylayers were investigated in a laborato

The results of physical andmechanicof recycled material and by using nermance asphalt

90128 Palermo, Italy

y study aiming at perfectioning recycled asphalt with hightructural layers of exible pavements.the samematerial themaximumpossiblequantityof recycledalt layers, together with high structural performance of thety, load spreading properties, rutting and fatigue resistance)than those offered by traditional asphalt mixture, made with

xtures, close-graded and with high mechanical performance,sphalt (up to 50%) and designed for surface, binder and basedy.aracterization tests showthat, by controlling thehomogeneityumen with adequate rheological properties, it is possible to

338 C. Celauro et al. / Resources, Conservation and Recycling 54 (2010) 337347

Table 1Qualitative characteristics of the bitumen as recovered from the RA.

Characteristic Minimum value Maximum value Range Units Standard

Bitumen content b% 4.64 4.87 0.23 % ASTM D1856 (ASTM, 1979)Penetration 3 [dmm] EN 1426 (EN, 2000a,b)Ring&Ball Te 2 [C] EN 1427 (EN, 2000b)Penetration UNI 4163 (UNI, 1959)

Table 2Physical and m ction of the mixtures studied.

Characterist Filler Units Standard

Particle den 2.89 g/cm3 EN 1907-6 (EN, 2000c)Apparent pa g/cm3 EN 1907-6 (EN, 2000c)Los Angeles % EN 1097-2 (EN, 1998b)Micro-Deval % EN 1097-1 (EN, 1996)Sand equiva % EN 933-8 (EN, 1997b)Polished sto EN 1097-8 (EN, 1999b)Flakiness ind EN 933-3 (EN, 1997a,b)Percent frac 100 % EN 933-5 (EN, 1998a,b)Rigden voids 32.95 % EN 1907-4 (EN, 1999c)

compacaccordi

Marsha2004a);

indirect2003a);

indirectimmers1991);

Cantabrto Stand

for the opprevious dynami

temperter curv

dynamiappliedf=35Hz

test forStandar

2.1. Results

2.1.1. ReclyThe RA u

be classiedEN 13108-8reference toIndeed, it issurface layeknown.

The rheothe RA accoin Table 1.

The resuization of th

The grad12697-2 (Emakes it pohomogenei

2.1.2. CharaAmongs

study a spe

proes th

refortain

llowiwitrmeing vaintes).

sphaaro

clasrdan), UNhe fo

e nee sa=51.

Physil aggminsingmbinat 25 C Pen 18 21mperature R&B TR&B 64 66Index I.P. +0.1

echanical characterization of the recovered mineral aggregates, used for the produ

ic Mineral aggregate

sity (r) 2.87rticle density (a) 2.85Abrasion (L.A.) 19.78abrasion resistance in water (M.D.U.) 9.2lent (SE) 78ne value (PSV) 0.40ex (FI) 1.43

tured face 100of compacted ller

tibility test at the Shear Gyratory Compactor SGC,ng to Standard EN 12697-10 (EN, 2002);ll stability test, according to Standard EN 12697-34 (EN,

tension test, according to Standard EN 12697-23 (EN,

tension test at 25 C, after 7 and 15 days of waterion, according to Italian StandardCNRB.U. 134/91 (CNR,

o loss of weight test on Marshall specimen, accordingard EN 12697-17 (EN, 2004b);timized surface mixture only, as determined from thetests:c test for complex moduli determination, at differentatures and loading frequency, for determining the mas-es of the mixtures studied;c test for fatigue resistance, via repeated bending forceat T=15 C and with a loading frequency set equal to;determining mixtures rutting resistance, according tod EN 12697-22 (EN, 2003b).

from preliminary testing of component materials

cled asphalt characterizationsed for the present study, after due consideration, is toas high-quality RA of type F1, according to Standard(EN, 2005a), totally free from foreign materials, with

natingit mak1986).

Thesen, oband foformed perfofollowfour msatura

Ic = (a

Thein acco2000bvided t

for th for th

TR&B

2.1.3.minera

Thefrom athe coboth its component materials and their homogeneity.a RA from a single source, obtained by down-milling ofrs only, whose composition and origin were perfectly

logical characteristics of the bitumen recovered fromrding to Standard ASTM D1856 (ASTM, 1979), are given

lts from testing for physical and mechanical character-e recovered mineral aggregates are given in Table 2.ation analysis carried out according to Standard EN

N, 2008) on the aggregate as recovered from the RAssible to underline the high level of consistency and

ty of this characteristic (see Table 3).

cterization of the new rejuvenating bindert those commercially available, for the purposes of thiscial bitumen was selected, characterized by rejuve-

available at

Table 3Gradation anathe mixtures s

Riddle or sie

Riddle 40Riddle 30Riddle 25Riddle 15Riddle 10Riddle 5Sieve 2Sieve 0.4Sieve 0.18Sieve 0.074perties (fully dispersed structure, SOL type) so thate use of other additives superuous (Bicheron et al.,

e, a 70/100 graded highly aromatic bitumen was cho-ed via propane deasphalting of selected raw bitumensng uxing with aromatic oils. The S.A.R.A. Analysis per-h an MK-5 Iatroscan (Thin Layer Chromatography (TLC)d with a Flame Ionisation Detector (FID)) provided thealue for the Colloidal Index, Ic, based on the ratio of thechemical components (asphaltenes, resins, aromatics,

ltenes + saturates)matics + resins = 0.17

sical tests for rheological characterization, carried outce with Standards EN 1426 (EN, 2000a), EN 1427 (EN,I 4163 (UNI, 1959) and EN 12607-1 (EN, 2005b), pro-llowing results:

w bitumen, Pen=73dmm: TR&B =46 C and I.P. =1.4;me bitumen, after aging at the RTFOT: Pen=50.4dmm,2 C.

cal and mechanical characterization of the virginregateeral aggregate used for this experimental plan comesle quarry. Thus, the mixtures studied are obtained fromation of the different sized fractions of aggregate as

the production plant, denominated from a1 to a4, with

lysis of the recovered mineral aggregates, used for the production oftudied.

ve Nominal size,d (mm)

Cumulative passing (%)

Test A Test B Test C Test D Average

32 100 100 100 100 100.0024 100 100 100 100 100.0020 100 100 100 100 100.0012 97.7 95.3 100 99.6 98.28 95.9 91.4 97.3 96.5 95.34 72.5 71.0 75.1 73.7 73.12 47.4 45.6 49.5 48.6 47.80.4 19.9 23.1 21.7 21.4 21.50.18 15.1 13.9 16.2 15.4 15.10.074 10.4 9.9 11.5 11.6 10.9

C. Celauro et al. / Resources, Conservation and Recycling 54 (2010) 337347 339

Fig. 1. Gradation of the aggregate fractions used for the production of the mixturesstudied.

the additionofmineral ller, as needed. For each aggregate fraction,the gradation is shown in Fig. 1.

The laboratory tests for physical and mechanical characteriza-tion, carried out for each aggregate fraction as indicated above,provided the results presented in Table 4.

2.2. Denition of mixtures studied

2.2.1. Aggregate gradingFor this study, already optimized recipes for asphalt mixture

were chosen, characterized by gradations and component mutualproportions that are in accordance with the typical range of val-

ues as suggested by the most commonly used Italian technicalSpecications for road and airport maintenance, construction orreconstruction work.

The target mixtures can be ascribed to each possible intendeduse in a exible pavement, that is to say mixtures for:

thin surface layers for maintenance purposes; structural surface layers; binder courses; base courses.

The formulation criterion aimed at preliminarily guaranteeingadequate workability and compactibility of the recycled asphalt,thanks to the use of both high bitumen content (that, in what fol-lows, is expressed via the richness modulus, K) and high masticcontent (Celauro et al., 2004).

As far as themixture gradationwas concerned, for eachdifferentlayer to consider (surface, binder and base layer), reference wasmade to those indicated by the current standard specication forhot mix asphalt (MIT, 2002; ANAS, 2003).

The mixtures to be used for surface layers were denominated asU3 andU5,with reference to the typical layer thickness (3 and 5 cm,respectively) to be considered for each of them. For the binder andbase course, a mixture denominated Bi was chosen (falling withinthe gradation band for the AC16 dened by Swiss Standard 640431-1aNA (SNV, 2003), because it complies with the prescriptionsof technical Standards and specications for both the layers, aswellas for surface layers: the only distinguishing factor would be thebitumen content (richness modulus).

Therefore, the mixtures studied are those presented in Table 5:

Table 4Physical and mechanical characteristics of the virgin aggregate used for the production of the mixtures studied.

Aggregate property Fraction a1 (20/25) Fraction a2 (10/15) Fraction a3 (6/10) Fraction a4 (0/6) Filler Units Standard

Particle density (r) 2.89 2.89 g/cm3 EN 1907-6 (EN, 2000c)Apparent particle density (a) 2.83 2.84 2.86 2.87 g/cm3 EN 1907-6 (EN, 2000c)Los Angeles Abrasion, (L.A.) 17.7 19.6 19.7 % EN 1097-2 (EN, 1998a,b)Micro-Deval abrasion resistance in

water (M.D8.5 % EN 1097-1 (EN, 1996)

Sand equivaPolished stoFlakiness indShape indexWater absorRigden voids

Table 5Composition o

Riddle or sie

Riddle 40Riddle 30Riddle 25Riddle 15Riddle 10Sieve 5.6Riddle 5Sieve 2Sieve 1Sieve 0.5Sieve 0.4Sieve 0.18Sieve 0.074Sieve 0.063

Bitume

T.U.)lent (SE)ne value (PSV) 0.40ex (FI) 2.02 1.70(SI) 3.96 3.24ption 0.31 0.44 0.70of compacted ller

f the mixtures studied and related typical laying thicknesses.

ve Nominal sizes (mm) Mixture U3

32 100

24 10020 10012 1008 965.64 612 3510.50.4 140.18 110.074 90.063

n content b% (richness modulus, K) b0 = 5.17 (K0 = 3.25),b1 = 5.57 (K1 = 3.50),b2 = 6.03 (K2 = 3.75)

ypical laying thickness (mm) 253577 % EN 933-8 (EN, 1999b) UNI 1097-8 (EN, 1999b) EN 933-3 (EN, 1997a,b)% EN 933-4 (EN, 1999d)

0.97 % EN 1907-6 (EN, 2000c)32.70 % EN 1907-4 (EN, 1999c)

Mixture U5 Mixture Bi

100 100100 100100 97100

8593

805633 52

31

1311 128 10

b1 = 5.03 (K1 = 3.25),b2 = 5.55 (K2 = 3.50)

b1 = 4.48 (K1 = 2.90),b2 = 4.87 (K2 = 3.15),b3 = 5.26 (K3 = 3.40)

3550 4570

340 C. Celauro et al. / Resources, Conservation and Recycling 54 (2010) 337347

Table 6Richness Modulus and binder content chosen for the studied mixture and recommended range.

Mixture Recommended value Adopted value

b (%) (SNV, 2003) b (%) (MIT, 2002) Richness modulus, K b (%)

Thin surface 5.26.2

K0 = 3.25 b0 = 5.17K1 = 3.50 b1 = 5.57K2 = 3.75 b2 = 6.03

Structural su 5.06.0

K1 = 3.25,K2 = 3.50

b1 = 5.03,b2 = 5.55

Thick surfac 4.55.5

K3 = 3.40 b3 = 5.26

Binder (BiK2 4.05.0 K2 = 3.15 b2 = 4.87

Base (BiK1) 4.05.0

K1 = 2.90 b1 = 4.48

Note: Accordin of trafc.

2.2.2. BitumThe bitu

fall within terence andaggregatewNA (see Tab

2.2.3. SelecThe sele

reason behhigh-perforconsiderati

the consis the homo

essarily h(AIPCR, 20

the rejuve the chara

modieda high per

Thereforered: 0%, 40following p50%, respec

F0: refere F40: mixt

percentagture (SETstudied;

F50:mixtchosen forials as wplant.

The prevat differentthe mixture

Thereformodulus) w

t res

mpa

pacout97-3. 2 aes ouenn coing tso me dusicade iramethe

bilitym thmixtt whnnecfor maintenance purposes (U3)6.2 L6.0 N5.8 S

rface layer (U5)

5.8 wearing course L5.6 wearing course N5.4 wearing course Sor4.8 binder Sor5.2 base L5.0 base N

e (BiK3)5.4 wearing course L5.5 wearing course N

) 4.4 binder4.8 base L4.8 base N5.4 base S

g to Swiss Standard, L, N, S refer respectively to road for high, normal or low levels

en content (richness modulus)men content for each mixture was chosen in order tohe range given by the Italian Specications taken as ref-also with respect to the minimum bitumen content (byeight) recommended by Swiss Standard SN 640 431-1ale 6).

ting the recycling percentagection of the recycling percentage was made on theind this study (maximum reuse of RA, for producingmance recycled mixtures) as well as on some technicalons such as:

tency of the mixtures properties to be guaranteed;geneity and consistency of the RA to be used (to be nec-igh, when using a high percentage of recycled material)02);nating characteristics of the selected virgin bitumen;cteristics of the asphalt production plant, specicallyand calibrated with a parallel drum for the RA, to allowcentage of recycling.

e, the following percentage of recycling were consid-

3. Tes

3.1. Co

ComcarriedEN 126

Figsmixturthe inbitume

Durwas almixtur

DenSGC mthe papart ofworka

Froof thecontenthis co%, and 50%, respectively indicated with Therefore, theercentage of recycling were considered: 0%, 40%, andtively indicated with:

nce mixture, without recycled material;ure characterized by the maximum allowable recyclinge (40%), as recommended by the technical litera-RA, 2004), when using high-quality RA, like the one

ure characterized by themaximumquantity of RA (50%)r this study, in consideration of the available mate-ell as of the special facilities available at the asphalt

iously detailed recycling percentages were evaluatedbinder content, by varying the new bitumen content in.e, an identication code (Layer Code RAP%-richnessas adopted, as detailed in Table 6.

Fig. 2. CompaU3K0.ult and discussion

ction test at the Shear Gyratory Compactor

tion tests at the Shear Gyratory Compactor (SGC) wason specimen of bituminousmixture, in accordancewith1 (EN, 2004c).

nd 3 depict, by way of example, the results obtained forf type U3, and compare them all in order to highlightce of the RA content on this characteristic, for a xedntent of the mixtures.he test, the gyratory shear ratio (Celauro et al., 2004)easured, in order to monitor the internal stability of thering compaction.ation curves recorded during the compaction test at thet possible to obtain the residual void content, and alsoters k and C, the slope and the intercept of the straightcurves, which are useful for dening, respectively, theand the densication of the mixtures (see Table 7).e results, it is possible to note that the workability, k,ures studied can be considered independent of the RAilst the latter has an inuence on the densication, C. Intion, it is simple to observe that the compaction straightctibility curve at the SGC, for different RA contents mixtures of type

C. Celauro et al. / Resources, Conservation and Recycling 54 (2010) 337347 341

Fig. 3. Compactibility curve at the SGC, for different RA contents mixtures of typeU3K1.

Table 7Residual void content obtained with the SGC.

Mixture vPG at 10Ng (%) vPG at 100Ng (%) C (%) k R2

U3 F0 K0 13.10 5.44 20.8 0.031 0.996U3 F0 K1 11.69 4.63 18.7 0.034 0.986U3 F0 K2 12.32 4.51 20.2 0.033 0.994U3 F40 K0 11.62 3.71 19.5 0.034 0.994U3 F40 K1 10.64 2.87 18.4 0.034 0.988U3 F50 K0 11.44 3.13 19.8 0.036 0.994U3 F50 K1 10.86 2.16 19.6 0.038 0.996

U5 F0 K1 12.01 4.74 19.3 0.032 0.992U5 F0 K2 12.25 4.26 20.2 0.034 0.998U5 F40 K1 14.55 5.53 23.5 0.039 0.998U5 F40 K2 14.34 5.12 23.5 0.040 0.998U5 F50 K1 13.54 4.15 22.9 0.041 0.998U5 F50 K2 13.37 3.91 22.8 0.041 0.998

Bi F0 K1 13.52 5.03 21.7 0.035 0.999Bi F0 K2 13.16 5.12 21.2 0.035 0.999Bi F0 K3 10.08 2.16 17.9 0.034 0.998Bi F40 K1 12.75 4.28 21.2 0.037 0.994Bi F40 K2 12.13 3.57 20.7 0.037 0.997Bi F40 K3 11.33 2.17 20.4 0.040 0.995Bi F50 K1 13.11 4.25 21.9 0.038 0.997Bi F50 K2 12.10 3.26 20.9 0.038 0.997Bi F50 K3 10.35 1.53 19.2 0.039 0.995

lines have, for the same bitumen content and different RA content,a slope that is quite constant, and thus they prove parallel to eachother, theoneswithRAhavinghigher compactionvalues than thosemeasured for the corresponding control mixtures (see Fig. 2).

3.2. Cantabro test

Due to the introduction of high quantities of RA in the studiedmixtures and, therefore, to the consequent high amount of agedbitumen, it was thought appropriate to adopt a testingmethod thatmade it possible to evaluate the quality of the bitumen/aggregatebond, in order to guarantee satisfactory durability of the mixtures,once in place.

For this purpose, the abrasion loss Cantabro proved to be quitequick to perform, effective and sufciently adequate for evaluatingthe behaviour of the binder in the mixture, as deriving from bindercharacteristics such as cohesion, thermal susceptivity, adhesionand ageing. This test was carried out in accordance with StandardEN 12697-17 (EN, 2004b), at 18 C. The results obtained, expressedas average Cantabro loss value, are given in Fig. 4 as a function ofthe RA percentage in the mixture.

For each mixture Fig. 4 clearly shows a worsening trend of theinternal cohesion with an increase in the RA percentage. Further-more, for each mixture, a reduction in the percentage mass loss canbe observed for higher bitumen contents.

3.3. Marshall test and results

The Maperformedability inprrequiremen

The testExamini

tures considlevels for Mian Specicby this resecerned, onlycorrespond

Fig. 4. Cantabro loss for the mixtures studied, at diffrshall test as well as the indirect tensile test werefor each studied mixture in order to evaluate their suit-ovidinghighmechanical performances, according to thets given in Table 8, for each intended use.results are summarized in Table 9.ng the test results, it is easy to observe that all the mix-ered in this study comply not only with the minimumarshall stability and quotient as required by the Ital-ations but also with the higher performances pursuedarch. As far as the Marshall residual air voids are con-typeU3mixtures for thin surfaces have too lowvalues,

ing with the higher bitumen contents. Therefore, for

erent RA contents.

342 C. Celauro et al. / Resources, Conservation and Recycling 54 (2010) 337347

Table 8Marshall target values for the studied mixtures with high percentage of RA.

Type of mixture Marshall stability,MS (kN)

Marshall quotient,QM (kN/mm)

Marshall voids,vM (%)

Voids lled withbitumen, VFB (%)

Surface course >12 QM >3.5 35 10 QM >3.5 36 9 QM >3.0 37

C. Celauro et al. / Resources, Conservation and Recycling 54 (2010) 337347 343

Table 10Testing results for the indirect tensile strength, ITS, for the mixtures studied.

Mixture ITS (N/mm2) at 25 C ITS7gg (N/mm2) after 7 daysof soaking at 40 C

ITS14gg (N/mm2) after 14 daysof soaking at 40 C

R7 = ITS7ggITS R14 =ITS14gg

ITS

U3 F0 K0 1.316 1.287 1.281 0.98 0.97U3 F0 K1 1.569 1.515 1.479 0.97 0.94U3 F40 K0 2.210 2.053 2.074 0.93 0.94U3 F40 K1 2.037 1.838 1.866 0.90 0.92U3 F50 K0 2.361 2.25 2.220 0.95 0.94U3 F50 K1 2.185 2.112 2.049 0.97 0.94U5 F0 K1 1.393 1.328 1.336 0.95 0.96U5 F0 K2 1.318 1.293 1.270 0.98 0.96U5 F40 K1 2.248 2.158 2.154 0.96 0.96U5 F40 K2 1.896 1.828 1.806 0.96 0.95U5 F50 K1 2.612 2.548 2.485 0.98 0.95U5 F50 K2 1.975 1.893 1.873 0.96 0.95Bi F0 K1 1.387 1.341 1.335 0.97 0.96Bi F0 K2 1.272 1.231 1.235 0.97 0.97Bi F0 K3 1.148 1.083 1.136 0.94 0.99Bi F40 K1 2.422 2.090 2.011 0.86 0.83Bi F40 K2 2.212 1.844 1.876 0.83 0.85Bi F40 K3 1.821 1.557 1.520 0.86 0.83Bi F50 K1 2.963 2.602 2.632 0.88 0.89Bi F50 K2 2.667 2.312 2.292 0.87 0.86Bi F50 K3 2.234 1.984 1.936 0.89 0.87

The same decreasing trend with the bitumen content can beobserved for the Marshall quotient, QM. By contrast, when examin-ing the results as a function of the RA content, an increasing trendof the Marshall stability, MS, can be noticed.

This result is consistentwithwhatwas expected (Pratic, 2004),since the hardness of the total bitumen in the mixture increaseswith the RAresults for tin RA conte

For thecontent, anwith bitum

Using ain fact, is thclimates, mtent to impmodulus), t

3.4. Indirect tension test and results

The very high content of recycled material in the mixture madeit necessary to evaluate the resistance of the mixtures studiedto water-induced damage by performing indirect tensile strengthtests, before and after soaking in water. The tests were conducted

, aftdardt 40

(CNm Tah tht tenalt m

m thhe inseecontent. The previous result is corroborated by theheMarshall quotient, which increaseswith the increasent as well.same reason, the Marshall voids increase with the RAd consequently, the calculated values for voids lleden, VFB, decrease (see Table 9).high percentage of recycled material in the mixture,e same as using harder bitumen, which, for warmerakes it possible to accept quite a high bitumen con-rove fatigue resistance and bearing capacity (complexhough maintaining high rutting resistance.

at 25 Cto stanbath a134/91

Froply witindirecof asph

Frowith talreadyFig. 6. Indirect tensile strength ITS [N/mm2], as a funer standard conditioning of asphalt specimen accordingEN 12697-23 (EN, 2003a) or after soaking in a waterC for 7 or 14 days, according to Italian Standard CNRR, 1991). Results are given in Table 10.ble 10 it can be seen that all the mixtures studied com-e requirements of the Italian Specications for both thesile strength and the water-induced damage resistanceixtures, as depicted in Figs. 6 and 7.

e results given it can be noticed that the ITS decreasescrease in binder content (richness modulus, K), as

n for the Marshall stability MS.ction of RA content.

344 C. Celauro et al. / Resources, Conservation and Recycling 54 (2010) 337347

fter 14

Finally, ato conclude

1. for all thments of

2. as expecsevere cosome spe

3. in any caian Specof bindersuchas ththe Durie(AASHTOration of

Apart frreduction operiod in w

Furthermsile strengtwhat was oconstant levbitumen haasphalt.

Again, folated for thSpecicatioconsidered:days.

Lastly, thon the type

3.5. Rutting

Inorderwere carrieConsideringtypical layeied, it waswith typica

indetenttion

previore

sultstingin ththermateriresi

respwn b1, w

of bowit

ny cer coof wparFig. 7. Retained tensile strength ratio R as a function of RA content, a

s far as thewater susceptivity is concerned, it is possiblethat:

e mixtures the ratio R fully complies with the require-the Italian Specications;ted, testing after 14 days of soaking at 40 C is morempared with testing after 7 days, also considered bycications;se, the testing methods considered by most of the Ital-ications, are not able to take into account the effectcontent, as happens for other experimental methodse standard testdescribed inASTMD4867 (ASTM,2004),z test and the modied Lottman test AASHTO T283, 2007) that, conveniently, account for the water satu-specimens.

om the normal scattering of testing results, a certainf the indirect tensile strength for a longer conditioningater at 40 C can be noticed.ore, regardless of bitumen content, the indirect ten-

h increases with the RA content. This result matches

each bRA conapplica

Aseven mtest rethe rutbinder

Furcled mruttingthe coras shoTable 1termsculatedRA.

In ain bindmationrelatedbserved for Marshall stability and has to be related, at ael of the bitumen content, with the steady increase inrdening due to the use of larger quantities of recycled

r all the mixtures studied, the value obtained as calcu-e ratio R complies with the requirements of the Italianns (R>0.70) for both the water conditioning periodsthe shorter one, of 7 days, and the longer one, of 14

e water-induced damage seems to be more dependenton mixture than on the RA content in the mixture.

resistance

toevaluate themixtures rutting resistance, rutting testsd out according to Standard EN 12697-22 (EN, 2003b).the meaning of this test and taking into account the

r thickness associated with each type of mixture stud-decided to test only the mixtures for wearing courses,l laying thicknesses of 5 cm, that is type U5 mixtures, at

slope in air,manent def

Fig. 8. Cumuleach RA contedays of soaking in a water bath at 40 C.

r and RA content. For these mixtures, at each different, the rut depth as a function of the number N of loads is given in Fig. 8.ously seen from the Marshall testing results, but nownoticeably from the mechanicistic point of view, the rutshow that the use of recycled material greatly increasesresistance as a consequence of the hardening of the totale mixture.ore, it is possible to observe that mixtures with recy-

als, even though with high binder content, have goodstance, with rut depths lower that those obtained foronding controlmixtures (type F0mixtures,without RA),y the average values for rut depth in air, RDair, given inhere the results obtained for each mixture are given inth the absolute value measured and the percentage cal-h respect to the value for the control mixture, without

ase, consistently with what was expected, the increasentent worsened the rutting resistance. Further conr-hat was said above can be obtained by calculating the

ameters of the rutting curve, that is the wheel-tracking

WTSair, directly associated with the cumulating of per-ormation for the different mixtures, given in Table 12.

ative rut depth as a function of the number N of load applications, fornt.

C. Celauro et al. / Resources, Conservation and Recycling 54 (2010) 337347 345

Table 11Rut depth results, RDair.

Richness modulus (b%) RDair (mm) Ratio (%)

U5FO U5F40 U5F50 F40/F0 F50/F0

K1 = 3.25 (b=5.03%) 3.63 2.12 1.6 58.32 44.02K2 = 3.50 (b=5.55%) 5.26 2.54 2.19 48.24 41.69

Table 12Wheel-tracking slope in air, WTSair for the mixtures studied.

Richness modulus (b%) U5 FO U5 F40 U5 F5O

K1 = 3.25 (b=5.03%) 0.169 0.047 0.047K2 = 3.50 (b=5.55%) 0.226 0.068 0.055

Again, it is possible to notice a worsening of this performancewith an increase in the binder richness modulus, K: this matchesthe increase in the wheel-tracking slope WTSair when moving fromthe modulufor the samtically reduthe slope Win the mixtdoubled serpavement dhot climate

3.6. Comple

For the slaboratoryRA contentperformed.

ComplexBending Tesinusoidal sThe deformModulus te(T=0, 10, 2were taken

Figs. 9diagrams (ilus), in addmodulus |Eperature TRtime-tempetor T calcset an activH=50kca

Examiniclearly seeinto the mix

Fig. 10. ColeCole diagram mixture U5F40K2.

Fig. 11. ColeCole diagram mixture U5F50K2.

an bpart

, theh temss) ttureed bytroltem

an exi calcl ass K1 to the higher value K2. It can be concluded that,e richness modulus, the use of recycled material dras-ces the cumulating of ruts at high temperatures, sinceTSair decreases with an increase in the RA percentageure. Based on these results, it is possible to consider avice life of the surface layer with respect to this specicamage (which is particularly severe in countries withs).

x modulus test and results

ole surfacemixture selected on the basis of the previousresults for industrial production (U5K2, with different), complex modulus tests and fatigue tests were also

modulus tests were carried out using a Three-pointst Device, obtained by imposing in the centre-line atrain, of constant amplitude (strain controlledmethod).ation amplitude level was set about equal to =35/m.sts were performed at ve different temperature levels0, 30 and 40 C); for each temperature, measurementsat a range of frequencies (f=30100Hz).11 show the results obtained in terms of ColeCole.e. elastic vs. viscous component of the complex modu-ition, Fig. 12 depicts the master curves of the complex*| for the different mixtures at the reference tem-=10 C. These curves were obtained by applying therature superposition principle (with translation fac-ulated according to Arrhenius formula) and havingation apparent energy value common to all mixtures,l/mol.ng the results of the complex modulus tests, one canthe inuence of the introduction of recycled materialstures.

As cand, indationfor eac(stiffne

Mixprovidthe contesting

Asmodulas welFig. 9. ColeCole diagram mixture U5F0K2.Fig. 12. Mastecontents.e observed by examining the complex modulus curvesicular, by comparing them at the same aggregate gra-mixtures with 50% of recycled materials (F50) offer,perature and loading frequency, higher performance

han those with lower RA content.s with 40% of RA (F40) have moduli just below thosethe type F50 mixtures but always higher than those ofmixtures (F0), this effect being more evident at higherperatures.ample, Table 13 provides a summary of the stiffnessulated for the different mixtures at 20 C and 35Hz,the values for the E modulus (purely elastic mod-r curves of complex modulus mixture type U5 K2, at different RA

346 C. Celauro et al. / Resources, Conservation and Recycling 54 (2010) 337347

Table 13Complex modulus at different RA content for the type U5K2 mixtures.

Mixtures Modulus |E| at 20 C, 35Hz (MPa) Estimated E modulus (MPa)U5 FO K2 11,600 32,000U5 F4O K2 13,000 36,000U5 F5O K2 13,300 37,500

ulus, which the mixture has for extremely low temperatures orextremely high loading frequencies), estimated for each mixturefrom the ColeCole diagrams previously seen.

Testing results prove the improvement in stiffness gained bymixtures with higher RA content, when compared with the controlmixture without RA, and therefore a better capacity of spreadingthe load application or, which is the same thing, a better struc-tural performanceof theproposedmixtures,whenused in aexiblepavement.

3.7. Fatigue test and results

Fatigue resistancewas determined by subjecting the specimens,prismatic in shape and with a constant section, to repeated ex-ural loading with procedures analogous to those of the complexmodulus test. Tests were carried out at a temperature set equal toT=15 C, for a xed loading frequency equal to f=30Hz. The fail-ure criterion adopted is the traditional one which considers a 50%reduction in the initial stiffness modulus. The testing temperatureselected is the one that best represents the most signicant ther-mal regime for the onset of fatigue damage in exible pavementsin countries with warm climates, such as Italy.

The testshown in Fi(, and Rthe fatigue

From thmate the aloading app

By compmen conten

Fig. 13. F

Table 14Estimated reapplications.

Mixture

U5F0 K1U5 F40 K1U5 F50 K1

recycled material did not jeopardize the mechanical performancesof the mixtures studied.

Mixtureswithhigher percentageof recycledmaterial (F50) havebetter fatigue performance of those with lower RA content (F40)the latter, imixture F0

In particadopted, thhigh-perfo

high fatigN=106 cyfatigue lin

good valuulus tests

4. Conclus

The neetal sustainamethodoloof recyclednance of roaimproveme

Differenmixtures, a

governingorder totics, main

harated ftingindeacteratorizinledgcom

ity foidat

age)

mecall td dag coith vssiblSpecd as yersarm

nces

. Stanced Dciatioecyclaon; 20apitolaNazio1856:results made it possible to obtain the Whler curvesg. 13. Table 14 summarizes the regression coefcients2) obtained for the different mixtures, as estimated forstraight line, i.e. =N.e regressions previously given, it was possible to esti-dmissible strain level corresponding to one millionlications, (N=106).arison of the fatigue straight lines, for the high bitu-ts considered, it can be noticed that the introduction of

atigue straights for mixture type U5K2, at different RA content.

gression coefcients and admissible strain at N=106 loading

the cselec

selecold b

charlabor

optimknowgoodqualto oxdam

The(Marshinducewearineven wit is poItaliandeneface lawith w

Refere

AASHTOInduAsso

AIPCR. Rciati

ANAS. CEnte

ASTM. D

R2 (N=106) 15 C, 35Hz

1520 0.19 0.945 991075 0.16 0.846 1171103 0.16 0.881 121

method. Adards, vol.

ASTM. D4867paving miStandardsn turn, being better than those attained by the control, without RA.ular, also taking into account the testing conditionse mixtures with higher RA content can be dened asrmance since they offer:

ue performance (high level of admissible strain atcles, together with low values for the slope of thee;es for stiffness, as determinedduring the complexmod-.

ions

d for good quality, cost-effectiveness and environmen-bility of road construction led to the denition of a

gy for studying bituminous mixtures with high contentasphalt, to be used for both construction and mainte-d and airport pavements, togetherwith the consequentnts in asphalt production plants.t stepswere involved in the design phase of the recyclednd specically:

of the recovery and handling of recycled asphalt, inassure the required homogeneity of its characteris-ly with regard to the identication of the source andcterization of the component materials related to theuture use;an appropriate virgin bitumen (able to rejuvenate ther contained in the RA);izing each component of the mixtures produced in ay, consistently with the selected use;g the mixtures to be produced so that, thanks to thee on mix design of traditional bituminous mixtures, apromisebetween in-serviceperformancesand requiredr agood layingprocess anddurability (suchas resistanceion and sun radiance or resistance to water-inducedcan be achieved.

hanical characterization tests carried out in this studyest, indirect tensile test, test for resistance to water-mage, Cantabro loss test and also, for the optimizedurses, complex modulus and fatigue tests) showed thatery high percentages of recycled materials (up to 50%)e to comply with the requirements of the most commonications and Standards for bituminous mixtures to behigh-performance, i.e. those that are designed for sur-of roads with very high levels of heavy trafc, in regionsclimates.

dard T 283. Resistance of CompactedBituminousMixture toMoisture-amage. AASHTO Provisional Standards. Washington, D.C.: Americann of State Highway and Transportation Ofcials; 2007.ge des chausses souples existantes. AIPCR/PIARC World Road Asso-02, ISBN 2-84060-139-7.to Speciale dAppalto per lavori stradali. Norme tecniche. Roma, Italy:nale per le Strade; 2003 (in Italian).Standard test method for recovery of asphalt from solution by Absonmerican Society for Testing and Materials 96 Annual Book of Stan-04.03. Conshohocken, Pennsylvania, 2003; 1979.: Standard test method for effect of moisture on asphalt concretextures. American Society for Testing and Materials. Annual Book of, vol. 04.04. Conshohocken, Pennsylvania; 2004.

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EN. EuropeanaggregatesCommitte

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EN. EuropeanaggregatesCEN - Euro

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Production of innovative, recycled and high-performance asphalt for road pavementsIntroductionMaterial studied and experimental planResults from preliminary testing of component materialsReclycled asphalt characterizationCharacterization of the new rejuvenating binderPhysical and mechanical characterization of the virgin mineral aggregate

Definition of mixtures studiedAggregate gradingBitumen content (richness modulus)Selecting the recycling percentage

Test result and discussionCompaction test at the Shear Gyratory CompactorCantabro testMarshall test and resultsIndirect tension test and resultsRutting resistanceComplex modulus test and resultsFatigue test and results

ConclusionsReferences