Embed Size (px)
Citation preview
This article was downloaded by: [Nipissing University]On: 09 October 2014, At: 06:39Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office: MortimerHouse, 37-41 Mortimer Street, London W1T 3JH, UK
Road Materials and Pavement DesignPublication details, including instructions for authors and subscription information:http://www.tandfonline.com/loi/trmp20
Effect of Recycling Rate and Asphalt Binder onthe Performance of Recycled Asphalt Concrete forAirport Pavement RehabilitationKai Su a , Yoshitaka Hachiya b & Ryota Maekawa aa Airport Research Center , Port and Airport Research Institute , 3-1-1, Nagase,Yokosuka, 239-0826, Japan E-mail:b Service Center of Port Engineering , 3-3-1, Kasumigaseki, Chiyoda-ku, Tokyo, 100-0013,Japan E-mail:Published online: 19 Sep 2011.
To cite this article: Kai Su , Yoshitaka Hachiya & Ryota Maekawa (2009) Effect of Recycling Rate and Asphalt Binder onthe Performance of Recycled Asphalt Concrete for Airport Pavement Rehabilitation, Road Materials and Pavement Design,10:2, 361-371
To link to this article: http://dx.doi.org/10.1080/14680629.2009.9690199
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) containedin the publications on our platform. However, Taylor & Francis, our agents, and our licensors make norepresentations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose ofthe Content. Any opinions and views expressed in this publication are the opinions and views of the authors,and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be reliedupon and should be independently verified with primary sources of information. Taylor and Francis shallnot be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and otherliabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to orarising out of the use of the Content.
This article may be used for research, teaching, and private study purposes. Any substantial or systematicreproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in anyform to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions
Road Materials and Pavement Design. Volume 10 – No. 2/2009, pages 361 to 371
SCIENTIFIC NOTE
Effect of Recycling Rate and AsphaltBinder on the Performance of RecycledAsphalt Concrete for Airport PavementRehabilitation
Kai Su* — Yoshitaka Hachiya** — Ryota Maekawa*
* Airport Research CenterPort and Airport Research Institute3-1-1, Nagase, Yokosuka, 239-0826, [email protected]@pari.go.jp
** Service Center of Port Engineering3-3-1, Kasumigaseki, Chiyoda-ku, Tokyo 100-0013, [email protected]
ABSTRACT. Aimed to prompt the extensive use of reclaimed asphalt aggregate (RAA) in airportpavement rehabilitation, a series of laboratory tests are conducted to intensively evaluate theeffect of recycling rate and asphalt binder on the performances of recycled asphalt concrete(RAC). The results indicate that rutting resistance of RAC using either straight or modifiedasphalt binder increases with the increase of recycling rate, while the opposite trend is foundin low temperature properties (increase in stiffness) and fatigue performance. The modifiedasphalt used does not exhibit superiority for producing RAC compared with straight asphaltexcept in rutting resistance. Increasing the recycling rate to 70% is feasible in the case ofRAC using straight asphalt judging from its comparable and even superior performance tothe control SRAC (contain 40% RAA) in terms of resistance to rutting, ravelling, moisturestripping and thermal cracking. It seems possible to use it in surface courses devoted toairport sections where fatigue processes are not prevalent.KEYWORDS: Recycled Asphalt Concrete, Recycling Rate, Asphalt Binder, Airport PavementRehabilitation.
DOI:10.3166/RMPD.10. 361-371 © 2009 Lavoisier, Paris
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
06:
39 0
9 O
ctob
er 2
014
362 Road Materials and Pavement Design. Volume 10 – No. 2/2009
1. Introduction
Now the general focus of infrastructure development in Japan has shifted frominitial development and construction to maintenance and rehabilitation (Hachiya etal., 2006). More and more airport asphalt pavements are scheduled to be repaired inthe next few years. Due to resources conservation, cost savings and protection ofenvironment, recycled asphalt concrete (RAC) by reusing the reclaimed materialsfrom airport is becoming more attractable compared with the use of virgin asphaltconcrete in the upcoming rehabilitation works.
Today, the use of reclaimed asphalt aggregate (RAA) in hot-mix asphalt (HMA)is not a new concept and has been widely accepted worldwide (William et al., 1981;Kandhal et al., 1995; Oliver, 2001). When adding some rejuvenating agents, a largepercentage of RAA can be used in base course and surface course (Sullivan, 1996;Pereira, 2004; Shen et al., 2007). However, recycling rate, defined as the amount ofRAA divided by the amount of total aggregates, is strictly restricted within 40% bythe national specification on airport in Japan (MLIT, 2004). As a result, a largerquantity of RAA still remains unutilized and needs disposal by the airport agencies.This has become an obstacle to fully use RAA in airport paving works. Therefore,research is highly needed to study the potential of incorporating more RAA in RACto prompt the use of RAA and reduce the rehabilitation cost.
2. Research objective and plan
This study is mainly aimed at giving an objective evaluation of the effect ofRAA content and asphalt binder properties on the performance of RAC and a morepractical recycling rate for guiding the future airport pavement rehabilitation inJapan. In order to accomplish these objectives, the performances of eight RAC withmodified or straight asphalt binder at four recycling rates (0%, 40%, 70% and100%) were in detail investigated in terms of their resistance to rutting, moisture,cracking and ravelling. Here, 0% recycling rate meant that RAC was entirelycomposed of new aggregates and asphalt. Meanwhile, the asphalt binder from eachRAC was extracted and recovered by Abson recovery test (ASTM D1856) and werefurther evaluated by means of penetration, ductility and softening point tests.
3. Experimental program
3.1. Materials
The single source of new aggregates and RAA used in this study was providedby Japan Road Company. The coarse aggregates (new) were crushed sand stoneproduced near Tokyo, and the fine aggregate consisted of the screenings ( 5 mm)and natural sand. The RAA were reclaimed from abolished asphalt pavements in an
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
06:
39 0
9 O
ctob
er 2
014
Effect of Recycling Rate and Asphalt Binder on RAC 363
airport near Tokyo and separated into three portions according to the particle size(13-20 mm, 5-13 mm and 2.5-5 mm). The asphalt content of 13-20 mm, 5-13 mmand 0-5 mm RAA were 3.7%, 3.3% and 4.0%, respectively. The penetration ofrecovered asphalt binder from RAA was 26 (1/10 mm), which met the limited valueof 20 (MLIT, 2004). Table 1 summarized the properties of used new aggregates,RAA (after recovery) and mineral filler (hydrated lime).
Table 1. Summary of properties of used aggregates
Materials New aggregates Recovered RAA Sand Filler
Particle size(mm) 30-20 13-20 5-13 0-5 13-20 5-13 0-5 0-5 <0.075
Specification
Apparentspecific gravity
(g/cm3)2.684 2.653 2.652 2.652 2.533 2.541 2.478 2.593 2.759
Aggregate:>2.45
Filler: >2.6
Waterabsorption
(%)0.63 0.31 0.7 0.92 - - - 1.49 0.15
Aggregate:<3.0
Filler: <1.0
L.A. abrasion(%) 30.2 32.5 - - <35
Two kinds of asphalt binders routinely used in Japan were selected in this study,a straight asphalt with the penetration of 60-80 (1/10mm) and a modified asphalt.The properties of two asphalt binders were illustrated in Table 2, which all satisfiedthe specified limits (MLIT, 2004).
Table 2. Properties of used asphalt
Straight 60 – 80 Modified IIProperty
Test value Specification Test value Specification
Penetration at 25°C (0.1mm) 68 60-80 53 >40
Softening point (°C) 49.0 44-52 63.0 56-70
Ductility at 15°C (cm) 100+ >100 97 >30
Viscosity at 60°C (Pa . s) 222 - 1084 -
Density at 15°C (g/cm3) 1.030 - 1.031 -
In this study, a commercially produced rejuvenating agent with lower viscosityand little asphaltenes was used. It could recover the aged binder included in RAA tothe same level as new asphalt by reconstituting its chemical composition (Shen et
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
06:
39 0
9 O
ctob
er 2
014
364 Road Materials and Pavement Design. Volume 10 – No. 2/2009
al., 2007). The amount of rejuvenating agent was determined with the penetration-based blending chart as shown in Figure 1 (Takahashi et al., 2000). The penetrationof RAA asphalt mixed with 5%, 10% and 15% rejuvenating agent was measured.Then, a straight line was drawn to connect these points. The horizontal dashed linewas the target penetration measured from new asphalt after exposure to thin filmoven test (TFOT) for 45 minutes to simulate aging during production. Theprojection of intersection point of horizontal and bias lines yielded the estimate ofthe amount of percent rejuvenating agent required to meet the target penetration inthe blend. By this procedure, the quantity of rejuvenating agent was determined, thatis, 11.4% for RAC using straight asphalt and 9.6% for using modified asphalt.
5 6 7 8 9 10 11 12 13 14 150
20
40
60
80
100
RAA asphalt straight asphalt modified asphalt
Pene
tratio
n af
ter T
FOT
(1/1
0mm
)
Content of rejuvenating agent (%)
6152
Figure 1. Blending chart to determine the content of rejuvenating agent
3.2. Aggregate gradation
The aggregate gradations used in RAC at different recycling rates were as closeas practically possible to the medium value of the specified gradation range in aneffort to minimize additional factors that can affect the results (MLIT, 2004). Eachgradation had a maximum particle size of 20 mm as shown in Figure 2.
0
20
40
60
80
100
0.30
Perc
ent p
assi
ng (
%)
Sieve size (mm)
recycled 0% recycled 40% recycled 70% recycled 100% range
0.075 0.15 0.60 2.36 4.75 13.2 19.0 26.5
Figure 2. Aggregate gradation curves in RAC
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
06:
39 0
9 O
ctob
er 2
014
Effect of Recycling Rate and Asphalt Binder on RAC 365
3.3. Mix design and sample preparation
According to the selected aggregate gradation, RAA with different proportionswas then blended with new aggregates, new asphalts and rejuvenating agents at theappropriate percentages to produce RAC. They were mixed at approximately 165°Cwhen using straight asphalt (SRAC) and 175°C for using modified asphalt (MRAC)according to the viscosity-temperature criteria. The mix design followed the generalMarshall procedure with 75 blows at each side (ASTM D 1559). The optimal asphaltcontent (OAC) for SRAC at the recycling rate of 0%, 40%, 70% and 100% was5.4%, 5.4%, 5.3% and 5.1%, respectively, and 5.4%, 5.3%, 5.3% and 5.1% forMRAC. Either SRAC or MRAC at various recycling rates had similar air voids.
Samples for performance tests were prepared duplicate at OAC for each mixture.The air voids were same with that of Marshall specimen and the average of the testresults were used to analyze. Notice that in this study, SRAC at the recycling rate of40% was used as a control mixture for comparing RAC performance because it wasthe baseline permitted by the national specification.
3.4. Test methods
To comprehensively evaluate the performances of recycled asphalt concretes, aseries of laboratory tests were conducted as described follows (JRA, 2007):
– Wheel tracking test was used to determine the deformation resistance of RACunder high temperature. The specimens were compacted by a rolling compactor, andthen held in an environmental chamber for a minimum of 6 hours at the prescribedtemperature of 60°C to reach the temperature equilibrium. In the test, a rubber facedtire with a high load pressure of 1.38 MPa at the speed of 21 cycles/min moved backand forth across the surface of the 300×300×50 mm specimen at 60°C for 60minutes. From the measured rutting depth, dynamic stability (DS), defined as thenumber of load repetitions to generate 1 mm rutting during the last 15 minutes of theone-hour testing was used as the indicator of rutting resistance.
– The moisture resistance of RAC is evaluated by the residual Marshall stability.Six standard Marshall specimens were placed in the water bath at 60°C. After30 min, the control set of three samples were tested for Marshall stability, followedby testing the conditioned set after 48 hours. The ratio of Marshall stability betweenthe conditioned and the control was defined as the residual Marshall stability.
– Bending tests were carried out on three specimens, each one being 50 mmwide, 50 mm high and 300 mm long. The strain at failure was determined at 20°C,and the stiffness was measured at -10°C at the loading rate of 10mm/min(1.2×10-3 /s of strain rate at the bottom of the specimen).
– To evaluate the ability of RAC to resist ravelling, ravelling tests at -10°C werecarried out. Specimens of 150 mm wide, 50 mm thick and 400 mm long used werefixed under a non-contact rotating wheel. During the test, steel chains mounted on
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
06:
39 0
9 O
ctob
er 2
014
366 Road Materials and Pavement Design. Volume 10 – No. 2/2009
this wheel abraded the surface of the specimen as the wheel moved back and forth atthe speed of 200 cycles per minute. After 1.5 hours, the abraded area was recordedto indicate the ravelling resistance.
4. Results and discussion
4.1. Recovered asphalt binder properties
The basic properties of asphalt binder extracted from eight RAC are illustrated inTable 3. It can be seen that similar penetration, softening point and density are foundin asphalt binders recovered from RAC at different recycling rates whether it usesstraight or modified asphalt binder. This is mainly attributed to the recycling effectby the rejuvenating agent. On the contrary, ductility decreases with the increase ofrecycling rate, more significantly in asphalt binders recovered from MRAC. So theductility results indicate that asphalt binders recovered from RAA are in fact neverrestored to the same level as new straight or modified asphalt by recycling.However, in the case of SRAC, if produced with an appropriate recycling rate (40%or 70%), a satisfactory fatigue performance can be expected because the ductility ofthe binders from the two SRAC is just slightly lower than that of new asphalt.
Table 3. Properties of recovered asphalt binder
Asphalt Recyclingrate (%)
Penetration(1/10mm)
Softeningpoint (oC)
Ductility(cm)
Density(g/cm3)
0(new) 58 50.5 56 1.044
40 54 51.5 49 1.049
70 56 50.0 45 1.058Straight
100 56 53.0 34 1.056
0(new) 52 69.5 52 1.047
40 53 64.5 15 1.057
70 51 59.5 9 1.057Modified
100 52 55.5 4 1.058
4.2. Rutting resistance
Figure 3 presents the dynamic stability of RAC at different recycling rates, as aresult of wheel tracking tests. A first observation is that recycled asphalt concrete(RAC) exhibited better resistance to rutting than new asphalt concrete (recyclingrate of 0%) regardless of whether the asphalt binder is straight or modified. A higher
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
06:
39 0
9 O
ctob
er 2
014
Effect of Recycling Rate and Asphalt Binder on RAC 367
recycling rate leads to an extreme increase in DS for both two RAC. At the samerecycling rate, e.g., 70% or less, MRAC shows greater DS than SRAC. It can bepostulated that the positive impact of recycling rate on the rutting performances ismainly due to the increasing amount of RAA in recycled asphalt concrete, whichprovides stiffer asphalt binders and therefore higher resistance to rutting.
0% 40% 70% 100%0
200
400
600
800
Dyn
amic
stab
ility
(cyc
le/m
m)
Recycling rate
SRAC MRAC
Control line
Figure 3. Results of wheel tracking test
4.3. Moisture susceptibility
The results of residual Marshall stability (see Figure 4) show that adding RAA inRAC decreases the resistance of both SRAC and MRAC to moisture compared withnew asphalt concrete (recycling rate of 0%). However, compared with the controlrecycled asphalt concrete, both SRAC and MRAC with the recycling rate over 40%show comparable residual stability. It is principally because using hydrated lime asmineral filler can reduce the water sensitivity. The above analysis indicates thatstripping by moisture is not an issue for RAC at a higher recycling rate.
0% 40% 70% 100%0
25
50
75
100
125
Res
idua
l Mar
shal
l sta
bilit
y (%
)
Recycling rate
SRAC MRAC Control line
Figure 4. Results of residual Marshall stability
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
06:
39 0
9 O
ctob
er 2
014
368 Road Materials and Pavement Design. Volume 10 – No. 2/2009
4.4. Stiffness at low temperature
Low stiffness is generally desirable to achieve better low temperature properties.Figure 5 shows the results of stiffness tests at -10°C. It can be seen that both SRACand MRAC at the recycling rate of 40% or more exhibit obviously greater stiffnessthan new asphalt concrete, respectively (except at the recycling rate of 100% in thecase of MRAC) and in turn more susceptible to low temperature cracking. Again, itcan be explained by the fact that the addition of RAA results in stiffer asphalt binderand consequently the reduction of resistance of RAC to thermal cracking. Apartfrom this exception (possibly due to testing errors), SRAC gives a lower stiffnessthan MRAC when the recycling rate is same.
0% 40% 70% 100%0
60
120
180
240
300
Stiff
ness
(MPa
)
Recycling rate
SRAC MRAC Control line
Figure 5. Results of stiffness tests at -10° C
4.5. Fatigue performance
The strain at failure during a bending strength test is used to indirectly evaluatethe fatigue performance of RAC. Higher strain at failure is interpreted to indicate agiven asphalt concrete can tolerate higher strains before failing under tensileloading. Asphalt concrete with high strain at failure at the intermediate temperaturestends to exhibit a longer fatigue life. This is logically accepted for the purpose ofqualitative evaluation. The results shown in Figure 6 are obtained at 20°C.
The same phenomenon is observed with SRAC and MRAC: a higher recyclingrate always corresponds to a lower strain at failure and therefore to a short fatiguelife. This trend is generally reasonable based on the fact that a higher percentage ofRAA makes the RAC more brittle and its resistance to fatigue could be potentiallycompromised. Compared with the control RAC, SRAC at the recycling rate of 70%shows slightly lower strain at failure. MRAC at the recycling rate of 70% and 100%and SRAC at 100% give significantly lower value.
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
06:
39 0
9 O
ctob
er 2
014
Effect of Recycling Rate and Asphalt Binder on RAC 369
0% 40% 70% 100%0
5
10
15
20
25
Stra
in a
t fai
lure
(10-3
)
Recycling rate
SRAC MRAC
Control line
Figure 6. Results of strain at failure at 20° C
4.6. Resistance to ravelling
Figure 7 shows that when increasing the recycling rate, the ravelling of SRACspecimen firstly decreases and then slightly increases after 70% recycling rate, whilea monotonic increase of ravelling is observed in MRAC specimen. Therefore, it ispossible to design a satisfactory RAC when using straight asphalt considering that itprovides a higher ravelling resistance (lower abrasion surfaces) than the new straightasphalt concrete, even up to 100% recycling rate. MRAC can still be properly used(for instances in surface courses) with the recycling rates of 70% and 100% as itsresistance to ravelling equals the one of the control RAC.
0% 40% 70% 100%0.0
0.1
0.2
0.3
0.4
0.5
Abr
asio
n (c
m2 )
Recycling rate
SRAC MRACControl line
Figure 7. Results of ravelling test at -10° C
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
06:
39 0
9 O
ctob
er 2
014
370 Road Materials and Pavement Design. Volume 10 – No. 2/2009
5. Concluding remarks
This study investigated the influence of recycling rate and asphalt binder on theperformance of RAC through a series of laboratory tests. The obtained conclusionscan provide an experimental basis for future airport pavement rehabilitation.
– Resistance to rutting of both SRAC and MRAC increases with the increase ofrecycling rate, while the opposite trend is found in low temperature properties(increase of stiffness) and fatigue performance.
– Increasing the recycling rate to 70% is feasible in the case of SRAC judgingfrom its comparable and even superior performance to the control RAC (SRAC at40% recycling rate) in terms of resistance to rutting, ravelling, moisture strippingand thermal cracking. It seems possible to use it in surface courses devoted to airportsections where fatigue processes are not prevalent.
– The routinely used modified asphalt (modified П) does not exhibit superiorityfor producing RAC compared with straight asphalt except in rutting resistance. If weintend to further increase the recycling rate as high as 100% for MRAC, in-depthresearch is needed to exploit a new modified asphalt in order to improve its fatigueresistance and low temperature performance.
6. Bibliography
ASTM, Annual Book of ASTM Standards, American Society for Testing and Materials, Vol.4.03, Philadelphia, PA, 1997.
Civil Aviation Bureau, Ministry of Land, Infrastructure and Transportation (MLIT),Guideline for Common Civil Airport works, Part 2, 2004, p. 26-33 (In Japanese).
Hachiya Y. and Hao P.W., “Utilization of waste asphalt concrete as cement–treated bases forairport pavements”, Road Materials and Pavement Design, Vol. 7, No. 2, 2006, p. 247-260.
Japan Road Association (JRA), Manual for Test Method of Pavements, 2007, (in Japanese).
Kandhal P.S., Rao S.S., Watson D.E. and Young B., “Performance of recycled hot mixasphalt mixtures”, NCAT Report No. 95-1, National Center for Asphalt Technology,1995.
Oliver J., “The influence of the binder in RAP on recycled asphalt properties”, RoadMaterials and Pavement Design, Vol. 2, No. 3, 2001, p. 311-325.
Pereira P.A.A., Oliveira J.R.M., Picado-Santos L.G., “Mechanical characterization of hot mixrecycled materials”, The International Journal of Pavement Engineering, Vol. 5, No. 4,2004, p. 211-220.
Sullivan H., “Pavement recycling executive summary and report”, No. FHWA-SA-95-060,Federal Highway Administration, 1996, p. 15-18.
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
06:
39 0
9 O
ctob
er 2
014
Effect of Recycling Rate and Asphalt Binder on RAC 371
Shen J., Amirkhanian S. and Tang B, “Effects of rejuvenator on performance-based propertiesof rejuvenated asphalt binder and mixtures”, Construction and Building Materials, Vol.21, No. 5, 2007, p. 958-964.
Takahashi O. and Hachiya Y., “A study on the characteristics of recycled asphalt mixtureusing different kinds of recycling additives”, JSCE Journal of Pavement Engineering,Vol. 5, 2000, p. 23-30.
William W., Hicks R.G. and Escobar S.J., “Evaluation of a unified design for asphaltrecycling by means of dynamic and fatigue testing”, Journal of the Association of AsphaltPaving Technologists, Vol. 50, 1981, p. 1-31.
Received: 4 March 2008Accepted: 6 October 2008
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
06:
39 0
9 O
ctob
er 2
014
