Materials and Structures DOI 10.1617/s11527-015-0602-x

ORIGINAL ARTICLE

Green pavements: reuse of plastic waste in asphalt mixtures Silvia Angelone • Marina Cauhape´ Casaux Manuel Borghi • Fernando O. Martinez

•

Received: 1 November 2014 / Accepted: 18 March 2015 Ó RILEM 2015

Abstract Nowadays, the disposal of plastic waste is an issue of major concern worldwide because of its considerable volume and growth. An option to tackle this problem is to recycle this waste. This alternative reduces the quantity of net discards, conserves both material and energy and provides a comparatively simple way to make a substantial reduction in the overall volume of solid waste. The purpose of this study is to investigate an environmentally friendly approach about the influence of recycling different percentages of urban and rural plastic waste by adding them in a dry process on an asphalt mixture, through a comparative laboratory study. The resulting mixtures are analyzed considering their volumetric parameters and the values from diverse laboratory mechanical tests. The performance tests include, Marshall stability, Marshall quotient, indirect tensile strength, fracture energy, resilient modulus, permanent deformation and creep compliance, which were carried out

S. Angelone  M. Cauhape´ Casaux (&)  M. Borghi  F. O. Martinez Road Laboratory, National University of Rosario, Riobamba 245 bis, S2000EKE Rosario, Argentina e-mail: [email protected] S. Angelone e-mail: [email protected] M. Borghi e-mail: [email protected] F. O. Martinez e-mail: [email protected]

on unmodified and modified hot asphalt mixtures. The obtained results are presented and discussed in this paper showing that the reuse of recycled plastics in asphalt mixtures is a viable alternative that contributes to the reduction of plastic wastes as well as the protection of the environment. Keywords Green pavement  Sustainability  Recycled plastics  Environment

1 Introduction Nowadays, environmental care and sustainability have become main statements in any project. Particularly, to find a solution of the problem of where and how to dispose the large volume of waste produced every day is one of the issues of most concern worldwide, even more considering that the volume of waste produced is increasing more and more. In order to tackle this environmental issue, different recycling techniques and many research studies about the incorporation of plastics waste into bitumen and asphalt mixtures have been developed. Hinislioglua and Agar [7] investigated the possibility of modified bituminous binders using various plastic wastes containing high density polyethylene (HDPE) in different percentages and use them in an asphalt concrete. Binders used in hot mix asphalt (HMA) were prepared by mixing the HDPE in 4, 6 and

Materials and Structures

8 % (by weight of optimum bitumen content) and AC20 at temperatures of 145, 155 and 165 °C and 5, 15 and 30 min of mixing time. They concluded that the mix with 4 % HDPE, mixed at 165 °C for 30 min has the highest stability and the smallest flow, and so the highest Marshall quotient (MQ). Moreover, this mix was also highly resistant to permanent deformation (rutting). Hence, they obtained pavements more resistant to permanent deformation as well as a partial solution to solid waste disposal problem. Attaelmanan et al. [1] studied the viability of using HDPE as a modifier for asphalt paving materials. They modified 80/100 paving grade asphalt by adding different ratios of HDPE by weight of asphalt. The standard binder testing indicated that the penetration values and the temperature susceptibility decrease and the softening point increases as the HDPE’s content increases. Tests results of asphalt mixtures showed that HDPE-modified asphalt mixtures performances were better than conventional mixtures with greater stability, MQ, tensile strength ratios (TSRs) and resilient modulus values at high temperatures with smaller strain values. Finally, they concluded that flexible pavements with higher performance and durability and lower costs than conventional mixtures can be obtained with 5 % HDPE. Fuentes-Aude´n et al. [6] conducted a study about the influence of polymer concentration on a recycled polyethylene (RPE) modified bitumen. The base asphalt used for these tests was a 150/200 penetration grade bitumen. In order to analyze the evolution of microstructure and thermal and rheological behavior of the blends, several tests were carried out including optical microscopy, modulated differential scanning calorimetry (MDSC) measurements, steady and oscillatory shear tests and dynamic mechanical thermal analysis (DMTA), respectively. Tests indicated that the addition of RPE to bitumen results in a remarkable modification of its rheological response and enhances some mechanical characteristics such as higher resistance to permanent deformation or rutting, and also to thermal and fatigue cracking. They concluded that low polymer content blends (up to 5 % RPE by weight) could be potentially used for road paving applications; whereas high polymer content blends (5–15 % RPE by weight) could be suitable for roofing membranes in building construction. In Spain, Vin˜as Sanchez [20] presented the improvement of compatibility and stability on

polyethylene modified bitumen by means of different compatibilizers. The analysis indicated that a stable binder on storage could be obtained by adding a stabilizer agent which percentage of adding and type would be according to the asphalt base used. In Colombia, the incorporation of plastic waste and tire rubber to asphalt binder and asphalt mixes has been studied by Reyes et al. [18, 19] with positives results. In Argentina, in the Institute of Applied Mechanics and Structures—Road Laboratory, similar researches on modifying asphalts and mixtures with materials such as fly ash [11] and rubber have been conducted [12]. Regarding environmental issues, authors like Spray et al. [22] have made studies about sustainability and life cycle cost (LCC) of pavements, (life cycle assessment, LCA). Generally, they define LCA as the environmental aspects and potential environmental impacts, (e.g. use of resources and the environmental consequences of releases) throughout a product’s life cycle from raw material acquisition through production, use, end-of-life treatment, recycling and final disposal. As a subset, carbon footprint is often used to estimate global warming potential of greenhouse gas (GHG) emissions of product life cycles. Molenaar [16] proposes the possibility of reducing carbon footprint on road construction by using recycled materials from asphalt pavements and demolition waste and durable pavements.

2 Materials and test methods 2.1 Polyethylene from silo bags Silo bags are big plastic bags for low cost on-farm storage of grains, which are approximately 60–80 m long and 3–4 m in diameter as shown in Fig. 1. These plastic bags are made from a membrane combining three very thin layers of a low-density polyethylene (LDPE), a HDPE and a UV resistant layer containing titanium dioxide. After several uses and due to the damage produced by the weather, loading equipment rodents and birds, silo bags must be replaced and then large amounts of polyethylene are available for recycling. The recycling process is made in a recycling company where first the polyethylene is washed and

Materials and Structures

Fig. 1 Silo bags used in Argentina

dried. Then, two types of RPE are produced: a chopped RPE in scales or flakes with a maximum size between 6 and 10 mm as shown in Fig. 2a and pellets with sizes between 2 and 5 mm as shown in Fig. 2b. Both types of RPE were considered in this study and were incorporated in a dry process during the mixture preparation as is described later. 2.2 Recycled polypropylene (PP) Polypropylene is present in a wide range of products like bottle caps, bags, appliance parts, toys, medicine and food containers, among others. The recycling process takes place in special processing plants and the final product may have different shapes. This research uses PP recycled in chips, as seen on Fig. 3. 2.3 Asphalt mixture In this study eleven different types of asphalt mixes for base courses are used. In order to make a comparative study on adding recycled plastics in asphalt mixtures, a control mixture identified as CA30 is considered. This mixture consists of a dense asphalt concrete for base layers with conventional asphalt cement (CA30), and it is designed according to the Marshall mix design procedure. The resulting optimum asphalt content is 5 % by weight. Granitic aggregates and hydrated lime are used according to the requirements established in Argentina for this kind of asphalt mixtures. The resulting gradation is shown in Fig. 4. Also, another mixture, with the same characteristics of CA30, is defined; the only difference is that the conventional

Fig. 2 Types of SB: a chopped; b pellets

bitumen is replaced by SBS polymer modified bitumen commercially produced in Argentina. This mixture is identified as AM3. Both asphalt mixtures will serve as control parameters. 2.4 Asphalt mixtures with recycled plastics In order to incorporate the plastics to the asphalt mix it is necessary to establish a dosage criterion and a mixing method. 2.4.1 Dosage criterion Three different percentages of various recycled plastics are incorporated to the base mix CA30: 2, 4 and 6 % by the total weight of the mixture. The different

Materials and Structures

Fig. 4 Aggregate gradation for the asphalt mixtures

Fig. 3 PP chips

plastics used are silo bag flakes of polyethylene (SBF), silo bag pellets of polyethylene (SBP) and polypropylene chips (PPC). The asphalt content for all the mixes was 5 % by weight. It was determined by Marshall mix design method applied to the base mix. SBF mixtures They are prepared adding each percentage of plastic by the total weight of the mixture, to the control mix, without any aggregates replacement. These mixtures are identified as 2, 4 and 6 % SBF. SBP mixtures In these cases, pellets were added replacing the same amount by weight of the fraction of aggregates passing the 4.8 mm sieve and retained in the 2.4 mm sieve. These mixtures are identified as 2, 4 and 6 % SBP. PPC mixtures They are prepared similarly to the SBP mixtures with the difference that the fraction of aggregates replaced in the same amount by weight is that passing the 9.5 mm sieve and retained in the 0.075 mm sieve. These mixtures are identified as 2, 4 and 6 % PPC or PP. 2.4.2 Mixing method steps In order to incorporate plastics into de mixture a dry blending method is used: First, asphalt and aggregates are heated to each mixing characteristic temperature. This mixing temperature is based on the viscosity of the asphalt.

Second, aggregates and filler are mixed with plastics. Third, the required amount of bitumen is added and mixed. The mixture in a loose condition is placed in an oven at 160 °C during 1 h covered with an aluminium foil. Finally, the mixture is taken off the oven, mixed again and compacted. This procedure was considered in order to simulate the period of time that the asphalt mixture is carried from the production plant to the construction location at high temperature. To perform the laboratory tests, specific asphalt mixture samples are made. Most specimens are prepared using the Marshall Compactor. The standard number of 75 blows per face was used. However, an additional set of samples compacted with 25 blows per face was prepared in order to obtain a higher air void content for the moisture susceptibility tests. Specimens for wheel tracking test (WTT) are made in a special mould with an electric compactor hammer. 2.4.3 Volumetric properties The volumetric properties of all mixes studied are summarised in Table 1. The asphalt mixtures meet the volumetric requirements used in Argentina for this kind of materials for base courses of asphalt pavements except those made with PP. The nine mixtures containing plastics show a lower bulk specific gravity compared to the control mix.

Materials and Structures Table 1 Average volumetric properties of the mixtures CA30

AM3

2 % SBF

4 % SBF

6 % SBF

2 % SBP

4 % SBP

6 % SBP

2 % PP

4 % PP

6 % PP

Gmm (kg/m3)

2.591

2.580

2.502

2.412

2.333

2.472

2.431

2.333

2.496

2.397

2.298

Dm (kg/m3)

2.482

2.491

2.364

2.281

2.217

2.391

2.306

2.242

2.346

2.220

2.126

Va (%) VMA (%)

4.2 16.4

3.6 15.8

5.5 17.1

5.4 16.6

VFA (%)

74.3

77.4

67.8

67.3

5.0 15.8

3.3 15.0

5.1 16.4

68.6

78.1

68.8

3

3.9 14.9

6.0 17.5

7.4 18.3

7.5 17.9

73.7

65.7

59.5

58.3

3

Gmm maximum specific gravity of the mixture (kg/m ), Dm bulk specific gravity (kg/m ), Va air voids content in the total mix (%), VMA voids in the mineral aggregates (%), VFA voids filled with asphalt (%)

Fig. 5 Marshall stability

Fig. 6 Marshall flow

3 Results and discussion

3.1.1 Marshall test

3.1 Engineering properties of asphalt mixtures

Marshall tests were carried out according to EN12697-34 [3]. The obtained average results for the Marshall stability and flow are presented in Figs. 5 and 6. Also, the MQ calculated as the ratio of the stability over the flow is presented in Fig. 7. As seen in Fig. 5, mixtures containing SBF and SBP have greater values of Stability than the base mixture CA30 and AM3 mixture. They also show

The engineering properties of the considered asphalt mixtures are comparatively evaluated with different laboratory mechanical tests including Marshall, dynamic modulus, moisture susceptibility, indirect tensile strength (ITS), creep compliance and WTTs as it is described in the following paragraphs.

Materials and Structures Fig. 7 Marshal quotient MQ

Fig. 8 Indirect tensile strength test

Fig. 9 Fracture energy

Table 2 Average TSR values CA30

AM3

2% SBF

4% SBF

6% SBF

2% SBP

4% SBP

6% SBP

2% PPC

4% PPC

6% PPC

ITS dry group (MPa)

0.89

0.71

1.03

0.81

0.90

0.90

0.84

0.78

0.71

0.64

0.49

ITS wet group (MPa)

0.86

0.60

0.94

0.80

0.75

0.74

0.82

0.64

0.63

0.53

0.42

TSR (%)

97

84

92

99

83

83

98

82

88

83

85

Materials and Structures Table 3 Permanent deformation values CA30

AM3

2% SBF

4% SBF

6% SBF

2% SBP

4% SBP

6% SBP

2% PPC

4% PPC

6% PPC

d5000 (mm)

7.7

2.7

0.6

0.3

0.4

1.9

0.6

1.4

1.3

0.9

0.8

d10000 (mm)

10.0

3.0

0.9

0.6

0.5

2.2

0.7

1.5

1.4

1.0

0.9

PRD10000 (%)

19.6

8.2

1.4

0.8

0.9

4.1

0.6

2.7

2.7

1.8

1.7

higher values of this parameter with higher percentages of addition. On the contrary, PPC mixtures seem to have the opposite behavior, the values of stabilities decreased as the content of plastic increased. When analyzing Fig. 6 it is observed that Marshall flow has the same tendency as described for the Stability values for all the mixtures. The MQ is of the similar order of magnitude as in the CA30 mixture for SBF and SBP. However, PPC mixtures have lower MQ, approximately 40 % of the CA30 value. MQ can be used as a measure of the material’s resistance to permanent deformation in service, high MQ values indicate a mix with high stiffness, which has a greater ability to spread the applied load and resist creep deformation [10]. 3.1.2 Indirect tensile test Indirect tensile strength tests are carried out following a procedure quite similar to the one described in EN12697-23 [2], at a temperature of 10 °C and at a constant rate of deformation of 6.35 mm/min. This test defines the tensile characteristics of the asphalt which can be further related to the cracking properties of the pavement. To compute the ITS, the following equation is used: ITS ¼ 2 Pmax =ðp  d  tÞ

ð1Þ

where ITS is the indirect tensile strength (KN/mm2), Pmax is the maximum applied load (KN), t is the thickness of the specimen (mm), d is the diameter of the specimen (mm). Also the fracture energy (FE), calculated from the area under the load versus vertical deformation curve, is measured for the eleven mixtures [23]. It has been reported that the FE is a good indicator of the fatigue and thermal cracking resistance of asphalt mixtures. The increase in this parameter

represents a potential enhancement of the asphalt fatigue life. Moreover, lower thermal cracking should be expected as the FE is increased [8, 9]. The results of these tests are shown in Figs. 8 and 9. It is observed that compared to the control mixtures, SBF and PP ones have lower tensile strength and SBP ones have similar values. FE is higher for SBF and SBP mixtures and lower for PP ones than the control mixtures. 3.1.3 Moisture susceptibility test Moisture susceptibility tests were carried out following a procedure very similar as it is described in EN 12697-12 [2]. Samples compacted with 25 blows per face were used in order to obtain an average air void content of 7 %, as minimum for all the mixtures. Two Marshall specimens for the dry group and two for the wet group were prepared. A TSR of wet group to dry group was computed from the ITS test results at 25 °C and at a constant rate of vertical deformation of 50 mm/min. The higher the TSR value is, the weaker the influence of the water soaking condition is. Normal specification used in Argentina requires a TSR value of 80 % or more. According to this all mixtures meet this requirement. Table 2 presents TSR values for all the plastic modified mixtures. 3.1.4 Dynamic modulus test The dynamic modulus E* is the main input material property of asphalt mixtures for modern mechanisticempirical flexible pavements design methods. It determines the distribution of stress and strains into the pavement structure and also, it can be correlated with the rutting and fatigue cracking behaviour of the bituminous layers. [17]. The dynamic modulus E* was experimentally measured with the indirect tension (IDT) mode with

Materials and Structures

Fig. 11 Average creep compliance results at 10 °C: a SBF; b SBP; c PPC

Fig. 10 Dynamic modulus, E: a SBF; b SBP; c PPC

sinusoidal (haversine) loadings [13, 14]. Based on results obtained previously [15] it could be concluded that the indirect tensile test with sinusoidal loads (haversine) is able to produce reliable dynamic

modulus values and in excellent agreement with those obtained in uniaxial compression at the same frequencies and temperatures. Testing is performed using a servo-pneumatic machine, developed at the Road Laboratory of the University of Rosario, using a 5000 N load cell, which is capable of applying loads over a range of frequencies ranging from 0.01 to 5 Hz. The data acquisition system was also developed at the

Materials and Structures Table 4 Compliance parameters CA30

AM3

2% SBF

4% SBF

6% SBF

2% SBP

4% SBP

6% SBP

2% PPC

4% PPC

6% PPC

D1 (1/ MPa)

0.00023

0.00029

0.00015

0.00020

0.00020

0.00019

0.00018

0.00024

0.00018

0.00023

0.00022

m

0.415

0.313

0.313

0.269

0.287

0.335

0.296

0.230

0.306

0.295

0.359

Road Laboratory of the University of Rosario which is capable to measure and record data from three channels simultaneously: two for horizontal displacements and one for the load cell. In this study, five temperatures (0, 10, 20, 30 and 40 °C) and seven frequencies (5, 4, 2, 1, 0.5, 0.25 and 0.1 Hz) are used. Based on the frequency-temperature superposition principle, the measured data is used to construct average master curves showing the variation of the dynamic modulus E* as a function of the temperature for a reference frequency of 10 Hz related to a loading time equal to 0.016 s. This loading time was arbitrarily selected because is approximately equal to the loading frequency of trucks moving at 80 km/h on conventional asphalt pavements [20]. The compared dynamic modulus E* master curves for the nine mixtures are presented on three graphics on Fig. 10a (SBF), b (SBP) and c (PPC) and for comparison purposes the E* master curves for the CA30 and AM3 mixtures are also presented. The mixtures SBF and SBP show a reduced thermal susceptibility with smaller E* values at low temperatures and higher E* values at high temperatures. This behaviour is very promising against fatigue failure at low temperatures and rutting at high temperatures. The mixture PPC shows approximately the same E* values than the control mixtures for the 2 and 4 % of added PP. 3.1.5 Permanent deformation test Worldwide, there are numerous test methods and mixture response parameters to characterize rutting. This work evaluates the resistance against rutting by means of the WTT according to the EN-12697-22 [4] procedure using a small-size device in air (procedure B). Two specimens of each mixture are tested and the obtained results are resumed in Table 3, where di is the rut depth after i cycles and PRD10000 is the

proportional rut depth for the material under test at 10000 cycles. All mixtures with plastics show better permanent deformation behavior than the control mixtures. In many cases the mixtures with plastics show PRD 5 to 10 times smaller than the PRD values for the control mixtures. 3.1.6 Creep compliance test The creep compliance D(t) is defined as the relationship between the time-dependant strains divided by the constant axial stress for a viscoelastic material subjected to a constant loading. Creep compliances were determined at 10 °C with the IDT mode with constant loads with the same experimental equipment used for the dynamic modulus determination as was presented in a previous paper [11]. The creep compliance D(t) as a function of time was calculated as:   DhðtÞ  h 1 DðtÞ ¼ ð2Þ P0 K1 þ l  K2 where Dh(t) is the resulting average horizontal deformation at time t, h is the thickness of specimen, P0 is the constant applied load, K1, K2 is the coefficients depending on the specimen diameter and gauge length, l is the Poisson’s ratio. Figure 11 shows the average creep compliance results for the eleven mixtures considered in this paper at 10 °C. Smaller creep compliance implies stiffer mixture; the creep compliances at 300 s were approximately three times smaller for the mixtures containing RP than the CA30 mix. The creep compliance D(t) as a function of time was modelled according to: DðtÞ ¼ D1  tm

ð3Þ

where D1 is the creep compliance at time 1 s, m is the rate of change in compliance.

Materials and Structures

Table 4 shows the resulting compliance parameters D1 and m for the mixtures. The creep compliance could be considered the strain as a function of time for an applied stress equal to the unity. In all cases the mixtures prepared with added plastics are stiffer than the control mixtures with smaller D1 and m values.

3.

4.

5.

4 Conclusions Based on the test results and calculations presented in this paper, the following conclusions can be drawn: Generally the addition of RPE from silo bags improves the mixture performance over the control mixture. Flake form was slightly better than pellet ones. Regarding the addition of polypropylene pellets, the results are positive, the properties decrease as adding content increases and the values of the parameters analyzed showed a mixture of lower quality than the control one. Preliminary results show the possibility of dispose these residues in pavements. Based on the results, it can be considered that the mixture with an addition of 2 % SBF has better performance. Regarding production costs of mixtures employing SBF achieves a significant reduction. In conclusion, an asphalt mixture with addition of recycled plastics with improved physical and mechanical characteristics could be achieved in the laboratory as well as provide a sustainable solution at the disposal of such waste, meeting the main objective raised. Recommendations for future research are: expand and continue the analysis of the addition of recycled plastic mixtures based on the resulting optimum (addition of 2 % by weight of SBF), evaluate the mixtures in situ and analyze the LCC.

6.

7.

8.

9.

10.

11.

12.

13.

14.

15.

16.

References 1. Attaelmanan M, Feng CP, Al-Haididy AI (2011) Laboratory evaluation of HMA with high density polyethylene as a modifier. Constr Build Mater 25(5):2764–2770 2. European Committee for Standardization (2008) Bituminous mixtures—test methods for hot mix asphalt—part 12:

17.

18.

Determination of the water sensitivity of bituminous specimens, EN 12697-12:2008 European Committee for Standardization (2003) Bituminous mixtures—test methods for hot mix asphalt—part 22: Wheel tracking EN 12697-22:2003 European Committee for Standardization (2003) Bituminous mixtures—test methods for hot mix asphalt—part 23: Determination of the indirect tensile strength of bituminous specimens, EN 12697-23:2003 European Committee for Standardization (2012) Bituminous mixtures—test methods for hot mix asphalt—part 34: Marshall test, EN 12697-34:2012 Fuentes-Aude´n C, Sandoval JA, Jerez A, Navarro FJ, Martı´nez-Boza FJ, Partal P, Gallegos C (2008) Evaluation of thermal and mechanical properties of recycled polyethylene modified bitumen. Polym Test 27:1005–1012 Hinislioglua S, Agar E (2004) Use of waste high density polyethylene as bitumen modifier in asphalt concrete mix’’. Mater Lett 58:267–271 Kaloush KE, Biligiri KP, Zeiada W, Rodezno M, Reed J (2010) Evaluation of fiber-reinforced asphalt mixtures using advanced material characterization tests. J Test Eval 38(4):1 ASTM International Lee SJ, Rust JP, Hamouda H, Kim YR, Borden RH (2005) Fatigue cracking resistance of fiber-reinforced asphalt concrete. Text Res J 75(2):123–128 Malkoc G, Topal A, Sengoz B (2012) Improving mechanical properties of hot-mixed asphalt using plastic waste (polyethylene terephthalate). In: 5th Eurasphalt & Eurobitume Congress, Istanbul Martı´nez F, Andreoni R, Poncino H (1997) Utilizacio´n de cenizas volantes como filler de mezclas asfa´lticas, IX Congreso Ibero Latinoamericano del Asfalto, Paraguay Martı´nez F, Angelone S, Andreoni R, Martinuzzi R (2007) Caracterizacio´n de mezclas asfa´lticas modificadas con adicio´n de caucho reciclado de neuma´ticos descartados. XIV Congreso Ibero Latinoamericano del Asfalto, Cuba Martinez F, Angelone S (2009) The estimation of the dynamic modulus of asphalt mixtures from creep test results. In: Proceedings of the 7th international RILEM symposium on advanced testing and characterization of bituminous materials (ATCBM09), Rhodes, Greece Martinez F, Angelone S (2010) The estimation of the dynamic modulus of asphalt mixtures using artificial neural networks. In: Proceedings of the 11th international conference on asphalt pavements, Nagoya, Japan Martinez F, Angelone S (2011) Validacio´n del modulo dina´mico de mezclas asfa´lticas usando el ensayo de traccio´n indirecta. In: Proceedings of the XVI Congreso Ibero Latinoamericano del Asfalto, Rio de Janeiro, Brasil Molenaar A (2012) Durability, a prerequisite for sustainable pavements. In: 5th Eurasphalt & Eurobitume Congress, Istanbul National Research Council (2004) Mechanistic-empirical design of new and rehabilitated pavement structures. Draft report, NCHRP 1-37a, Washington DC, USA Reyes Lizcano F, Figueroa Infante A (2008) Usos de desechos pla´sticos en mezclas asfa´lticas. Coleccio´n libros de investigacio´n, Pontificia Universidad Javerian, Sı´ntesis de la investigacio´n Colombiana, Colombia. ISBN 978-958716-136-6

Materials and Structures 19. Reyes F, Rondo´n H, Moreno L (2009) Caracterizacio´n dina´mica de una mezcla densa en caliente modificada con un desecho de policloruro de vinilo (PVC). XV Congreso Ibero Latinoamericano del Asfalto, November, Portugal 20. Sanchez Vin˜as MT, Pa´ez A, Sa´nchez Caba J (2012) Improvement of compatibility and stability on polyethylenemodified bitumen by use of an aromatic extract as compatibilizer. In: 5th Eurasphalt & Eurobitume Congress, June, Istanbul

21. Shell International Petroleum Company Ltd (1978) Shell pavement design manual 22. Spray A, Huang Y, Parry T (2012) Importance of some aspects of methodology in pavement life cycle assessment. In: 5th Eurasphalt & Eurobitume Congress, June, Istanbul 23. Witczak M, Kaloush K, Pellinen T, El-Basyouny M, Von Quintus H (2002) Simple performance test for superpave mix design. NCHRP report 465, National Cooperative Highway Research Program. National Academy Press, Washington