the effect of polyethylene terephthalate particle size and ... · thermosetting materials....

1Progress in Rubber, Plastics and Recycling Technology, Vol. 31, No. 1, 2015

The Effect of Polyethylene Terephthalate Particle Size and Concentration on the Properties of Asphalt and Bitumen as an Additive

©Smithers Information Ltd, 2015


Chris Maharaj1*, Rean Maharaj2, and Julian Maynard1

1Department of Mechanical and Manufacturing Engineering, The University of the West Indies, St. Augustine Campus, St. Augustine, Trinidad

2Process Engineering, The University of Trinidad and Tobago, Point Lisas Campus, Brechin Castle, Trinidad

Received: 8 December 2013, Accepted: 11 March 2014

SuMMARy

Research is extremely limited on the combination of polymeric materials, such as discarded polyethylene terephthalate (PET), with asphaltic materials indigenous to Trinidad and Tobago. This paper examines the effect of both concentration and particle size of added PET on the rheological properties of Trinidad Lake Asphalt (TLA) and Trinidad Petroleum Bitumen (TPB). The PET particle size ranges under study were >0.30 mm to 0.60 mm, >0.60 mm to 0.85 mm, and >0.85 mm to 1.18 mm. These particle sizes were added in concentrations by weight ranging from 2% to 8% PET for TPB and 2% to 4% PET for TLA.

Incorporating the waste polymeric material PET in TLA and TPB influenced the physical properties of the resulting blends. For TLA-PET blends, the largest particle size range produced values of complex shear moduli that were higher than pure TLA. The smallest particle size range had the opposite effect. The optimal concentration for fatigue cracking and rutting resistance occurred at 2% PET with the largest particle size range.

For TPB-PET blends, the peak value of complex shear modulus generally occurred at concentrations above pure TPB for all particle size ranges and temperatures tested. As the particle size range increased, these peak values occurred at lower concentrations of PET. The 2% concentration for the largest

* Corresponding author, Tel: 1 868 662 2002 ext. 84158, E-mail addresses: [email protected] (C. Maharaj), [email protected] (R. Maharaj), [email protected] (J. Maynard).

2 Progress in Rubber, Plastics and Recycling Technology, Vol. 31, No. 1, 2015

Chris Maharaj, Rean Maharaj, and Julian Maynard

particle size range provided the best fatigue cracking resistance, whereas the particle size range >0.60 mm to 0.85 mm produced the best rutting resistance.

This study demonstrated that incorporating waste PET as an additive in road paving mixtures could improve the overall quality of roads and also be a sustainable waste disposal option. Further research is recommended on the effect of PET particle size range and concentrations on TLA/TPB combinations commonly used in road paving applications along with accelerated weathering studies.

Keywords: Polyethylene terephthalate; Asphalt; Bitumen; Complex shear modulus; Phase angle; Fatigue cracking resistance; Rutting resistance; Recycling

IntRoDuctIon

Asphalt is a dark brown to black cementitious material. The predominant constituents are bitumens that occur in nature or are derived from petroleum processing [1]. Chaitan and Graterol [2] defined asphalt as various dark-coloured, solid bituminous substances, native in various areas of the earth and composed mainly of hydrocarbon mixtures. Bitumen as defined by Eurobitume [3] is an oil based, semi-solid hydrocarbon product which is produced by the removal of lighter fractions of petroleum products such as diesel, petrol, kerosene and liquid petroleum gas from heavy crude oil during the refining process. Trinidad Petroleum Bitumen (TPB) is obtained from the Petroleum Company of Trinidad and Tobago Limited.

The construction of roads or pavements is achieved with the use of either asphalt or bitumen (or both) added to mineral aggregate. The asphalt or bitumen is considered the binder in the mixture. These binders exhibit certain properties which result in the performance of the pavement. The performance is classified as the response of the pavement to traffic loading and elements in the environment such as rain and ultraviolet rays over a period of time. Trinidad Lake Asphalt (TLA) is a binder which was used in the first asphalt pavement in the United States more than one hundred years ago [4].

Plastics are generally classified into two categories; thermoplastic and thermosetting materials. Polyethylene terephthalate (PET) is a thermoplastic that is commonly utilized in the food and beverage industry for beverage bottles, water bottles, disposable dishes, and plastic containers [5]. Plastics are durable and degrade very slowly hence disposing them in landfills is an accumulation problem. Each year it is estimated that more than 500 million empty plastic bottles are placed in Trinidad landfills [6]. Plastic bottles and other plastic litter improperly disposed of accumulate in drains and precipitate flooding in certain areas around the country. Heaps of plastic litter are seen at sea when floodwaters subside [7].



To alleviate the environmental problems, as well as to improve the overall quality of roads, waste plastics can be incorporated as an additive in road paving mixtures. Benefits such as enhanced fatigue resistance, improved resistance to thermal stress cracking, decrease in temperature susceptibility and reduction of rutting (permanent deformation especially in the early life of the pavement) have been derived from the modification of asphalt and bitumen with polymer additives [8].

This paper investigates the influence of different concentrations of waste PET on the rheological properties of complex shear modulus (G*) and phase angle (δ) of TPB and TLA on different PET particle size ranges. The influence of waste PET on rutting and fatigue cracking resistance is also investigated.

LIteRAtuRe RevIew

Asphalt and bitumen with mineral aggregate are the materials used to construct many roads. The performance of these roads or pavements depends on the properties of the asphalt and the bitumen which are the sole deformable components in the mixture [9].

TLA is found in La Brea, Trinidad. This Pitch Lake has an approximate area of 35 hectares, a depth of 90 meters and an estimated ten million tonnes of the material [10]. Chaitan and Graterol [2] classify asphalt as a chemical emulsion of oil, clay and water. The asphalt is in the form of a brittle rock.

The refining of crude oil results in the by-product bitumen. Although bitumen occurs naturally in certain parts of the world, petroleum bitumen is most relied upon. It should be noted, that in North America the term asphalt means bitumen while in Europe the term asphalt refers to a mixture of bitumen and aggregate [10]. In this paper, the term asphalt refers to the naturally occurring substance found in pitch lakes while the term bitumen refers to the product obtained from the refining process of crude oil.

The increased use of bitumen in pavements, as opposed to naturally occurring asphalt, is due to the quantity of crude oil that is refined around the world, and the difficulty of introducing hardened bulk asphalt into manufacturing plants [4].

The properties of asphalt and bitumen can be evaluated through rheological analysis. The rheology of asphalt and bitumen can generally be characterized under two viscoelastic parameters, namely complex shear modulus and phase angle [11]. The complex shear modulus is denoted with the symbol G* and can be referred to as a material’s resistance to deformation irrespective of whether that deformation is recoverable (elastic) or non-recoverable (viscous) [12]. The phase angle is denoted by the symbol δ and is the lag between the



applied shear stress and the resulting shear strain [13]. Phase angle is used to describe the viscoelastic reaction of the material. Complex shear modulus and phase angle of asphalt and bitumen binders are measured using a Dynamic Shear Rheometer (DSR). The DRS is a device which has an upper and lower circular plate which is used to sandwich the binders for testing. The lower plate is fixed while the upper plate rotates at various frequencies to simulate traffic loads. This device uses software to perform calculations governed by Equations (1) and (2) [13].

τmax =2Tπr3

(1)

γmax =θrh

(2)

Where: τmax is the maximum applied stress, γmax is the maximum resultant strain, T is the maximum applied torque, r is the specimen radius (either 4 or 12.5 mm), θ is the deflection (rotation) angle (in radians), and h is the specimen height (either 1 or 2 mm).

The complex shear modulus (G*) is determined by Equation (3) [13].

G* = τmax

γmax (3)

The phase angle (δ) is the time lag between occurrence of τmax and γmax. Some of the distresses or major factors which result in failure of pavements are low temperature cracking, permanent deformation or rutting, fatigue cracking, and moisture susceptibility [14]. Fatigue failure or fatigue cracking is caused by repeated traffic load on the pavement, which results in successive tensile strain [14]. Fatigue cracking is a major concern later in the pavement’s life. In order to resist fatigue cracking, asphalt and bitumen binders should possess properties such as high ductility and low stiffness [13]. Low phase angle values indicate a more elastic response which is usually related to high stiffness and increased brittleness [11]. Rutting is a major concern early in the pavement’s life and is associated with permanent deformation under loading. Resistance to rutting is achieved when asphalt and bitumen binders display high stiffness [13].

The Strategic Highway Research Program made an important correlation between rheology measurements and traffic loading performance. The pavement is composed of viscoelastic binders and for every traffic load experienced, it is deformed. Some of this work is recovered by rebounding (elastic property) while some is dissipated in the form of permanent deformation and cracking. Therefore to minimize this deformation, the work dissipated per load cycle (Wc) must also be minimized. Wc at a constant stress, Wc1, is expressed in Equation (4) [15].



Wc1 = ps02 (1/G∗/sinδ) (4)

Where so is the stress applied during the load cycle. Therefore in order to minimize rutting deformation, G*/sinδ should be increased.

Wc2 is the work dissipated per load cycle at a constant strain and is expressed as shown in Equation (5) [15].

Wc2 = pe02 (G∗sinδ) (5)

Where eo is the strain during load cycle. Therefore in order to minimize fatigue cracking, G*sinδ should be minimized.

G*sin δ and G*/sinδ respectively can be directly related to fatigue cracking and rutting resistance. In order to maximize the rutting resistance parameter, high values of G* and low values of δ are required. Superpave specification [16] promotes a stiff but elastic structure to reduce rutting. To reduce the fatigue parameter, low values of G* and δ are required. The Superpave specification requires the use of elastic but compliant binders [16]. Rutting and fatigue cracking resistance may depend on the chemical composition and source of asphalt/bitumen, the particle size of crumb rubber as well its concentration and texture [17, 18].

Paving mixtures are expected to be of the highest quality to avoid some of the aforementioned distresses encountered in the pavements as vehicular traffic increases. One way to overcome these problems is through the use of additives. Waste PET as an additive can be a viable solution due to the abundance of the material. A study conducted by Ahmadinia et al. [5] on the addition of waste PET in stone mastic asphalt (SMA) indicated that the addition of polymer had a positive effect on the properties of the final mixture. This research involved the use of bitumen, which was heated at 160°C. Aggregate was added to the bitumen followed by incremental increases of PET in the percentages 0%, 2%, 4%, 6%, 8% and 10% by weight of bitumen. The samples were then evaluated using the resilient modulus test, wheel tracking test, drain down test and moisture susceptibility test. The particle sizes of PET used ranged from 0.425 mm to 1.18 mm. Results of the experiment conducted indicated a 16% increase in the resilient modulus value was achieved using 6% PET in the mixture as compared to the conventional mix. Also, the 4% PET mixture recorded a reduction in rut depth by 29% compared to the conventional mixture. The prevention of excessive down drain was achieved with an increase in PET content in the samples. Ahmadinia et al. [5] concluded that overall, the addition of waste PET to SMA improved the performance properties of the mixture and could satisfy standard requirements.



Research conducted by Moghaddam et al. [14] on the dynamic properties of SMA mixtures containing waste plastic bottles resulted in three main conclusions. The first was that the stiffness of the mixture changed as a result of the addition of PET to the SMA mixture. The higher percentage of PET in the SMA mixture resulted in lower stiffness of the SMA. Secondly, increasing amounts of PET in the SMA mixture corresponded to a greater resistance to fatigue. The final conclusion from the research was that the flexibility of the mixture was increased with the addition of the PET, substantiating reduction of cracking in pavements. Particle sizes of 2.36 mm and smaller were used in this research. The researchers used two main tests in their experiment namely, indirect tensile stiffness modulus test and indirect tensile fatigue test. The research included the heating of asphalt at 130°C while aggregate was heated at 160°C before the two were mixed. PET particles in concentrations of 0%, 0.2%, 0.4%, 0.6%, 0.8% and 1% were then added to the mixture with the mixing temperature kept constant between 160°C and 165°C.

Another study conducted by Kalantar et al. [8] involved the use of PET of particle sizes ranging between 0.450 mm and 0.701 mm as a modifier to bitumen. The percentage concentrations of PET used in this analysis was 0%, 2%, 4%, 6%, 8% and 10% by weight of bitumen. Bitumen was heated in small tins at a temperature of 160°C for approximately one hour. The various percentages of PET were added to the tins and mixed manually for approximately two minutes. Samples were then tested using the penetration test and the softening test. Kalantar et al. [8] recorded that values for penetration with the modified bitumen decreased as PET content increased when compared to a standard bitumen sample. The final result achieved was a harder and more consistent bitumen sample with the ability to withstand rutting. However, a harder and stiffer bitumen affects the flexibility of the pavement and can result in fatigue cracking. The softening point test indicated that with an increase in PET content, softening point also increased and modified bitumen resistance to heat was augmented. Dynamic Shear Rheometer testing was also conducted by Kalantar et al. [8]. Comparisons were made of complex shear modulus and phase angle versus temperature. An increase in complex shear modulus occurred with the increase in PET percentage in the samples. Higher values of complex shear modulus had benefits of greater resistance to rutting. Regarding phase angle and PET addition, a decrease in phase angle was noted as PET percentage increased. Kalantar et al. [8] stated that the lower values of phase angle results in a more elastic than viscous mixture which will return to its original condition without dissipating energy. Also the reduction of permanent deformation was achieved with low values of phase angle at high temperatures. The researchers concluded generally that mixtures with PET resulted in higher resistance to permanent deformation and rutting.



There was very little research that focused on the effect of different particle size ranges on the properties of the final mixture. All tests conducted involved the use of bitumen and no research was conducted on natural asphalt. Oyekunle [19] conducted research which focused on certain relationships between chemical compositions and properties of petroleum asphalts from different origins. Petroleum asphalts are considered to be refined asphaltic materials and mixed based crude oils. The researcher stated that the chemical composition and the structure of the substances is a result of the production process. The chemical composition also determines the properties of the asphalts with different behaviours of asphalts from different regions. It therefore was important to conduct this research to observe the changes in properties of TPB and TLA if any, with the addition of PET.

MethoD

Waste PET, the additive used in the experiment, was obtained from the company Recycling In Motion Limited, located in Trinidad. This company shreds, packages, and ships various types of plastics to overseas markets. PET bottles that were manufactured incorrectly due to machine malfunctions or any other faults during the process are classified as post-industrial PET. These PET bottles are not labelled or capped but are sent to the recycling company to be recycled. A total of 4624.80 grams were collected from the company to be used in the experiment. The melting temperature of the material is documented to be in the range of 250°C to 270°C [20]. A sieve analysis of the waste PET material collected was conducted. Table 1 displays the different sieve sizes used with associated passing by weight. Three particle size ranges were then chosen from the material sieved and used in the experiment. These are documented in Table 2. The particles size range values in Table 2 corresponded to the largest linear dimension captured using the sieves. The smallest linear dimension for each of the particle size range is 0.15 mm, which is equal to the minimum thickness of the plastic bottle. The three particle size ranges were selected based on particle sizes used in two similar experiments conducted in other studies. Ahmadinia et al. [5] used particle sizes ranging from 0.85 mm to 1.18 mm while Kalantar et al. [8] used particle sizes ranging from 0.45 mm to 0.701 mm.

The percentage of waste PET by weight used in the samples was researched by Ahmadinia et al. [5] who concluded that the appropriate range by weight of PET was 4% to 6% for the most desirable characteristics. Based on those findings, the percentages used in this experiment were 0%, 2%, 4%, 6% and 8% PET. These percentages were similar to those used by Kalantar et al. [8]. Asphaltic blends greater than 4% were untestable using the DSR most likely



due to too high a stiffness at the testing temperatures. The total weight of each sample was 25 grams with each sample varying in percentage PET by weight. Table 3 displays the concentrations tested in this study which numbered 20 samples in total. TLA for the experiment was obtained from Lake Asphalt of Trinidad and Tobago Limited and its composition is shown in Table 4 [21]. A 60/70 penetration refinery TPB was obtained from the Petroleum Company of Trinidad and Tobago Limited.

Table 3. PET concentrations testedRange % Pet (by weight) in tLA % Pet (by weight) in tPB

A, B, C 0, 2, 4, 6, 8 0, 2, 4

Table 4. Composition of TLA [21]component % (by weight)

Bitumen 55

Minerals 37.5

Water of Hydration of Minerals 4.3

Other Organic matter 3.2

Table 1. Sieve analysis of PET particlesSieve Size (mm) weight of Particles Passing (g)

9.500 4624.80

4.750 3810.00

4.000 2673.00

2.360 515.40

2.000 356.40

1.700 214.20

1.180 89.40

0.850 65.40

0.600 40.20

0.300 19.80

0.150 14.40

0.075 7.80

Table 2. PET particle size ranges used in this studyRange Range (mm)

A Greater than 0.30 but less than or equal to 0.60

B Greater than 0.60 but less than or equal to 0.85

C Greater than 0.85 but less than or equal to 1.18



Cylindrical stainless steel containers were individually placed on a digital scale, zeroed, and the required amount of TLA or TPB was placed inside and weighed. The samples were then heated in a controlled temperature oven. The TLA samples were heated at a temperature of 170°C while the TPB samples were heated at a temperature of 160°C. These temperatures were consistent with those used by Ahmadinia et al. [5] and Kalantar et al. [8]. A total heating time of two hours was used for the samples. All the samples were initially heated for one hour to get the substances into a molten state. These were then removed from the oven individually and placed on a digital scale where the percentage PET for each sample was placed in the container and weighed. This is known as the dry mix method when the additive is mixed with the binder after heating [5]. These samples were then placed on a hot plate and mixed manually with a stirrer for two minutes. These were then placed back into the oven, removed every twenty minutes in the final hour of heating, placed on the hot plate, and stirred manually for one minute. The temperature of the hot plate was maintained at the approximate temperature at which the samples were heated at in the oven.

After the heating process was completed, all samples were then casted in a sample ring for analysis in the Controlled Dynamic Shear Rheometer. The samples were allowed to cool slightly and then casted into a 25 mm diameter, 1 mm thick sample mould. These samples were then allowed to cool and kept at room temperature for one day before being tested.

The DSR test was conducted in accordance with the standards of the American Association of State Highway and Transport Officials (AASHTO) [13]. The upper and lower plates of the DSR were preheated to allow the samples to stick to the plates. Sample moulds were individually placed between the test plates and then moved together until the required testing gap (1mm) was obtained. The excess material around the edge of the test plates was removed. The DSR plates were then brought up to a temperature of 60°C for the TPB samples and 80°C for the TLA samples before testing started. The DSR testing was software controlled with the lower plate of the machine fixed and the upper plate oscillating backward and forward at a frequency of 1.59Hz creating a shearing action. This frequency corresponds to vehicles travelling at 80 km/hr separated by a recommended safety practice of 3 car lengths between each vehicle. The DSR recorded measurements over a number of cycles and the software analysed the data producing values of complex shear modulus and phase angle. Viscosity measurements were recorded in the temperature range of 60°C to 100°C for the TPB samples and 80°C to 100°C for the TLA samples. The maximum temperature of the pavements in actual service ranges from 55oC to 65oC. The test geometries were plate to plate (diameter of 25 mm) with a 1 mm gap. The maximum strain was maintained below the limit of the linear viscoelastic region.



The Scanning Electron Microscope (SEM) was used to analyse the structure of the samples using 30 kV of secondary electrons. Elemental analysis was also performed. Samples were gold sputtered to minimize charging effects.

ReSuLtS

Figure 1 shows the variation of Complex Shear Modulus (G*) with PET in TPB at different temperatures and 1.59Hz for Range A particle sizes. It is observed that there was not much of a variation in G* from 0% to 6% of PET in TPB. However, a noticeable increase in G* occurred at the 8% concentration. This was the finding for all temperatures tested. For the Range B particle size shown in Figure 2, a maximum G* value was produced at the 6% concentration for

Figure 2. Variation of Complex Shear Modulus G* (Pa) with PET in TPB at different temperatures and 1.59Hz for Range B particle sizes

Figure 1. Variation of Complex Shear Modulus G* (Pa) with PET in TPB at different temperatures and 1.59Hz for Range A particle sizes



test temperatures of 60oC and 100oC. The Range C particle size produced a maximum G* value at the 4% concentration as shown in Figure 3. The peak value of complex shear modulus occurred at concentrations above pure TPB (0% PET) with the exception of Range C at 60oC.

Figure 4, Figure 5, and Figure 6 show the variation of phase angle with PET in TPB at different temperatures and 1.59Hz for Range A, B, and C particle sizes respectively. Lower phase angles tended to occur at the higher testing temperatures.

Figure 7, Figure 8, and Figure 9 reveal the variation of G* with PET in TLA at different temperatures and 1.59Hz for Range A, B, and C particle sizes respectively. As with the TPB blends, G* decreased with increasing temperature. Figure 9 shows the largest particle size range (C) produced values of complex

Figure 4. Variation of Phase Angle (Degrees) with PET in TPB at different temperatures and 1.59Hz for Range A particle sizes

Figure 3. Variation of Complex Shear Modulus G* (Pa) with PET in TPB at different temperatures and 1.59Hz for Range C particle sizes



Figure 7. Variation of Complex Shear Modulus G* (Pa) with PET in TLA at different temperatures and 1.59Hz for Range A particle sizes

Figure 6. Variation of Phase Angle (Degrees) with PET in TPB at different temperatures and 1.59Hz for Range C particle sizes

Figure 5. Variation of Phase Angle (Degrees) with PET in TPB at different temperatures and 1.59Hz for Range B particle sizes



shear moduli that were higher than pure TLA (0% PET). The smallest particle size range (A) had the opposite effect as observed in Figure 7.

Figure 10, Figure 11, and Figure 12 show the variation of phase angle with PET in TLA at different temperatures and 1.59Hz for Range A, B, and C particle sizes respectively. The opposite effect occurred with the TLA compared to the TPB, where the phase angle increased with increasing temperature for TLA.

Figure 13 and Figure 14 are plots of G* and δ respectively against particle size range of PET in TPB for a temperature of 60 °C. In Figure 13, it is observed that the 8% and 6% PET concentrations for Ranges A and B respectively provided G* values that were higher than 0% concentration. Figure 14 reveals

Figure 9. Variation of Complex Shear Modulus G* (Pa) with PET in TLA at different temperatures and 1.59Hz for Range C particle sizes

Figure 8. Variation of Complex Shear Modulus G* (Pa) with PET in TLA at different temperatures and 1.59Hz for Range B particle sizes



Figure 12. Variation of Phase Angle (Degrees) with PET in TLA at different temperatures and 1.59Hz for Range C particle sizes

Figure 11. Variation of Phase Angle (Degrees) with PET in TLA at different temperatures and 1.59Hz for Range B particle sizes

Figure 10. Variation of Phase Angle (Degrees) with PET in TLA at different temperatures and 1.59Hz for Range A particle sizes



that 4% PET concentration for Range C provided the lowest phase angle. In Figure 13, no clear upward or downward trend was observed with respect to the complex shear modulus versus PET concentration for each particle size range. This is different from the findings of Kalantar et al. [8] who observed an increase in complex shear modulus with increasing PET concentration. However Figure 14 shows an overall decrease in phase angle occurred with

Figure 14. Phase Angle (Degrees) vs. Particle Size Range at 1.59Hz and 60°C for TPB

Figure 13. Complex Shear Modulus G* (Pa) vs. Particle Size Range at 1.59Hz and 60°C for TPB



increasing PET concentration for Ranges A and B. This concurs with the findings of Kalantar et al. [8].

Figure 15 and Figure 16 illustrate G* and δ respectively against particle size range of PET in TLA for a temperature of 80 °C. From Figure 15, it is observed that 4% and 2% PET concentrations for Ranges B and C respectively provided

Figure 16. Phase Angle (Degrees) vs. Particle Size Range at 1.59Hz and 80°C for TLA

Figure 15. Complex Shear Modulus G* (Pa) vs. Particle Size Range at 1.59Hz and 80°C for TLA



G* values that were higher than the 0% concentration. Figure 16 reveals that the 2% PET concentration provided the lowest phase angle.

Figure 17 and Figure 18 show the variation of G*/sinδ and G*sinδ respectively with PET in TPB at 60°C and 1.59Hz for the three particle size ranges. Figure 19 and Figure 20 show the variation of G*/sinδ and G*sinδ respectively with PET in TLA at 80°C and 1.59Hz for the three particle size ranges.

Figure 18. Variation of G* sinδ with PET in TPB at 60°C and 1.59Hz for the three particle size ranges

Figure 17. Variation of G*/ sinδ with PET in TPB at 60°C and 1.59Hz for the three particle size ranges



DIScuSSIon

Figure 1, Figure 2, and Figure 3 reveal a trend as shown in Table 5 where, as the particle size range increased, the peak values of complex shear moduli occurred at lower concentrations of PET. Table 5 also shows the concentration at which δ was generally a minimum (for each of the testing temperatures) as obtained from Figure 4, Figure 5, and Figure 6. A lower δ

Figure 20. Variation of G* sinδ with PET in TLA at 80°C and 1.59Hz for the three particle size ranges

Figure 19. Variation of G*/ sinδ with PET in TLA at 80°C and 1.59Hz for the three particle size ranges



is desirable for both rutting and fatigue cracking resistance as it is associated with increased elasticity. Table 6 documents the concentration at which G* and δ was generally a maximum and minimum respectively for PET in TLA. This information was obtained from Figure 6 to Figure 12.

Table 5. Concentration at which G* and δ was generally a maximum and minimum respectively for PET in TPBRange concentration at which G*

was generally a maximum (%)concentration at which δ was

generally a minimum (%)

A 8 8

B 6 Inconclusive

C 4 4

Table 6. Concentration at which G* and δ was generally a maximum and minimum respectively for PET in TLARange concentration at which G* was

generally a maximum (%)concentration at which δ was

generally a minimum (%)

A 0 0

B 4 4

C 2 2

From Figure 17, Figure 18, Figure 19, and Figure 20, optimum fatigue cracking and rutting resistance values were obtained for each concentration. This is documented in Table 7 and Table 8 for TPB and TLA respectively. Values in bold font in the Tables represent the most desirable concentration. It is noted that for TLA, the optimal concentration occurred at 2% for particle size Range C. For TPB, the 2% concentration for particle size Range C provided the best fatigue cracking resistance, whereas the particle size Range B produced the best rutting resistance.

Table 7. Optimum Fatigue cracking (Minimum G*sin δ value) and Rutting resistance (Maximum G*/sin δ value) for PET in TPBcR concentration (%)

Minimum G*sin δ value

Particle Size Range for Minimum

G*sin δ value

Maximum G*/sin δ value

Particle Size Range for


0 5,480 5,480

2 2,950 C 4,310 A

4 3,560 B 6,140 C

6 3,990 C 9,020 B

8 2,960 C 7,290 A



Table 8. Optimum Fatigue cracking (Minimum G*sin δ value) and Rutting resistance (Maximum G*/sin δ value) for PET in TLA

cR concentration (%)

Minimum G*sin δ value

Particle Size Range for Minimum

G*sin δ value


Particle Size Range for


0 6,720,000 6,720,000

2 1,230,000 C 11,400,000 C

4 1,250,000 A 7,960,000 B

Figure 21 is a SEM image showing the interaction between a PET particle of Range C size at 4% concentration in TLA. The PET particle is separate and distinct from the TLA matrix. However, there appears to be sufficient bonding of the TLA with the PET particle.

Figure 21. SEM image of the interaction at the 4% concentration of PET in TLA for Range C particle size

concLuSIonS

The results of this study clearly demonstrated that incorporating the waste polymeric material PET in TLA and TPB influenced the rheological properties of the resulting blends. Higher concentrations of PET in TLA resulted in blends with lower complex shear moduli. However, when larger particle sized of PET was utilized, higher values of complex shear moduli were observed.



A distinct trend was observed with respect to the concentration of PET in TPB. The peak value of complex shear modulus generally occurred at concentrations above pure TPB for the particle size ranges and temperatures tested. As the particle size range increased, peak values occurred at lower concentrations of PET. The 2% concentration for particle size Range C provided the best fatigue cracking resistance, whereas the particle size Range B produced the best rutting resistance.

For TLA, the largest particle size range produced values of complex shear moduli that were higher than pure TLA. The smallest particle size range had the opposite effect. The optimal concentration for fatigue cracking and rutting resistance occurred at 2% PET concentration for particle size Range C. For TPB, the 2% concentration for particle size Range C provided the best fatigue cracking resistance, whereas the particle size Range B produced the best rutting resistance.

Further research should include the effect of PET particle size range and concentrations on TLA/TPB mixtures that are commonly used in road paving applications. Accelerated weathering tests can also be conducted to correlate aging simulations observations with the results of laboratory rheological findings.

The accelerated weathering tests can also accommodate the investigation of larger particle size ranges, which are readily available from plastic recycling depots.

RefeRenceS

1. ASTM International., Standard Terminology Relating to Materials for Roads and Pavements. United States: ASTM International, 2002.

2. Chaitan W.B., Graterol V.R., A Gravity Investigation of the Pitch Lake of Trinidad and Tobago. Geology of Trinidad and Tobago: The Geological Society of Trinidad and Tobago; <http://www.gstt.org/geology/pitch%20lake.htm>; 2009 accessed [19.02.13].

3. Eurobitume, What is Bitumen? <http://www.eurobitume.eu/bitumen/what-bitumen>; 2009 accessed [01.10.12].

4. National Center for Asphalt Technology, LTPP Data Shows RAP Mixes Perform As Well As Virgin Mixes, Asphalt Technology News, Auburn, 2009.

5. Ahmadinia E., Zargar M., Karim M.R., Abdelaziz M., Performance evaluation of utilization of waste Polyethylene Terephalate (PET) in stone mastic asphalt, Construction and Building Materials, 36 (2012) 984-989.



6. Guardian Media, Towards a Cleaner, Healthier and Greener T&T, <http://m.guardian.co.tt/gie/2011/12/05/towards-cleaner-healthier-and-greener-tt>, 2011 accessed [04.09.12].

7. Ramnarine K., Recycling plant will add value to the industry, Trinidad Express: One Caribbean, 2012.

8. Kalantar Z., Mahrez A., Karim M., Properties of Bituminous binder modified with waste Polyethylene Terephthalate, Proceeding of Malaysian Universities Transportation research Forum and (MUTRFC) Conferences: Universiti Tenaga Nasional, 2010, pp. 333-344.

9. Maharaj R., Balgobin A., Singh-Ackbarali D., The influence of Polyethylene on the Properties of Trinidad Lake Asphalt and Trinidad Petroleum Bitumen, Asian Journal of Materials Sciences, 1 (2009) 36-44.

10. Read J., Whiteoak D., The Shell Bitumen Handbook. 5th ed. London: Thomas Telford Publishing, 2003.

11. Widyatmoko I., Elliott R., Characteristics of elastomeric binders in contact with natural asphalts, Construction and Building Materials, 22 (2008) 239-249.

12. Rheology School, Rheology Glossary, <http://www.rheologyschool.com/rheology_glossary.html>, 2012 accessed [22.10.12].

13. Pavement Interactive. Dynamic Shear Rheometer, <http://www.pavementinteractive.org/article/dynamic-shear-rheometer/>, 2011 accessed [21.10.12].

14. Moghaddam T., Karim M., Syammaun T., Dynamic properties of stone mastic asphalt mixtures containing waste plastic bottles, Construction and Building Materials, 34 (2012) 236-242.

15. Kennedy T.W., Huber G.A., Harrigan E.T., Cominsky R.J., Hughes C.S., Quintus H.V., Superior performing asphalt pavements (Superpave): The product of the SHRP asphalt research program. Strategic Highway Research Program: National Academy of Sciences, 1994.

16. Canadian Strategic Highway Research Program (C-SHRP). Specification for SuperPave Binders. Canada,1995.

17. FHWA and EPA. A study of the use of recycled paving materials – report to Congress. Report FHWA-RD-93-147, EPA/600/R-93/095. Washington, DC.: Transportation Research Board, 1993.

18. Bahia H., Davies R., Effect of crumb rubber modifiers (CRM) on performance-related properties of asphalt binders, Journal of the Association Asphalt Paving Technology, 63 (1994) 414-449.



19. Oyekunle L.O., Influence of chemical composition on the physical characteristics of paving asphalts, Petroleum Science and Technology, 25 (2007) 1401-1414.

20. Margolis J.M., Engineering Thermoplastics Properties and Applications. New York: Marcel Dekker Inc., 1985.

21. Lake Asphalt of Trinidad and Tobago (1978) Ltd. Trinidad Lake Asphalt (TLA), <http://www.trinidadlakeasphalt.com/home/products/trinidad-lake-asphalt-tla.html>, 2012 [accessed 01.11.12].

the effect of polyethylene terephthalate particle size and ... · thermosetting materials....

Documents