The Influence of Waste Polyvinyl Chloride

European Journal of Scientific Research ISSN 1450-216X / 1450-202X Vol.121 No.1, 2014, pp.48-56 http://www.europeanjournalofscientificresearch.com

The Influence of Waste Polyvinyl Chloride (PVC) on the Flow Properties of Trinidad Lake Asphalt (TLA) Rean Maharaj University of Trinidad and Tobago, Point Lisas Industrial Estate Point Lisas, Trinidad & Tobago, W. I E-mail: [email protected] Tel: 1 868 642 8888; Fax: 1 868 642 1617 Dimple Singh-Ackbarali University of Trinidad and Tobago, Point Lisas Industrial Estate Point Lisas, Trinidad & Tobago, W.I E-mail: [email protected] Tel: 1 868 642 8888; Fax: 1 868 642 1617 Lebert H. Grierson Department of Chemistry, The University of the West Indies St. Augustine Trinidad & Tobago, W.I E-mail: [email protected] Tel: 1 868 662 6013; Fax: 1 868 645 3771 Nazim Mohamed University of Trinidad and Tobago, Point Lisas Industrial Estate Point Lisas, Trinidad & Tobago, W.I E-mail: [email protected] Tel: 1 868 642 8888; Fax: 1 868 642 1617 Abstract This paper investigates the influence of waste Polyvinyl chloride (PVC) on the rheological properties of Trinidad Lake Asphalt (TLA) as part of a wider study of evaluating waste plastics, e.g. PVC, as a filler additive in asphaltic materials. Rheology of modified TLA blends containing 1, 2, 5 and 8 wt % waste PVC were investigated using oscillating rheometry. Rheological properties, complex modulus (G*) and Phase Angle (δ), of the various blends were measured over the frequency range 0-16Hz and temperature range 80, 100, 120 and 140oC. The addition of waste PVC to TLA resulted in changes in the rheological properties, demonstrated by changes in the phase angle, δ (elasticity) and the complex modulus, G* (stiffness) of the blends. TLA-PVC blends containing between 25% PVC produced superior, optimum performance (enhanced rutting) compared to unmodified TLA; i.e. higher G* and lower δ values. This study demonstrated the capability of customized TLA-PVC blends as suitable for special modified applications and furthermore offers an environmental friendly alternative for waste PVC. Keywords: TLA, Polyvinyl chloride (PVC), rheological properties, complex shear modulus, phase angle

The Influence of Waste Polyvinyl Chloride (PVC) on the Flow Properties of Trinidad Lake Asphalt (TLA)

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1. Introduction Asphalt and bituminous materials are often used together with mineral aggregates as construction road materials from time in memorial. The performance of these road pavements depend on the intrinsic properties of the asphalt which is the main deformable component in the mixture. In asphalt concrete, the shape of colloidal aggregates also affect the durability, workability, shear resistance, tensile strength, stiffness, fatigue response and optimum binder content of mixtures. Recent work by Arasan et al, 2010 have implicated the role of; fractal geometry on blend properties (e.g. increasing fractal dimension will lead to increased stability) and colloidal aggregates (defined as fractal size distribution) affecting the role of binders such as PVC, and hence the reason for full characterization of PVC/asphalt mixtures, being the purpose of this paper. Polyvinyl chloride, also known as PVC, is the third-most widely produced plastic, after polyethylene and polypropylene (Allsopp and Vianello 2012). PVC is used in construction because it is more effective than traditional materials such as iron, copper or wood in pipe and profile applications. It can be made more flexible and softer by the addition of plasticizers, the most widely used being phthalates. In this form, it is also used in clothing and upholstery, inflatable products, electrical cable insulation, and many applications in which it replaces rubber. Literature (Kridan et al, 2011) indicates that addition of PVC reduces the optimal amount of bitumen in control asphalt mixes and also modifies the viscosity of the binder allowing mixing and compaction temperature to below that of conventional mixes. Combined mixes of mineral aggregate and bitumen via hot and warm asphaltic concrete mixes, modified with plastic fillers such as PVC, can perform two functions as it allows for recycling of waste material in a safe environmental alternative and it can also be used to affect the mechanical properties of such asphaltic materials. Asphaltic systems have thermal susceptibilities and often experience cracking in cold environments and creep/distortion at high temperatures (Kortschot et al, 1984). There is a need to modify the rheological behavior of asphalt, mainly due to the inability of the currently produced bituminous materials from conventional crude petroleum refinery practices to resist distresses. The chemical composition of petroleum asphalt and its resulting physical/mechanical performance characteristics are highly dependent on the crude source and the refining process. Asphalt in most modern day refineries is produced as a secondary product and in most instances has to be modified to produce a material that meet performance standards, i.e. climate, traffic, and pavement structure requirements. In a recent United States federal state highway agencies study, 35 out of 47 agencies indicated their intentions to expand the use of modified asphalts in their road construction programme. The agencies indicated that modified asphalts were generally used to reduce the occurrence of rutting and fatigue cracking which increased the initial cost of construction (Bahia et al, 1998). Patents on asphalts modification have been produced dating back from 1823 (Isacsson and Lu, 1995); by 1982 over 1000 technical articles had been published on polymer modified asphalts or mixtures. There is a continuing emphasis on this subject (Bahia et al, 2001). One area of emphasis is the use of waste materials such as tyre rubber, polyethylene and used car oil to alter/enhance rheological and mechanical properties of Trinidad Lake Asphalt (TLA) and Trinidad Petroleum Bitumen 60/70 (TPB). A study by SWMCOL (1995) commercial company in Trinidad and Tobago showed that on a daily basis plastics make up between 13-20% of the total landfill, similar studies have been done (Zurbrugg, 2003; OECD, 1999). Research using TLA and TPB as base materials have shown that small additions of waste polymeric materials (< 10%) can enhance the complex modulus (G*) and phase angle (δ) rheological parameters of the resulting blends (Maharaj et al, 2009a, Maharaj et al, 2009b, Maharaj and Ackbarali, 2011). Singh et al, (2003) employed micronized polyvinyl chloride (PVC) pipe waste as soft filler in bituminous products and the results of the study indicated that optimized mix can be used as alternative waterproof roof mastic to conventional bituminous materials. Literature shows that the performance of asphalt is highly dependent on composition and source of material (Oyenkunle, 2006; 2007, Andersen and Speight, 2001, Trejo et al, 2004). Asphalts and bitumen with similar composition can often produce pavements of varying physical properties, performance and serviceability; hence it maybe premised that bitumen

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Rean Maharaj, Dimple Singh-Ackbarali, Lebert H. Grierson and Nazim Mohamed

and asphalt materials may interact with other components differently. The famous natural solid lake deposit of asphalt (occupying about 0.4km2 and of uniform composition to a depth of 87m) Trinidad Lake Asphalt (TLA), is located in La Brea, Trinidad pointing towards the northeast coast of Venezuela (Abraham, 1960; Miller and Dunstan, 1938). Trinidad Lake Asphalt material comprises a unique mixture of bitumen, 63% and mineral matter which is kaolinitic in nature (Maharaj, 2009). TLA has been internationally well established as “commercial gold standard” superior quality asphalt (due to its consistent properties, resistance to cracking, stability and durability), and is often specified as a mandatory ingredient for paving in high demand situations such as those encountered in airport runways (Widyatmoko and Elliott, 2008). The use of the dynamic (oscillatory) testing technique and a combination of the complex modulus (G*) and phase angle (δ) has been recommended for the characterization of the viscoelastic properties of asphaltic material (Kim, 2009). The viscoelastic properties of asphalt and, in particular, the magnitude of the complex modulus (G*) and phase angle (δ) can be directly related to pavement performance and the occurrence of various failure mechanisms such as rutting, fatigue damage and thermal cracking as described by Kim (2009). Generally speaking, larger G* values and lower δ values are consistent with superior rutting and fatigue cracking performance, but they are unfavorable for the thermal cracking performance of the material. Since very little work exists in the literature on the rheological properties of polyvinyl chloride (PVC) asphalt blends. This paper assesses the effect of waste PVC (0% to 8%) on rheological properties of TLA using small angle dynamic (oscillatory) testing technique; to evaluate the potential use of PVC waste.

2. Experimental 2.1. Raw Materials The TLA used in this study was supplied by Lake Asphalt Company of Trinidad and Tobago. The waste PVC used in the study was spent household water pipes. The waste PVC samples were dried, crushed, ground and sieved through a 250µm sieve size mesh. 2.2. Procedures Modified asphalt materials used for the rheological studies were prepared according to procedure by Polacco et al (2004). Approximately 250g of the TLA was placed in aluminum cans and heated to 180◦C in a Thermo Scientific Precision (Model 6555) Mechanical Convection Oven. Amounts of the PVC, to produce TLA blends containing 0, 1, 2, 5, and 8% of PVC by weight was added incrementally (5g/min) to the mixture while continuously stirring. The material was thoroughly mixed using a digital IKA (Model RW20D) Overhead Stirrer, at 3,000 rpm for 30 minutes and the material was cooled to room temperature and stored in a refrigerator at -10oC for subsequent testing. 2.3. Sample Characterization The rheological properties of the asphaltic blend materials were determined using an ATS RheoSystems Dynamic Shear Rheometer (Viscoanalyzer DSR). The analyses were performed under the strain –control mode and the applied strain was restricted to low values to ensure linear viscoelastic behavior. Measurements were done using the test plate–plate configuration geometry (diameters 25mm) with a 1 mm gap conducted at the temperatures 80, 100, 120 and 140oC with oscillation frequency range of 0-16 Hz (corresponds to a shear stress between 0 and 580Pa). The rheological data obtained at different oscillating shear frequencies and temperatures were stored in the computer and results analyzed using the Viscoanalyzer software. The complex modulus and phase angle were calculated at the different oscillating frequencies and temperatures using the instrument’s software.


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3. Results and Discussion The plots of complex modulus (G*) and the phase angle (δ) of TLA versus frequency (ω) over the temperature range 80-140oC are shown in Figure 1. Figure 1: Variation of the complex shear modulus, (G*) and phase angle (δ) with the frequency (ω) at different temperatures for TLA.

In Figure 1, the G* and δ values of TLA over the frequency range 0 – 16 Hz range from 2.91x106 Pa to 2.4 x 106 Pa and 35.5 – 86.4 degrees respectively as sample temperature increaased from 333 to 373 K, clearly showing that TLA moved from exhibiting an elastic response to an almost viscous liquid. The effect of the higher load frequency was more pronounced at lower temperatures, i.e. it affected the phase angle and G*, as the material tended to be more elastic and stiffer at higher load frequencies. Figure 2: Shows the effects of the addition of PVC on the complex shear modulus (G*) of TLA-PVC blends at different measurement temperatures

Figure 2 shows for TLA/PVC blends (1 – 8%) the complex modulus G* ranged from 5 x 106 to 8 x 10 Hz depending on PVC %, frequency and temperature. The addition of PVC to TLA at low levels (1%) (at 0.4 Hz shearing frequency and temps 354 to 414K) resulted in a decrease in the G*; i.e. a softer material resulted. However on further additions of PVC (2 to 8%) resulted firstly in an increase 2

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in G* (stiffness) (at all temperatures) up to a maxima G* values at 5% PVC blend followed thereafter by gradual reduction of G* a common value (1.0 x 105 Pa) regardless of the temperature. The TLAPVC blends (2 to 8% PVC) had a significantly higher G* for all temperatures than the pure TLA. The results of Figure 3, showed a similar trend for G* versus % PVC in various TLA blends at different frequencies. Figure 3: The effect of increasing % PVC on complex shear modulus, (G*) of the TLA-PVC blends at different frequencies at 80oC

Figures 4 and 5 show phase angle studies for TLA/PVC blend (1 – 8%), the phase angle (δ) ranged from 11 to 79.4o depending on, PVC %, frequency (0.1 Hz to 15.9 Hz) and temperature (354 to 414 K) as seen in the case of G*. Note: phase angles between 5 – 45o are typical of viscoelastic behavior as examplified by asphalt mixtures, and > 5o shows dominantly viascoelastic behavior, < 5o dominantly elastic behavior (Biligiri et al, 2010). As expected from G* results, the phase angle (δ) of the TLA-PVC blends decreased with increasing % PVC (reflective of an increase in the elasticity of the blends) until a minimum δ value 13.3 of at approximately 5% added PVC. Hence the 5% PVC blend behaves almost as a completely elastic solid. The further addition of PVC resulted in a gradual increase in the phase angle (δ) of the TLA-PVC blends as the viscosity of the blends trended towards that of the pure TLA. Hence for both TLA and TLA/PVC blends (PVC > 5%) reduction of G* and increase in δ values on elevation of temperature is reflective of a decrease in the rigidity and elasticity of the materials– note rheological analysis of TLA below 333K was not possible as the material existed as a rigid solid. Kim (2009) and C-SHRP (1995), suggest that TLA-PVC blends containing between 2-5% PVC should exhibit superior rutting performance as they have higher G* values and lower δ values.


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Figure 4: The effect of increasing % PVC on the phase angle (δ) for TLA-PVC blends for different temperatures at a frequency of 0.4Hz

Figure 5: The effect of increasing % PVC on the phase angle (δ) of the TLA-PVC blend for different frequencies at 80oC.

Further mechanistic elucidation is provided by plot of Black curves (G* vs. δ) (Fig. 6) of TLA and various TLA-PVC blends. Figure 6: The Black Curves (G* vs. δ) for TLA and TLA-PVC blends at 80oC and 0.4Hz.

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As explained by Teugels, (2000) and Widyatmoko and Elliott, (2008), ‘‘a series of bitumens differing in penetration but not temperature susceptibility (penetration index) will give a single black curve’’, and any deviations from this single curve by either processing, ageing, or polymer addition will indicate changes in composition or variation in structure of the bitumen, or in our case TLA/PVC blend. The results in this study, as exemplified in Figure 6, imply that the addition of waste PVC (up 5%) to TLA results in the black curves shifting towards left of TLA and hence a more stiffer and more elastic response than TLA.

4. Summary and Concluding Remarks The addition of waste PVC to TLA resulted in changes in the rheological properties of the blends as demonstrated by changes of both the phase angle, δ (elasticity) and the complex modulus, G* (stiffness) of the blends. TLA-PVC blends containing between 2-5% PVC exhibited higher G* and lower δ values compared to the unmodified TLA. These changes in the rheological properties are expected to be associated with improved performance characteristics such as superior rutting and fatigue cracking performance. This comprehensive study supports the work of Kim et al, (2009) and demonstrates the capability to create customized TLA-PVC blends to suit special applications by formulating specific quantities of TLA and PVC. The results therefore confirm waste PVC has enormous potential to be used as a modifier of TLA and offers environmentally attractive option for improving the use of asphalt.

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