Performance of Stone Matrix Asphalt and Asphaltic Concrete Using Modifiers Downloaded from ascelibrary.org by University Of Florida on 10/25/17. Copyright ASCE. For personal use only; all rights reserved. M. S. Ranadive, Ph.D., M.ASCE 1; H. P. Hadole 2; and S. V. Padamwar 3 Abstract: Waste plastic is harmful and affects the environmental cycle. This paper proposes the use of fiber extracted from refrigerator door panels (FERD) and waste plastic in bituminous mixes for road construction. The effect of modification of bituminous mixes like stone matrix asphalt (SMA) and asphalt concrete (AC) with FERD and processed waste plastic in granular form was studied. The FERD was used to modify the SMA and AC, whereas waste plastic was used to modify AC. Different mixes of SMA and AC were prepared with and without filler material. Furthermore, the study was done with varying lengths of fibers (2, 4, 6, and 8 mm), which were added to the SMA and AC mixtures. Asphalt concrete mixtures with 0, 4, 6, 8, 10, and 12% waste plastic by weight of bitumen were prepared. The effect of the preceding on drain down, Marshall stability, and indirect tensile strength was promising. DOI: 10.1061/(ASCE)MT.19435533.0002107. © 2017 American Society of Civil Engineers. Author keywords: Stone matrix asphalt (SMA); Asphalt concrete (AC); Drain down; Marshall stability; Indirect tensile strength (ITS). Introduction In developing countries like India, it is necessary to strengthen the infrastructure, which helps to fulfill the needs of an increasing population. Highway traffic in India is increasing at a fast rate. To balance this increasing traffic rate, it is necessary to develop a good road network. Due to the variation in, e.g., temperature, soil type, and material used for road construction, the quality of roads can vary greatly, which further leads to major distress in flexible pavements. Rutting is one of the main problems every road engineer faces and needs to be resolved. Scientists and engineers have developed various techniques to overcome these problems, using data pertaining to organizations such as the Central Pollution Control Board. As per the report from the Central Pollution Control Board (2015), in India nearly 12 million tons of plastic products are consumed every year, of which approximately 60% is converted into waste. This report also discusses an action plan for plastic waste management; its main action points; its setting, collection, and segregation at source; and its transportation to a place of disposal. Stone matrix asphalt (SMA) is one of the bituminous mixes that cause a minimum rutting problem, and is used in the construction of road as a wearing course. Stone matrix asphalt was developed in Germany in the mid-1960s and has been used successfully by many countries in the world because it is highly rut-resistant. Stone matrix asphalt is based on the concept of stone-to-stone contact. In 1990, a European asphalt study brought the same German-mix technology known as Splittmatrixasphalt, the English translation of which is stone mastic asphalt. According to Prowell 1 Associate Professor, Dept. of Civil Engineering, College of Engineering, Pune, Maharashtra 411005, India. E-mail: [email protected] 2 M.Tech. Student, Dept. of Civil Engineering, College of Engineering, Pune, Maharashtra 411005, India (corresponding author). E-mail: [email protected] 3 M.Tech. Student, Dept. of Civil Engineering, College of Engineering, Pune, Maharashtra 411005, India. E-mail: [email protected] Note. This manuscript was submitted on October 30, 2015; approved on June 9, 2017; published online on October 25, 2017. Discussion period open until March 25, 2018; separate discussions must be submitted for individual papers. This paper is part of the Journal of Materials in Civil Engineering, © ASCE, ISSN 0899-1561. © ASCE et al. (2002), the American version of this is stone matrix asphalt. On the other hand, asphalt concrete (AC)–bituminous concrete (BC) is commonly used as a wearing coat. Engineers are trying hard to increase the performance of AC in different ways. As a result, different types of fibers and polymers are added to the AC mix, which gives better performance as compared to conventional mixtures. This paper will focus on the investigation from the strength point of view of bituminous material after the addition of fiber, filler, and processed waste plastic. Here fiber extracted from refrigerator door panels (FERD) and cement as filler material was used. Chowdary and Raghuram (2013) explained that in artificial fiber, FERD gives better results against rutting and deformation in flexible pavements. In this work, an attempt is made to optimize the length of FERD with the help of results obtained after performing various tests, like Marshall stability, drain down, stripping value, and indirect tensile strength (ITS). Because fiber extracted from waste door panels of refrigerators can be used in an efficient manner, this will create awareness in the market regarding waste management. Scherocman (1991) followed the gradation of SMA according to the 30–20–10 rule, whereby 30% should have pass through a 4.75-mm sieve, 20% through a 2.36-mm sieve, and 10% through a 0.075-mm sieve. According to Brown and Manglorkar (1993), SMA is a gap-graded aggregate asphalt hot mix that maximizes the asphalt content and course fraction, which provides stable stone-on-stone contact that is held together by a rich mix of asphalt content, filler, and stabilizing additives. Brown and Mallick (1994) explained that as the percentage of aggregate passing through a 4.75-mm sieve decreases, the voids in the mineral aggregate (VMAs) remain nearly constant and begin to increase when the former reaches 30–40%. According to Brown et al. (1997a, b) and Brown and Haddock (1997), the percentage of aggregate passed through a 4.75-mm sieve must be lower than approximately 30% to ensure the formation of stone-on-stone contact. Marshall hammer, Superpave gyratory compactor (SGC), dry rodded test, vibrating table, and vibrating hammer are the tests discussed by Brown et al. (1997a) to determine the stone-to-stone contact of SMA. The gradation of SMA is considerably different from dense-graded asphalt mixes, which is reported in Ministry of Road Transport and Highways (MoRTH 2012). According to Chowdary and Raghuram (2013), it is necessary to look again into the usage of 04017250-1 J. Mater. Civ. Eng., 2018, 30(1): 04017250 J. Mater. Civ. Eng. Downloaded from ascelibrary.org by University Of Florida on 10/25/17. Copyright ASCE. For personal use only; all rights reserved. fly ash in SMA mixes because it is observed that minimum drain down is achieved when fly ash is used as a filler in combination with fibers such as coconut, fiber extracted from refrigerator door panels, and modified binders PMB-70 and CRMB-60. It was concluded that FERD exhibited lower drain down than SMA mixes using other fibers, and added that FERD and jute fibers resulted in a higher stability value and showed improved properties of rut-resistance. Abtahi et al. (2010) discussed the behavior and properties of various fibers and their behavior on AC. This work pointed out that due to the use of fibers in AC, there was a significant improvement in dynamic modulus, moisture susceptibility, creep compliance, rutting resistance, and freeze-thaw resistance. Bahia and Anderson (1995) studied the viscoelastic nature of binders, and found that the complex modulus and phase angles of the binders need to be measured at temperatures and loading rates that resemble different climatic and loading conditions. Shukla and Jain (1984) described that the effect of wax in bitumen can be reduced by adding ethylene vinyl acetate (EVA) and aromatic resin in the waxy bitumen. The addition of 4% EVA or 8% resin in waxy bitumen effectively reduces susceptibility and bleeding at high temperatures, or brittleness at low temperatures, of the mixes. According to Rajasekaran et al. (2013), waste plastic from both the domestic and industrial sectors can be used in the production of asphalt mix. Waste plastic used mainly for packaging is made up of polyethylene, polypropylene, and polystyrene. Various food packaging plastics are used to coat hot aggregates at 160°C, and this becomes the raw material for construction of pavement. Khan et al. (2009) reported significant improvement in the properties of the Marshall stability value, retained stability, and indirect tensile strength. In addition, control over rutting was observed with the modification of AC using waste plastic in shredded form (particle size diameter 2–3 mm). Vasudevan et al. (2007) and Yildrim (2007) suggested the use of various polymers such as rubber, styrenebutadiene-styrene, styrene-butadiene-rubber, and elvaloy (ethylene glycidyl acrylate) in AC. Ravishankar et al. (2013) studied the effect of waste plastics from garbage in shredded form in semidense bituminous concrete (SDBC), and came to the conclusion that the optimum bituminous content (OBC) for conventional mixes was found to be 4.93 and 5.1% for Grade 1 and Grade 2, respectively. Also, the optimum plastic content (OPC) was observed as 10 and 12% for Grade 1 and Grade 2, respectively. The work done by Patekar and Ranadive (2014) was referred to as guidelines for preparing the statistical analysis, and the conclusions are reported in this paper. Based on the preceding literature review, it is observed that the areas related to SMA and AC modified with plastic and cellulose fiber are usually focused and studied separately. From the report of the Website Material on Plastic Waste Management (2013), it is seen that an abundant quantity of waste products, such as plastic and refrigerator door panels, that are difficult to dispose of are available in India and even worldwide. Pavements are one of the largest areas for the consumption of such material, for its improvement in strength. This paper aims to analyze the properties of SMA and AC modified with FERD, AC modified mixture with use of granular plastic, and the optimization of length of FERD for SMA and AC mixtures, and compare the results of SMA and AC fiber modification, as well as the optimization of the percentage of plastic for the AC mixture with a corresponding discussion on the behavior of fiber in SMA and AC. Materials It is always better to get all required aggregates from the same quarry site. However, getting the aggregates from the same source does not necessarily guarantee that properties of aggregates are the same over time. In different seasons aggregates were collected and tested for specific gravity, aggregate impact value, and soundness. In addition, the Los Angeles abrasion test and shape test were performed, and it was observed that there was a deviation of 0.5% in the results, so seasonal deviation in results is negligible. However, the test results are not reported here. Hence, it was verified and ensured that different batches in different seasons from the same quarry site did not make much difference in their basic properties. Aggregates were obtained from a local quarry located nearby the city of Pune, Maharashtra, India, and the same source was used throughout the research. Physical properties of the aggregate used are shown in Table 1. In this work, cement was used as filler. As per the guidelines provided by IRC: SP: 79 (IRC 2008), the mineral filler should consist of finely divided mineral matter, and fly ash should not be used as filler. The addition of filler reduces the drain down of the asphalt binder, which is due to an increase in surface area. A mineral filler of 5% by weight of aggregate was used, which consisted of 3% stone dust and 2% cement. Bitumen of penetration grade 60/70, i.e., VG30, was used as a binder. The physical properties of bitumen obtained from laboratory tests are given in Table 1. Fibers used in this work were extracted from outdated and nonserviceable refrigerator door panels, which served as stabilizers; hence these were waste fibers. The lengths of fibers used were 2, 4, 6, and 8 mm. The FERD making up the plastic matrix was epoxy, a thermosetting plastic, and most often polyethylene terephthalate (PET). The study of properties of polyester was done by Yu and Sun (2010) and Table 1. Physical Properties of Aggregate and Bitumen Value (%) Test sample Aggregate Property Standard Required as per IRC: SP: 79 Observed values Impact value Los Angeles abrasion value IS 2386 (P-4) (IS 2007c) IS 2386 (P-4) (IS 2007c) ASTM C131 (ASTM 2006b) IS 2386 (P-3) (IS 2007b) ASTM C127-88 (ASTM 1988) IS 2386 (P-1) (IS 2007a) ≤24 ≤25 7.05 15.37 ≤2 1.4 ≤30 29.7 IS 1203 (IS 1978b) ASTM D5 (ASTM 2013) IS 1205 (IS 1978c) ASTM D36 (ASTM 1995) IS 1208 (IS 1978d) ASTM D113 (ASTM 2007) IS 1202 (IS 1978a) ASTM D70 (ASTM 2009) 60–70 67 40–55 48 >75 78 Water absorption Combined flakiness and elongation index Bitumen Penetration (100 g, 5 s at 25°C) Softening point, ring and ball apparatus (°C) Ductility at 27°C and 5 cm=min pull (cm) Specific gravity at 27°C © ASCE 04017250-2 J. Mater. Civ. Eng., 2018, 30(1): 04017250 1 0.99 J. Mater. Civ. Eng. Downloaded from ascelibrary.org by University Of Florida on 10/25/17. Copyright ASCE. For personal use only; all rights reserved. is referred to here. The physical and chemical properties of PET were taken directly from the technical design guide provided by Molded Fiber Glass Companies (2015) and were not investigated separately. As per Brown et al. (1997a), it was suggested to use 0.3% of fiber by weight of total mix of aggregates because aggregates begin to force apart as the fiber content exceeds this percentage, affecting various properties of SMA. As per IRC: SP: 79, the dosage rate for fiber suggested was 0.3% minimum by weight of total mix of aggregates because it gives draindown test results within permissible limits for the design mix of SMA, as per ASTM D6390 (ASTM 2005). These are the main reasons for fixing the dosage rate at 0.3% by weight of total mix of aggregate so that an investigation could be undertaken to optimize the length of fibers. Processed granular plastic from plastic waste was used in this investigation. The granular plastic was 3–5 mm size, so that the process of mixing with aggregates with ease was possible, and there were no emissions at the time of mixing waste plastics with aggregates. 2006a). The MSN is representative of the strength of the bituminous mixture. The bituminous mixture design was performed to determine the OBC of the mixtures. As per the previous discussion, with reference to Brown and Mallick (1994) and and Brown et al. (1994) the SMA mixture was prepared with 50 blows. The mixing and compaction temperatures were 160 and 150°C, respectively. Gradation of Aggregates Indirect Tensile Strength Test The gradation for mix design of SMA and AC mix is as per guidelines, provided by MoRTH (2012), IRC 29 (IRC 1988), AASHTO PP 41-02 (AASHTO 2004), and AASHTO MP 8-05 (AASHTO 2005). In this test, a uniform tensile stress was developed perpendicular to the direction of applied load and along the same vertical plane, causing the specimen to fail by splitting. This test is also otherwise known as the splitting test. The test was conducted using a Marshall apparatus, with a deformation rate of 51 mm=min. A unidirectional compressive load was applied, and corresponding failure load was recorded, as per guidelines given in ASTM D6931 (ASTM 2012). Methodology The mix design procedure for SMA, as proposed in National Asphalt Technology Report by Brown and Cooley (1999) and by IRC: SP: 79, was followed. The compaction process of SMA mixture played a vital role in achieving proper density of the sample. According to the study by Brown and Mallick (1994), compaction should be performed by a gyratory testing machine. The study further concluded that air voids produced by gyratory compaction and with the Marshall stability test with 50 blows are the same. In the AC mixture, plastic in granular form was used. Initially, aggregates were heated at approximately 170°C, followed by bitumen and granular plastic at approximately 170°C each. Then bitumen and plastic were mixed thoroughly and added to aggregates. For each bitumen content, three samples of the Marshall stability test and ITS were prepared and tested. The mean values are reported in Tables 2 and 3. Experimental Investigation Various tests like the draindown test, Marshall stability test, boiling test, and indirect tensile strength were performed and brief descriptions for these are given below. Boiling Test The test was carried out as per ASTM D36 (ASTM 1995). A 250-g sample of clean, oven-dried aggregate passed through a 20-mm sieve and retained on a 12.5-mm sieve was heated to 160°C, and 14 g of bitumen, heated separately to 150°C, was mixed with the aggregates. The mixture was allowed to cool down to 80–100°C, and then was added to boiling water. The content was boiled for 10 min and results were recorded for its stripping value and are discussed subsequently. Results and Discussion The preceding test results are reported in Tables 2 and 3, while graphical presentation of the properties of AC are presented in Figs. 2–13. Test results for the SMA mixture are reported in Table 2. Graphs were drawn but are not reported here. Draindown Test Results Fig. 1 shows the results of the draindown test for the different mixtures of SMA, and shows draindown as a function of the filler and length of fiber. It is observed that the mix without filler shows a higher draindown percentage. A draindown reduction is observed with an increase in surface area due to the use of cement as a filler, resulting in higher bitumen content. The draindown is less than 0.3% when the filler and fibers are used as stabilizers. As the length of fiber increases, the draindown percentage decreases, but for study purposes every sample of SMA was tested for MSN and for indirect tensile strength to ascertain the strength of the mix. For AC samples, this test was not conducted because the percentage of fine aggregates was higher. Schellenberg Draindown Test The test developed by the Schellenberg Institute in Germany was adopted for drain down. Using this test, the draindown percentage of binder was discovered, as per the procedure outlined in ASTM D6390 (ASTM 2005). Marshall Stability Test Bituminous samples were prepared for the Marshall stability number (MSN), as per guidelines provided in ASTM D6926 (ASTM 2010), and testing was done as per ASTM D6927 (ASTM © ASCE Marshall Test Results The observed values of MSN, flow value, and volumetric properties, like percentage air voids, voids in mineral aggregate, and voids filled with bitumen, for the different bituminous mixtures are given in Tables 2 and 3. The three minimum values in a set were observed, and the average of the same is reported in these tables. The results of the MSN of AC mixes modified with fibers are shown in Fig. 2. From the results, it can be clearly observed that the MSN of AC mixes is also a function of filler material and fiber length and percentage of bitumen in the mix. One can observe that 04017250-3 J. Mater. Civ. Eng., 2018, 30(1): 04017250 J. Mater. Civ. Eng. Table 2. Test Results for SMA and AC Modified with Fibers and Statistical Analysis Engineering and statistical parameters Without filler and no fiber Cement as filler and no fiber Cement as filler and 2-mm fiber length Cement as filler and 4-mm fiber length Cement as filler and 6-mm fiber length Cement as filler and 8-mm fiber length For SMA mix Optimum binder content (%) Stability (kN) Mean Standard deviation UCL LCL Drain down at OBC (%) Mean Standard deviation UCL LCL Flow values Mean Standard deviation UCL LCL VMA (%) Mean Standard deviation UCL LCL Air voids filled by bitumen (%) Mean Standard deviation UCL LCL Air voids (%) ITS (kPa) 7.1 8.9 8.58 0.94 11.38 5.77 1.1 1.05 0.15 1.5 0.6 4.2 3.66 0.59 5.43 1.89 22.37 20.54 1.84 26.08 15 81.39 78.96 4.30 91.86 66.05 4 492 6.5 12.2 11.08 1.12 14.46 7.69 0.4 0.38 0.03 0.48 0.28 2.6 2.62 0.34 3.66 1.57 19.96 20 1.27 23.82 16.19 76.71 77.90 4.37 91.03 64.77 4 510 6.5 12.8 11.64 1.16 15.12 8.15 0.12 0.12 0.02 0.1 0.05 2.8 2.94 0.49 4.43 1.46 19.5 19.68 1.36 23.77 15.62 78.94 79.92 4.63 93.81 66.01 4 515 6.3 14.1 12.36 1.39 16.53 8.18 0.09 0.09 0.01 0.14 0.03 2.2 2.32 0.48 3.76 0.88 19.12 19.91 1.02 22.97 16.84 80.78 78.05 4.94 92.87 63.23 4 527 6 15.6 14.24 1.05 17.39 11.08 0.07 0.074 0.0054 0.09 0.05 2.1 2.3 0.32 3.24 1.35 18.28 19.53 1.54 24.14 14.92 77.91 79.43 3.71 90.58 68.28 4 603 6.5 14.8 13.12 1.26 16.92 9.31 0.034 0.047 0.011 0.08 0.01 2.4 2.4 0.52 3.97 0.83 19.7 19.45 1.53 24.04 14.86 79.32 78.09 4.98 93.06 63.12 4 477 For AC mix Optimum binder content (%) Stability Mean Standard deviation UCL LCL Flow values Mean Standard deviation UCL LCL VMA (%) Mean Standard deviation UCL LCL Air voids filled by bitumen (%) Mean Standard deviation UCL LCL Air voids (%) ITS (kPa) 5.5 13.2 11.86 1.54 16.50 7.21 4 4.16 0.3 5.05 3.27 18.02 17.47 0.93 20.22 14.59 68.67 77.60 6.78 98 57 5.64 419 5.5 13.5 12.8 1.33 16.17 8.18 3.4 3.94 0.29 4.8 3.08 18.83 18.84 1.23 22.54 15.14 69.26 75.026 5.85 92.60 57.40 5.78 447 6 14.8 13.8 0.85 16.39 11.28 2.8 3.7 0.32 4.58 2.66 19.4 19.32 1.23 23 15.61 71.61 72.11 6.65 92.18 52.23 5.5 477 6 14.2 13.84 0.54 16.73 0.99 2.3 2.6 0.62 4.73 0.99 18.98 18.89 1.22 22.58 15.20 73.10 73.81 6.77 94.14 53.49 5.1 496 6 15.1 13.48 0.79 16.62 22.82 3.16 2.7 0.59 4.47 0.92 19.01 18.9 1.38 22.95 14.67 73.14 74.23 5.96 92.14 56.33 5.1 501 6 14.4 14.20 0.64 15.40 11.55 2.6 2.4 0.48 30.86 26.06 18.85 18.71 1.036 21.87 15.66 73.55 74 6.53 93.60 54.40 3.87 477 Downloaded from ascelibrary.org by University Of Florida on 10/25/17. Copyright ASCE. For personal use only; all rights reserved. Bituminous mix test sample Note: LCL = lower control limit; UCL = upper control limit. Table 3. Test Results for AC Modified with Waste Plastic Engineering parameters of AC mix 0% waste plastic 4% waste plastic 6% waste plastic 8% waste plastic 10% waste plastic 12% waste plastic Optimum binder content (%) Stability (kN) Flow values Air voids (%) VMA (%) Air voids filled by bitumen (%) ITS (kPa) © ASCE 5.5 13.2 2.9 5.64 18.07 68.75 410 5.5 14 2.6 5.24 17.62 70.25 503 6 14.8 2.9 4.48 17.84 74.84 634 04017250-4 J. Mater. Civ. Eng., 2018, 30(1): 04017250 5.5 16.8 2.4 4.85 17.22 71.79 587 5.5 15.4 2.8 4.45 16.84 73.55 603 5.5 12.2 3 4.06 16.45 75.29 477 J. Mater. Civ. Eng. Downloaded from ascelibrary.org by University Of Florida on 10/25/17. Copyright ASCE. For personal use only; all rights reserved. Fig. 1. Draindown percentage for SMA Fig. 4. Flow value for AC modified with fiber Fig. 2. Marshall stability for AC modified with fiber Fig. 5. Flow value for AC modified with waste plastic Fig. 3. Marshall stability for AC modified with waste plastic Fig. 6. Percentage air voids for AC modified with fiber the MSN of the AC mix is greatest for the sample having filler and 6-mm fiber length for 6% bitumen content by total weight of mix. Hence, the OBC of cement- and fiber-modified mixtures is higher than the unmodified mixture. From Fig. 3, it is clearly observed that the MSN of AC mixes is also a function of the plastic modifier. One can observe that the MSN for the AC mix modified with waste plastic is greatest for the sample with a bitumen content of 5.5% by weight of aggregate and 8% waste plastic by weight of bitumen. © ASCE 04017250-5 J. Mater. Civ. Eng., 2018, 30(1): 04017250 J. Mater. Civ. Eng. Downloaded from ascelibrary.org by University Of Florida on 10/25/17. Copyright ASCE. For personal use only; all rights reserved. Fig. 10. Voids filled with bitumen for AC modified with fiber Fig. 7. Percentage air voids for AC modified with waste plastic Fig. 8. Voids in mineral aggregate for AC modified with fiber Fig. 11. Voids filled with bitumen for AC modified with waste plastic Fig. 9. Voids in mineral aggregate for AC modified with waste plastic Fig. 12. ITS for AC modified with fiber Figs. 4 and 5 show that the flow value for AC modified with fiber and waste plastic is within the permissible limits, i.e., 2– 4 mm (MoRTH 2012) at OBC. Because the length of fiber is longer, there is a tendency to obstruct the flow of the bituminous mixtures. Therefore, the flow value decreases, which does not occur in the case of plastic. This is due to the addition of plastic in granular size. As per Brown et al. (1997a, b), the air voids should be designed close to 4% to minimize rutting and spots. For samples of AC, © ASCE 04017250-6 J. Mater. Civ. Eng., 2018, 30(1): 04017250 J. Mater. Civ. Eng. Downloaded from ascelibrary.org by University Of Florida on 10/25/17. Copyright ASCE. For personal use only; all rights reserved. Fig. 14. Comparison of stability between SMA and AC Fig. 13. ITS for AC modified with waste plastic as per MoRTH (2012), the percentage of air voids should be within 3–6%. Figs. 6 and 7 show the percentage of air voids for different mixes of AC, with fiber and plastic as the modifiers. For SMA, as per IRC: SP: 79, VMAs should be a minimum of 17%. The variation of VMAs with a variation in filler and length of fiber is shown in Figs. 8 and 9. All the SMA and AC mixes under study modified with fiber and plastic satisfy the minimum requirement of VMAs. The variation in air voids filled by bitumen (VFB) with filler, type of fiber, and waste plastic content can be seen in Figs. 10 and 11. It is expected to fill 65–75% of the air voids with bitumen. Hence the limit is satisfied. From the preceding discussion, as well as Figs. 6–11, it is clear that various mixes are within permissible limits. Fig. 15. Comparison of flow value between SMA and AC Boiling Test Stripping values were observed for various bituminous mixes modified with waste plastic. As per MoRTH, the stripping value should not be greater than 5%. For the AC mix without plastic, the stripping value was observed as 4%. However, for AC with 4, 6, 8, and 10% plastic, the stripping observed was 2, 0, 0, and 0%, respectively. Indirect Tensile Strength Test The ITS of the bituminous mixture helps assess the resistance to thermal cracking of given mixtures. In this study, the effect of the length of fiber on ITS was studied at a temperature of 25°C. From Figs. 12 and 13, it is clear that for AC mixtures the ITS is greatest for the sample with filler and 6-mm fiber length, as compared with the samples of different lengths. For the sample with plastic as a modifier, the ITS increased up to 6% by addition of waste plastic, and thereafter it decreased. Comparison between SMA and AC Modified with Fibers From Fig. 14, it is clear that the sample with cement as the filler and 6-mm fiber length gives a higher MSN as compared with other bituminous mixes. From Fig. 15, it can also be observed that the MSN of the SMA mix is more than that of the AC mix. As the length of fiber increases, the MSN also increases in the case © ASCE Fig. 16. Comparison of VMA between SMA and AC of SMA mixtures. The flow in the Marshall stability analysis is the deformation caused during loading. From Fig. 15, it is very clear that deformation of the SMA mixture is less when compared with the AC mix. For all SMA mixtures the flow values are within 2 to 4 mm. A comparison of VMAs in Marshall stability analysis for both SMA and AC mixes is shown in Fig. 16. A comparison of ITS for both SMA and AC mixes is shown in Fig. 17. The final observations and corresponding conclusion are discussed in the next section. 04017250-7 J. Mater. Civ. Eng., 2018, 30(1): 04017250 J. Mater. Civ. Eng. Downloaded from ascelibrary.org by University Of Florida on 10/25/17. Copyright ASCE. For personal use only; all rights reserved. Fig. 17. Comparison of ITS between SMA and AC Comparison between AC Modified with Plastic and Fibers, and SMA The variation in the MSN and flow value for the different bituminous mixtures is observed for 6% bitumen content from Tables 2 and 3. The MSN is the smallest for plastic (although it is more than the minimum requirement) in comparison to the SMA and AC with fibers, and is less by 5 and 2%, respectively. The flow value is comparatively greater for the use of plastic as compared with the SMA and AC fiber-modified mixtures, by 20 and 7%, respectively. This may be due to the fact that plastic makes bitumen less viscous than the original mixture, but in the case of the fiber-modified bituminous mixes the bitumen must have been held by fibers. Conclusions The following conclusions are drawn based on the results obtained from the bituminous mixes modified with FERD. The MSN is mainly affected by the extent of the aggregate proportion. Longer fibers push the aggregate apart in the mixture, resulting in a decrease in the MSN. Furthermore, it was noted that at the time of compaction of the mixture, the fibers may break due to the long length. Using short fibers, the VMA increases for an increase in OBC, which results in a loss of MSN, but at an 8-mm fiber length the VMA increases, which may be due to the same fact. Hence, fiber should be used up to its optimum length. It is logical that when the length of fiber increases, the tensile strength will also increase, but for 8-mm fiber length it decreases, which may be due to a loss of density. However, a study done by Brown and Manglorkar (1993) noted that when mineral fibers were used there was no loss in density. The MSN of the SMA mixes is increased by 75.28%, whereas for the AC mixes it increased by 14.39% as compared with conventional mixes. For both mixes, the optimum dosage of fiber is found to be 0.3% of total weight of mix, with a length of 6 mm. The flow value is within the limits for SMA and AC mixes, as per specifications provided by MoRTH and IRC: SP: 79 (i.e., 2–4 mm). The ITS value increased by 22.57 and 19.57% for the SMA and AC mixes, respectively, at optimum dosage, as compared with conventional to mixes. As compared with other samples of SMA, the sample prepared with 6-mm fiber length was compacted properly so that a 4% void ratio was achieved at the minimum bitumen percentage. For the SMA, proper compaction was the main criteria to maintain stone-to-stone contact and the MSN of the sample. As per the study by Qiu and Lum (2006), in the case of SMA the volume of coarse © ASCE aggregate has a significant influence on the percentage of air voids and VMA achieved. The following conclusions are drawn based on the results obtained on the bituminous mixes modified with waste plastic: The maximum MSN was obtained for the mix with 8% waste plastic, and it increased by 21.73% as compared with conventional mixes. The flow value was also within the permissible limits. The optimum bitumen contents for the conventional AC mix and the AC mix with 8% plastic were found to be equal, but the MSN achieved in the modified mixes was larger. Thus, 8% waste plastic can be used to enhance the pavement quality compared with the conventional AC mix. The ITS value increased by 42.97% for the AC mix with 6% waste plastic, as compared with the ITS of the conventional mix. The ITS of the bituminous mixes increased with an increase in plastic content of up to 6%, and decreased with a further increase in the plastic content. The boiling test results showed that the mixes modified with waste plastic were strip-resistant, even when subjected to the worst moisture condition. The modification of AC will further help to maximize the use of waste plastics in the construction of pavements, and will also avoid its disposal by incineration and landfill. In general, the MSN required, as per MoRTH, is 9 kN. However, by using waste plastic the MSN achieved is much greater, which may result in a reduction of the bitumen content, saving the cost of the work. The average air voids of each mixture type at different binder contents are shown in Fig. 7. By comparing the mixtures’ mechanical or physical properties, the air void content should be within 0.5%, according to the standard, but in this case the air void variation is bit high, which might affect the comparison of results, especially the ITS. The following conclusions are drawn based on the statistical analysis: The process was found to be more stable for the AC modified with fiber than for the AC modified with both plastic and SMA. The process was controlled, and results were predictable from the run chart (not shown here) for AC. For SMA, the results of flow values bounced about its center in random fashion, which implies that its process was stable and predictable, but from a stability point of view the mean level drifting upward implies that the process was unstable. Acknowledgments The authors would like to thank the reviewers for their helpful comments and suggestions on improving this paper. References AASHTO. 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