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Laboratory investigation of rutting and fatigue in glassphalt containing waste plastic bottles
Construction and Building Materials 116 (2016) 378–383
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Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat
Laboratory investigation of rutting and fatigue in glassphalt containing waste plastic bottles Mahyar Arabani a, Makan Pedram b,⇑ a b
Department of Civil Engineering, University of Guilan, Rasht, Iran Department of Civil Engineering, International Campus, University of Guilan, Rasht, Iran
h i g h l i g h t s The effect of different HDPE contents on dynamic properties of asphalt mixes was studied in this research. ITFT and RLA tests were used to evaluate the fatigue and rutting effect on asphalt mixes. The optimum content of HDPE was determined as 10% through the ITSM, RLA and ITFT tests. The results showed that HDPE performance at high temperature is not effective as moderate temperature. Since HDPE can reduce pavement failures, it would be cost effectiveness.
a r t i c l e
i n f o
Article history: Received 26 November 2015 Received in revised form 10 April 2016 Accepted 26 April 2016
Keywords: HDPE (High Density Polyethylene) Dynamic properties of asphalt Waste materials Recycled glass Environment
a b s t r a c t Waste glass and plastic bottles are among the materials that have caused a wide range of environmental pollution, since they decompose too slowly. Therefore, the use of materials in recycling glass and plastic bottles (High Density Polyethylene) can preserve renewable resources and decrease their negative environmental effects. Considering the present of recycled High Density Polyethylene in the total weight of bitumen used in glassphalt mixture in the wet method, a laboratory investigation on the rutting and fatigue phenomena in High Density Polyethylene-containing asphalt mixtures and the effect of High Density Polyethylene on improvement of dynamic features of glassphalt is performed in the present research. The results of repeated load axial, indirect tensile fatigue, and indirect tensile stiffness modulus tests on 54 samples of asphalt shows improvement in elasticity and reversibility after unloading the asphalt samples with the optimum amount of 10% of material added to the bitumen. The test results also indicate that other properties of the asphalt samples such as modulus of resilience as well as creep and fatigue resistance (that lead to the durability of the asphalt mixture) are increased as well. Ó 2016 Elsevier Ltd. All rights reserved.
1. Introduction Significant destructions such as fatigue and rutting are among the most important causes of early up keep and repair of asphalt pavements. Pavement durability refers to its ability to resist detachment under traffic and environmental loads. Long durability of asphalt mixture requires the maintenance of its characteristics and mechanical properties as long as it is in service. Considering the variety of climatic conditions and nature of asphalt pavement implementation, it seems impossible to prevent pavement destruction whatsoever. Therefore, in order to prevent early pavement
⇑ Corresponding author. E-mail addresses: [email protected] (M. Arabani), [email protected] (M. Pedram). http://dx.doi.org/10.1016/j.conbuildmat.2016.04.105 0950-0618/Ó 2016 Elsevier Ltd. All rights reserved.
destructions and heavy maintenance costs, a suitable solution has to be found about this issue. On the other hand, as a result of the fast industrial development and ongoing increase in waste production, a large amount of waste material is spread through the natural environment, which has caused many environmental problems. One way to reduce and control this difficulty is to recycle such materials and reuse them in road construction. In addition to the decrease in environmental issues, the use of such materials improves the asphalt properties and reduces the exploitation of raw materials from the natural resources. Considering the visco-elastic nature of bitumen and asphalt mixtures, it seems necessary to provide laboratory conditions at different levels of stress, temperature, and frequency in order to investigate the pavement performance and behavior accurately. Fatigue caused by repeated loading and rutting is among the most
379
M. Arabani, M. Pedram / Construction and Building Materials 116 (2016) 378–383
important structural destructions and significant parameters considered in the modern methods of pavement design. There have been many studies on the causes of such destructions and the methods applied to improve them. One of the most important and practical methods is to use different additional materials in order to improve the characteristics and performance of bitumen and asphalt mixtures. Destructions caused by fatigue and rutting, the parameters that cause or deteriorate such conditions, and the strategies to resist and reduce them are firstly investigated in this research. Then, the behavior of modified concrete asphalt mixed with different percentages of glass and HDPE is investigated compared with the normal asphalt under different conditions (temperature and loading). Many studies have been performed on the promotion of dynamic properties of asphalt mixtures. Since 1960, glassphalt has been considered a suitable approach to use waste glass. According to the results of the study by Nansu and Chen (2002), the increase in the amount and size of glass in asphalt pavements caused some problems such as deficient friction and lock resistance. It was also indicated using higher amounts of glass with bigger pieces in lower layers of pavement could be more suitable [1]. Airey et al. (2004) showed that the performance of glassphalt pavement was improved through adding 10–15% of glass pieces. Considering the authorized limits and technical features including safety issue (surface edges and tire puncture), the maximum size of glass pieces that could be used in asphalt pavements was usually limited to 4.75 mm [2]. Arabani (2010) investigated the dynamic behavior of hot asphalt mixtures with various gradations. The results indicated that the dynamic behavior of asphalt mixtures containing waste glass (glassphalt) was improved at different percentages of this additional material [3]. Since 2005, several studies have been performed on improving the resistance of asphalt mixtures against fatigue. Topeka and Binder gradations have been applied to make the asphalt samples in these studies. The effect of different parameters such as temperature, loading, percent of the applied bitumen, and amount of woven roving on construction of the samples is also investigated. Moreover, the mechanical properties of asphalt samples such as modulus of stiffness, capability of creep, capability against repeated axial load, and fatigue life are investigated [4]. Zoorob et al. (2000) applied waste plastic as an alternative to a part of stone materials to modify bitumen. In the aforesaid study, 30% of stone material (between 2.36 and 5 mm) was replaced by cold asphalt with waste plastics that mainly consisted of LDPE, which decreased the density of the mixture by up to 16%. The results indicated that Marshall stability was increased up to 250% and the tensile strength of the asphalt mixture was improved as well [5]. Sinan and Emine (2004) indicated that the stability of the mixture decreased with an increase in HDPE that was caused by the reduction of mixture adhesion. They also concluded that the maximum sustainability was obtained through adding 4% HDPE at 165 °C within 30 min [6]. Use of HDPE to enforce asphalt pavements was investigated by Attaelmana et al. [7]. In this research, different HDPE proportions were mixed by 80–100 bitumen to produce asphalt pavements. Performance tests including Marshall resistance (MQ), tensile
strength, tensile strength ratio, flexural strength, and resilience modulus were performed on non-modified and modified hot asphalt mixtures. The results of these analyses showed that the performance of modified asphalt containing HDPE was better than that of the common asphalt mixture. Bindu and Beena (2010) studied the effect of waste plastic as a sustaining additional material to Mastic asphalt. According to the results of Marshall, tensile strength, and triaxial compression tests, it was concluded that a flexible pavement with good performance and long durability can be obtained through adding 10% shredded waste plastic [8]. Awwad and Shabeeb (2007) demonstrated that the characteristics of asphalt mixtures modified by HDPE were more improved compared with those containing LDPE [9]. Moghaddam and Karim (2012) stated that the use of waste material in asphalt pavements was a suitable method to increase their service life. It was also concluded that, compared with none-modified asphalt mixtures, those modified by PET had more sustainability, flow, and fatigue strength [10].
2. Problem statement and objectives As to the present study, the dynamic behavior of the modified asphalt mixture by glass and modified bitumen by HDPE, choosing stone materials from the Garkanrud River in Guilan Province. The effect of these two additional materials on improving the asphalt destructions caused by fatigue and rutting was investigated through laboratory studies.
3. Laboratory investigations 3.1. Consumed materials 3.1.1. Aggregate materials The physical, chemical, and mechanical properties of aggregates play a significant role in the performance of pavement. X-ray fluorescence spectroscopy (XRE) was applied in order to assess and measure the existing elements in the samples (determine element percentage). The results of XRE analysis, presented in Table 1, showed high levels of silicon dioxide in stone materials. Therefore, the aggregates of this mine could be categorized as silicon materials. Moreover, according to ASTM D-2419, the sand equivalent of the sand applied in this research was equal to 89; also, according to ASTM D-5821, the percentage of fractured particles of the gravel applied in this research was equal to 98.2 and 96.9 on one and two sides, respectively. According to ASTM D-131, L.A abrasion loss was equal to 27.2. Surface layer gradation sieves, which were selected from the materials screened by 19 and 12.5 mm and #4, #8, #50, and #200 sieves, were applied for the gradation of aggregates applied in this research the gradation documented in AASHTO green book was applied in order to produce the sample of solid asphalt mixture. All the stone materials were sieved in the lab. Therefore, there was no difference in the gradation of the samples. The material
Table 1 Results of XRE analysis on hydrated lime and fillers of aggregates for the laboratory samples. Features of sample material
Sio2 (%)
Al2O3 (%)
Fe2O3 (%)
CaO (%)
MgO (%)
Na2o (%)
K2O (%)
CO2 (%)
Weight loss on ignition (L.O.I) (%)
Gravel Sand Filler
48.36 48.11 47.07
12.5 8.67 11.05
6.4 5.8 5.2
15.5 18.48 16.92
2.2 1.86 2.5
2.16 1.71 2.10
0.96 0.94 1.03
10.41 12.75 12.11
12.23 14.42 14.13
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Fig. 1. Aggregate gradation chart along with AASHTO gradation limits.
gradation chart is illustrated in Fig. 1. The suggested limits of AASHTO green book are included as well. 3.1.2. Bitumen The bitumen applied in asphalt mixtures is chosen depending on several important parameters. Therefore, parameters such as climatic conditions of the area, traffic type and intensity, type of pavement, type and gradation of aggregates, and pavement construction method are considered. The higher the annual average temperature in the area, or the more and heavier the vehicles, the more fluent would be the cutback bitumen that is needed for asphalt mixtures. The PG64-16 (performance grade) bitumen was applied in this study, because of its application in the construction of asphalt pavements in the temperate districts of northern Iran. The characteristics of the bitumen applied in the research are illustrated in Table 2. 3.1.3. Waste glass The waste glasses of a glass cutting manufactory were used in this study. The maximum size of the glass pieces was 4.75 mm. The applied gradation curve for the glass is illustrated in Table 3.
3.1.4. Waste plastic bottles The applied plastic bottles were taken from the recycled materials of disposable containers produced by factories. Such materials consisted of HDPE. After providing the mentioned waste material from the landfill sites, they were completely cleaned of any other materials. They were cut in order to obtain pieces with suitable size to be mixed and digested within the bitumen. Finally, they were converted into much smaller pieces through cryogenic process. Fig. 2 illustrates a sample of waste materials getting prepared to be mixed with bitumen. 3.2. Experimental set up and procedure The experimental flow chart of this study is shown in Fig. 3. Since Marshall test has been applied in the asphalt design procedure in Iran, the selected variations in the Marshall optimum amount of bitumen is determined through the same test in order to investigate the effect of variations in its parameters such as bitumen percentage, empty space, etc. Glass and HDPE were added and mixed with the bitumen through dry and wet methods, respectively. As to the wet method,
Table 2 Results of bitumen performance tests in order to make the laboratory asphalt sample. AASHTO T48 flash point (°C) ASTM D4402 viscosity AASGTO T315 dynamic shear
290 Test: Test: Test: Test:
temperature (°C) viscosity (P/s) temperature (°C) (G⁄/Sind)KP
135 0.250 64 1.8
70 0.8
Table 3 Gradation range of the waste glass for the laboratory samples. Sieve
#4
#8
#16
#30
#50
#100
#200
Remainder percentage
100
63
42
27
14
9
2
Fig. 2. Additional material of the recycled pieces of plastic bottles applied in the present study.
M. Arabani, M. Pedram / Construction and Building Materials 116 (2016) 378–383
Modification of asphalt binder with 0, 2, 4, 6, 8 and 10 percent of HDPE
Marshal mix design according to the ASTM D1559 test mixtures
Measurement behavior of base and modified glassphalt with ITSM, ITFT and RLA tests Fig. 3. Flow chart of experimental design procedures.
the modified bitumen mixed with 2, 4, 6, 8, and 10% of HDPE was prepared by high shear mixer. Considering the promoted reflex of bitumen to the smaller pieces of additional materials and its better improvement, the pieces remaining on #100 and #200 sieves were applied in this research. The mixing process took place at 180 °C and the mixer speed of 4500 rpm. It was proceeded under the control of an opt-counter and microcontroller within 40 min. Fig. 4 illustrates the image obtained through electronic microscope photography of the bitumen and the additional material after being mixed. Fig. 5 shows a clearer image in a bigger scale. As can be observed in these images, all the HDPE pieces were completely digested to make a uniform homogenous mixture. The prepared samples were divided into 15 1200 g specimens in order to investigate Marshall strength and determine the optimum amount of bitumen. Also, 45 specimens were kept for the required dynamic tests. Indirect tensile stiffness modulus (ITSM), indirect tensile fatigue test (ITFT) and repeated load axial (RLA) tests were performed on each sample in three replicates. For each aggregate blend and
Fig. 4. Electronic microscopic images taken from the mixing process of bitumen and HDPE (additional material applied in this research).
381
asphalt binder, at least three separate samples were produced to determine the reproducibility of the results. In order to evaluate the dynamic performance, modulus of stiffness was tested through ITSM, fatigue was evaluated ITFT, and creep was tested using RLA. 3.2.1. ITSM test The stiffness modulus of the samples was determined by the indirect tensile strength method (ITSM) using a Nottingham Asphalt Testing system. The stiffness modulus test was performed by applying a linear force along the diameter axis of the specimen. Each loading cycle was 0.1 s long. Thus, given the total duration of loading and unloading of 1 s, the rest time period of each cycle is 0.9 s. 3.2.2. ITFT test The fatigue life of the specimens was measured using a Nottingham Asphalt tester in constant stress mode (the stress was held constant to increase the strain within the sample) by applying repeated loads with fixed amplitude along the diametrical axis of the specimen. The repeated load consisted of 0.1 s loading time followed by a 0.4 s of rest time. Cylindrical specimens with a diameter and height content of 101.6 mm and 40 mm respectively were tested at 25 °C. 3.2.3. RLA test The RLA test applies a repeated pulsed uniaxial stress on an asphalt specimen and measures the resulting deformations in the same direction using linear variable differential transducers (LVDTs). For the RLA test, cylindrical specimens of 60 mm 101.6 mm (thickness diameter) were prepared. 4. Result and analysis The values of the modulus of resilience for the samples made by different amounts of HDPE at 5, 25, and 40 °C and stress level of 250 KP were obtained based on ASTM-D4123. A semi-sinusoidal loading with 1 Hz frequency, 1 s loading cycle, 0.1 s loading duration 0.9 s relief duration, and 0.35 Poisson’s ratio was applied in this test. The results of resilience test on the tested samples are illustrated in Fig. 6. As can be observed, the values of modulus of resilience were decreased as temperature increased, which was because of the reduction in the elasticity of bitumen and asphalt mixture and the decrease in its viscosity. For example, the ITSM values of base asphalt mixture are 20,797, 2423 and 396 MPa in 5, 25 and 40 °C, respectively. On the other hand, with the increase in the volume of HDPE polymer at average and high temperatures, the resilience of bitumen and mixture increased. The increase in this value compared with the observed sample was equal to 51.5 and 38.4% at 25 and 40 °C, respectively. As can be seen in Fig. 6, the highest
Fig. 5. Electronic microscopic images taken from the mixing process of bitumen and HDPE (additional material applied in this research).
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10000
10000
Loading Cycle
Loading cycle
100000
1000 100 Temprature 5( C)
10
Temprature 25( C)
1000
100 25( C) Temprature in 250 Kp stress
10
25( C) Temprature in 400 Kp stress2
Temprature 40( C)
1
0%
2%
4%
6%
8%
10%
HDPE percent
40( C) Temprature in 250 Kp stress22
1
%0
%2
%4
%6
%8
%10
HDPE percent Fig. 6. Chart of modulus of resilience for HDPE-containing glassphalt. Fig. 8. Results of indirect tensile fatigue test on asphalt mixtures.
Loading Cycle
slope of the increase in modulus of resilience through adding HDPE was related to 5 °C. As the temperature further increased, the increase in the resilience slope was reduced compared with the sequential percentages. Modulus of resilience also increased while more HDPE was added, but it was still lower than the control sample. This decrease in modulus of resilience might be caused by the chemical structure of this additional material and the behavior of its hydro-carbonic structure at different temperatures. The dynamic creep test was also applied to the asphalt mixture samples with different amounts of glass pieces and HDPE at 60 °C and stress levels of 150 and 300 KP. This test was performed based on BS: DD226 in order to evaluate the asphalt destruction derived by rutting phenomenon. The results of this test at the end of loading are illustrated in Fig. 7. According to the observed process in Fig. 7, it can be concluded that the number of cycles needed to obtain the strain of 8% was increased as more HDPE was added. In other words, because of the link developed between the hydro-carbonic canines of HDPE molecules and bitumen, the resistance of this structure against constant deformations was increased. On the other hand, with the increase in the level of applied stress and resistance cycle of the asphalt mixture is decreased up to the strain of 8% and the compared to the samples under 300 KP of loading, samples under the load of 150 KP resist longer against the rutting. According to Fig. 7, it can be observed that the gradient of the increase in number of the needed cycles increased as more material was added; thus, there was a significant increase in the slope between 6 and 10% (particularly, between 8 and 10%). Therefore, larger amounts of the additional material improved the reaction of bitumen; as a result, the resilience and reversibility of the mixture were increased after unloading. Based on EN12697-24, indirect tensile fatigue test was applied to the asphalt samples made by different amounts of HDPE at 25 and 40 °C and stress levels of 250 and 400 KP. Results are illustrated in Fig. 8. Loading cycle of 1.5 s with the loading duration 5000 4500 4000 3500 3000 2500 2000 1500 1000 500 0
150 Kp 300 Kp
0%
2%
4%
6%
8%
10%
HDPE Percent Fig. 7. Results of dynamic creep test on the asphalt mixtures modified with different amounts of HDPE at various levels of stress.
of 0.25 s and relief duration of 1.25 s was applied in this test. Fatigue was defined as sample failure and diametric deformation of 9 mm. As can be observed in Fig. 8, at the average temperature (25 °C), the fatigue life was prolonged with an increase in the percent of additional material, showing that the additional material had good resilience at low and average temperatures. For example, the fatigue life values of asphalt mixtures are 1429, 2440, 3028, 4921, 10,369 and 10,885 cycles in 0, 2, 4, 6, 8 and 10% of HDPE, respectively. This additional material was depolymerized in reaction to the bitumen and their hydro-carbonic chains were well-linked. Considering Fig. 8, the optimum percent of additional material was between 6 and 8%. At the stress level of 250 KP and 25 and 40 °C, the fatigue life was increased by more than six times. Moreover, this additional material was weakened at high temperature and stress levels and the significant effect was observed at low and average temperatures and lower levels of stress is shown no longer. As can be observed, the obtained resistance at 40 °C and tension level of 400 KP was less than the loading stress level. Finally, at 40 °C and stress level of 250 KP, the incense was up to 2.5 times. 5. Conclusion Considering the performed studies, the following results were obtained: 1. Investigation of the results related to the dynamic behavior of the asphalt mixtures modified through adding waste materials indicated that this additional material increased the elasticity and reversibility of asphalt mixtures after unloading up to a good level. 2. For the fatigue phenomenon, considering the increase in the number of loading cycles, the optimum percent of HDPE was between 6 and 10% with an increasing slope. Investigating the results of fatigue, creep, and resilience tests, it was indicated that about 6–8% of this additional material can be followed by an optimum state of step-by-step promotion of the properties. Besides, the absolute value of the optimum use of this additional material was equal to 10% under any circumstances. 3. Since HDPE is depolymerized in reaction to bitumen, during which it absorbs the aromatic part of bitumen and swallows, the hydro-carbonic chains would be well-joint. So, it can be concluded that this additional material has good resilience at low and average temperatures. 4. Investigation of the results achieved through the tests on the asphalt mixtures showed that, in addition to a decrease in asphalt production costs, using 10% of waste glass and 10% of HDPE improved the performance of these mixtures as long as they were in service, since their characteristics and properties
M. Arabani, M. Pedram / Construction and Building Materials 116 (2016) 378–383
were promoted. This issue would also decrease the pavement maintenance costs. 5. Results also indicated that, at 25 and 40 °C and the most optimum percent of HDPE, the repeated loads of 10,885 and 129 were achieved. Also, at average temperatures (25 °C), the use of HDPE provided proper results compared with pure bitumen. Therefore, it can be concluded that the use of the asphalt mixtures modified by HDPE is more suitable in the areas with temperate climate and average temperature.
References [1] Nansu, J.S. Chen, Engineering properties of asphalt concrete made with cycled glass, Resour. Conserv. Recycl. 35 (Essue4) (2002) 259–274. June 2002. [2] G.D. Airey, A.C. Collop, N.H. Thom, Mechanical performance of asphalt mixtures incorporating slag and glass secondary aggregates, in: Proceeding of the 8th Conference On Asphalt Pavements for Southern Africa (CAPSA’04), 2004. Sun City, South Africa.
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[3] M. Arabani, Effect of glass cullet on the improvement of the dynamic behavior of asphalt concrete, Resour. Constr. Build. Mater. (2010). [4] M. Arabani, A.K. Haghi, S.M. Mirabdolazimi, M. Haghgoo, Increment of fatigue resistance of HMA by waste tire thread, in: 7th International Congress on Civil Engineering, 2006. Tehran, Iran. [5] S.E. Zoorob, L.B. Supreme, Laboratory design and investigation of the properties of continuously graded asphalt containing recycled plastics aggregates replacement (plastiphalt), Cem. Concr. Compos. 22 (2000) 233–242. [6] H. Sinan, A. Emine, Use of waste high density polyethylene as bitumen modifier in asphalt concrete mix, Mater. Lett. 58 (2004) 267–271. [7] A. Moatasim Attaelmanan, Cheng Pei Feng, A.I. Al-Hadidy, Laboratory Evaluation of HMA with High Density Polyethylene as a Modifier, Northeast Forestry University (NEFU), Harbin, PR China Civil Engineering Dept. North East Forestry University (NEFU), Harbin, PR China, Civil Engineering Dept. Mosul University, Mosul, Iraq, 2010. [8] C.S. Bindu, K.S. Beena, Waste plastic as a stabilizing additive in SMA, Int. J. Eng. Technol. 2 (2010) 379–387. [9] M.T. Awwad, L. Shbeeb, The use of polyethylene in hot asphalt mixtures, Am. J. Appl. Sci. 4 (2007) 390–396. [10] T.B. Moghaddam, M.R. Karim, Properties of SMA mixtures containing waste polyethylene terephthalate, Int. J. Chem. Biol. Eng. 6 (2012) 188–191.
Contents lists available at ScienceDirect
Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat
Laboratory investigation of rutting and fatigue in glassphalt containing waste plastic bottles Mahyar Arabani a, Makan Pedram b,⇑ a b
Department of Civil Engineering, University of Guilan, Rasht, Iran Department of Civil Engineering, International Campus, University of Guilan, Rasht, Iran
h i g h l i g h t s The effect of different HDPE contents on dynamic properties of asphalt mixes was studied in this research. ITFT and RLA tests were used to evaluate the fatigue and rutting effect on asphalt mixes. The optimum content of HDPE was determined as 10% through the ITSM, RLA and ITFT tests. The results showed that HDPE performance at high temperature is not effective as moderate temperature. Since HDPE can reduce pavement failures, it would be cost effectiveness.
a r t i c l e
i n f o
Article history: Received 26 November 2015 Received in revised form 10 April 2016 Accepted 26 April 2016
Keywords: HDPE (High Density Polyethylene) Dynamic properties of asphalt Waste materials Recycled glass Environment
a b s t r a c t Waste glass and plastic bottles are among the materials that have caused a wide range of environmental pollution, since they decompose too slowly. Therefore, the use of materials in recycling glass and plastic bottles (High Density Polyethylene) can preserve renewable resources and decrease their negative environmental effects. Considering the present of recycled High Density Polyethylene in the total weight of bitumen used in glassphalt mixture in the wet method, a laboratory investigation on the rutting and fatigue phenomena in High Density Polyethylene-containing asphalt mixtures and the effect of High Density Polyethylene on improvement of dynamic features of glassphalt is performed in the present research. The results of repeated load axial, indirect tensile fatigue, and indirect tensile stiffness modulus tests on 54 samples of asphalt shows improvement in elasticity and reversibility after unloading the asphalt samples with the optimum amount of 10% of material added to the bitumen. The test results also indicate that other properties of the asphalt samples such as modulus of resilience as well as creep and fatigue resistance (that lead to the durability of the asphalt mixture) are increased as well. Ó 2016 Elsevier Ltd. All rights reserved.
1. Introduction Significant destructions such as fatigue and rutting are among the most important causes of early up keep and repair of asphalt pavements. Pavement durability refers to its ability to resist detachment under traffic and environmental loads. Long durability of asphalt mixture requires the maintenance of its characteristics and mechanical properties as long as it is in service. Considering the variety of climatic conditions and nature of asphalt pavement implementation, it seems impossible to prevent pavement destruction whatsoever. Therefore, in order to prevent early pavement
⇑ Corresponding author. E-mail addresses: [email protected] (M. Arabani), [email protected] (M. Pedram). http://dx.doi.org/10.1016/j.conbuildmat.2016.04.105 0950-0618/Ó 2016 Elsevier Ltd. All rights reserved.
destructions and heavy maintenance costs, a suitable solution has to be found about this issue. On the other hand, as a result of the fast industrial development and ongoing increase in waste production, a large amount of waste material is spread through the natural environment, which has caused many environmental problems. One way to reduce and control this difficulty is to recycle such materials and reuse them in road construction. In addition to the decrease in environmental issues, the use of such materials improves the asphalt properties and reduces the exploitation of raw materials from the natural resources. Considering the visco-elastic nature of bitumen and asphalt mixtures, it seems necessary to provide laboratory conditions at different levels of stress, temperature, and frequency in order to investigate the pavement performance and behavior accurately. Fatigue caused by repeated loading and rutting is among the most
379
M. Arabani, M. Pedram / Construction and Building Materials 116 (2016) 378–383
important structural destructions and significant parameters considered in the modern methods of pavement design. There have been many studies on the causes of such destructions and the methods applied to improve them. One of the most important and practical methods is to use different additional materials in order to improve the characteristics and performance of bitumen and asphalt mixtures. Destructions caused by fatigue and rutting, the parameters that cause or deteriorate such conditions, and the strategies to resist and reduce them are firstly investigated in this research. Then, the behavior of modified concrete asphalt mixed with different percentages of glass and HDPE is investigated compared with the normal asphalt under different conditions (temperature and loading). Many studies have been performed on the promotion of dynamic properties of asphalt mixtures. Since 1960, glassphalt has been considered a suitable approach to use waste glass. According to the results of the study by Nansu and Chen (2002), the increase in the amount and size of glass in asphalt pavements caused some problems such as deficient friction and lock resistance. It was also indicated using higher amounts of glass with bigger pieces in lower layers of pavement could be more suitable [1]. Airey et al. (2004) showed that the performance of glassphalt pavement was improved through adding 10–15% of glass pieces. Considering the authorized limits and technical features including safety issue (surface edges and tire puncture), the maximum size of glass pieces that could be used in asphalt pavements was usually limited to 4.75 mm [2]. Arabani (2010) investigated the dynamic behavior of hot asphalt mixtures with various gradations. The results indicated that the dynamic behavior of asphalt mixtures containing waste glass (glassphalt) was improved at different percentages of this additional material [3]. Since 2005, several studies have been performed on improving the resistance of asphalt mixtures against fatigue. Topeka and Binder gradations have been applied to make the asphalt samples in these studies. The effect of different parameters such as temperature, loading, percent of the applied bitumen, and amount of woven roving on construction of the samples is also investigated. Moreover, the mechanical properties of asphalt samples such as modulus of stiffness, capability of creep, capability against repeated axial load, and fatigue life are investigated [4]. Zoorob et al. (2000) applied waste plastic as an alternative to a part of stone materials to modify bitumen. In the aforesaid study, 30% of stone material (between 2.36 and 5 mm) was replaced by cold asphalt with waste plastics that mainly consisted of LDPE, which decreased the density of the mixture by up to 16%. The results indicated that Marshall stability was increased up to 250% and the tensile strength of the asphalt mixture was improved as well [5]. Sinan and Emine (2004) indicated that the stability of the mixture decreased with an increase in HDPE that was caused by the reduction of mixture adhesion. They also concluded that the maximum sustainability was obtained through adding 4% HDPE at 165 °C within 30 min [6]. Use of HDPE to enforce asphalt pavements was investigated by Attaelmana et al. [7]. In this research, different HDPE proportions were mixed by 80–100 bitumen to produce asphalt pavements. Performance tests including Marshall resistance (MQ), tensile
strength, tensile strength ratio, flexural strength, and resilience modulus were performed on non-modified and modified hot asphalt mixtures. The results of these analyses showed that the performance of modified asphalt containing HDPE was better than that of the common asphalt mixture. Bindu and Beena (2010) studied the effect of waste plastic as a sustaining additional material to Mastic asphalt. According to the results of Marshall, tensile strength, and triaxial compression tests, it was concluded that a flexible pavement with good performance and long durability can be obtained through adding 10% shredded waste plastic [8]. Awwad and Shabeeb (2007) demonstrated that the characteristics of asphalt mixtures modified by HDPE were more improved compared with those containing LDPE [9]. Moghaddam and Karim (2012) stated that the use of waste material in asphalt pavements was a suitable method to increase their service life. It was also concluded that, compared with none-modified asphalt mixtures, those modified by PET had more sustainability, flow, and fatigue strength [10].
2. Problem statement and objectives As to the present study, the dynamic behavior of the modified asphalt mixture by glass and modified bitumen by HDPE, choosing stone materials from the Garkanrud River in Guilan Province. The effect of these two additional materials on improving the asphalt destructions caused by fatigue and rutting was investigated through laboratory studies.
3. Laboratory investigations 3.1. Consumed materials 3.1.1. Aggregate materials The physical, chemical, and mechanical properties of aggregates play a significant role in the performance of pavement. X-ray fluorescence spectroscopy (XRE) was applied in order to assess and measure the existing elements in the samples (determine element percentage). The results of XRE analysis, presented in Table 1, showed high levels of silicon dioxide in stone materials. Therefore, the aggregates of this mine could be categorized as silicon materials. Moreover, according to ASTM D-2419, the sand equivalent of the sand applied in this research was equal to 89; also, according to ASTM D-5821, the percentage of fractured particles of the gravel applied in this research was equal to 98.2 and 96.9 on one and two sides, respectively. According to ASTM D-131, L.A abrasion loss was equal to 27.2. Surface layer gradation sieves, which were selected from the materials screened by 19 and 12.5 mm and #4, #8, #50, and #200 sieves, were applied for the gradation of aggregates applied in this research the gradation documented in AASHTO green book was applied in order to produce the sample of solid asphalt mixture. All the stone materials were sieved in the lab. Therefore, there was no difference in the gradation of the samples. The material
Table 1 Results of XRE analysis on hydrated lime and fillers of aggregates for the laboratory samples. Features of sample material
Sio2 (%)
Al2O3 (%)
Fe2O3 (%)
CaO (%)
MgO (%)
Na2o (%)
K2O (%)
CO2 (%)
Weight loss on ignition (L.O.I) (%)
Gravel Sand Filler
48.36 48.11 47.07
12.5 8.67 11.05
6.4 5.8 5.2
15.5 18.48 16.92
2.2 1.86 2.5
2.16 1.71 2.10
0.96 0.94 1.03
10.41 12.75 12.11
12.23 14.42 14.13
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Fig. 1. Aggregate gradation chart along with AASHTO gradation limits.
gradation chart is illustrated in Fig. 1. The suggested limits of AASHTO green book are included as well. 3.1.2. Bitumen The bitumen applied in asphalt mixtures is chosen depending on several important parameters. Therefore, parameters such as climatic conditions of the area, traffic type and intensity, type of pavement, type and gradation of aggregates, and pavement construction method are considered. The higher the annual average temperature in the area, or the more and heavier the vehicles, the more fluent would be the cutback bitumen that is needed for asphalt mixtures. The PG64-16 (performance grade) bitumen was applied in this study, because of its application in the construction of asphalt pavements in the temperate districts of northern Iran. The characteristics of the bitumen applied in the research are illustrated in Table 2. 3.1.3. Waste glass The waste glasses of a glass cutting manufactory were used in this study. The maximum size of the glass pieces was 4.75 mm. The applied gradation curve for the glass is illustrated in Table 3.
3.1.4. Waste plastic bottles The applied plastic bottles were taken from the recycled materials of disposable containers produced by factories. Such materials consisted of HDPE. After providing the mentioned waste material from the landfill sites, they were completely cleaned of any other materials. They were cut in order to obtain pieces with suitable size to be mixed and digested within the bitumen. Finally, they were converted into much smaller pieces through cryogenic process. Fig. 2 illustrates a sample of waste materials getting prepared to be mixed with bitumen. 3.2. Experimental set up and procedure The experimental flow chart of this study is shown in Fig. 3. Since Marshall test has been applied in the asphalt design procedure in Iran, the selected variations in the Marshall optimum amount of bitumen is determined through the same test in order to investigate the effect of variations in its parameters such as bitumen percentage, empty space, etc. Glass and HDPE were added and mixed with the bitumen through dry and wet methods, respectively. As to the wet method,
Table 2 Results of bitumen performance tests in order to make the laboratory asphalt sample. AASHTO T48 flash point (°C) ASTM D4402 viscosity AASGTO T315 dynamic shear
290 Test: Test: Test: Test:
temperature (°C) viscosity (P/s) temperature (°C) (G⁄/Sind)KP
135 0.250 64 1.8
70 0.8
Table 3 Gradation range of the waste glass for the laboratory samples. Sieve
#4
#8
#16
#30
#50
#100
#200
Remainder percentage
100
63
42
27
14
9
2
Fig. 2. Additional material of the recycled pieces of plastic bottles applied in the present study.
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Modification of asphalt binder with 0, 2, 4, 6, 8 and 10 percent of HDPE
Marshal mix design according to the ASTM D1559 test mixtures
Measurement behavior of base and modified glassphalt with ITSM, ITFT and RLA tests Fig. 3. Flow chart of experimental design procedures.
the modified bitumen mixed with 2, 4, 6, 8, and 10% of HDPE was prepared by high shear mixer. Considering the promoted reflex of bitumen to the smaller pieces of additional materials and its better improvement, the pieces remaining on #100 and #200 sieves were applied in this research. The mixing process took place at 180 °C and the mixer speed of 4500 rpm. It was proceeded under the control of an opt-counter and microcontroller within 40 min. Fig. 4 illustrates the image obtained through electronic microscope photography of the bitumen and the additional material after being mixed. Fig. 5 shows a clearer image in a bigger scale. As can be observed in these images, all the HDPE pieces were completely digested to make a uniform homogenous mixture. The prepared samples were divided into 15 1200 g specimens in order to investigate Marshall strength and determine the optimum amount of bitumen. Also, 45 specimens were kept for the required dynamic tests. Indirect tensile stiffness modulus (ITSM), indirect tensile fatigue test (ITFT) and repeated load axial (RLA) tests were performed on each sample in three replicates. For each aggregate blend and
Fig. 4. Electronic microscopic images taken from the mixing process of bitumen and HDPE (additional material applied in this research).
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asphalt binder, at least three separate samples were produced to determine the reproducibility of the results. In order to evaluate the dynamic performance, modulus of stiffness was tested through ITSM, fatigue was evaluated ITFT, and creep was tested using RLA. 3.2.1. ITSM test The stiffness modulus of the samples was determined by the indirect tensile strength method (ITSM) using a Nottingham Asphalt Testing system. The stiffness modulus test was performed by applying a linear force along the diameter axis of the specimen. Each loading cycle was 0.1 s long. Thus, given the total duration of loading and unloading of 1 s, the rest time period of each cycle is 0.9 s. 3.2.2. ITFT test The fatigue life of the specimens was measured using a Nottingham Asphalt tester in constant stress mode (the stress was held constant to increase the strain within the sample) by applying repeated loads with fixed amplitude along the diametrical axis of the specimen. The repeated load consisted of 0.1 s loading time followed by a 0.4 s of rest time. Cylindrical specimens with a diameter and height content of 101.6 mm and 40 mm respectively were tested at 25 °C. 3.2.3. RLA test The RLA test applies a repeated pulsed uniaxial stress on an asphalt specimen and measures the resulting deformations in the same direction using linear variable differential transducers (LVDTs). For the RLA test, cylindrical specimens of 60 mm 101.6 mm (thickness diameter) were prepared. 4. Result and analysis The values of the modulus of resilience for the samples made by different amounts of HDPE at 5, 25, and 40 °C and stress level of 250 KP were obtained based on ASTM-D4123. A semi-sinusoidal loading with 1 Hz frequency, 1 s loading cycle, 0.1 s loading duration 0.9 s relief duration, and 0.35 Poisson’s ratio was applied in this test. The results of resilience test on the tested samples are illustrated in Fig. 6. As can be observed, the values of modulus of resilience were decreased as temperature increased, which was because of the reduction in the elasticity of bitumen and asphalt mixture and the decrease in its viscosity. For example, the ITSM values of base asphalt mixture are 20,797, 2423 and 396 MPa in 5, 25 and 40 °C, respectively. On the other hand, with the increase in the volume of HDPE polymer at average and high temperatures, the resilience of bitumen and mixture increased. The increase in this value compared with the observed sample was equal to 51.5 and 38.4% at 25 and 40 °C, respectively. As can be seen in Fig. 6, the highest
Fig. 5. Electronic microscopic images taken from the mixing process of bitumen and HDPE (additional material applied in this research).
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10000
10000
Loading Cycle
Loading cycle
100000
1000 100 Temprature 5( C)
10
Temprature 25( C)
1000
100 25( C) Temprature in 250 Kp stress
10
25( C) Temprature in 400 Kp stress2
Temprature 40( C)
1
0%
2%
4%
6%
8%
10%
HDPE percent
40( C) Temprature in 250 Kp stress22
1
%0
%2
%4
%6
%8
%10
HDPE percent Fig. 6. Chart of modulus of resilience for HDPE-containing glassphalt. Fig. 8. Results of indirect tensile fatigue test on asphalt mixtures.
Loading Cycle
slope of the increase in modulus of resilience through adding HDPE was related to 5 °C. As the temperature further increased, the increase in the resilience slope was reduced compared with the sequential percentages. Modulus of resilience also increased while more HDPE was added, but it was still lower than the control sample. This decrease in modulus of resilience might be caused by the chemical structure of this additional material and the behavior of its hydro-carbonic structure at different temperatures. The dynamic creep test was also applied to the asphalt mixture samples with different amounts of glass pieces and HDPE at 60 °C and stress levels of 150 and 300 KP. This test was performed based on BS: DD226 in order to evaluate the asphalt destruction derived by rutting phenomenon. The results of this test at the end of loading are illustrated in Fig. 7. According to the observed process in Fig. 7, it can be concluded that the number of cycles needed to obtain the strain of 8% was increased as more HDPE was added. In other words, because of the link developed between the hydro-carbonic canines of HDPE molecules and bitumen, the resistance of this structure against constant deformations was increased. On the other hand, with the increase in the level of applied stress and resistance cycle of the asphalt mixture is decreased up to the strain of 8% and the compared to the samples under 300 KP of loading, samples under the load of 150 KP resist longer against the rutting. According to Fig. 7, it can be observed that the gradient of the increase in number of the needed cycles increased as more material was added; thus, there was a significant increase in the slope between 6 and 10% (particularly, between 8 and 10%). Therefore, larger amounts of the additional material improved the reaction of bitumen; as a result, the resilience and reversibility of the mixture were increased after unloading. Based on EN12697-24, indirect tensile fatigue test was applied to the asphalt samples made by different amounts of HDPE at 25 and 40 °C and stress levels of 250 and 400 KP. Results are illustrated in Fig. 8. Loading cycle of 1.5 s with the loading duration 5000 4500 4000 3500 3000 2500 2000 1500 1000 500 0
150 Kp 300 Kp
0%
2%
4%
6%
8%
10%
HDPE Percent Fig. 7. Results of dynamic creep test on the asphalt mixtures modified with different amounts of HDPE at various levels of stress.
of 0.25 s and relief duration of 1.25 s was applied in this test. Fatigue was defined as sample failure and diametric deformation of 9 mm. As can be observed in Fig. 8, at the average temperature (25 °C), the fatigue life was prolonged with an increase in the percent of additional material, showing that the additional material had good resilience at low and average temperatures. For example, the fatigue life values of asphalt mixtures are 1429, 2440, 3028, 4921, 10,369 and 10,885 cycles in 0, 2, 4, 6, 8 and 10% of HDPE, respectively. This additional material was depolymerized in reaction to the bitumen and their hydro-carbonic chains were well-linked. Considering Fig. 8, the optimum percent of additional material was between 6 and 8%. At the stress level of 250 KP and 25 and 40 °C, the fatigue life was increased by more than six times. Moreover, this additional material was weakened at high temperature and stress levels and the significant effect was observed at low and average temperatures and lower levels of stress is shown no longer. As can be observed, the obtained resistance at 40 °C and tension level of 400 KP was less than the loading stress level. Finally, at 40 °C and stress level of 250 KP, the incense was up to 2.5 times. 5. Conclusion Considering the performed studies, the following results were obtained: 1. Investigation of the results related to the dynamic behavior of the asphalt mixtures modified through adding waste materials indicated that this additional material increased the elasticity and reversibility of asphalt mixtures after unloading up to a good level. 2. For the fatigue phenomenon, considering the increase in the number of loading cycles, the optimum percent of HDPE was between 6 and 10% with an increasing slope. Investigating the results of fatigue, creep, and resilience tests, it was indicated that about 6–8% of this additional material can be followed by an optimum state of step-by-step promotion of the properties. Besides, the absolute value of the optimum use of this additional material was equal to 10% under any circumstances. 3. Since HDPE is depolymerized in reaction to bitumen, during which it absorbs the aromatic part of bitumen and swallows, the hydro-carbonic chains would be well-joint. So, it can be concluded that this additional material has good resilience at low and average temperatures. 4. Investigation of the results achieved through the tests on the asphalt mixtures showed that, in addition to a decrease in asphalt production costs, using 10% of waste glass and 10% of HDPE improved the performance of these mixtures as long as they were in service, since their characteristics and properties
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were promoted. This issue would also decrease the pavement maintenance costs. 5. Results also indicated that, at 25 and 40 °C and the most optimum percent of HDPE, the repeated loads of 10,885 and 129 were achieved. Also, at average temperatures (25 °C), the use of HDPE provided proper results compared with pure bitumen. Therefore, it can be concluded that the use of the asphalt mixtures modified by HDPE is more suitable in the areas with temperate climate and average temperature.
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