Sustainable use of waste plastic modifiers to strengthen the adhesion properties of asphalt mixtures

Construction and Building Materials 235 (2020) 117496

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Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat

Sustainable use of waste plastic modifiers to strengthen the adhesion properties of asphalt mixtures Safeer Haider a,⇑, Imran Hafeez a, Jamal b, Rafi Ullah a a b

Department of Civil Engineering, University of Engineering & Technology Taxila, Pakistan Department of Civil Engineering, Royal Malborne Institute of Technology (RMIT University), Melbourne City Campus, Australia

h i g h l i g h t s
Moisture damage resistance of waste plastic modified asphalt mixtures was conducted.
Wet method of mixing was found relatively better than dry method of mixing to resist moisture damage in asphalt mixtures.
Calcium carbonate and dolomite type aggregate quarries were found relatively better against moisture resistance due to high polarity, basic and

hydrophobic nature of aggregate.
Waste plastic modifiers in asphalt pavement extends pavement service life as well as reduction of raw material to maintain sustainable environment.

a r t i c l e

i n f o

Article history: Received 21 July 2019 Received in revised form 31 October 2019 Accepted 4 November 2019

Keywords: Moisture Aggregate minerals Wet process Rock type

a b s t r a c t Low pavement performance increases environmental degradation and reduces natural reserves. This reduction in pavement’s service life is attributed towards moisture susceptibility, rutting and fatigue failures of asphalt pavements. To overcome this, waste plastic modifiers were used in this research study to improve the asphalt mixtures moisture damage resistance and hence the asphalt pavement’s service life. Four different sources of aggregate based on petrography of rock were selected to ascertain the effect of different minerals on moisture damage. Qualitative as well as quantitative tests were utilized to assess moisture sensitivity. The analysis of test data showed that high density polyethylene and wet method of mixing has relatively better adhesion properties. Moreover, acidic aggregates containing granite minerals showed more loss of adhesion than basic aggregate quarries due their less polarity and hydrophilic nature. Modified Lottman as well as Hamburg wheel track test were found relatively better for compacted asphalt mixture than Marshall stability test for moisture damage assessment. This study recommends using waste plastics in the asphalt mixtures to improve performance life of the pavement and reduces the environmental degradation. Ó 2019 Elsevier Ltd. All rights reserved.

1. Introduction Moisture damage plays a prominent role in asphalt pavement performance. Although, moisture doesn’t initiate the permanent deformation, fatigue cracking and raveling but it only increases their severity [1–4]. Moisture damage is either failure of cohesion with in asphalt binder or adhesion that is bond failure between aggregate and asphalt binder interface [5–7]. Historically, this phenomenon can be explained by any of the following six mechanisms i.e. spontaneous emulsification, detachment, displacement, hydraulic scouring pore pressure and environmental effect on asphalt mixture. Moisture damage is not due to single phenomena ⇑ Corresponding author. E-mail address: [email protected] (S. Haider). https://doi.org/10.1016/j.conbuildmat.2019.117496 0950-0618/Ó 2019 Elsevier Ltd. All rights reserved.

but it is the combination of processes [8–15]. First water interacts with asphalt binder and reduce cohesive strength as well as stiffness of asphalt mixture. Second, water enters the spaces between asphalt binder film and aggregate, cause adhesive failure and finally stripping of binder film from aggregate. Stripping usually occurs at the bottom layer of flexible pavement. Adhesion is fundamental property of asphalt mixture and highly effect the pavement quality and durability [15–19]. Moisture can infiltrate into asphalt pavements through rising of ground water table, rainwater and absorption of aggregates. This infiltration of water shortens the design life of asphalt pavement and increase maintenance cost. In service life every pavement needs maintenance at some points. Maintenance ensures that pavement is in operational condition, minimizes expenditures and inconvenience of road users. Moisture damage mechanism

2

S. Haider et al. / Construction and Building Materials 235 (2020) 117496

consists of two steps i.e. moisture transport and response of the system. In transport process moisture infiltrates into asphalt mixture either in liquid or vapor state and reaches to aggregateasphalt binder interface. While response of the system includes loss of load carrying capacity due to internal change in structure [8,9,20,21]. The main constituents of asphalt mixtures are aggregate and asphalt binder. Their physical and chemical properties have direct influence on moisture damage failure [8,9,22–27]. The asphalt mixture exhibits different behavior when subjected to traffic loading. The behavior is classified into three categories i.e. viscous, elastic or viscoelastic. Viscoelastic material exhibit both behavior viscous as well as elastic when undergoing to traffic load deformation. Asphalt binder offer elastic and stiff behavior under low temperature while viscous under high temperature. Composite of both asphalt binder and aggregates i.e. asphalt mixture offer intermediate (visco-elastic) properties. Traffic loads reduce the internal strength of asphalt pavement. As a result, distresses like fatigue cracking, rutting and raveling occur in asphalt pavement. After that adhesive or cohesive forces in asphalt mixtures are primary responsible to hold aggregate and asphalt binder together [4,28– 30]. Several research studies indicated that aggregate characteristics such as cleanliness, surface texture, minerology, porosity, surface charge and energy, aggregate adsorption sites and polarity, asphalt binder’s chemistry and interaction between asphalt binder and aggregate significantly affect the moisture susceptibility [31,32]. Asphalt mixture contain approximately 95% aggregates. To get better mechanical interlocking, angular aggregates are relatively more favorable. Usually, basic nature aggregates have less adhesion properties than acidic nature [33,34]. Aggregate and asphalt binder make strong bond when they incorporate with different polarities. In case of aggregates, it is achieved by selecting different aggregate quarries with different minerals composition for preparation of asphalt mixture. Different chemical composition of aggregates results different properties of asphalt mixtures. While asphalt binder is the most important part and mainly determines the properties of asphalt mixture. Its moisture resistance can be enhanced by modification. Modified asphalt binder has higher TSR values as a result modified asphalt mixture gives better moisture resistance. However, asphalt binder with high viscosity show relatively better adhesion properties [30,35–38]. Aggregate quarries were selected based on the petrography of rock sources. Acidic or basic behavior of rock depends upon amount of silica (SiO2 ). A rock source rich in silica having acidic behavior and contains minerals like quartz, biotite and feldspar. Basic nature of rock source contains less amount of silica and minerals like olivine and pyroxene. They also rich in the metals like magnesium and iron. Asphalt mixtures consists of acidic nature of aggregates have less adhesion properties than basic nature of aggregates [8,9,29,39–41]. In this research study waste plastic modifiers i.e. low-density polyethylene (LDPE) and high-density polyethylene (HDPE) were utilized to access moisture damage resistance of asphalt mixtures. Polymers are used to enhance the performance properties of asphalt mixtures [29]. In recent years, polymer use and production has increased drastically that cause environmental, health and territorial problems [7]. Polyethylene is mostly used in the world. It is a semi crystalline material having good fatigue, chemical and wear resistance and wide range of properties. Molecular structure of polyethylene consists of long chain of carbon atom with two hydrogen atoms attached with each carbon atom. Low density polyethylene has less moisture susceptibility, good corrosion resistance but not relatively useful where high stiffness and structure strength is required. However, high density polyethylene offers relatively high impact resistance, tensile strength, low moisture adsorption and light weight [42–44]. Polymers products increase

the quantity of accumulated urban solid waste. Plastics are utilized by most finish use of economy and their use extends with development of plastic trade. As a result there is successively increase in plastic waste [45]. Approximately, 30% of the total received material is processed by plastic recycling plant while 70% is disposed of in landfills that change the ecological system [45,46]. Instead of left freely of this waste plastic polymers in nature and landfilled, recovery of this ecological harmful waste must be taken into consideration. Researchers should develop new methods and policies to make plastic waste beneficial otherwise it will become un-solvable drawback [47]. An alternative use of waste plastic is its incorporation with asphalt mixtures. Waste plastic modifiers enhance the performance properties of asphalt mixture. They also have relatively higher potential to increase pavement service life [48,49]. Use of plastic waste in asphalt mixture will reduce the amount of asphalt binder as a result it will not be only ecofriendly but also will reduce the cost of whole project [50]. There are two mixing methods (i.e. dry and wet) used to add polymers in asphalt binder. In wet process, polymer is mixed with asphalt binder at high temperature. Then modified binder is used to prepare the asphalt mixture. While in dry mixing method, polymer is mixed to aggregates before adding the asphalt binder [29]. The tests to access moisture sensitivity of asphalt mixtures can be classified into two categories. The first test technique consists of, test on loose coated asphalt mixture such as boiling water test. While second one consists of, tests on compacted asphalt mixture such as Modified Lottman test (AAHTO T283). These test techniques access moisture sensitivity of asphalt mixtures considering cumulative effect of environmental conditions, different design parameters of asphalt mixture and material properties [7,44,51]. This research article accessed the adhesion properties of waste plastic (LDPE&HDPE) modified asphalt mixtures. Four different aggregate sources based on petrography of rock were selected to prepare the asphalt mixture to ascertain the effect of different aggregate minerals on moisture damage. Moreover, two different test regimes i.e. qualitative (tests on loose coated asphalt mixtures) and quantitative (tests on compacted asphalt mixtures) were utilized to access moisture resistance of asphalt mixtures. Qualitative tests include static water immersion test, total water immersion test, boiling water test and rolling bottle test. While quantitative test regime was consist of Marshal immersion test, Hamburg wheel track test and Modified Lottman test. 2. Objectives of research study This research study has following primary objectives: & & & &

To reduce environmental degradation and preservation of natural resources. To compare the effect of different waste plastic modifiers and aggregate minerals on adhesion properties of asphalt mixtures. To evaluate the performance of two mixing methods i.e. dry and wet process. To rank the aggregate quarries by determining variations in all laboratory test results.

3. Test materials and asphalt mix design A research study was divided into three phases. In first phase, to prepare asphalt mixture, single asphalt binder, four aggregate quarries and two waste plastic modifiers low density polyethylene (LDPE) and high-density polyethylene (HDPE) were selected. Based on petrography results aggregate quarries were selected. Margalla, Rohi, Sargodha and Gari Habib Ullah aggregate quarries contain

S. Haider et al. / Construction and Building Materials 235 (2020) 117496

calcium carbonate, dolomite, dolerite and granite minerals respectively. Asphalt binder i.e. commonly used in flexible pavements of Pakistan was taken from Attock Oil Refinery (ARL) Pakistan. In second phase of research study specimens were prepared for both qualitative and quantitative test regime. While in last phase all laboratory tests were performed to assess moisture sensitivity of asphalt mixtures. The flow chart of Research Methodology has been given in Fig. 1. 3.1. Aggregates Aggregate quarries were selected based on the petrography of rock sources. Amount of silica (SiO2 ) is responsible for acidic or basic behavior of rock. Acidic nature rock commonly rich in silica while basic nature aggregate quarries contain less amount of silica. Four different types of aggregate quarries locally available in Pakistan i.e. Margalla and Rohi aggregate quarries are basic in nature. Sargodha aggregate quarry has intermediate behavior. Gari Habib Ullah aggregate quarry due to rich in silica has acidic behavior. Selected aggregate quarries location has been shown in Fig. 2. As shown in Fig. 2 Margalla, Rohi and Sargodha quarry represents the northern part of country. While Gari Habib-Ullah represents North-West Frontier Province of Pakistan. For quantitative tests Bailey gradation shown in Fig. 3 was used to prepare specimens. Percentage of aggregate minerals of all selected aggregate quarries have been given in Fig. 4. According to ASTM C295 petrographic analysis was performed of all aggregate quarries. It may be noted from Fig. 4 that Margalla and Rohi aggregate quarries contain limestone. Sargodha aggregate quarry maximum

3

consists of plagioclase and chlorite while Gari Habib Ullah aggregate quarry is rich in Silica. Different tests were conducted to measure the physical and mechanical properties of aggregate in the laboratory. Aggregate engineering properties have been summarized in Table 1. It may be noted from Table 1 that fractured particles of all aggregate source are 100%. While having less than 15% of flakiness and elongation index. No aggregate quarry has loss angles abrasion value more than 30% and sand equivalent value less than 70%. Uncompacted voids percentage is almost in 47 ± 2% range in the selected gradation. 3.2. Asphalt binder The selected asphalt binder is commonly used in Pakistan road network and basically consists of four generic fractions based on molecular size and chemical reactivity. These four groups consist of saturates, aromatics, resins and asphaltenes. As aromatics are the 40–65% of total asphalt binder volume that is the main reason of the non-polar behavior of asphalt binder. Material properties of control and modified asphalt binder has been given in Table 2. 3.3. Modifiers Two different waste plastic modifiers i.e. low-density polyethylene (LDPE) and high-density polyethylene (HDPE) were selected for asphalt binder modification. Both LDPE and HDPE were added by the weight of asphalt binder of the amount of 3, 6, 9 and 12% in asphalt mixtures. Marshal method was used to optimize the dose of modifiers. Marshal molds have maximum stability at 9% waste plastic by the weight of asphalt binder in both dry and

Fig. 1. Flow Chart of Adopted Research Methodology.

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S. Haider et al. / Construction and Building Materials 235 (2020) 117496

Fig. 2. Location Map of Aggregate Quarries.

100

Passing (%)

80

60 NHA-B lower limit Selected Gradation

40

NHA-B upper limit 20

0 0

0.075 0.15 0.3 0.6

1.18

2.36 4.75

6.3

9.5

Sieve Size raised to 0.45 power Fig. 3. Bailey Gradation Curve.

12.5

19.0

5

S. Haider et al. / Construction and Building Materials 235 (2020) 117496

Cremish Brown limestone 2% Dark Grey to Grey Veined Limestone 9% Light Grey Limestone 14%

Quartzwacke 1%

Met dolerite 2%

Grey meta dolerite 2%

Grey Limestone 44%

Dark Grey Limestone 30%

Greenish grey dolerite 95%

Margallah

Sargodha

Pyrite 1%

Feldspar 5%

Quartz 8%

Orange red Rhyolite 1%

Soda 4% Potasium Oxide 5%

calcite 9%

Iron Lime 2% 1%

magnesia 1%

Alumina 11%

Dolospar 44%

Silica 76%

Dolomicrite 33%

Gari Habib Ullah

Rohi

Fig. 4. Mineral Composition of Different Aggregate Quarries.

Table 1 Engineering properties of aggregates. Test Title

Standard

Margallah

Rohi

Sargodha

Gari-Habib

Limits

Type of Rock Fractured particles (%) Flakiness Index (%) Elongation index (%) Sand equivalent value (%) Los Angeles abrasion (%) Water absorption (%) Soundness (coarse) (%) Soundness (fine) (%) Uncompacted Voids (fine) (%)

—— ASTM D 5821 BS 812.108 BS 812.109 ASTM D 2419 ASTM C 131 ASTM C 127 ASTM C 88 ASTM C 88 ASTM C 1252

calcium carbonate 100 4.83 6.4 73 23 0.95 1.4 2.5 43.4

Dolomite 100 4.79 7.1 74 22.5 1.07 4.6 4.6 45.5

Dolerite 100 8 7 73 20 0.96 2.3 2.6 48

Granite 100 9 8 72 22.7 1.02 6.5 3.8 49

——— 90(min) 10(max) 10(max) 50(min) 30(max) 2(max) 8(max) 8(max) 45(min)

Table 2 Material Properties of Control and Modified Asphalt Binder. Test Name

Softening Point (°C) Penetration (0.1 mm) Ductility in cm (25 °C) Flash &Fire Point (°C)

Standard

ASTM ASTM ASTM ASTM

D36 D5 D70 D92

Asphalt Binder (ARL 60/70)

Range

Control Binder

LDPE Modified Binder

HDPE Modified Binder

48 66 123 248&252

77 30 27 274&277

87 25.5 24.5 284&288

46–54 60–70 100 (min) 232–450

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S. Haider et al. / Construction and Building Materials 235 (2020) 117496

wet method of mixing. So, 9% of both LDPE and HDPE were added by the weight of asphalt binder. 3.4. Asphalt mix design and specimen preparation

Table 3 Optimum Values of Control Binder and Modifiers. Type of Mix

Rock Source

Modifiers quantity

Conventional Mix (Control Binder)

Calcium carbonate Dolomite

4.30% (optimum value by weight of aggregate)) 4.28% (optimum value by weight of aggregate) 4.37% (optimum value by weight of aggregate) 4.28% (optimum value by weight of aggregate) 9% by the weight of asphalt binder

Specimens were prepared for qualitative as well as quantitative tests. For quantitative test samples preparation, bailey gradation was used while for loose coated asphalt mixtures single size aggregate i.e. ranges from 6.3 to 9.5 mm were selected. Both wet and dry methods were used to modify asphalt mixture with waste plastic. In wet process, asphalt binder was modified with LDPE and HDPE first and then the modified binder was used to prepare asphalt mixture while in dry process, the plastic was added and homogenized with aggregates and then the control asphalt binder was added. Pictorial view of specimen’s preparation has been given in Fig. 5. It may be noted from Fig. 5 that specimens were prepare for both loose as well as compacted asphalt mixtures. Hamburg wheel Track test and modified Lottman test specimens were compacted in Gyratory compactor. After that they were cut into standard dimensions to perform both tests. Optimum values of control binder and modifiers are given in Table 3.

It may be noted from Table 4 that for each qualitative test three replicates were prepared. In case of quantitative tests six replicates were prepared, three for conditioned and three for unconditioned.

3.5. Testing program

4. Results and discussion

Experimental program was divided into two categories i.e. qualitative tests (performed on loose coated asphalt mixtures) and quantitative tests (performed on compacted asphalt mixtures). Qualitative tests include static water immersion test (SWIT), total water immersion test (TWIT), boiling water test (BWT) and rolling bottle test (RBT). While Marshal Immersion test, Modified Lottman test and Hamburg Wheel Track test comes under the umbrella of quantitative tests. List of tests has been given in Table 4.

In first phase qualitative tests has been analyzed while second one consists of quantitative test results discussion.

Dolerite Granite LDPE Modified Mix

HDPE Modified Mix

Calcium carbonate Dolomite Dolerite Granite Calcium carbonate Dolomite Dolerite Granite

9% by the weight of asphalt binder

4.1. Qualitative tests The static water immersion test (SWIT) was performed according to ASTM D1664. In this test single size aggregates coated with molten asphalt binder were used. Then the sample was immersed

Fig. 5. Pictorial View of Specimens Preparation.

7

S. Haider et al. / Construction and Building Materials 235 (2020) 117496 Table 4 List of laboratory tests used in this research study. Type of Test

Test Name

Standard

Sample dimension

Test Condition

Total samples

Qualitative Tests

Static Immersion Test Total Immersion Test Boiling Water Test

ASTM D1664 ASTM D1664 ASTM D3625 BS EN 12697 AASHTO T283 AASHTO T324 ASTM D1559

6.3 to 9.5 mm Agg. coated with asphalt 6.3 to 9.5 mm Agg. coated with asphalt 6.3 to 9.5 mm Agg. coated with asphalt 6.3 to 9.5 mm Agg. coated with asphalt Height = 63.5 mm Diameter = 150 mm Height = 63 mm Diameter = 150 mm Height = 63 mm Diameter = 100 mm

Temperature 25 °C Immersing time = 16–18 h

15  4 = 60

Temperature 40 °C Immersing time = 3 h

15  4 = 60

Temperature 100 °C Immersing time = 10 min.

15  4 = 60

Temperature 25 °C Rotations per minute = 60 Rotation time = 6 h, 24 h, 48 h, 72 h Air voids = 7% ± 1.0 Conditioning time, temperature = 24 h, 60 °C Load rate = 25 mm/min Wheel load = 705.0 + 4.5 N Pass rate = of 52 ± 2/minute Temperature 50 °C wheel passes = 20000 Conditioning time and temperature = 24 h,60 °C

15  4 = 60

Rolling Bottle Test Quantitative tests

Modified Lottman test Hamburg wheeltrack test Marshall Immersion Test

30  4 = 120 15  4 = 60 30  4 = 120

Fig. 6. Pictorial view of qualitative laboratory test work.

in water at 25 °C for 16–18 h. After that average asphalt binder cover loss was visually observed. Total water immersion test (TWIT) was conducted according to ASTM D1664. In this test loose coated sample was immersed for 3 h while temperature was 40 °C rather than of 25 °C. The boiling water test (BWT) was performed in accordance with ASTM D3625. Boiling water test take less time than other qualitative tests. In this test each loose coated sample was boiled in distilled water for 10 min. The rolling bottle test (RBT) was performed according to BS EN 12697. In this test 170 g of single size oven dried aggregate sample coated with 8 g of molten asphalt binder was used. Asphalt binder cover loss was observed visually after 24 h, 48 h and 72 h. Pictorial view of qualitative tests has been given in Fig. 6. Results of all qualitative tests performed in laboratory are shown in Fig. 7. It may be noted from Fig. 7 in all qualitative tests, wet method of mixing for waste plastic modifiers has less asphalt binder coating loss than dry method. HDPE has higher resistance against moisture sensitivity with all aggregate quarries than LDPE. Based on 20% minimum failure criteria adopted, all aggregate quarries and

modifiers have percentage loss less than 20% except rolling bottle test. In rolling bottle test Margalla and Rohi aggregate quarries with LDPE has less percentage loss than minimum adopted failure criteria. Sargodha and Gari Habib aggregate quarries have less adhesion properties i.e. percentage loss up to 25–35%. Moreover, it may be noted from all test results that wet method of mixing has less asphalt binder coating loss than dry method of mixing. Aggregate quarries consist of calcium carbonate and dolomite minerals have less coating loss due to hydrophobic and basic nature of aggregates. In modifiers, LDPE was found relatively better in adhesion properties as compared to HDPE.

4.2. Quantitative tests 4.2.1. Modified Lottman test Modified-Lottman test was performed according to AASHTO T283. Specimens having air voids above or below 7% ± 1.0 were discarded. Six specimens were prepared for each modifier i.e. three were for unconditioned and three for conditioned.

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S. Haider et al. / Construction and Building Materials 235 (2020) 117496

10

%Loss

8 6 4 2 0 Control Binder

Dry

Wet

Dry

(a)

LDPE

Wet HDPE

14 12

%Loss

10 8 6 4 2 0 Control Binder

Dry

Wet

%Loss

LDPE

Wet HDPE

18 16 14 12 10 8 6 4 2 0 Control Binder

Dry

Wet LDPE

%Loss

Dry

(b)

40 35 30 25 20 15 10 5 0

Dry

(c)

Wet HDPE

Mini. failure criteria 20%

Margallah Rohi Sargodha Gari Habib

Control Binder

Dry

Wet

Dry

(d)

LDPE

Wet HDPE

Modifier Type Fig. 7. Qualitative test results (a) SWIT (b) TWIT (c) BWT (d) RBT.

The maximum indirect tensile force ‘P’ at failure of specimen was recorded, TSR value calculated as following;

Tensilestrengthratio ðTSR%Þ ¼ Scond ¼ Sdry ¼

2000Pcond ptd

2000Pdry ptd

Scond Sdry

ð1Þ ð2Þ ð3Þ

where: Scond = Avg. tensile strength of conditioned specimens, kPa Sdry = Avg. tensile strength of dry specimens, kPa P = maximum load (N) T = specimen thickness (mm) D = specimen diameter, mm Results are shown in Fig. 8.

9

S. Haider et al. / Construction and Building Materials 235 (2020) 117496

100

Mini. failure criteria 80%

95

Margallah

90

Rohi

%TSR

85

Sargodha

80 Gari Habib 75 70 65 60 Control Binder

Dry

Wet

Dry

LDPE

Wet HDPE

Type of Modifiers Fig. 8. Effect of Plastic Type, Mixing Method & Aggregate Quarry on Tensile Strength Ratio of Asphalt Mixtures.

It may be noted from Fig. 8 that Sargodha aggregate quarry have tensile strength ratio greater than specified limit due to addition of HPDE waste plastic modifier. Calcium carbonate and dolomite aggregate quarries have tensile strength ratio greater than 80% with both HPDE and LDPE. While Gari Habib Ullah aggregate quarry containing granite, aggregate minerals have less tensile strength ratio with all type of modifiers. As greater the TSR values, asphalt mixture would be less susceptible to moisture damage and vice versa. So, it can be concluded that Calcium carbonate and dolomite aggregate quarries are more resistant against moisture damage due to hydrophobic and basic nature of aggregates. While granite minerals being nonpolar and hydrophilic in nature have less adhesion properties. 4.2.2. Hamburg wheel-track test Hamburg Wheel Track test (HWTT) was used to determine moisture damage of asphalt mixture. A wheel having load of

705.0 ± 4.5 N passes at the rate of 52 ± 2 pass per/minute on each asphalt specimen. Results of Hamburg wheel track test are shown in Figs. 9 and 10. It may be noted from Figs. 9 and 10 that wet method of mixing modifiers has low rut depth as compared to dry method of mixing for all four types of aggregate sources. Calcium carbonate and dolomite type aggregate quarries being hydrophobic in nature have less adhesion properties. That is why they are less sensitive to water. On the other hand, aggregates containing granite minerals are more sensitive to water that cause high rut depth due to their non-polar behavior.

4.2.3. Marshall immersion test Marshall Immersion Test was performed in accordance with ASTM D1559. Marshal molds were prepared for both wet and dry conditioned mode. For loss of stability, specimens were

8

7

LDPE (Wet) Margallah

LDPE(Dry) Margallah

HDPE (Dry) Margallah

Control binder (Margallah)

HDPE (Wet) Margallah LDPE(Wet) Rohi

LDPE(Dry) Rohi

HDPE(Wet) Rohi

HDPE(Dry) Rohi

Control Binder (Rohi)

6

RUT DEPTH

5

4

3

2

1

0 0

2000

4000

6000

8000

10000

12000

14000

16000

NO.OF CYCLES Fig. 9. Rut depth (mm) of Margalla and Sargodha aggregate quarries.

18000

20000

10

S. Haider et al. / Construction and Building Materials 235 (2020) 117496

12

10

LDPE(Wet) Sargodha

LDPE(Dry) Sargodha

HDPE(Wet) Sargodha

HDPE(Dry) Sargodha

Control Binder (Sargodha)

LDPE(Wet) Gari Habib

LDPE(Dry) Gari Habib

HDPE(Wet) Gari Haibib

HDPE (Dry) Gari Habib

Control Binder (Gari Habib)

RUT DEPTH

8

6

4

2

0 0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

NO.OF CYCLES Fig. 10. Rut depth (mm) of Sargodha and Gari Habib aggregate quarries.

35

Minimum failure criteria adopted 20%

%Stability Loss

30

Margallah

25

Rohi

20

Sargodha

15

Gari Habib

10 5 0 Control Binder

Dry

Wet

Dry

LDPE

Wet HDPE

Type of Modifiers Fig. 11. Percentage Marshal Stability Loss.

conditioned by keeping them in water bath at 60 °C for 24 h before testing. Percentage loss of stability is given in Fig. 11. It may be noted from Fig. 11 again aggregate quarries containing granite minerals have percentage stability loss greater than 20%. However, when HDPE is added by wet method of mixing, asphalt mixture is less susceptible to moisture damage. Margalla and Rohi aggregate quarry has less stability loss with both LDPE and HDPE waste plastic modifiers. Moreover, control binder is less susceptible to the moisture damage with limestone aggregate quarries.

4.3. Effect of aggregate source It can be concluded from laboratory test results; calcium carbonate and dolomite minerals aggregate quarries have relatively better adhesion properties. Basic nature aggregates are more resistant against stripping than acidic nature aggregates. As hydrophobic aggregates more polar than hydrophilic nature aggregates, form a better bond, therefore, it is hard for water to access the surface of aggregates. Limestone i.e. calcium carbonate and dolomite type aggregate source are principally composed of double

11

S. Haider et al. / Construction and Building Materials 235 (2020) 117496

50

TSR(mean % damage loss)

45

Margalah

y = -0.3887x + 50.199 R² = 0.9627

40

Rohi

35

Sargodha

30

Gari habib

25 y = -0.3085x + 16.744 R² = 0.9568

20 15 10

y = -0.3363x + 40.389 R² = 0.952 y = -0.5033x + 24.872 R² = 0.9762

5 0 0

10

20

30

40

50

60

70

80

90

100

Rolling Bottle test (%damage loss) Fig. 12. Correlation between rolling bottle test results and TSR (%).

100

Hamburg wheel track test (mean % damage loss)

90 y = -0.8012x + 97.462 R² = 0.9098

80

Margalah Rahi

y = -0.9382x + 65.803 R² = 0.9862

70

Sargodha

60

Gari habib

50 40 30 y = -0.5622x + 75.915 R² = 0.9894

20 y = -1.1734x + 68.504 R² = 0.979

10 0 0

10

20

30

40

50

60

70

80

90

100

Rolling Bottle test (%damage loss) Fig. 13. Correlation between rolling bottle test and Hamburg wheel track test results.

carbonate of magnesium and calcium or calcium carbonate. SWIT and TWIT are not suitable to distinguish between calcium carbonate and dolomite type aggregates. BWT and RBT provide better results in related to their bonding properties. Almost, all qualitative tests can be used to distinguish between acidic and basic nature aggregate source. TWIT can also provide a very reasonable reference to distinguish these aggregate types.

4.4. Correlation between qualitative and quantitative test results Four different equations for four aggregate quarries has been developed to access correlation between qualitative and quantitative test results. Results are given in Figs. 12 and 13. It may be noted from above Figs. 12 and 13 rolling bottle test results are widely acceptable and reliable that is the main reason

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S. Haider et al. / Construction and Building Materials 235 (2020) 117496

Fig. 14. Mean percentage loss of aggregate quarries.

of the selection of rolling bottle test in qualitative testing. While in quantitative tests, Modified Lottman test and Hamburg wheel track test has relatively higher confidence level than Marshal

stability test. With the help of these equations, if we have results of qualitative tests then we can easily access the quantitative test results.

Fig. 15. Mean percentage loss of modifiers.

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S. Haider et al. / Construction and Building Materials 235 (2020) 117496

Fig. 16. Percentage tensile strength ratio of different modifiers.

4.5. Statistical analysis Statistical analysis was carried out using Tukey method and box plot in SPSS software package. The box plot (a.k.a. box and whisker diagram) is used to display the distribution of data based on five number summaries i.e. minimum, first quartile, median, third quartile and maximum. Rectangular segment shows the median while whiskers above and below the box show the locations of minimum and maximum. The simplest box plot displays full range in the variation of data (minimum to maximum), typical value (the median) and the likely range of variation i.e. the inter quartile range (IQR). Results are shown in Figs. 14 and 15. It may be noted from Figs. 14 and 15, laboratory test results of all four types of qualitative tests has same ranking of asphalt binder modifiers as well as aggregate sources. Anyone of the qualitative test can be used to rank the aggregate and asphalt binder modifiers. Moreover, aggregate quarry containing granite minerals is more sensitive to water than other aggregate quarries. That is why Gari Habib aggregate quarry have less rut resistance, TSR values and higher marshal stability loss. The key reason behind this is the more affinity towards water of these aggregate quarries. In box plot, results analysis of quantitative testing i.e. TSR (%) which is relatively better moisture sensitivity assessment as compared to other two types of tests have been shown in Fig. 16. It may be noted from Fig. 16 that wet method of mixing has relatively higher values of tensile strength ratio than dry method. HDPE modified asphalt mixtures have less TSR loss and less susceptible to moisture damage. However, LDPE also improves the performance of asphalt mixture than control binder. Tukey method is basically multiple comparison single step procedure. It is used to determine means that are notably different from each other.

Formula used in Tukey Method:

qs ¼

YA þ YB SE

ð4Þ

where qs = mean, Y A = larger of two means being compared, Y B = smaller of two means being compared, SE = standard error of sum of means. To perform this method all qualitative as well as quantitative test results were imported in data view. After this name were given to all variables in variable view. Results of Tukey method has been given in Table 5. It may be noted from Table 5 that static water immersion test and total water immersion test are in same subset. Anyone out these both qualitative tests can be used to check moisture sensitivity of proposed asphalt binder modifiers as well as aggregate quarries. Boiling water test and rolling bottle test have different subset as a result they have different results from each other. As, rolling bottle test have more reliability than boiling water test, so it is commonly used to access moisture sensitivity of loose coated asphalt mixtures. Overall in this research article four qualitative and three quantitative tests were utilized to assess moisture damage. Based on results of these laboratory tests, it was found that Margalla, Rohi Table 5 Tukey Method Results. Mean Percentage Loss (%) Type of Test Tukey Ba,b

N SWIT TWIT BWT RBT

20 20 20 20

Subset at 95% confidence interval 1 2 3 4.35 6.63 10.85 22.90

14

S. Haider et al. / Construction and Building Materials 235 (2020) 117496

aggregate quarries being highly polar, hydrophobic and basic nature of aggregate with both LDPE and HDPE waste plastic modifiers were found relatively more resistant against moisture damage. In mixing methods of modifiers, wet method of mixing was found relatively better than dry method. However, dry method of mixing also improves the performance of asphalt mixtures.

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5. Conclusion Based on all the laboratory test results, &

&

&

&

Aggregate physical and chemical properties strongly influence the performance of asphalt mixtures. Based on results of these laboratory tests, it was found that Margalla and Rohi aggregate quarries being high polar, hydrophobic and basic nature of aggregates have relatively strong adhesion properties. Aggregate quarry containing granite minerals was more susceptible to moisture damage due less polarity, hydrophilic and acidic nature of aggregates. In modifiers, high density polyethylene (HDPE) is less sensitive to moisture damage. However, low density polyethylene (LDPE) also enhances the performance properties of asphalt mixtures. In mixing methods, wet method of mixing was found relatively better than dry method of mixing. When modifiers were mixed through wet method, then there is less percentage coating loss of asphalt binder as well as less rut depth, marshal stability loss and more TSR values. In statistical analysis, 70% test samples of aggregate quarries containing calcium carbonate and dolomite minerals have percentage cover loss less than 15% due to high polarity, hydrophobic and basic nature of aggregate.

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Declaration of Competing Interest

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The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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Acknowledgement

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The authors thank the Transportation Engineering Department for providing material and friendly environment to conduct this research study.

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