Investigation of Crumb Rubber Modification on the Performance of Bitumen and Asphalt Mixtures

doi:10.21203/rs.3.rs-3246241/v1

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Investigation of Crumb Rubber Modification on the Performance of Bitumen and Asphalt Mixtures

https://doi.org/10.21203/rs.3.rs-3246241/v1

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The performance of flexible pavements is greatly influenced by rutting, fatigue, and durability. The limitations of traditional bitumen in flexible asphalt pavements are due to the significant rise in traffic loads and volumes. The reason for incorporating tire waste into bitumen is its incredible qualities and economical price as a bitumen modifier. The quality of crumb rubber-modified bitumen (CRMB) mainly depends on the concentration of crumb rubber (CR) dispersed into the base bitumen. The primary target of this research is to modify the bitumen with CR to improve the thermal properties, rheology, rutting resistance, fatigue resistance, and moisture-damaged performance. The three concentrations, i.e., 5%, 10%, and 15% of CR, were prepared by dispersion in conventional 60/70 penetration grade bitumen. The consistency and mixture test results concluded that the optimum dosage of CR-10% provides appropriate thermal, rheological, rut, fatigue, and moisture-damaged performance.

Civil Engineering

Crumb rubber (CR)

Rutting

Rheology

Rolling Bottle Test

Four-point Beam Fatigue Test

Flexible pavements have become more popular globally based on their ease of use, structural stability, low maintenance cost, functional performance, and good skid resistance compared to rigid pavements [1]. Bitumen is an indispensable binder that significantly impacts the mechanical performance of asphalt mixtures [2, 3]. However, asphalt pavements are susceptible to permanent deformation, cracking, and moisture damage due to their high sensitivity in the summer season [4–7]. In Pakistan, uncontrolled axle loads, high traffic volume, construction errors, and high ambient temperatures also promote premature failures [8]. These problems associated with the typical asphalt pavements are addressed effectively with polymer-modified asphalt, specifically, styrene butadiene styrene (SBS), polyethylene, and ethyl vinyl acetate (EVA) modified asphalt [6].

Conversely, these polymer modifiers require significant energy and hydrocarbon products derived from crude oil [9, 10]. As a result of their inherent need for non-renewable energy sources, traditional hot asphalt mixtures may not be consistent with the sustainable development idea in Pavement engineering [11]. Therefore, the introduction of scrap tire rubber powder, a recycled material made by grinding scrap rubber tires, is mixed into bitumen for specific modification techniques. With the rising trend of modifying the bitumen with scrap tires to resolve the issue of premature asphalt-pavement failures, this procedure utilizes a sizeable quantity of discarded rubber tires to address environmental and public health concerns [12].

Recent technological advancements have upgraded living standards and improved the quality and quantity of automobiles [13]. The substantial increase in vehicles per year has boosted the economy and rapidly increased the number of waste tires [14–16]. It is estimated that almost 1.5 billion tires are disposed of worldwide annually, and this trend would grow due to an increase in automobiles and traffic volume [17–19]. In 2018, developed countries like China and America produced scrap tires, approximately 380 and 300 million pieces [14, 20]. Previously, the discarded tires were disposed of in open plants, landfilled without treatment, and open burning. It generates severe environmental consequences, health problems, and fire hazards and consumes a substantial portion of land space [21–24]. Therefore, many nations and environment protection agencies have banned landfill disposal and encouraged adopting other tire recycling techniques. Many efforts have been accomplished in the past to recycle waste tires to overcome the accretion in landfills while providing beneficial effects. It includes manufacturing new tires, thermal decomposition, fuel, agricultural, recreational, sporting goods, and other civil engineering applications [25–27]. One of the recycling techniques is the consumption of waste tires on flexible pavements. For this purpose, the steel and fabrics are removed from the scrap tires; the residue is passed through shredding and converted into chips. The tire chips are either pulverized at room temperature or cryogenically in liquid nitrogen to develop CR powder, one of the most frequently approved bitumen additives for modifying asphalt. The transformation of scrap tires into rubber powder has many potential applications, including producing rubber products and modifying asphalt [11, 14]. The component that makes the tires are elastomeric compounds, textiles, and metals. The discarded tire comprises vulcanized rubber, including polymers with long chains and cross-linked via sulfur bonds [28].

Tire rubber is a perishable material that completes its design life generally within 3 to 5 years. CR is a recycled material reproduced from scrap tires with particle sizes ranging from 4.75 mm to 0.075 mm. Its fiber content is lower than 0.5% and has a specific gravity of 1.15 [25]. Adding CR to base asphalt could extend the pavement design life [29]. CR has been incorporated into bitumen, resulting in a cost-effective waste management solution that benefits the pavement industry [30]. Various countries have adopted CRMB in constructing motorways and airfield pavements [25]. Crumb Rubber Modified Asphalt (CRMA) positively impacted and increased the resistance against alligator cracking and rutting; and enhanced the skid resistance of the pavements [18, 22, 31, 32].

Rubber has been famous as an additive in asphalt for many years due to its elastic qualities. Natural Rubber has been employed for asphalt paving since 1843 by the British, and then other studies were conducted in the 1930s based on its positive environmental and noise reduction effects [33, 34]. The state of California investigated the use of scrap tires in asphalt mixtures in the 1950s. Charles McDonalds pioneered bitumen modification with CR in the early 1960s. Since then, significant progress has been made in the process, and CRMA guidelines have been developed by many US states [25]. Rubber was incorporated into asphalt from two methods, i.e., wet and dry [18, 31, 32]. The first method is called the 'Wet process,' used to prepare high and low-viscosity rubberized asphalt (a terminal blend "TB"). CR was obtained by converting scrap tires or other rubber into crumbs. Rubber was blended into the hot bitumen to produce rubberized bitumen [18, 31]. 'Dry process' that produces asphalt rubber, also indicated as a rubber-modified hot mix, is the second method of adding coarse rubber into the heated aggregates and mixing for a specific time before interacting with the bitumen [35, 36]. The level of interaction between the CR and the bitumen is an essential factor in determining the properties of CRMB. The CR particle's interaction with bitumen results in the formation of two distinct processes, i.e., swelling and dissolution. When the temperature is below 190°C, the swelling process predominates, while depolymerization takes center stage when the temperature rises above that mark [37].

In contrast, a prolonged interaction time may also lead to the depolymerization of CR particles, even at a temperature lower than 190°C [38]. The asphalt rubber engineering application was constrained by its poor elasticity, construction temperature, and inadequate storage stability value. At the same time, thermal depolymerization of rubber chips in terminal blend hot asphalt produced low viscosity and reduced mixing and compaction temperatures [39]. However, TB asphalt exhibits lower rutting resistance at high temperatures than SBS [18, 39]. Furthermore, the high rubber powder concentration in the asphalt compromises TB storage stability [18, 32]. The expansion of CR is primarily due to the diffusion of oils (maltene fractions) from bitumen into CR particles, which causes the CR particles to swell [40]. The swelling method is affected by various factors, including the type of bitumen and the CR modifier, i.e., source, composition, production method, particle size, and morphology [19, 41–44].

The effects of different mixing temperatures and processing equipment on the rheological properties of rubberized bitumen were studied by Navarro et al. [45–47]. Their investigation revealed that blending bitumen and CR at 180°C utilizing a particular processing apparatus and impeller geometry did not affect the rheological properties of CRMB. Nevertheless, the depolymerization of CR particles begins at around 180°C at a much slower rate. However, Lo Presti et al. [48] reported the impact of mixer speed and applied shear rate on the CRMB.

The characteristics of bitumen vary based on the composition and the refinery process of crude oil. Previous research studies abundantly evidenced that the CR dosage is a highly influential parameter affecting the CRMB properties. However, the consolidated research on the impact of CR concentrations on bitumen and asphalt performance against thermal susceptibility, high-temperature cracking, fatigue, and moisture susceptibility is limited [49, 50]. Therefore, due to the lack of enough knowledge in Pakistan, this study aims to evaluate the impact of CR on thermal susceptibility, rheological, rutting resistance, fatigue, and moisture susceptibility performance of modified bitumen and asphalt mixtures produced in Pakistan. Three concentrations of CR, i.e., 5%, 10%, and 15% by weight of bitumen, were used along with 60/70 penetration grade bitumen for producing three blends by a wet process. These blends are CRMB-5%, CRMB-10%, and CRMB-15%. The following are the main objectives of this study:

Effects of CR on physical properties and thermal susceptibility of modified bitumen.
Influence of CR dosages on modified bitumen's rheological properties, performance grading, and rutting resistance.
Investigation of the fatigue performance of base and CR-modified asphalt mixtures.
Determine the moisture susceptibility performance of CR-modified asphalt mixtures.

The road map and the approach adopted in this study are illustrated in Fig. 1. Permanent deformation of asphalt highways is highly dependent on aggregate properties, whereas low-temperature cracking and fatigue cracking are considerably less dependent. For this investigation, limestone aggregates were procured from the Margalla quarry in Pakistan. The qualitative and mechanical properties of bitumen and aggregates were evaluated using standard laboratory procedures.

2.1. Materials

Bitumen, aggregates, and crumb rubber (CR) additives are the three primary materials used in this study. The following sections provide a concise summary of each:

2.1.1. Aggregates

The limestone aggregates were procured from the Margalla quarry in the capital city of Pakistan, i.e., Islamabad. The mechanical and physical properties of aggregates were recorded as per ASTM and BS standards. The recorded results of Margalla aggregates included 5.8% Flakiness Index (FI), 9.5% Elongation Index (EI), 0.88% absorption, 75% sand equivalent, 21% Los Angeles Abrasion value, 0.9 deleterious material, and 4.7% sodium sulfate soundness value. It was validated that the recorded values of different aggregates properties are within the prescribed specification limits, indicating relatively good quality material [51].

2.1.2. Bitumen

Bitumen was procured from Attock Refinery Limited (ARL) Morhgah, located in Rawalpindi, Punjab, Pakistan. The qualitative properties of bitumen "60/70 penetration grade" were validated as per ASTM standards before the trial and have been discussed in the test section. The recorded test results confirmed that all the values were within prescribed limits.

2.1.3. Crumb Rubber (CR)

The CR samples were procured from a local processing plant where the truck and car scrap tires were reduced to ambient size. The scrap tires were processed through different operations like shredding, magnetic iron separation, granulation or milling, and sieving.

2.2. Gradation

The aggregates were heated at 110°C for one day. The NHA Class-B gradation of Pakistan's National Highway Authority was adopted in this study. The materials were sieved into various sizes with similar mineralogical compositions, as illustrated in Fig. 2.

2.3. Crumb Rubber Modified Bitumen Prepared in Lab

This study utilized CR particle sizes ranging from 0.60 mm to 0.15 mm. CR powder was mixed with bitumen in the lab at 5%, 10%, and 15% by mass of total bitumen, respectively, using a low-speed wet process for about five minutes. The maximum dosage of 15% by weight of the bitumen was selected, as published in previous studies [8, 44, 52, 53]. It was also reported that a dosage of more than 15% increased the bitumen viscosity to a limit where it became no longer feasible for field execution [54]. High-speed mechanical stirring at 3000 rpm was used at a temperature between 175 and 185 degrees Celsius while the mixture was swirled continuously for 45 minutes [8, 52]. The optimum percentage of CR was calculated using the maximum rutting resistance.

3.1.1. Conventional Bitumen Tests

The typical bitumen tests, such as penetration, softening, ductility, flash, and fire point tests, were performed according to the procedure described in ASTM standards [55–58]. These tests aim to determine the characteristics of change in the bitumen with the addition of CR.

3.1.2. Storage Stability Test

The storage stability test (SST) for the CRMB is mandatory to confirm the dispersion of CR into the bitumen and determine the stability of the product with time. This experiment was accomplished per the guidelines of ASTM D 5892, and the same acceptance criteria were adopted. In this test, a bitumen sample weighing fifty grams was crammed into an aluminum tube measuring 140 mm in height and 28 mm in diameter. The difference between the top and bottom segments' softening temperatures is known as the "Separation Index," which should not exceed 2.2°C. Despite this, the SP is the most commonly used method to calculate the SST; nonetheless, it is not an objective approach [59]. For accuracy, the performance grade of all the modifications was also revealed by DSR, which is briefed in the next section.

3.1.3. Fourier Transform Infrared Spectroscopy

The FTIR test was performed on base and modified CR (5%, 10%, and 15%) bitumen to examine the macromolecules of the blend. The test was conducted between 4000 cm^− 1 to 400 cm^− 1 wavenumbers to detect the spectrum of each sample [60]. Due to the replicates' consistency, the trials were performed in attenuated total reflectance (ATR) mode rather than transmission mode [61]. It took thirty consecutive scans at a resolution of one per centimeter to obtain data for each spectrum acquired using this method.

3.1.4. Dynamic Mechanical Analysis

A DSR is also known as an Oscillatory shear rheometer, as illustrated in Fig. 3(a). It was used to predict bitumen's rheological, performance grading (PG), and high-temperature behavior while considering both elastic and viscous factors [62]. When shear stress is applied to a material, the complex shear modulus (G*) measures its resistance to deformation. Elastic (recoverable) and viscous mechanisms are involved (non-recoverable). On the other hand, the phase angle indicates the relative amounts of recoverable and non-recoverable deformation, and both properties depend on loading frequency and temperature.

The impact of CR modification on bitumen PG was determined using a 25 mm plate at a frequency of 10 Hz, considering rut resistance (G*/sinδ) greater than 1.00 kPa. The selected parallel plate geometry set based on geometry holds a bitumen sample of the required quantity, as seen in Fig. 3(b). The plate remains stationary while its spindle oscillates. It completes one cycle, which is repeated throughout the entire operation. Each phase includes stress and strain measurements, with the oscillation frequency being 10 radians per second (approximately 1.59 Hz).

3.1.5. Cooper Wheel Tracker Test (CWTT)

This CWTT was done according to the European standard [63] using Wheel Tracking Device, as illustrated in Fig. 4. The CWTT detects the sensitivity of bituminous material to a rut when subjected to a wheel load. Checks for rutting can be done with samples manufactured in a laboratory or taken straight from where the pavement is located. A CWTT was applied at specified temperatures and stress to simulate the conditions applied to the pavement surface.

According to the given Standard, the load applied to the specimen through the attached wheel assembly should be 520 N or 720 N, but this amount can be changed. The sample can be tested at temperatures ranging from 30 to 60 degrees Celsius. The temperatures in this study represent the actual daytime pavement temperatures in Pakistan. The wheel tracking test is carried out at 40°C and 55°C, with a load of 720N. The wheel-tracking specimens were prepared using Roller Compactor at a specified temperature, as shown in Fig. 5. This process of compaction involves four steps. First, the sample was compacted with ten passes under 2 bars of pressure. Then, the specimen was packed with ten, ten, five, and five-wheel passes under 5, 4, and 3 bars of pressure, respectively.

After the compacted specimen is placed in the wheel-tracking machine, samples are conditioned at a specified temperature. The loaded wheel was brought into contact with the slab, and the rut depth was measured with an automatic displacement measuring device are shown in Fig. 6.

During the test, the specimen's specific temperature and chamber were maintained at 40°C and 55°C. The automatic displacement measuring device transferred the measured rut depth to the attached computer at increments of 100 cycles. The tracking continued for 10,000 cycles or when the specified rut depth of 12.5 mm was achieved. Test parameters used in this research for laboratory testing are described in Table 1.

Table 1

Test Parameters Cooper Wheel Tracking Test
Test Used	Aggregate Source	Gradations (WC)	Bitumen	Load (N)	Temperature (ºC)
Cooper Wheel Tracking Test	Margalla	NHA-B	ARL 60/70 CRMB	720	40 55

Test matrix of laboratory tests performed as shown in Table 2:

Table 2

Test Matrix
Test Matrix: Cooper Wheel Tracker Test
Load		720 N
No. of Passes		10000
Gradations		NHA-B
Temperature		40 ˚C
Temperature		55 ˚C
Replicates		2
Aggregates (Margalla)	Bitumen 60/70	4
	CRMB-5%	4
	CRMB-10%	4
	CRMB-15%	4
Total number of samples		16

3.1.6. Rolling Bottle Test

Rolling Bottle (RB) machine, as illustrated in Fig. 7, is a qualitative, subjective tool for determining the moisture susceptibility of loosely compacted asphalt mixtures per BS EN 12697-11. This test aims to evaluate the Bitumen-Aggregate adhesive bond during water mechanical abrasion. Clean and thoroughly dried aggregates weighing 170 g were passed through an 11 mm sieve and retained in 6.3 mm sizes in the first phase. After that, 8 grams of each base and modified bitumen sample were blended with the heated aggregates until the aggregates were completely uniformly coated with a 0.1 mm thick layer of bitumen and left at room temperature for 12 to 64 hours before being tested. The coated aggregates and deionized water were roughly filled into the test glass bottle up to its shoulder level in the second phase, and then the stirrer was added. These sealed glass bottles with screw caps were rotated at 60 rpm for 72 hours on the positioning rack in the RB machine. After six hours, the samples were placed in a dish of sterile water, and the bitumen loss from aggregate particles was visually monitored. Then the mean of the data from three expert operators was averaged out, and the result was rounded up to 5%. The test bowl was partially emptied by removing water in the third phase. The remaining aggregates were reincorporated into the glass bottle, and the beaker was refilled with fresh water. The rolling procedure continued after placing sealed glass with screw caps in the RB machine. The methodology was carried out three more times after 24, 48, and 72 hours, with the percentage of aggregates, covered being visually evaluated in the same manner as before. Finally, the average result was calculated to obtain an average bitumen loss from the aggregates [64]. The Rolling Bottle Test Protocol is mentioned in Table 3:

Table 3

Rolling Bottle (RB) Test Protocol
Aggregate Size	8 mm pass and 6.3 mm retain
Aggregate mass	170 g
Bitumen Quantity	8 g
Drying Time	24 Hours
RPM	60 Cycles
Bottle Volume	500 ml with stirrer
Aggregate mass in Bottle	150 g
Readings were taken after	6, 24 & 48, and 72 Hours [65]

3.1.7. Four-Point Beam Fatigue Test

Fatigue cracking concerns flexible pavement when the surface temperature is near or below freezing [66–68]. When it comes to the design of flexible pavement, fatigue damage is a crucial aspect to take into consideration [69]. It was used to assess the accumulation of deterioration of the pavement under repeated traffic load due to the loss of stiffness [70]. As per AASHTO T-321, the fatigue resistance of asphalt mixtures is measured in loading cycles using the four points bending beam fatigue test (FPBBFT). The asphalt specimen beam size of 380 x 50 x 63 mm³ was compacted to achieve the required 5.5.% air voids. Three test parameters were selected: conditioning slab at an intermediate temperature of 20 ± 0.5°C for 120 minutes before trial, controlled stress 200 kPa, and sinusoidal loading at a frequency of 10 Hz. The beam absorbed the applied energy at four different points, initiating the bottom cracking in the specimen due to stiffness loss and generating fatigue damage. The repeated loading cycle was used on asphalt beams until the failure criteria were achieved, i.e., the initial stiffness of specimens was reduced to 50%. The asphalt specimen beam was compacted to achieve 5.5% air voids. On the other hand, the stiffness value at the 50th load cycle is referred to as the initial stiffness [71].

4.1. Bitumen Test Results

The conventional bitumen and CRMB test results of penetration, softening, ductility, flash point, fire point, and specific gravity is presented in Table 4. From the results, it could be confirmed that CR substantially impacts the stiffness and elastic properties of base bitumen because CR absorbs the maltene fractions from the bitumen and increases the remaining asphaltene content. Therefore, increasing the CR concentration leads to improved stiffness.

Table 4

Properties of traditional bitumen and CRMB Test Results
Sr. No	Description	ARL 60/70	CRMB-5%	CRMB-10%	CRMB-15%
1	Penetration (1/10 of mm)	62	49	45	40
2	Softening Point (°C)	49	53	59	62
3	Ductility @ 25°C (cm)	102	30	27	24
4	Flash Point (°C)	242	290	309	316
5	Fire Point (°C)	247	295	313	321
6	Specific Gravity	1.029	1.08	1.082	1.10
7	Penetration Index (PI)	-0.9474	-0.5240	0.5706	0.8769
8	Thermal Susceptibility (A)	0.0463	0.0433	0.0368	0.0352

The solidity of the modified samples was determined at 25°C using a penetration test. Generally, the harder bitumen reflects smaller penetration values. Figure 8 illustrates the lowering penetration values observed by the increase in CR. It demonstrates an increase in the values of stiffness exhibited by the base bitumen when it is heated to an intermediate temperature. The CRMB dosages of 5%, 10%, and 15% reduced the penetration values to 21%, 27%, and 35% compared to based bitumen. CR particles may have absorbed the base bitumen's lightweight components, limiting its fluidity and increasing its hardness. These results are in agreement with the previous similar study [72].

Softening point (SP) is generally used to reflect the high-temperature performance of bitumen. The high-temperature stability of bitumen with high softening point values is better. Figure 8 illustrates the increase in the softening values with the addition of dosages of CR. Compared to base bitumen, the softening point values of 5%, 10%, and 15% CR increased by 8%, 20%, and 27%, respectively. This improvement may be due to a relatively more stable cross-linked network structure formed after swelling, thus considerably improving the deformation-resistant capacity of bitumen under high temperatures. Another possible reason for this increment is attributed to the increase in the bitumen molecular weight after interacting with the CR particles. The SP findings follow previous past similar studies [73].

The base and CR-modified bitumen's thermal susceptibility (A) were assessed in terms of penetration Index (PI). The change in the behavior of bitumen due to temperature variations is recorded in PI values. It was computed empirically by using the equation below:

$$PI= \frac{1952-500 \times \text{log} \left(penetration at 25 ^\circ C\right) - 20 \times Softening Point}{50 \times \text{log}\left(penetration at 25 ^\circ C\right)-softening point-120}$$

PI values range from − 3 to + 7, where a lower number suggests increased temperature susceptibility, and a higher one demonstrates less [74]. Figure 9 illustrates s that as CR is added, the PI value of the modified bitumen rises, indicating lower temperature susceptibility.

4.2. Storage Stability Test Results

The softening point test results for the top and bottom sections of the tube are presented in Table 5:

Table 5

Storage Stability Test Results for CRMB
Softening Point (°C)	ARL 60/70	CRMB-5%	CRMB-10%	CRMB-15%
Top Section	48.4	53	59	62
Bottom Section	49	51.8	57.3	64.3
Difference	0.6	1.2	1.7	2.3

The SP difference between the top and bottom parts of the ARL 60/70, CRMB-5%, and CRMB-10% tests was less than 2.2°C, indicating the product is stable during storage. However, the Separation index value of CRMB-15% is more significant than 2.2°C, which directs that the high dosage of CR makes the modified bitumen towards an unstable position. Therefore, based on the above results, mixing up to 10% CR is storage stable [75].

4.3. FTIR SPECTROSCOPY

FTIR test aimed to detect the chemical changes during the blending process of CR into the bitumen. The FTIR spectra of neat and modified bitumen with CR (5%, 10%, and 15%) are illustrated in Fig. 10. The spectrum qualitatively indicates and identifies the functional group present in the modified-CR bitumen. The intensities of each modification are changed due to the modification process. The wavenumbers region around 1400 cm^− 1 to 400 cm^− 1 reveals the fingerprint regions known as the complex regions due to the overlap of bands variety with each other. The two sharp peaks were detected at 2920 cm^− 1 and 2852 cm^− 1 in bitumen samples, which represents the C-H stretch of alkanes. The small peaks at around 1670–1760 cm^− 1 and 970–1070 cm^− 1 are ascribed to C = O and S = O stretch in corresponding carbonyl and sulphoxide molecules, respectively. The peak at 1602 represents the C = C stretching vibrations in the aromatic molecules. The asymmetric deformation of the C-H bond in CH₂ and CH₃, whereas the symmetric deformation of the C-H bond in CH₃, followed in the range of 1405–1500 cm^− 1 and 1350–1400 cm^− 1, respectively. The small peaks between 640 and 820 cm^− 1 correspond to the C-H vibrations in the benzene ring. FTIR spectrum of the base and all modified bitumen with CR reflects similar peaks at the identical wavenumber positions.

4.4. FREQUENCY SWEEP TEST RESULTS

The effect of CR on bitumen's rheological and rut resistance properties was determined using a frequency sweep test on a Dynamic Shear Rheometer (DSR) machine. The relationship of the reduced angular frequency with the complex shear modulus (G*), phase angle (δ), and rut resistance (G*/sin δ) is illustrated in Fig. 11 at a reference temperature of 50°C. The modification effect was compared at the specific test protocol: a temperature range of 10–80°C, a strain of 12%, and an angular frequency range of 0.1 to 10 rad/s. Arrhenius Shift factors were calculated, and master curves were plotted on Rheoplus software. The Master Curves were plotted to determine the impact of G*, δ, and G*/sin δ on bitumen modification at various temperatures. Figure 11a presents that at ten rad/s, among the four types of mixes, base bitumen ARL 60/70 has the smallest value of G*. It is recorded that CR modification improved the G* at higher frequencies, which is more prominent at CRMB-15%. It reflects that CR has increased stiffness and resists permanent deformation at high temperatures. At CRMB-10% showed slightly better G*/sinδ than field CRMB-5%. Among all the other specimens, CRMB-15% had a prominent effect on G*.

The viscoelastic characteristics of the bitumen were represented by the phase angle (PA), which was calculated as an angle between the storage and loss modulus. According to Superpave, the PA is the delay between the shear stress imparted to the bitumen and the strain resulting from that stress [76]. Adding CR into the base bitumen ARL 60/70 lowers the phase angle values at higher temperatures, enhancing the modified bitumen elasticity, which is more prominent at CRMB-15% on all loading frequencies, as illustrated in Fig. 11b. The swelling process decreases the inter-particle distance and increases the modified bitumen's viscosity, resulting in sufficient resistance to flow. CR particles store the imparted energy simultaneously, producing a more elastic overall material response.

Rut resistance (G*/sinδ) was calculated using the G* and PA values at each frequency and high temperature. The trend of G*/sinδ was similar in the manner of G* that the unmodified ARL bitumen 60/70 has the lowest master curve G*/Sinδ value compared with the other four modified mixes, as illustrated in Fig. 11c. The resulting graph shows that CRMB-15% performed significantly better than base bitumen. The CRMB-10% improved the rut factor values more than the CRMB-5%. Among all the other specimens, CRMB-15% developed the best rut resistance (rut factor) due to increased stiffness by incorporating CR into the bitumen. Thus, it can be concluded that adding CR into the base bitumen increased the G*, elastic properties, and G*/sin of the bitumen at higher temperatures, making it suitable for hot regions.

The rut factor was calculated at 10 Hz frequency and various temperatures to determine the feasibility of PG 70 in Pakistan. Temperature influence on G*/Sin reveals that CRMB-15% outperforms ARL pen 60/70 significantly. ARL bitumen has the lowest Rut Factor G*/Sin among the four mixes. CRMB-15% has given substantially better results than the base bitumen ARL. CRMB-10% produces better rut factor results than CRMB-5%. Among all the other specimens, CRMB with 15% has given the best development of rut resistance (rut factor), as shown in Fig. 12. Similar results have been recorded in the previous study [77].

Performance Grade is the temperature at which the rut factor is close to 1 kPa. The rut factor value at 70°C is close to 1 kPa, indicating that PG 70 was achieved using crumb rubber-modified bitumen in a laboratory. Failure temperature, i.e., a temperature at which bitumen G*/sinδ < 1, was determined using a PG test according to Superpave criteria. The failure result values are present in Fig. 13, highlighting the changes in the PG grade of the base bitumen after incorporating the CR. The failure temperature for the ARL 60/70 base bitumen is 63°C which shows the PG 58, as per the criteria. It was expected that incorporating the CR would increase the PG of the modified bitumen. A similar study has also recorded the same trend [78]. The same PG was enhanced by the addition of CRMB-5%, which changed the PG from 58 to 64, and the failure temperature was recorded as 68°C.

Similarly, the significant rise in the failure temperature, i.e., 72°C, was recorded at CRMB-10%, and the PG 70 was noted. The failure temperature of CRMB-15% was recorded as 75°C, and the same PG 70 was observed. It was observed that the CR had improved the failure temperatures and increased the two PG jumps, i.e., from 58 to 70. The failure temperatures for CRMB-10% and CRMB-15% are different, but the recorded PG for both modifications is 70.

Results concluded in Table 6 that ARL bitumen has the lowest Rut Factor G*/Sin value of all the four types of mixes at ten rad/s and low frequency. CRMB-10% prepared in the lab has better rut factor results than CRMB-5%. CRMB-15% produced the best development of resistance (rut factor) against rut and other specimens. Results have shown that CRMB-15% gave the best DSR results of all four types and was ranked first. After that, CRMB-10% produced the best results at both temperatures and was ranked second. Following that, CRMB-5% generated acceptable results, so it was rated third, and finally, ARL bitumen had the expected results. The absorption of oily parts into the crumb rubber enhances the stiffness of the resultant CRMB. This diffusion process leads to the modified bitumen's swelling, making it thicker due to the mass increase of rubber particles in the base bitumen.

Table 6

Ranking of Modification based on DSR Results
Sr. No	Temperature °C	Measured \|G*\|/sin(delta) at 10 rad/sec
Sr. No	Temperature °C	1st	2nd	3rd	4th
1	70	CRMB-15%	CRMB-10%	CRMB-5%	ARL 60/70
2	80	CRMB-15%	CRMB- 10%	CRMB-5%	ARL 60/70

4.5. Marshall Mix Design Test Results

The Marshall mix design was performed on each mixture to compute the optimum bitumen content (OBC). The fifteen Marshall cake samples were prepared, including three replicates for each asphalt mixture at 3%, 3.5%, 4%, 4.5%, and 5% weight of the bitumen for a mix. Hence, 60 Marshall molds were prepared with different modified-bitumen contents (5% CR, 10% CR, and 15% CR) to determine each mix's OBC. This OBC was then used to prepare the Cooper Wheel Tracker test (CWTT) slabs and four-point bending beam samples. The Marshall Mix results and volumetrics for each modified mix are given in Table 7. The test results predict that incorporating CR into base bitumen has a noticeable increase in stability values. This trend is more prominent in the CRMB-10% asphalt mix, which tends to reduce at high dosages of CR mix. The Marshall tests results indicated that 10% CR is the optimum dosage percentage for 60/70 penetration grade bitumen.

Table 7

Marshall Mix Design Test Results
Aggregate source	Mix Types	Optimum AC Contents (%)	Stability (Kg)	Flow (0.25 mm)	Gsb	Gmm	Gmb	VA (%)	VMA (%)	VFA (%)
Margalla	ARL (60/70)	4.20	1040	11.1	2.63	2.475	2.361	4.61	14.00	67.10
	CRMB-5%	4.28	1296	11.66	2.63	2.489	2.389	4.02	12.98	69.04
	CRMB-10%	4.38	1465	12.57	2.63	2.497	2.396	4.04	12.72	68.21
	CRMB-15%	4.32	1398	14.39	2.63	2.491	2.379	4.50	13.34	66.30

4.6. Cooper Wheel Tracker Test (CWTT) Results

The CWTT is essential in designing and predicting the asphalt mix behavior via determining the rut depth [79]. The wheel tracker slabs were prepared and tested at optimum bitumen content in a wheel tracking machine. The effect of different factors, such as the number of passes, the impact of crumb rubber modification on bitumen, and temperature on the rutting depth of asphalt mixtures, was recorded. Figure 14 illustrates that at 40°C, the base bitumen, "ARL Pen 60/70 bitumen," has the least resistance against rutting depth among the four mixes. The base bitumen has a high value of rut depth after 10000 passes, whereas CRMB-10% has significantly 55% less rut resistance than the base sample. CRMB-15% showed 36% less rut resistance than the base bitumen and 10% better-rutting depth results than CRMB-5%. Overall, incorporating CR into the asphalt mixes reduced the permanent deformation at 40°C; even the smaller dosage of CRMB-5% reduced the rut resistance by 26% compared to base bitumen. CRMB-10% has given the best development of resistance against rutting among all the other specimens after 10000 passes.

Figure 15 shows that at 55°C, the base asphalt has the least resistance against rut among the four mixes. The base asphalt has a high value of rut depth after 10000 passes.CRMB-10% has given significantly 51%, 20%, and 31% better results than conventional asphalt, CRMB-15%, and CRMB-5%, respectively. Similarly, the CRMB-15% recorded 31%, and 11% recorded less permanent deformation than the base and CRMB-5% asphalt mixes. CRMB-10% has given the best development of resistance against rutting among all the other specimens.

Table 8 shows that CRMB-10% being prepared has given the least permanent deformation at 40°C and 55°C on wheel trackers among all four types and ranked in 1st number. CRMB-15% gave satisfactory results on both temperatures and ranked the 2nd number. After that, CRMB-5% was placed on the 3rd number, and at last, ARL 60/70 bitumen gave the typical results. The findings agree with the previous studies [73, 80, 81].

Table 8

Ranking of mixes Measured on Wheel Tracker
Temperature °C	Ranking of Mixes
Temperature °C	1st	2nd	3rd	4th
40	CRMB-10%	CRMB-15%	CRMB-5%	ARL (60/70)
55	CRMB-10%	CRMB-15%	CRMB-5%	ARL (60/70)

4.7. Moisture Susceptibility

The RB test was performed on a total of four (4) loose asphalt samples (0%, CRMB-5%, CRMB-10%, and CRMB-15%), including base asphalt, to check the bitumen loss during six (6), twenty-four (24), forty-eight (48), and seventy-two (72) hours. Each sample was visualized physically by three (3) skill operators. The RB test results after six, twenty-four, forty-eight (48), and seventy-two (72) hours are presented in Table 9:

Table 9

RB Test Results after six (6), twenty-four (24), forty-eight (48), and seventy-two (72) Hours
Description	Percentage coating after (6, 24, 48, and 72) hours based on photographic evidence
Description	6 Hours	24 Hours	48 Hours	72 Hours
Base Asphalt	80%	55%	35%	15%
CRMB-5%	85%	65%	40%	20%
CRMB-10%	90%	75%	45%	25%
CRMB-15%	95%	80%	50%	30%

The mean value of the test results indicated that after six (6) hours, the percentage coating area recorded for base asphalt was 80%, as seen in Fig. 16. The CRMB-5%, CRMB-10%, and CRMB-15% modified loose asphalt showed 85%, 90%, and 95% percent coating area, respectively. Thus, based on coating area results, CRMB-5% improved 5% of the strength between the bitumen and aggregates compared to neat bitumen. In contrast, CRMB-10% and CRMB-15% exhibited the same pattern of improvement, 10%, and 15%, respectively, in the adhesive strength of asphalt. CRMB-15% showed 5% and 10% better performance than CRMB-10% and CRMB-5%, respectively. Hence, after six hours, CRMB-15% shows the strongest affinity between the bitumen and the aggregates.

The CR loose asphalt also showed the same pattern, i.e., improvement in the percentage coating area after the twenty-four (24) and forty-eight (48) hours. The CRMB-15% loose asphalt prepared in the laboratory revealed comparatively better results than the CRMB-10% and base asphalt. It is evident from the effects that the bitumen coverage after 72 hours was 15% and was slightly increased to 20% and 25% when CR 5% and 10% were added into base bitumen, respectively. The same pattern continues to 30% after incorporating 15% CR into base bitumen.

Figure 17 illustrates the graphical representation between the rolling time and the percentage of bitumen loss. It is clear from the above graph that the affinity between the bitumen and aggregates reduced significantly for all the mixes with an increase in rolling test time. This loss is more prominent after the 72 hours of test duration. The percentage of bitumen loss after 72 hours was 85%, 80%, 75%, and 70% for loose asphalt, CRMB-5%, CRMB-10%, and CRMB-15%, respectively. A higher degree of bitumen coverage after 72 hours for 15% CR indicated that 15% less bitumen was lost than base asphalt during the rolling test, which indicates the solid adhesive bond between the bitumen and the aggregates.

Similarly, the 15% CR showed 5% and 10% more resistance to bitumen loss after 72 hours compared to the CRMB-10% and CRMB-5%, respectively. The improvement in the coating coverage may be ascribed to the presence of CR in bitumen, which makes bitumen stiff due to the hydrophobic nature of CR. Overall, 15% CR lab shows the strongest affinity between the bitumen and the aggregates after 72 hours, revealing the solid adhesive bond between the loose asphalt and high resistance to moisture damage.

4.8. Bitumen Bond Strength Analysis

The purpose of bitumen bond strength (BBS) analysis was to determine the influence of CR on the adhesive or cohesive strength available between the bitumen and the aggregates in dry and wet conditions. Figure 18 illustrates the BBS test results of base and modified-CR bitumen additives recorded in dry and wet conditions. It was observed that the CRMB-10% dosages had increased the POTS strength by 26% compared to conventional bitumen, but after increasing the dosages of CR, the BBS value was slightly reduced. Similarly, the CRMB-5% and CRMB-15% have improved the BBS values to 16% and 11%, respectively. It was because the dosage of CR greater than 10% by weight of bitumen becomes part of the system's phase or matrix. Thus dosages greater than 10% have no significant benefit on BBS. Further, it was also noticed that cohesive failure was recorded in each additive sample, and the aggregate has no main contribution to the adhesive failure at dry conditions. The research findings are in agreement with the previous findings [82].

The effect of moisture harms the BBS values of the base and CR additives Bitumen. It was recorded that the POTS of the CRMB-10% had comparatively better results among all the additives. The CRMB-5% and 15% had improved the POTS values to 13% and 7% compared to base bitumen, respectively. A noticeable improvement of 24% was recorded in the case of CRMB-10% for BBS values. Thus, CR dosage at 10% remains vital in resisting moisture damage in wet conditions.

4.9. Fatigue Analysis of Asphalt Mixtures

Fatigue cracking is generally observed at the wearing course of flexible pavements. The bar chart illustrated in Fig. 19 shows that incorporating CR into the asphalt revealed strong resistance against fatigue damage. This resistance can be verified in the number of loading cycle values that were increased against the high doses of CR in the bitumen. This improvement was prominent at the 15% CR concentration compared to the CRMB-10% and CRMB-5%. The CRMB-15%, CRMB-10%, and CRMB-5% showed 10%, 8%, and 5% more resistance to fatigue cracking at intermediate 20°C compared to base bitumen, respectively. The improvement in fatigue life is due to the enhanced bond between the bitumen and the aggregates. The fatigue damage results of this research concur with the outcomes of the previous study [83].

In this work, a research laboratory testing platform was designed and conducted on commonly used asphalt mix on ARL 60/70 bitumen. Samples were prepared at optimum asphalt content and were tested to observe permanent deformation and moisture susceptibility. The following conclusions are drawn from this work:

FTIR results concluded no change in the peaks after incorporating the bitumen. Further, the peaks formed after the modification were similar in trend to the base bitumen. The intensity of peaks like sulphoxides increased with the dosages of CR. It reflects that no other functional groups were formed after adding CR to the bitumen.
The crumb rubber assimilation positively affects the properties of the conventional bitumen. It can be confirmed through the penetration and Ductilometer test, whereby the bitumen properties are reduced by 35% and 76%, respectively, when CRMB-15% is added to the bitumen. Similarly, ring and ball test results revealed that CRMB-15% softening values are 27% higher than conventional bitumen's. It means incorporating CR additives increases the stiffness and lowers the traditional bitumen's temperature susceptibility and thermal stability. Hence, the inclusion of CR into conventional bitumen increases the standard viscosity of the bitumen.
The storage stability test (SST) results confirmed that a high dosage of CR, i.e., CRMB-15%, could not pass the criteria, i.e., Separation index greater than 2.2°C. All the other medium and lower dosages successfully fulfill the criteria. Therefore, based on the SST results, the optimum dosage for modification is CRMB-10%.
The CRMB increases the complex modulus, elastic behavior, and rut resistance properties. CRMB-15% has more significant rutting parameters (more rutting resistance) than conventional bitumen. Adding 10% and 15% dosages of CR into the bitumen has changed the PG 58 to PG 70 by improving the failure temperature from 63°C to 72°C and 75°C, respectively. CRMB-15% showed 5% and 19% better permanent deformation performance than CRMB-10% and the neat bitumen, respectively. Similarly, CRMB-10% concluded 14% better rut resistance than the neat bitumen. Hence, CR is a prominent factor in improving modified bitumen's permanent deformation resistance at higher temperatures.
The CWTT results at 40°C and 55°C on CRMB (5%, 10%, and 15%) mixes revealed better resistance against rut than the conventional ARL 60/70 mix. The CRMB (5%, 10%, and 15%) showed the least permanent deformation by 26%, 55%, and 35, respectively, at 40°C. Similarly, at a higher temperature of 55°C, the CRMB (5%, 10%, and 15%) asphalt mix provides evidence of less rutting depth by 20%, 51%, and 31%, respectively, compared to base asphalt. Overall, CRMB-10% asphalt mix provided better rutting resistance at higher temperatures, i.e., 40°C and 55°C.
The rolling bottle (RB) test concluded that the inclusion of CR into the loose asphalt indicated less susceptibility to moisture. The higher dosages CR 15% and 10% modified bitumen showed a 15% and 10% strong affinity between bitumen and the aggregates, respectively, than base bitumen after seventy-two (72) hours.
The BBS test results confirmed the less susceptibility to the moisture of CR-modified bitumen both in dry and wet conditions. The CRMB-10% showed 26% and 24% improved cohesive bond strength in dry and moist conditions and reduced the moisture susceptibility of bitumen. Hence, based on BBS test results, it was concluded that CRMB-10% enhanced the durability of asphalt.
The incorporation of CR into bitumen significantly improves resistance to fatigue cracking. A high dosage of 15% CR shows a 10% more dominant effect in enhancing the fatigue life of asphalt mixtures compared to base bitumen.

Overall, based on the above conclusions deduced from the storage stability test, Marshall stability tests, and CWTT, the optimum dosage is CRMB-10% which also satisfies the Superpave rut resistance criteria, i.e., PG 70. In addition, the low rut depth values of CR-modified asphalt mixtures also substantiate the CRMB results that may be preferable in hot areas. It is suggested that further investigation may perform on low-temperature cracking resistance on CR-modified asphalt mixtures, which is suitable for cold regions of the country.

The authors declare that they have no known financial or interpersonal conflicts of interest that would have affected the research presented in this study.

Acknowledgment

The authors would like to thank Mr. Mumtaz Ahmad, Lab Technician, Taxila Institute of Transportation Engineering (TITE), Civil Engineering Department, UET Taxila, for guiding and supporting us during the experiments of asphalt materials. Further, we would also acknowledge the support given by Rana Muhammad Shahid, Lab Technician Department of Civil Engineering, International Islamic Univeristy, during the laboratory testing.

Yu, H., Zhu, Z., Zhang, Z., Yu, J., Oeser, M., Wang, D.: Recycling waste packaging tape into bituminous mixtures towards enhanced mechanical properties and environmental benefits. Journal of Cleaner Production. 229, 22–31 (2019). https://doi.org/10.1016/j.jclepro.2019.04.409
Ding, H., Hesp, SAM: Balancing the Use of Wax-Based Warm Mix Additives for Improved Asphalt Compaction with Long-Term Pavement Performance. ACS Sustainable Chemistry & Engineering. 9, 7298–7305 (2021). https://doi.org/10.1021/acssuschemeng.1c01242
Ren, S., Liu, X., Wang, H., Fan, W., Erkens, S.: Evaluation of rheological behaviors and anti-aging properties of recycled asphalts using low-viscosity asphalt and polymers. Journal of Cleaner Production. 253, 120048 (2020). https://doi.org/10.1016/j.jclepro.2020.120048
Wang, R., Xu, G., Chen, X., Zhou, W., Zhang, H.: Evaluation of aging resistance for high-performance crumb tire rubber compound modified asphalt. Construction and Building Materials. 218, 497–505 (2019). https://doi.org/10.1016/j.conbuildmat.2019.05.124
Mousavinezhad, S.H., Shafabakhsh, G.H., Jafari Ani, O.: Nano-clay and styrene-butadiene-styrene modified bitumen for improvement of rutting performance in asphalt mixtures containing steel slag aggregates. Construction and Building Materials. 226, 793–801 (2019). https://doi.org/10.1016/j.conbuildmat.2019.07.252
Duan, S., Muhammad, Y., Li, J., Maria, S., Meng, F., Wei, Y., Su, Z., Yang, H.: Enhancing effect of microalgae biodiesel incorporation on the performance of crumb Rubber/SBS modified asphalt. Journal of Cleaner Production. 237, 117725 (2019). https://doi.org/10.1016/j.jclepro.2019.117725
Huang, Y.H.: Pavement Analysis and Design. Pearson Prentice Hall, Upper saddle river, New Jersey (2004)
Kamal, M., Khan, K., Hafeez, I., Kumar, K.: Comparison of CRMB Test Sections with Conventional Pavement Section Under the Same Trafficking and Environmental Conditions. Arabian Journal for Science and. (2009)
Milad, A., Ali, A.S.B., Yusoff, N.I.M.: A review of the utilization of recycled waste material as an alternative modifier in asphalt mixtures. Civil Engineering Journal (Iran). 6, 42–60 (2020). https://doi.org/10.28991/cej-2020-SP(EMCE)-05
Ghavibazoo, A., Abdelrahman, M.: Effect of Crumb Rubber Dissolution on Low-Temperature Performance and Aging of Asphalt-Rubber Binder. Transportation Research Record: Journal of the Transportation Research Board. 2445, 47–55 (2014). https://doi.org/10.3141/2445-06
Pouranian, M.R., Notani, M.A., Tabesh, M.T., Nazeri, B., Shishehbor, M.: Rheological and environmental characteristics of crumb rubber asphalt binders containing non-foaming warm mix asphalt additives. Construction and Building Materials. 238, 117707 (2020). https://doi.org/10.1016/j.conbuildmat.2019.117707
Genever, M.: National market development strategy for used tyres. (2017)
Murali, G., Poka, L., Parthiban, K., Haridharan, M.K., Siva, A.: Impact Response of Novel Fibre-Reinforced Grouted Aggregate Rubberized Concrete. Arabian Journal for Science and Engineering. 44, 8451–8463 (2019). https://doi.org/10.1007/s13369-019-03819-5
Liu, S., Zhou, S.B., Peng, A., Xuan, W., Li, W.: Analysis of the performance and mechanism of desulfurized rubber and low‐density polyethylene compound‐modified asphalt. Journal of Applied Polymer Science. 136, 48194 (2019). https://doi.org/10.1002/app.48194
Ye, Y., Xu, G., Lou, L., Chen, X., Cai, D., Shi, Y.: Evolution of Rheological Behaviors of Styrene-Butadiene-Styrene/Crumb Rubber Composite Modified Bitumen after Different Long-Term Aging Processes. Materials. 12, 2345 (2019). https://doi.org/10.3390/ma12152345
Jiang, H., Liu, Y., Muhammad, Y., Pei, R., Guo, R., Li, J.: Preparation and Evaluation of Performance and Mechanism of Gallic Acid–Rubber Powder–Microalgae bio-oil/Styrene Block Copolymers Composite Modified Asphalt. Arabian Journal for Science and Engineering. (2022). https://doi.org/10.1007/s13369-022-07366-4
Crisman, B., Ossich, G., De Lorenzi, L., Bevilacqua, P., Roberti, R.: A laboratory assessment of the influence of crumb rubber in hot mix asphalt with recycled steel slag. Sustainability (Switzerland). 12, 1–21 (2020). https://doi.org/10.3390/su12198045
Han, L., Zheng, M., Wang, C.: Current status and development of terminal blend tyre rubber modified asphalt. Construction and Building Materials. 128, 399–409 (2016). https://doi.org/10.1016/j.conbuildmat.2016.10.080
Loderer, C., Partl, M.N., Poulikakos, L.D.: Effect of crumb rubber production technology on performance of modified bitumen. Construction and Building Materials. 191, 1159–1171 (2018). https://doi.org/10.1016/j.conbuildmat.2018.10.046
Association, RM: U . S . Scrap Tire Management Summary 2009. , Washington, DC 200005. USA (2013)
Liu, L., Liu, Z.H., Li, S.: The Preparation Technology and Performance Study of SBS and Rubber Powder Composite Modified Asphalt. Applied Mechanics and Materials. 361–363, 1617–1620 (2013). https://doi.org/10.4028/www.scientific.net/AMM.361-363.1617
Zhang, B., Chen, H., Zhang, H., Kuang, D., Wu, J., Zhang, X.: A Study on Physical and Rheological Properties of Rubberized Bitumen Modified by Different Methods. Materials. 12, 3538 (2019). https://doi.org/10.3390/ma12213538
Mashaan, N.S., Karim, M.R.: Waste tyre rubber in asphalt pavement modification. Materials Research Innovations. 18, S6-6-S6-9 (2014). https://doi.org/10.1179/1432891714Z.000000000922
Shu, X., Huang, B.: Recycling of waste tire rubber in asphalt and portland cement concrete: An overview. Construction and Building Materials. 67, 217–224 (2014). https://doi.org/10.1016/j.conbuildmat.2013.11.027
Lo Presti, D.: Recycled Tyre Rubber Modified Bitumens for road asphalt mixtures: A literature review. Construction and Building Materials. 49, 863–881 (2013). https://doi.org/10.1016/j.conbuildmat.2013.09.007
Bockstal, L., Berchem, T., Schmetz, Q., Richel, A.: Devulcanisation and reclaiming of tires and rubber by physical and chemical processes: A review. Journal of Cleaner Production. 236, 117574 (2019). https://doi.org/10.1016/j.jclepro.2019.07.049
Shah, S.F.A., Naseer, A., Shah, A.A., Ashraf, M.: Evaluation of Thermal and Structural Behavior of Concrete Containing Rubber Aggregate. Arabian Journal for Science and Engineering. 39, 6919–6926 (2014). https://doi.org/10.1007/s13369-014-1294-1
Beecham, M.: Global market review of automotive lighting - forecasts to 2017. , Worcestershire B60 3DX United Kingdom (2010)
Karger-Kocsis, J., Mészáros, L., Bárány, T.: Ground tyre rubber (GTR) in thermoplastics, thermosets, and rubbers. (2013)
Fini, E.H., Hosseinnezhad, S., Oldham, D.J., Sharma, B.K.: Investigating the effectiveness of liquid rubber as a modifier for asphalt binder. Road Materials and Pavement Design. 17, 825–840 (2016). https://doi.org/10.1080/14680629.2015.1124800
Xu, J., Li, R., Liu, T., Pei, J., Li, Y., Luo, Q.: Study on the Effect of Microwave Processing on Asphalt-Rubber. Materials. 13, 411 (2020). https://doi.org/10.3390/ma13020411
Tahami, S.A., Mirhosseini, A.F., Dessouky, S., Mork, H., Kavussi, A.: The use of high content of fine crumb rubber in asphalt mixes using dry process. Construction and Building Materials. 222, 643–653 (2019). https://doi.org/10.1016/j.conbuildmat.2019.06.180
Stroup-Gardiner, M., Wattenberg-Komas, T.: Recycled Materials and Byproducts in Highway Applications "Scrap Tire Byproducts, Volume 7. Transportation Research Board, Washington, DC (2013)
Ding, X., Ma, T., Zhang, W., Zhang, D.: Experimental study of stable crumb rubber asphalt and asphalt mixture. Construction and Building Materials. 157, 975–981 (2017). https://doi.org/10.1016/j.conbuildmat.2017.09.164
Moreno, F., Rubio, M., Martinez-Echevarria, M.: Analysis of digestion time and the crumb rubber percentage in dry-process crumb rubber modified hot bituminous mixes. Construction and Building Materials. 25, 2323–2334 (2011). https://doi.org/10.1016/j.conbuildmat.2010.11.029
Moreno, F., Rubio, M.C.M., Martinez-Echevarria, M.J.: The mechanical performance of dry-process crumb rubber modified hot bituminous mixes: The influence of digestion time and crumb rubber percentage. Construction and Building Materials. 25, 466–474 (2012). https://doi.org/10.1016/j.conbuildmat.2011.06.046
Jamrah, A., Kutay, M.E., Varma, S.: Backcalculation of Swollen Crumb Rubber Modulus in Asphalt Rubber Binder and Its Relation to Performance. Transportation Research Record: Journal of the Transportation Research Board. 2505, 99–107 (2015). https://doi.org/10.3141/2505-13
Wang, H., Liu, X., Apostolidis, P., Erkens, S., Scarpas, T.: Numerical investigation of rubber swelling in bitumen. Construction and Building Materials. 214, 506–515 (2019). https://doi.org/10.1016/j.conbuildmat.2019.04.144
Xiang, Y., Xie, Y., Long, G., Zeng, L.: Ultraviolet irradiation of crumb rubber on mechanical performance and mechanism of rubberized asphalt. Road Materials and Pavement Design. 20, 1624–1637 (2019). https://doi.org/10.1080/14680629.2018.1468801
Artamendi, I., Khalid, H.A., Page, G.C., Redelius, P.G., Ebels, L.J., Negulescu, I., Kennepohl, G.: Diffusion kinetics of bitumen into waste tyre rubber. Asphalt Paving Technology: Association of Asphalt Paving Technologists-Proceedings of the Technical Sessions. 75, 133–164 (2006)
Airey, G.D., Rahman, M.M., Collop, AC: Absorption of Bitumen into Crumb Rubber Using the Basket Drainage Method. International Journal of Pavement Engineering. 4, 105–119 (2003). https://doi.org/10.1080/1029843032000158879
Behl, A., Kumar, G., Sharma, G.: Performance of Low Energy Crumb Rubber Modified Bituminous Mixes. Procedia - Social and Behavioral Sciences. 104, 49–58 (2013). https://doi.org/10.1016/j.sbspro.2013.11.097
Liu, S., Cao, W., Fang, J., Shang, S.: Variance analysis and performance evaluation of different crumb rubber modified (CRM) asphalt. Construction and Building Materials. 23, 2701–2708 (2009). https://doi.org/10.1016/j.conbuildmat.2008.12.009
Santagata, E., Dalmazzo, D., Lanotte, M., Chiara, M., Barbara, Z., Torino, P.: Relationship between Crumb Rubber Morphology and Asphalt Rubber Viscosity. Proceedings of the 5th Asphalt Rubber International Conference. 513–532 (2012). https://doi.org/10.13140/2.1.1479.5524
Navarro, F.J., Partal, P., Martínez-Boza, F.J., Gallegos, C.: Influence of processing conditions on the rheological behavior of crumb tire rubber-modified bitumen. Journal of Applied Polymer Science. 104, 1683–1691 (2007). https://doi.org/10.1002/app.25800
Navarro, F.J., Partal, P., Martínez-Boza, F., Gallegos, C.: Influence of Crumb Rubber Concentration on the Rheological Behavior of a Crumb Rubber Modified Bitumen. Energy & Fuels. 19, 1984–1990 (2005). https://doi.org/10.1021/ef049699a
Navarro, F.., Partal, P., Martı́nez-Boza, F., Valencia, C., Gallegos, C.: Rheological characteristics of ground tire rubber-modified bitumens. Chemical Engineering Journal. 89, 53–61 (2002). https://doi.org/10.1016/S1385-8947(02)00023-2
Lo Presti, D., Airey, G., Partal, P.: Manufacturing Terminal and Field Bitumen-Tyre Rubber Blends: The Importance of Processing Conditions. Procedia - Social and Behavioral Sciences. 53, 485–494 (2012). https://doi.org/10.1016/j.sbspro.2012.09.899
Saeed, S.M., Aman, M.Y., Ahmad, K.A., Batari, A., Yero, A.T.A., Chinade, A.U.: Effect of Crumb Rubber Modifier on the Fatigue Performance of Warm Mix Asphalt. Presented at the (2019)
Chegenizadeh, A., Shen, P.J., Arumdani, I.S., Budihardjo, M.A., Nikraz, H.: The addition of a high dosage of rubber to asphalt mixtures: The effects on rutting and fatigue. Sustainability (Switzerland). 13, 1–13 (2021). https://doi.org/10.3390/su13179718
National Highway Authority: Government of Pakistan, Ministry of Communications, General Specifications. Sampak International Pvt Ltd, Engineering Design Supervision and Management Consultants, Lahore, Pakistan (1998)
Kamal, M.A., Shahid, S., Arshid, M.U., Hafeez, I.: Performance and Comparison of Crumb Rubber Modified and Conventional Mixes under Varying Temperature and Stress Levels. 21, 1–4 (2016)
Chandrawal, M., Anand, ), Pandey, S.: A Study of Rutting Characteristics of Conventional and Modified Bituminous Concrete Mix. IOSR Journal of Engineering (IOSRJEN) www.iosrjen.org ISSN. 06, 2–34 (2016)
Alfayez, S.A., Suleiman, A.R., Nehdi, M.L.: Recycling tire rubber in asphalt pavements: State of the art, (2020)
D5/D5M-13, A.: Standard Test Method for Penetration of Bituminous Materials. ASTM International. 1–5 (2013). https://doi.org/10.1520/D0005_D0005M-13
ASTM D36/ D36M-14e1: Standard Test Method for Softening Point of Bitumen (Ring-and-Ball Apparatus). ASTM International. 1, 1–5 (2014). https://doi.org/10.1520/D0036
ASTM D 113: Standard Test Method for Ductility of Bituminous Materials. Annual Book of ASTM Standards. 25–27 (1999)
ASTM D 92-18, ASTM D 92: Standard Test Method for Flash and Fire Points by Cleveland Open Cup Tester. Annual Book of ASTM Standards. i, 1–10 (2007). https://doi.org/10.1520/D0092-12B.
Zou, X., Sha, A., Ding, B., Tan, Y., Huang, X.: Evaluation and Analysis of Variance of Storage Stability of Asphalt Binder Modified by Nanotitanium Dioxide. Advances in Materials Science and Engineering. 2017, (2017). https://doi.org/10.1155/2017/6319697
Kumar, T.A., Sandeep, I.J.S., Nivitha, M.R., Chowdary, V., Krishnan, J.M.: Quantification of Aging Compounds in Evotherm-Modified Warm-Mix Asphalt Binder Using Fourier Transform Infrared Spectroscopy. Arabian Journal for Science and Engineering. 44, 8429–8437 (2019). https://doi.org/10.1007/s13369-019-03965-w
Dougan, J.A., Andrew Chan, K.L., Kazarian, S.G.: FT-IR Imaging in ATR and Transmission Modes: Practical Considerations and Emerging Applications. Infrared and Raman Spectroscopic Imaging: Second Edition. 9783527336, 397–444 (2014). https://doi.org/10.1002/9783527678136.ch9
Airey, G.D.: Use of Black Diagrams to Identify Inconsistencies in Rheological Data. Road Materials and Pavement Design. 3, 403–424 (2002). https://doi.org/10.1080/14680629.2002.9689933
BS EN 12697-22 : 2003: Bituminous Mixtures :Test Methods for Hot Mix Asphalt. Part 22: Wheel Tracking. European Committee for Standardization. 3, (2004)
Zaidi, S.B.A., Airey, G.D., Grenfell, J., Alfaqawi, R.M., Ahmed, I., Ahmad, N., Haynes, M.: Moisture susceptibility of hydrated lime modified mastics using adhesion test methods and surface free energy techniques. International Journal of Pavement Engineering. 0, 1–13 (2019). https://doi.org/10.1080/10298436.2019.1648811
Grönniger, J., Wistuba, M.P., Renken, P.: Adhesion in Bitumen-Aggregate-Systems. Road Materials and Pavement Design. 11, 881–898 (2010). https://doi.org/10.1080/14680629.2010.9690311
Raad, L., Saboundjian, S.: Fatigue Behavior of Rubber Modified Pavements. Transportation Research Record. 1639, (1998)
Ali, A., Ahmad, N., Adeel, M., Bilal Ahmed Zaidi, S., Jameel, M.S., Qureshi, F.A., Haroon, W., Asif, S.A.: Performance Evaluation of Bone Glue Modified Asphalt. Advances in Materials Science and Engineering. 2019, 13 (2019). https://doi.org/https://doi.org/10.1155/2019/3157152
Aman, A., Hafeez, I., Zubair, M., Zaidi, S.B.A.: Influence of phosphorous methyl compound on asphalt binder. International Journal of Pavement Engineering. 22, 1–15 (2020). https://doi.org/10.1080/10298436.2020.1726349
Ullah, R., Hafeez, I., Zaidi, S.B.A., Jamal, Haider, S.: Study the effect of substitution filler on performance of asphalt mixture. Civil Engineering Journal (Iran). 6, 1704–1714 (2020). https://doi.org/10.28991/cej-2020-03091576
Ullah, R., Hafeez, I., Haroon, W., Haider, S.: Evaluating the Effect of Plastomer Modified Asphalt Mixture on High/Low Temperature Performance. Mehran University Research Journal of Engineering and Technology. 40, 680–691 (2021). https://doi.org/10.22581/muet1982.2103.20
Hafeez, I., Kamal, M.A., Mirza, M.W.: An experimental study to select aggregate gradation for stone mastic asphalt. Journal of the Chinese Institute of Engineers, Transactions of the Chinese Institute of Engineers,Series A/Chung-kuo Kung Ch'eng Hsuch K'an. 38, 1–8 (2015). https://doi.org/10.1080/02533839.2014.953242
Nejad, F.M., Aghajani, P., Modarres, A., Firoozifar, H.: Investigating the properties of crumb rubber modified bitumen using classic and SHRP testing methods. Construction and Building Materials. 26, 481–489 (2012). https://doi.org/10.1016/j.conbuildmat.2011.06.048
Irfan, M., Ali, Y., Ahmed, S., Hafeez, I.: Performance Evaluation of Crumb Rubber-Modified Asphalt Mixtures Based on Laboratory and Field Investigations. Arabian Journal for Science and Engineering. 43, 1795–1806 (2018). https://doi.org/10.1007/s13369-017-2729-2
Elkholy, S.A., Abd El-Rahman, A.M.M., El-Shafie, M., Abo-Shanab, Z.L.: Physical and rheological properties of modified sulfur asphalt binder. International Journal of Pavement Research and Technology. 11, 838–845 (2018). https://doi.org/10.1016/j.ijprt.2018.07.005
Abdullah, M.E., Zamhari, K.A., Nayan, N., Hainin, M.R., Hermadi, M.: Storage Stability and Physical Properties of Asphalt Modified with Nanoclay and Warm Mix Asphalt Additives. World Journal of Engineering. 2, 3–4 (2011). https://doi.org/10.1080/10298436.2014.961020
Li, J., Xiao, F., Amirkhanian, S.N.: High temperature rheological characteristics of plasma-treated crumb rubber modified binders. Construction and Building Materials. 236, 117614 (2020). https://doi.org/10.1016/j.conbuildmat.2019.117614
Li, H., Dong, B., Zhao, D., Guo, P., Zhang, J.: Physical, Rheological and Stability Properties of Desulfurized Rubber Asphalt and Crumb Rubber Asphalt. Arabian Journal for Science and Engineering. 44, 5043–5056 (2019). https://doi.org/10.1007/s13369-018-3684-2
Al-Adham, K., Baig, M.G., Wahhab, H.A.-A.: Prediction of Dynamic Modulus for Elastomer-Modified Asphalt Concrete Mixes at Desert Environment. Arabian Journal for Science and Engineering. 44, 4141–4149 (2019). https://doi.org/10.1007/s13369-018-3348-2
Mirković, K., Tošić, N., Mladenović, G.: Effect of Different Types of Fly Ash on Properties of Asphalt Mixtures. Advances in Civil Engineering. 2019, (2019). https://doi.org/10.1155/2019/8107264
Khurshid, M.B., Qureshi, N.A., Hussain, A., Iqbal, M.J.: Enhancement of Hot Mix Asphalt (HMA) Properties Using Waste Polymers. Arabian Journal for Science and Engineering. 44, 8239–8248 (2019). https://doi.org/10.1007/s13369-019-03748-3
Abdelhak, B., Abdelmadjid, H.C., Mohamed, G., Hamza, G.: Effect of Recycled Asphalt Aggregates on the Rutting of Bituminous Concrete in the Presence of Additive. Arabian Journal for Science and Engineering. 41, 4139–4145 (2016). https://doi.org/10.1007/s13369-016-2125-3
Asif, S.A., Ahmad, N.: Experimental investigation of impact of crumb rubber on modified bitumen. Australian Journal of Civil Engineering. 00, 1–12 (2022). https://doi.org/10.1080/14488353.2022.2083410
Xiao, F., Wenbin Zhao, P.E., Amirkhanian, S.N.: Fatigue behavior of rubberized asphalt concrete mixtures containing warm asphalt additives. Construction and Building Materials. 23, 3144–3151 (2009). https://doi.org/10.1016/j.conbuildmat.2009.06.036

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Investigation of Crumb Rubber Modification on the Performance of Bitumen and Asphalt Mixtures

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Abstract

Figures

1. Introduction

2. Experimental Program

2.1. Materials

2.1.1. Aggregates

2.1.2. Bitumen

2.1.3. Crumb Rubber (CR)

2.2. Gradation

2.3. Crumb Rubber Modified Bitumen Prepared in Lab

3. Tests Performed

3.1.1. Conventional Bitumen Tests

3.1.2. Storage Stability Test

3.1.3. Fourier Transform Infrared Spectroscopy

3.1.4. Dynamic Mechanical Analysis

3.1.5. Cooper Wheel Tracker Test (CWTT)

3.1.6. Rolling Bottle Test

3.1.7. Four-Point Beam Fatigue Test

4. Results and Discussions

4.1. Bitumen Test Results

4.2. Storage Stability Test Results

4.3. FTIR SPECTROSCOPY

4.4. FREQUENCY SWEEP TEST RESULTS

4.5. Marshall Mix Design Test Results

4.6. Cooper Wheel Tracker Test (CWTT) Results

4.7. Moisture Susceptibility

4.8. Bitumen Bond Strength Analysis

4.9. Fatigue Analysis of Asphalt Mixtures

5. Conclusions and Future Recommendations

Declarations

Acknowledgment

References

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