Performance Evaluation of Asphalt Binder Modified by Natural Rock Asphalt

Asphalt is a dark brown to black cement material that is commonly used worldwide. In the 1830s, asphalt was widely used in France and England for sidewalks, flat roofs, and the lining of tanks. In the United States, more than 85% of asphalt is used to make asphalt concrete road surfaces. Both natural and petroleum-based asphalt are used commercially. It is the result of the deposition of organisms, microscopic algae, and other organisms in the mud of the ocean or the bottom of a lake. Thus, natural asphalt is generated by these residues in the Earth's heat (more than 50℃). However, most of the asphalt in use today is made from the finely refined residues of selected crude oil distillation. Anbar factory asphalt for oxidized asphalt was used in this study [1].

Asphalt is a thermoplastic, viscoelastic liquid that exhibits elastic behavior below its glass transition temperature and/or under rapid loading, and viscous behavior above the glass transition temperature and/or under slow loading. The rheological characteristics of asphalt binders are considered simple [2]. Natural Rock Asphalt (NRA) is a type of asphalt created by fuel seeping through rock splits. Millions of years of accumulation and modifications result in the formation of microbial sludge. The NRA is rich in asphalt and nitrogen and was created by the depositing of Jurassic marine animal fossils [3].

Natural asphalts, such as aljabhaa natural rock asphalt, are frequently utilized for asphalt binder modification in directive to increase the stiffness and deformation resistance of the asphalt mixture. Natural asphalt comes in a variety of forms and purity levels, including asphalt sediment, lake let tar, and rock asphalt. Aljabhaa natural rock asphalt is arguably the most well-known natural asphalt source [4]. To overcome the primary rutting deficiency of asphalt pavement, a new brand of enhanced asphalt with outstanding thermal stability is required. It must also meet asphalt pavement durability requirements, like lower temperature cracking durability, fatigue resistance, and moisture susceptibility. The outstanding characteristics of rock asphalt (RA) modified asphalt have recently garnered study attention [4-7].

Numerous researches displayed that the characteristics and modification results of rock asphalt depend on the rock asphalt sources and chemical composition. The rock asphalt in Xinjiang, China, was recycled to improve the petroleum bitumen. Dissimilar doses of RA with five different levels of dose were added to the petroleum mixture. The rock asphalt enhances high-temperature performance as well as wear resistance. Overall, the RA is a great way to increase the performance of petroleum bitumen [8]. Iraqi asphalt has been used in 20%, 35% and 50% of bitumen changes by weight in three studies. The mechanical characteristics of the mixtures made from different natural asphalt (NA) modified bitumen amounts were compared with 4% SBS modified bitumen. Overall, 35% NA, the blends showed higher performance, with the effect of repeated loads being strongly resisted [9].

Ma and Zhang [10] studied the potential of using natural rock asphalt as a modified base asphalt. They discovered that adding natural asphalt decreases the penetration and ductility characteristics while boosting the softening point. Modified asphalt's temperature sensitivity is also decreased. This study focused on the results of a sequence of valuations of the characteristics of asphalt binders by improving the temperature resilience and reducing the temperature sensitivity of asphalt. Liu et al. [11] used styrene butadiene rubber to evaluate the low-temperature performance of Buton rock asphalt (BRA) modified asphalt. Elementary mechanical property experiments, excluding penetration and soft point experiments, were used to establish the optimal SBR content. The fatigue test at ℃ was meant to evaluate the anti-friction capability of the styrene butadiene rubber-Buton rock asphalt-modified asphalt mixture in the low temperature range. The results of the tests showed that it had the same road performance as the SBS-modified asphalt mixture. Li et al. [12] studied the potential of using original RA and its reformed asphalt mixture, but not the rutting issue. The results showed that the freeze–thaw splitting strength ratios of modified asphalt mixtures were at least 9.5% greater than those of base asphalt mixtures. In addition, although modified asphalt and its blends exhibit a minor decrease in low temperature performance, they nonetheless meet the standards for zones with a minimum temperature of (-21.5℃). Furthermore, because the characteristics of rock asphalt can vary substantially based on the type and amounts of the components, it was discovered that the rock asphalt quality and sources had a considerable impact on the modification results [13].

Though considerable studies have been conducted on rock asphalt, there are still some research gaps at this time. The majority of present research focuses on specific characteristics of the rock asphalt binder or rock asphalt combination, like fatigue or high-temperature resistance. Simultaneously, little research has been conducted on the use of rock asphalt, established on anti-rutting enactment, among to the overall achievement of the rock asphalt combination.

Therefore, the focus of this paper is to modify asphalt by adding natural rock asphalt in various percentages. In this study, the asphalt was modified asphalt by adding natural rock asphalt in various percentages. Accordingly, the study obtained the modified asphaltic materials which can be used in paving according to the measuring of conventional tests such as ductility, penetration, and others. In order to achieve the paper's objectives, the paper’s layout includes materials and methods, results and discussion, and conclusion.

In the study, the enhanced bitumen was produced by adding El Jebha rock asphalt from ENRA. The addition of ENRA to the virgin bitumen (40-50), which is produced by Al-anbar Refinery with different percentages (5%, 10%, 20%, and 30% by weight of bitumen) of ENRA to pure bitumen. The rheological properties were found by testing asphalt for penetration, ductility, softening point, kinematic viscosity, flash point and fire point. The Softening Point test of asphalt binder is prepared to determine the consistency of bitumen.

This test provides an idea of the temperature at which the bitumen attains an assured viscosity. The results of the softening point in Figure 2 show that the temperature at which the bitumen reaches a particular degree of softening has increased with the addition of ENRA. The Penetration test of bitumen is used to measure the consistency of bitumen.

Figure 3 shows the effect of ENRA on the degree of penetration, as the addition percentage decreases the permeability of bitumen (penetration). The ductility test is used to label the ductile and tensile performance of bitumen binders. The Effect of ENRA on the Ductility of Virgin Bitumen shows that increasing ENRA percentage decreases ductility. The other test is viscosity. It is used to measure resistance to the flow of liquid under the influence of gravity.

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Figure 2. The effect of ENRA content on the softening Point of bitumen

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Figure 3. The effect of ENRA content on the penetration of bitumen

Figure 4 shows the results when increasing ENRA percentage due to an increase in viscosity at temperatures of 135Cº and 165Cº. The high value of viscosity means that the asphalt has high resistance to deformation at a given rate. The last test of bitumen is flash and fire point. It provides a degree of critical temperatures beyond which the asphalt binder should not be exposed to. Thus, these critical temperatures help in preventing a hazardous situation (5). The summary results for all the tests in this study are shown in Table 4.

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Figure 4. The effect of ENRA content on the ductility of bitumen

The results in Figure 5 indicate a decrease in the value of the specific gravity, which is considered as an indicator that the amount of mineral impurities is less, and this is an important indicator for extracting the impurities from the bitumen binder. The other test of bitumen is flash and fire point. It provides a degree of critical temperature beyond which the asphalt binder should not be exposed to. Thus, these critical temperatures help in preventing a hazardous situation.

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Figure 5. Effect of ENRA content on the specific gravity of bitumen

Figure 6 shows a decrease in the minimum temperature at which the drawing line causes vapors from the substance to ignite in the form of a flash under specific test conditions. But it remains within the safety limits.

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Figure 6. Effect of ENRA content on the flash point of bitumen

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Figure 7. Effect of ENRA content on the fire point of bitumen

Figure 7 shows the lowest temperature at which the application of the test flame leads to ignition and burning of the material, which is a very important test in terms of safety, as the results indicate a decrease in the ignition point, but it remains within the safety limits.

The last test is viscosity. It is used to measure resistance to the flow of liquid under the influence of gravity. Figure 8 shows the results when increasing ENRA percentage due to an increase in viscosity at temperatures of 135Cº and 165Cº. The high value of viscosity means that the asphalt has high resistance to deformation at a given rate.

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Figure 8. Effect of ENRA content on the viscosity at various temperature of bitumen

The authors would like to acknowledge the contribution of the University of Anbar (www.uoa.edi.iq) via their prestigious academic staff in supporting this research with all the required technical and academic support.