Rheological properties of bitumen containing nanoclay and organic warm-mix asphalt additives

https://doi.org/10.1016/j.conbuildmat.2020.118092Get rights and content

Highlights

Abstract

In recent years, utilization of warm mix asphalt (WMA) proven to be an environmental way for reducing carbon dioxide emissions in the production and laying process of asphalt mixtures by decreasing the mixing and compaction temperatures. On the other hand, increasing traffic volumes cause asphalt pavements exposed to higher stresses, which could lead to premature distresses. In order to improve the resistance to distresses and alleviate the drawback of WMA mixtures, modification of the bituminous material has grown significantly. In this research, Sasobit as a warm mix asphalt additive and nano-montmorillonite k10 as a bitumen modifier used to modify the 60/70 and 40/50 pen-grade bitumen. The contents of Sasobit were selected are 0%, 2.5%, 3.5% and 4%, while for nano-montmorillonite k10 these percentages are 0%, 2.5%, 3.5% and 5% (by weight of pure bitumen). The objective of this study is to investigate the effect of additives on the conventional and rheological properties of bitumen. To achieve this goal, conventional tests, rotational viscosity (RV), dynamic shear rheometer (DSR), bending beam rheometer (BBR), and direct tension tests were conducted to characterize the properties of pure and modified bitumen. The results indicated that Sasobit has a negligible effect on fatigue and low temperature cracking resistance. Conversely, when increasing the amount of nano-montmorillonite k10, these properties were improved. The results showed that nano-montmorillonite k10 improves the rheological properties of bitumen and reduced drawback effect of Sasobit, especially in low temperature cracking performance.

Introduction

With the increasing use of warm mix asphalt, which allows a reduction in the mixing and compaction temperatures, evaluation of conventional and rheological properties of WMA bitumen has been the foremost investigation challenge for the production of environmentally sustainable flexible pavements[1], [2], [3], [4], [5], [6]. Three main categories of WMA additives have been denoted in the literature: organic additives, chemical additives, and foaming technologies. Each of these groups causes the reduction of bitumen viscosity. The potential advantages of this viscosity reduction, which have discussed in the literature, are decreasing plant emissions, reducing energy consumption, extending haul distance and paving seasons, and also a provision of better work conditions for the staff [4], [6], [7], [8], [9], [10], [11], [12], [13]. However, there are also some concerns about the performance of this technology [14], [15], [16], [17], [18], [19]. Most of the available literature highlights the Sasobit “as organic WMA additives” advantages such as improves the workability, compactability, and rutting resistance of mixtures [6], [12], [20]. Also, some researches showed that the addition of Sasobit could have a detrimental effect on moisture damage resistance, low temperature cracking, and fatigue cracking of mixtures [11], [12], [19], [20], [21], [22], [23].

On the other hand, depending on the temperature and vehicle speed, the behavior of bitumen in the asphalt mixtures varies from the elastic solid to the viscous liquid. At high speed and low temperatures, bitumen behavior is more like elastic solid, and thermal cracks are the predominant failure modes of the pavement. At low speeds and high temperatures, which bitumen behavior likes as a viscous liquid, the most common distress types were found to be rutting. Finally, at intermediate temperatures and regular speeds, it shows viscoelastic properties. In this case, fatigue cracks are the most predominant distress types [24].

Increasing traffic volumes and axle loads, variations in the behavior of bitumen as a function of vehicle speed and temperature, and also a drawback of WMA mixtures performance reported in the literature, all of them tend to raise the demand for the use of modified bitumen in flexible pavement [24], [25], [26]. Numerous modifiers are that can be used to enhance binder engineering properties such as polymers, natural rubber, crumb rubber, Styrene Butadiene Styrene (SBS), Ethylene Vinyl Acetate (EVA), nanoclay, etc. [27], [28], [29], [30], [31], [32], [33], [34]. Different types of nanoclay materials have been used in pavement technology to enhance bitumen properties and reduce different types of pavement distress. Montmorillonite (MMT), Rectorite (REC), vermiculite (VMT), and kaolinite (KC) are the most common types of the materials above [35], [36], [37], [38].

Based on the main researches done so far and their findings, it appears that low temperature and fatigue cracking identified as major concerns and obstacles performance of bitumen containing Sasobit [23], [39]. Also, it seems that the addition of montmorillonite in bitumen could mitigate the detrimental impact of Sasobit on their low-temperature and fatigue performance [35], [36], [37], [38], [40], [41]. While the advantages of nano-montmorillonite to enhance the properties of bitumen extensively investigated by previous researchers, additional research is needed to better understand the conventional and rheological properties of bitumen with various amounts of nano-montmorillonite k10 and Sasobit. Therefore, it is crucial to determine the effect of various percentages of nano-montmorillonite k10 and Sasobit to rheological and conventional properties of bitumen. For this purpose, in this research study, Sasobit as an organic warm mix asphalt additive and nano-montmorillonite k10 as a bitumen modifier were used with different contents to modify the 60/70 and 40/50 pen-grade bituminous. Conventional and rheological behaviors of modified bitumen with multiple values of Sasobit and nano-montmorillonite k10 at low, intermediate, and high temperature have evaluated.

Section snippets

Bitumen

Penetration grade (PG) 60/70 and 40/50 bituminous obtained from Shiraz petroleum refineries were used as a base bitumen and labeled as B1 and B2 in this laboratory study, respectively. Characteristics of the base bitumen presented in Table 1.

WMA additives

The organic WMA additives Sasobit, which is described as an “asphalt flow improver,” in various percentages (0, 2, 2.5, 3, and 4% by weight of the bitumen) used in this research. The properties of Sasobit presented in Table 2.

Nano-montmorillonite k10

In this research study,

Testing program and methods

For investigating the influences of nano-montmorillonite k10 to WMA mixes containing Sasobit, conventional, and rheological properties of samples evaluated. Fig. 3 presents the experimental design of this laboratory research.

Test results and discussions

Three test replicates per sample were used in all tests, and the average test values applied in the subsequent discussion.

Conclusion

The objective of this study was to investigate the conventional and rheological properties of bitumen modified with various contents of Sasobit and nano- montmorillonite k10. In this work, these two types of additives were used simultaneously to improve the performance of bitumen. High, intermediate, and low temperature performances of samples evaluated, and the performance grade of samples determined. Based on the experimental results, presented in this paper, the main conclusions of this

CRediT authorship contribution statement

Behrooz Sedaghat: Data curation, Investigation. Reza Taherrian: Formal analysis, Investigation, Methodology, Supervision. Sayyed Ali Hosseini: Project administration, Methodology, Investigation, Supervision, Writing – original draft, Writing - review & editing, Validation. Seyed Mojtaba Mousavi: Data curation, Investigation.

Declaration of Competing Interest

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.

Acknowledgment

The authors thank Mr. Ahmad Jalili of the Fars province branch of Road and Transportation Ministry of Iran for his assistance in supplying the required materials for this project.

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