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Article

Performance Evaluation of Multiple Aging-Regeneration of SBS-Modified Bitumen Regenerated by a Composite Rejuvenator

by
Song Xu
1,2,*,
Bingtao Xu
1,
Shishui Liulin
3,
Shaoxu Cai
2,
Guangming Tang
1 and
Shilong Pan
1
1
School of Advanced Manufacturing, Fuzhou University, Quanzhou 362200, China
2
College of Civil Engineering, Fuzhou University, Fuzhou 350108, China
3
Fujian Transportation Development High-Tech Co., Ltd., Fuzhou 350004, China
*
Author to whom correspondence should be addressed.
Buildings 2024, 14(7), 2185; https://doi.org/10.3390/buildings14072185
Submission received: 24 June 2024 / Revised: 10 July 2024 / Accepted: 12 July 2024 / Published: 16 July 2024
(This article belongs to the Special Issue Advanced Asphalt Pavement Materials and Design)
Browse Figures
Versions Notes

Abstract

:
In this study, compound regeneration of SBS-modified bitumen (SMB) was carried out by a composite rejuvenator composed of furfural extraction oil (FEO) and 1,6-hexanediol diglycidyl ether (HDDGE) in the presence of catalyst triethanolamine (TEOA). SMB was subjected to three aging-regeneration cycles, and the physical and rheological properties, toughness and tenacity, and chemical structures of the SMB after each aging-regeneration cycle were tested to investigate the regeneration effect of the composite rejuvenator on SMB at different numbers of cycles. The ductility decreases and low-temperature properties deteriorate as the number of cycles increased, but the high-temperature properties of the SMB are improved. The complex modulus aging index and phase angle aging index indicate that the viscous behavior of SMB weakens after the second and third aging. The degree of viscoelasticity and toughness recovery decreases with the increase in the number of cycles, and the tenacity of SMB after the third aging-regeneration cycle is basically lost. The results of the Fourier transform infrared (FTIR) spectra tests prove that with the increase in the aging–regeneration cycles of SMB, the intensity of FTIR peaks of oxygen-containing functional groups is greater, and the recovery of aged SMB is gradually weakened.

1. Introduction

Styrene-Butadiene-Styrene (SBS) is a thermoplastic elastomer polymerized from styrene and butadiene as monomers. It has good processability at high temperatures and shows excellent rubber elasticity at ambient temperature. SBS has good compatibility with bitumen in the presence of some stabilizers and can form a three-dimensional spatial network structure in bitumen. This structure improves colloidal stability and exhibits superior high- and low-temperature properties in comparison with virgin bitumen. Therefore, SBS is widely used as a modifier for bitumen and endows bitumen with excellent physical and rheological properties to meet the high requirements of high-grade highway engineering [1,2,3,4]. Through continuous development, SBS-modified bitumen (SMB) has become a matured product and plays an important role in the construction of high-grade highways [5].
However, the performance of the SMB will deteriorate during the service life of the road due to the long-term exposure to heat, ultraviolet light, water, air and other inducements. With the evolution of aging, the four components of bitumen gradually change, usually manifested by the decrease in aromatic content and the increase in resins and asphaltenes content. Meanwhile, the SBS polymer degrades, leading to the destruction of the spatial network structure, and then phenomena such as low temperature cracking, flexibility decline, moisture damage and so on will occur [6,7].
The aging of bitumen makes its road performance deteriorate continuously. To prolong the service life of bitumen pavement, it is necessary to carry out regular maintenance and conservation [8,9]. In addition, a large amount of waste SMB mixture is generated during the road-repair process, which not only occupies a large area of land but also poses a serious threat to the ecological environment. Proper disposal of the waste SMB mixture is urgently needed [10,11]. Indeed, bitumen recycling has become a hot topic in road construction as it serves the purpose of reducing project costs while also minimizing the consumption of non-renewable resources. This has significant implications for the implementation of the “dual-carbon strategy” and the achievement of sustainable development goals [12]. The key problem in the recycling bitumen mixture lies in the regeneration of aged SMB binder. The volatilization of light components and the transformation of aromatics fractions into resins and asphaltenes constituents will make the bitumen hard and brittle. Additionally, the degradation of SBS polymers will disrupt the spatial structure, leading to further deterioration of the performance of SMB [13,14,15].
Currently, many studies have shown that adding oils rich in aromatics could regulate the proportion of various components of aged bitumen and soften the aged bitumen [16,17]. The study conducted by Shu et al. indicated that oils containing aromatics (OA) were able to replenish volatile light components and regulate the ratio of chemical components of aged bitumen when the OA reached 10%, resulting in good performance recovery [18]. Cong et al. [19] found that the best physical and rheological properties of regenerated SMB were obtained when the ratio of regenerated bitumen to fresh bitumen was 35:65 and the rejuvenator content was 5% to 10%. In view of the aging mechanism of SMB, some scholars have proposed reactive regeneration methods to rebuild the degraded crosslinked network structure in SMB, aiming to better restore the performance of SMB [20,21]. The research results from Cao et al. found that SBS produced oxygen-containing reactive end groups, hydroxyl (-OH) and carboxyl (-COOH) during the aging degradation process, and various reagents were able to react with these groups to connect the degraded SBS polymer fragments [22,23]. Li et al. [24] used bisphenol A type epoxy resin and anhydride curing agent to restore the properties of aged SMB, and the results suggested that the tensile strength, high- and low-temperature performance, and fatigue resistance of regenerated bitumen can be effectively improved.
However, most investigations have focused more on whether the rejuvenator could restore the aged SMB to its non-aging level, while neglecting the subsequent aging of the regenerated SMB. Therefore, the main objective of this article is to evaluate the regeneration effect of a composite rejuvenator composed of furfural extract oil (FEO) with rich aromatic and 1,6-hexanediol diglycidyl ether (HDDGE) with strong reactive epoxy groups on aged SMB by investigating the changes in physical properties, rheological properties, and microstructure of SMB after three aging-regeneration cycles.

2. Materials and Methods

2.1. Raw Materials

This study used 70# virgin bitumen and SBS polymer to prepare SMB. Virgin bitumen and 5% (by weight of bitumen) SBS (average molecular weight of 350,000 g/mol, and PS-PB block ratio is 30/70) were sheared by a high shearing mixer under 4500 rpm and 180 °C for 60 min. Then, the mixture was stirred under 800 rpm and 160 °C for 120 min and the SMB was finally obtained. The conventional properties of virgin bitumen and SMB are shown in Table 1.
An aromatic-rich furfural extraction oil (FEO) from Hebei Hengshui Shengkang Chemical Co., Ltd. (Hengshui, China) was adopted as a softener and composition regulator for the aged SMB, while the 1,6-hexanediol diglycidyl ether (HDDGE) with the catalyst of triethalonamine (TEOA) was selected to regenerate the degraded SBS fragment; the properties of the above materials are shown in Table 2.

2.2. Aging and Regeneration Process of SMB

Aging procedure: the short-term aging of SMB was carried out by the thin film oven test (TFOT, 163 °C, 5 h) according to the standard [25], and then the long-term aging was conducted on the TFOT aged SMB by a pressure aging vessel (PAV, 100 °C, 2.1 MPa, 20 h) according to the standard [26].
Regeneration procedure: the PAV-aged SMB was heated by an oil bath to maintain its temperature at 160 °C, and then 5% (by weight of SMB) of HDDGE, 10% (by weight of HDDGE) of catalyst TEOA, and 10% (by weight of SMB) of FEO were added into the aged SMB under continuous stirring. The mixture was blended for 30 min under a stirring spend of 800 rpm. Finally, the regenerated SMB was obtained, consisting of 5% SBS by weight of bitumen, 5% HDDGE, 10% FEO by weight of SMB, and 10% TEOA by weight of HDDGE.
Three aging–regeneration cycles were conducted in this experiment, and the performance of SMB after each aging and regeneration was measured and analyzed.

2.3. Physical Properties Tests

Physical properties including softening point, penetration (25 °C), ductility (5 °C), and viscosity (135 °C) were performed according to the ASTM standard [27,28,29,30], respectively.

2.4. Rheological Properties Tests

A dynamic shear rheometer (DSR, MCR 102) was adopted to record the viscoelastic responses of SMB under periodically changing strain or stress under different temperatures and loading frequencies. A temperature sweep test from 30 °C to 100 °C with an increment of 2 °C/min was conducted on samples under the strain-controlled mode with a constant frequency of 10 rad/s, the strains were chosen as 1%. The diameters of the parallel plates were 25 mm with a gap of 1 mm. The rheological parameters were obtained from the test to evaluate the aging and regeneration degree of SMB.
The permanent deformation resistance at high temperature of SMB was evaluated by the rutting factor (G*⁄sin δ). The complex modulus aging index (CMAI) and the phase angle aging index (PAAI) evaluated the deterioration degree of SMB after aging–regeneration cycles, and a greater CMAI or smaller PAAI meant worse performance for SMB. The CMAI and PAAI were calculated using Equations (1) and (2), respectively.
CMAI = |G*|/|G0*|
PAAI = δ/δ0
where, G0* and G* are the complex moduli of SMB before and after aging, respectively, δ0 and δ are the phase angles of the SMB before and after aging, respectively.

2.5. Toughness and Tenacity Test

The toughness and tenacity of SMB are expressed as the adhesion and holding power of SMB, which can be used to evaluate the modification effect of SBS polymer on virgin bitumen. The toughness and tenacity of SMB was performed by a toughness and tenacity tester (WSY-018) according to the ASTM standard [31], and the technical parameters of the used tester are shown in Table 3. In the toughness and tenacity experiment, the load-deformation curve was plotted within the deformation of 300 mm, and the calculation of toughness and tenacity can be derived by integrating the corresponding area enclosed by the curve. The tenacity value is the area to the right of the extension of the descending segment of the deformation curve, and the area enclosed by the entire graph is the value of toughness.

2.6. Fourier Transform Infrared (FTIR) Spectra Tests

The SMB samples were scanned by an FTIR spectrometer (Nicolet is50, Thermo Fisher Scientific, Waltham, MA, USA) to analyze the chemical structures. The sample was dissolved in CS2 solvent to form a homogeneous solution prior to testing, and then the solution was dropped on a KBr disc and dried to form a thin film for testing. The number of scans was 32, and the scanning range was 4000~500 cm−1 with a resolution of 4 cm−1.

3. Results and Discussion

3.1. Physical Properties

The effects of aging and regeneration times on the softening point, viscosity, penetration, and ductility of SMB are shown in Figure 1. After the initial aging, the softening point of SMB decreased, while the viscosity increased significantly, and the penetration and ductility decreased markedly. This was due to the evaporation of the light components under the action of heat and oxygen, and the continuous transformation of aromatic fractions into resins and asphaltenes during the aging process, resulting in increased polarity and viscosity of the bitumen.
After the first aging–regeneration cycle, the penetration of the regenerated SMB increased and the softening point decreased, which is because on the one hand the SBS polymer degraded into small molecules during the aging process, and the cross-linking network structure formed by the polymer was destroyed, from which the adsorbed light components were released to soften the hard components; on the other hand, it was probable that the aromatic component added during the first regeneration process softened, lubricated, and peptized the asphaltenes.
After the second aging–regeneration cycle, the penetration of regenerated SMB increased further, while the softening point continued to decrease. This can be attributed to two factors: firstly, SBS polymer degrades into smaller molecules during the aging process, leading to the destruction of the cross-linking network structure formed by SBS. Secondly, it is possible that the addition of aromatic components has a more significant effect on the softening, lubrication, and depolymerization of the asphaltenes after the second aging.
After the third aging–regeneration cycle, there was a more significant decline in the penetration rate during the second regeneration of SMB compared with the first regeneration. The softening point increased but remained lower than that of the original SMB. The viscosity declined further compared to the first and second regenerations, but remained higher than that of the original SMB. These findings indicate that, with an increase in the aging and regeneration cycles, there is a gradual deterioration in SBS recovery effectiveness by the rejuvenator, however, high-temperature performance improved.
Overall, the softening effect of the rejuvenator diminished as the number of aging cycles increased, while the softening point and viscosity gradually rose. Simultaneously, ductility and penetration decreased further, resulting in increased SMB hardness compared to its initial state. The addition of rejuvenator after each aging cycle restored the softening point, viscosity, penetration, and ductility of aged SMB due to FEO’s ability to regulate component ratios within the bitumen mixture. Additionally, incorporating light components dilutes and softens the bitumen while HDDGE reconnects broken SBS polymers and enhances component compatibility. However, with an increasing number of aging and regeneration cycles, it is evident that there are limitations to reversing the effects of aging on SMB.

3.2. Rheological Properties

The effects of multiple aging–regeneration on the complex shear modulus (G*) and phase angle (δ) of SMB are shown in Figure 2. As shown in Figure 2a, the G* shows a decreasing trend after multiple aging–regeneration cycles, and the rheological parameters of aged SMB can be recovered to the levels of initial SMB at the first cycles. As the aging–regeneration cycle increases, the difference of G* before and after aging-regeneration of SMB also increases. This indicates that the deformation resistance of SMB gradually weakens with an increase in the aging–regeneration cycle. This is because aging causes damage to the network structure of SBS in SMB. Although the addition of HDDGE and TEOA can repair the broken network structure, the degree of repair decreases with an increase in the aging–regeneration cycle. This also suggests that the recovery of composite rejuvenator to SMB after multiple aging is limited.
Figure 2b shows that the δ curve of the SMB after the aging–regeneration cycle is significantly steeper than that of the original SMB, and the plateau area gradually decreases, which implies that the SBS in the bitumen is damaged and this reduces the resilient behavior of SMB. From the first, second, and third regeneration, it was found that the δ curve of the SMB had a more obvious plateau area, but the δ rose faster with the increase in temperature, and the plateau area was not significant after the aging. The trends of the curves after the second and third aging–regeneration cycles are basically the same, but the significance of the plateau area on the δ curve gradually decreased as the cycle increased, which indicates that the regeneration effect of the composite rejuvenator was more effective in the first few cycles. However, as the aging–regeneration cycle increased, the amount of repairable SBS segments decreased, which caused SBS to lose the portion that provided SMB with elasticity. With the addition of the rejuvenator, the degraded SBS segments were repaired, and the linear HDDGE enhanced the elastic portion of the regenerated SMB, hence the phenomenon that the plateau areas were no longer significant after aging but were restored to some extent after regeneration. In addition, asphaltene-buildup reduced the regeneration effectiveness of the rejuvenator, and the whole became harder and more brittle, thus, the viscoelastic behavior was gradually lost. The addition of the composite rejuvenator had a good recovery on the component ratio of aged SMB, the crosslinking structure of SBS, and viscoelastic behavior, but with the increase in regeneration times, the recoverable degree of aged SMB decreases, and the regeneration effect weakens.
Figure 3 reflects the effect of cyclic aging–regeneration on the deterioration degree of SMB through the CMAI and PAAI indices. Figure 3a shows that the CMAI index gradually decreases with an increase in aging time. It can be found that the CMAI curve for the second aging is obviously lower than that for the first aging within the whole range, while the third aging curve is between them. In the scanning temperature range above 40 °C, the CMAI index of SMB increases slowly with increasing temperature, which implies that the SMB sample is more susceptible to aging under 40 °C. Based on the CMAI index, it can be concluded that SMB loses its elasticity after the second and third aging because the restorable degree of SBS in SMB is limited and decreases rapidly with an increase in the aging–regeneration cycle, resulting in the loss of elasticity conferred by the SBS, and this also illustrates the limited recovery of the aged SMB.
Figure 3b reflects the PAAI versus temperature curve. When the PAAI index approaches 1, it means that the SMB loses restorability. After the second and third aging–regeneration cycles, the PAAI indices are essentially the same for both, with increasing temperature, but the PAAI index curves after the third aging were closer to 1. This also means that there are fewer and fewer repairable SBS fragments in the aged SMB; as the aging–regeneration cycle increases, the restorability of the aging SMB gradually decreases, and the regeneration effect is no longer evident.
The rutting factors of SMB before and after aging–regeneration are determined by the temperature-scanning experiments to evaluate the high temperature performance of SMB. Figure 4 shows the rutting factors of SMB with different aging–regeneration cycles. The rutting factor of regenerated SMB decreases with the increase in the aging–regeneration cycles, which indicates that the high-temperature deformation resistance of SMB is improved compared with the original SMB in the first few regeneration events. This is because the regeneration process of SMB cannot avoid aging in the thermal and oxygen environment, which causes SMB to become hardened and brittle, and although the high-temperature deformation resistance of SMB improves at this time, the ductility of SMB deteriorates and SMB is prone to cracking at low temperatures.

3.3. Toughness and Tenacity

Toughness and tenacity reflect the maximum tensile deformation capacity of SMB after several aging–regeneration cycles, and measure the ability of bitumen to delay damage and resist fracture after tensile yielding. The toughness and tenacity load-deformation curves of virgin bitumen and SMB after multiple aging–regeneration cycles are shown in Figure 5, and the specific toughness (T0) and tenacity (Te) values are summarized in Table 4. By comparing the load-deformation curves of SMB and virgin bitumen, it can be seen that the evolutionary trend of the two curves is relatively similar, while due to the presence of SBS polymer forming the network structure in SMB, the toughness and tenacity performance of SMB is better than that of the virgin bitumen.
As the aging cycle increases, the maximum load that the regenerated SMB can withstand and the maximum deformation that can be produced decreases in turn, and the peaks in these curves become sharper. This indicates that there are decreasing SBS with complete network structures in the bitumen, the modification of SBS polymers become weak, and the tensile properties of SMB worsen.
Combining the load-deformation curves of SMB with the toughness and tenacity data, it was found that the toughness and tenacity were severely affected by the cycles and gradually weakened as the time of aging increased until SMB lost its tenacity completely after the third aging–regeneration cycle. Regeneration of SMB after each aging can make the toughness of SMB recover to twice or more the value of that before regeneration. Although the double peaks in the original SMB did not appear, the regenerated SMB still had a certain degree of tenacity, and this was due to the reconnection of the degraded SBS fragments after the addition of the composite rejuvenator, as well as the linear HDDGE which also provided some of the tenacity of the regenerated SMB. However, it was found that the tenacity of SMB was not recovered after the third aging–regeneration, which indicates that the SBS content in SMB after the third regeneration was already minimal, and the recovery of SBS in SMB after each aging–regeneration was limited.

3.4. FTIR

The infrared spectra of SMB after different aging–regeneration cycles are shown in Figure 6, and the relevant main characteristic absorption peaks are shown in Table 5. In order to quantitatively analyze the oxygen-containing functional groups in bitumen, the carbonyl index (IC=O) and the sulphoxide index (IS=O) were defined using Equations (3), (4), and (5), respectively.
IC=O = A1728/∑A
IS=O = A1032/∑A
∑A = A3600–3200 + A2990–2820 + A1728 + A1601 + A1125 + A1032 + A966
where A is the area of the corresponding spectral band, and the values of IC=O and IS=O reflect the changes in oxygen-containing functional groups. The functional group indices after different aging–regeneration cycles are shown in Table 6.
The characteristic absorption peaks in the infrared spectra of SMB change gradually with the increase in the number of aging–regeneration cycles, and the intensity of some absorption peaks also shows differences. The vibrational absorption band in the range of 3600~3200 cm−1, and peaks at 1720 cm−1, 1125 cm−1, and 1032 cm−1 are found to be gradually enhanced with the increased aging–regeneration cycle, which are the stretching vibration absorption band of hydroxyl group (OH), the stretching vibration peak of carbonyl group (C=O), the stretching vibration peak of ether bond (C-O-C), and the stretching vibration peak of sulphoxide (S=O), respectively. Moreover, in each aging–regeneration cycle, the intensity of the absorption peaks of the oxygen-containing groups in the aged SMB is greater than that of the regenerated SMB, and the curves are ranked in order of the peak strength of oxygen-containing groups as follows: f > d > b > g > e > c > a, which indicates that oxygen-containing groups are generated during the aging process of SMB, and the used compounds can restore the network structure of SBS in SMB by reacting with the degradation products of SBS. However, IC=O and IS=O gradually increase with the increase in the aging–regeneration cycle of SMB, the intensity of the characteristic absorption peaks of oxygen-containing groups increases, and the recoverability of SBS gradually deteriorates. The main chemical reactions between the oxygen-containing functional groups generated by SMB aging and the epoxy groups in the rejuvenator are shown in Figure 7.

4. Conclusions

In this study, HDDGE containing epoxy functional groups and FEO rich in aromatic oils were used to regenerate aged SMB. The effects of aging–regeneration cycles on the physical properties, rheological properties, toughness, tenacity properties, and microstructure of SMB were investigated by conducting three aging–regeneration cycles on SMB. The following conclusions and reference values can be drawn:
(1)
The addition of a compound rejuvenator can supplement the light components of SMB, which has been volatilized and transformed due to aging, and adjust the ratio of each component. In addition, it can also connect the degraded SBS to a certain extent and restore the cross-linking network structure of SBS. With the increase in the aging–regeneration cycle, the high temperature deformation resistance of SMB is improved.
(2)
As the time of aging–regeneration increases, the G* is never recovered to the level of the original SMB, the plateau domain in the δ curve gradually disappears, and the elastic portion provided to the SMB by the SBS is gradually lost. The recovery of the plateau domain is not obvious with the cycle increase.
(3)
After several aging–regeneration cycles, the CMAI index of the SMB is generally lower than that of the first aging, while the PAAI indexes of the second and third aging are approximately the same, which indicates that the recovery of SMB is gradually lost with the increase in the number of aging–regeneration cycles.
(4)
Compared to virgin bitumen, the incorporation of an SBS polymer can significantly improve the toughness and tenacity of SMB. With the increase in the aging–regeneration cycles, the repairable SBS polymers gradually become less, the restorability of SMB is gradually reduced, and the tenacity of SMB is basically lost after the third cycle.
(5)
With the increase in the aging–regeneration cycles, the content of oxygen-containing functional groups in SMB is increasing, and the regeneration effect of the rejuvenator will be gradually weakened, which will lead to a gradual decrease in the recoverability of the SMB.

Author Contributions

Conceptualization, S.X. and B.X.; methodology, S.L.; software, S.X. and B.X.; validation, S.C., G.T. and S.P.; formal analysis, S.X. and B.X.; investigation, B.X., G.T. and S.P.; resources, S.L.; data curation, B.X.; writing—original draft preparation, B.X.; writing—review and editing, S.X. and S.C.; supervision, S.X.; project administration, S.X.; funding acquisition, S.X. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the National Natural Science Foundation of China, grant number 52278446 and 52208411, Natural Science Foundation of Fujian Province, grant number 2023J01061, and Fuzhou University Testing Fund of precious apparatus, grant number No. 2023T025. The authors gratefully acknowledge their financial support.

Data Availability Statement

The data presented in this study are available on request from the author.

Acknowledgments

The authors gratefully acknowledge the supports from the funding agency and research platforms of our affiliations.

Conflicts of Interest

Author Shishui Liulin was employed by the company Fujian Transportation Development High-Tech Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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Figure 1. Effect of aging–regeneration cycles on (a) softening point, (b) viscosity, (c) penetration, and (d) ductility of SMB, where the dotted lines represent the values of unaged SMB.
Figure 1. Effect of aging–regeneration cycles on (a) softening point, (b) viscosity, (c) penetration, and (d) ductility of SMB, where the dotted lines represent the values of unaged SMB.
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Figure 2. Effect of different aging–regeneration cycles on the (a) complex modulus and (b) phase angle of SMB.
Figure 2. Effect of different aging–regeneration cycles on the (a) complex modulus and (b) phase angle of SMB.
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Figure 3. Effect of different aging times on (a) the CMAI and (b) the PAAI of SMB.
Figure 3. Effect of different aging times on (a) the CMAI and (b) the PAAI of SMB.
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Figure 4. Effect of different aging–regeneration cycles on rutting factors of SMB.
Figure 4. Effect of different aging–regeneration cycles on rutting factors of SMB.
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Figure 5. Effect of different aging and regeneration times on the toughness and tenacity of (a) virgin bitumen, (b) SMB, (c) first aging, (d) first regeneration, (e) second aging, (f) second regeneration, (g) third aging, and (h) third regeneration, where the area of the shadowed part represents the value of tenacity and the area of the whole graph represents the value of toughness.
Figure 5. Effect of different aging and regeneration times on the toughness and tenacity of (a) virgin bitumen, (b) SMB, (c) first aging, (d) first regeneration, (e) second aging, (f) second regeneration, (g) third aging, and (h) third regeneration, where the area of the shadowed part represents the value of tenacity and the area of the whole graph represents the value of toughness.
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Figure 6. FTIR spectroscopy of SMB after different aging and regeneration, where the dashed box represents the end hydroxyl stretching vibration range, and the solid box represents the image with a wavenumber range of 1800–500 cm−1.
Figure 6. FTIR spectroscopy of SMB after different aging and regeneration, where the dashed box represents the end hydroxyl stretching vibration range, and the solid box represents the image with a wavenumber range of 1800–500 cm−1.
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Figure 7. Main reactions of degraded polymers with epoxy functional groups.
Figure 7. Main reactions of degraded polymers with epoxy functional groups.
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Table 1. Physical Properties of Virgin bitumen and SMB.
Table 1. Physical Properties of Virgin bitumen and SMB.
Physical PropertyVirgin BitumenSMB
Penetration (25 °C, 0.1 mm)6656.3
Ductility (5 °C, cm)19.336.2
Softening point (°C)4875.2
Table 2. Relevant information of regenerated materials.
Table 2. Relevant information of regenerated materials.
ItemsHDDGETEOA
Molecular structureBuildings 14 02185 i001Buildings 14 02185 i002
Chromaticity (APHA)≤60≤20
25 °C Viscosity (mPa∙s)10–3015–25
Flash point (°C)120179
Stateliquidliquid
Density (g/cm3)1.0761.124
Epoxy value (eq/100 g)0.65–0.70%—
Table 3. Technical parameters of toughness and tenacity tester.
Table 3. Technical parameters of toughness and tenacity tester.
Experimental ParametersValue
Temperature(25 ± 0.1) °C
Tensile speed(500 ± 10) mm/min
Maximum deformation610 mm
Load sampling interval0.5 mm
Maximum loading capacity1 kN
Table 4. Toughness and tenacity of SMB after multiple aging–regeneration.
Table 4. Toughness and tenacity of SMB after multiple aging–regeneration.
Experimental IndicatorsVirgin BitumenSMBFirst AgingFirst RegenerationSecond
Aging		Second
Regeneration		Third AgingThird
Regeneration
Toughness T0 (N·m)12.8417.873.4214.023.018.810.634.52
Tenacity Te (N·m)5.55.581.365.771.091.200
Table 5. Main characteristic functional groups of SMB before and after aging and regeneration [32,33,34].
Table 5. Main characteristic functional groups of SMB before and after aging and regeneration [32,33,34].
Wavenumber (cm−1)Type of Vibration
3600~3200Hydroxyl Stretch Vibration (−OH)
2990~2820Alkane stretching vibration (−CH)
1728Carbonyl telescopic vibration (C=O)
1601Breathing vibration of asymmetric substituted benzene
1340~1465Alkane bending vibration (−CH)
1125Ether-based telescopic vibration (C−O−C)
1032Stretching vibration of sulphoxide (S=O)
966Out-of-plane bending vibration of C-H (−CH=CH−)
Table 6. Functional group index after different aging–regeneration cycles.
Table 6. Functional group index after different aging–regeneration cycles.
SamplesIC=OIS=O
SMB0.0130250.018912
First aging0.0148930.019632
First regeneration0.0149660.026130
Second aging0.0194090.026675
Second regeneration0.0232310.026851
Third aging0.0237510.030036
Third regeneration0.0319680.032779
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MDPI and ACS Style

Xu, S.; Xu, B.; Liulin, S.; Cai, S.; Tang, G.; Pan, S. Performance Evaluation of Multiple Aging-Regeneration of SBS-Modified Bitumen Regenerated by a Composite Rejuvenator. Buildings 2024, 14, 2185. https://doi.org/10.3390/buildings14072185

AMA Style

Xu S, Xu B, Liulin S, Cai S, Tang G, Pan S. Performance Evaluation of Multiple Aging-Regeneration of SBS-Modified Bitumen Regenerated by a Composite Rejuvenator. Buildings. 2024; 14(7):2185. https://doi.org/10.3390/buildings14072185

Chicago/Turabian Style

Xu, Song, Bingtao Xu, Shishui Liulin, Shaoxu Cai, Guangming Tang, and Shilong Pan. 2024. "Performance Evaluation of Multiple Aging-Regeneration of SBS-Modified Bitumen Regenerated by a Composite Rejuvenator" Buildings 14, no. 7: 2185. https://doi.org/10.3390/buildings14072185

APA Style

Xu, S., Xu, B., Liulin, S., Cai, S., Tang, G., & Pan, S. (2024). Performance Evaluation of Multiple Aging-Regeneration of SBS-Modified Bitumen Regenerated by a Composite Rejuvenator. Buildings, 14(7), 2185. https://doi.org/10.3390/buildings14072185

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