Laboratory Evaluation of High-Temperature Properties of Recycled PMA Binders
1
Material Science, Engineering, and Commercialization, Texas State University, San Marcos, TX 78666, USA
2
Korea Petroleum, Seoul 04427, Republic of Korea
3
Texas Department of Transportation, Austin, TX 78744, USA
4
Department of Regional Infrastructure Engineering, Kangwon National University, Chuncheon 24341, Republic of Korea
5
Department of Engineering Technology, Texas State University, San Marcos, TX 78666, USA
*
Authors to whom correspondence should be addressed.
Sustainability 2023, 15(17), 12744; https://doi.org/10.3390/su151712744
Submission received: 28 June 2023
/
Revised: 18 July 2023
/
Accepted: 3 August 2023
/
Published: 23 August 2023
(This article belongs to the Special Issue Innovative and Sustainable Infrastructure Materials for Construction Resilience and Improved Productivity)
Abstract
:Various environmentally friendly additives have been used to mitigate significant damage, such as plastic deformation and cracking, in asphalt pavements over the long term. Despite the existence of research demonstrating the efficacy of the materials for asphalt mixture, there has been a lack of studies focusing on the recycling of modified asphalt binders. Therefore, this study conveys the laboratory evaluation of the high-temperature properties of 12 recycled polymer-modified asphalt (PMA) binders as basic research. The data evaluation was carried out using crumb rubber modifier (CRM), styrene-butadiene-styrene (SBS), and styrene-isoprene-styrene (SIS) modified binders, depending on their recycled binders. To assess the properties of each binder, the viscosity and viscoelasticity were measured. Overall, the results of this study revealed that (1) an increasing trend for the viscosity of all asphalt binders was seen as the recycled binder was added and showed their characteristics depending on modifiers; (2) the tendency for using each modified binder in the original and rolling thin-film oven (RTFO) condition appeared for modifiers to have their properties when reusing them; (3) from the Jnr and %rec values, each property of modifiers kept its inherent characteristics, but a potential limit was seen in that a styrene block copolymer was mainly effective on this test method. To sum up, modifiers in asphalt mixture can have their unique properties even after reusing them in recycled asphalt mixture. Therefore, it is recommended that modifiers in asphalt mixture are considered as a potential factor in utilizing reclaimed asphalt pavement (RAP).
1. Introduction
In the long term, plastic deformation and cracking have been considered significant damages to asphalt pavements. Therefore, various additives were utilized to overcome those depletions and improve the pavement performance, such as styrene-butadiene-styrene (SBS), crumb rubber modifier (CRM), low-density polyethylene (LDPE), ethylene propylene diene monomers (EPDM), and styrene-isoprene-styrene (SIS). Through many kinds of research over the past five decades and beyond, polymer-modified asphalt has been proven for asphalt pavements. Nevertheless, despite the numerous benefits offered by these modifiers, there has been relatively little emphasis on innovating the mixing process for binder modification to directly impact the performance of the asphalt binder. These findings have been thoroughly documented with diverse facets [1,2,3,4,5].
These days global warming is considered a hot issue related to the generation of carbon dioxide. One of the leading causes is the generation of excessive carbon dioxide. In the asphalt pavement industry, polymer additives are trending for new pavement construction with sustainability. When new polymer additives are produced in the factory, generating amounts of carbon dioxide cannot be negligible. Therefore, it will substantially positively affect the environment as it diminishes CO2 generation if the pavement, including polymer additives, can be recycled. It is commonly well-known that recycling construction materials is beneficial in terms of environmental and financial aspects.
Recently, there has been an active pursuit among researchers to investigate the feasibility of utilizing various waste materials as modifiers for asphalt binders. The crumb rubber modifier (CRM), one of the most utilized recycled materials, serves multiple purposes. It enhances the performance of asphalt pavement and offers a viable alternative to polymers [6,7,8]. In addition, recycled crushed concrete, plastic, glass fiber, frying oil, and steel slag are examples of recycled materials used in asphalt mixtures. Incorporating waste materials into an asphalt mixture can help minimize the landfilling requirement, offering a cost-effective solution. This waste material serves as a beneficial component, reducing costs, and enhancing the performance of the asphalt mixture [9,10]. In addition, according to previous research [7,11], applying RAP is helpful regarding initial costs, natural resources, and disposal problems of waste materials. However, despite the existence of research demonstrating the efficacy of the recycled modifier for asphalt mixtures [10,12,13], there is a lack of studies focusing specifically on the recycling of modified asphalt binders in RAP. In addition, even though applying RAP in an asphalt mixture improves the resistance to plastic deformation, it increases the stiffness of the asphalt binder [7,14]. In contrast, the high stiffness can generate additional concerns about cracking performance. Thus, it is required to evaluate the rutting performance of recycled PMA binders considering the viscoelasticity as an essential study for asphalt binders to provide valuable insights into how the materials behave and perform at high temperatures, allowing for a better understanding of reusing RAP, including modifiers.
Since the multiple stress creep recovery (MSCR) test appeared in asphalt research, more than ten years have passed. As it is known, this test has been developed targeting polymer-modified asphalt binders to effectively evaluate the rutting performance, which is related to the viscoelastic properties of materials [15,16]. In general, it was found that the MSCR test method, which is based on creep and recovery, is effective in measuring the rutting resistance of polymer-modified asphalt binders that resist adverse effects on the pavement through improved viscoelastic behavior after modification. Therefore, it is thought that the MSCR test application to evaluate the rutting resistance of PMA binders is practical for measuring recycled binders’ remaining elastic properties.
The purpose of this research is to evaluate the high-temperature properties of recycled PMA binders based on the presence of polymer additives to determine whether the polymer additives in the recycled binder are effective on binder performance. The rotational viscosity and G*/sin δ are measured to evaluate the general performances of asphalt binders. Also, the short-term aging procedure is applied to produce artificially aged asphalt samples for the MSCR test. In addition, potential recommendations from this study will be provided for future research and practical application. Figure 1 shows a flow chart of the experimental design.
2. Experimental Design
2.1. Materials
This study’s base binder was performance grade (PG) 64-22. Also, a commercially-produced SBS binder was utilized for this study. Table 1 shows the properties of the base binder, which includes PG64-22 and an SBS-modified binder.
Considering the modification mechanism of polymer additives, the wet process was used to produce a 10% CRM binder in the laboratory at 177 °C for 30 min at a blending speed of 700 rpm [17,18]. The selection of the 10% CRM was to achieve a similar performance as other commonly used modified asphalts, particularly for performance at high temperatures [19]. A mechanical shredding method at an ambient temperature was employed to produce the crumb rubber used in this research. The asphalt binder made with this crumb rubber has been acknowledged for its superior performance characteristics compared to cryogenic crumb rubber [20]. The gradation of crumb rubber is shown in Table 2.
The next polymer additive is SIS, which contains isoprene (C5H8), produced by many plants and animals. Because SIS is the main component of natural rubber, its addition is expected to improve aging resistance, mixing stability, and elasticity, as well as cohesion, tensile strength, and low-temperature flexibility. In order to make the SIS-modified asphalt binder, 5% SIS was selected and modified with the same blending conditions as the CRM binder except for 60 min of blending time [21]. The characteristics of the SIS used in the study are shown in Table 3.
2.2. Superpave Binder Tests
Superpave asphalt binder tests are conducted to characterize binder performances. The viscosity test (AASHTO T 316) and the dynamic shear rheometer (DSR) test (AASHTO T 315) were selected considering the viscosity and rutting properties. Three duplicated samples were used for each test, and then the average value was reported as a result. At 135 °C, a Brookfield rotational viscometer with a number 27 spindle measured the binder viscosity. The DSR test was performed at a frequency of 10 radians per second, which is approximately 1.59 Hz, to determine the G*/sin δ of asphalt binders in their original (unaged) and short-time aged states.
2.3. Multiple Stress Creep Recovery (MSCR) Test
DSR equipment is used to perform MSCR tests on PMA binders. The test is carried out in accordance with AASHTO TP 70 specifications. All binders were tested in their original state and after being aged for a short period (RTFO). Creep and recovery tests were performed on the samples at two stress levels: 0.1 kPa and 3.2 kPa. The analysis of the MSCR test yields two parameters: nonrecoverable creep compliance (Jnr) and percent recovery (%rec). The binder is subjected to creep loading and unloading cycles of 1 s and 9 s, respectively and stress levels of 0.1 kPa and 3.2 kPa, and ten cycles of loading are applied at each stress level, as shown in Figure 2. The results of the MSCR test are used to calculate nonrecoverable creep compliance (Jnr) and percent recovery (%rec) to quantify asphalt binders’ rutting susceptibility. The nonrecoverable creep compliance (Jnr), which is calculated by dividing the nonrecoverable shear strain by the shear stress, is used to assess the rutting potential of an asphalt binder.
2.4. Statistical Analysis Method
The Statistical Analysis System (SAS) program was used to conduct an analysis of variance (ANOVA) and Fisher’s Least Significant Difference (LSD) comparison with α = 0.05 significance level. The ANOVA was used first to see if there were any significant differences in sample means. The significance level in this study’s analyses was 0.95, indicating that each finding had a 95% chance of being true. The LSD was calculated after determining that there were differences between sample means using the ANOVA. The LSD is defined as the observed difference between two sample means required to declare the population mean difference. After calculating the LSD, all pairs of sample means were compared. The population means were declared statistically different if the difference between two sample means was greater than or equal to the LSD [22].
3. Results and Discussion
3.1. Rotational Viscosity
Viscosity is considered a factor in establishing whether an asphalt binder has proper workability between periods of production and construction. As Figure 3 shows, there is a clear trend that modifiers affect the viscosity among all binders, increasing their value. The most significant effect of increasing the viscosity was seen by the SBS modifier.
This trend was shown even when using 15% and 30% recycled binders, resulting in the viscosity reaching a peak of approximately 4500 cP. On the other hand, the viscosity of the CRM asphalt binder was low at 1100 cP among modified asphalt binders. This value steadily increased to about 2500 cP in 30% recycled binders. In the case of the SIS binder, the viscosity rose marginally by 400 cP in 30% recycled binder from its 0% content. In particular, the result of the SIS binder was higher than that of CRM binders up to using 15% recycled binder, while in using 30% recycled binder, the value of the SIS binder was relatively lower than that of the CRM binder. The increasing trend of the viscosity for CRM binders shows that this modifier is relatively vulnerable to aging. These results considered that each binder used with modifiers was shown to have a certain result depending on modifiers, indicating a different tendency and that modifiers in asphalt mixture appear to have their unique properties even after reusing them in recycled asphalt mixture.
The statistical significance of the viscosity with a function of recycling content and modified asphalt binders is examined, as shown in Table 4. A significant difference was generally witnessed within each recycling content depending on modifiers. These results match those mentioned in the findings of the viscosity bar chart, showing a noticeable effect on using modifiers even though they are reused after the asphalt mixture is recycled.
3.2. Dynamic Shear Rheometer (DSR) Test
3.2.1. Original Condition
The approach to evaluating the viscoelastic properties for this study was to use DSR, measuring G*/sin δ. It is known that there is a strong relationship between G*/sin δ and permanent deformation. A higher G*/sin δ means a higher viscoelastic property showing a strong resistance from the deformation.
In its original condition, as shown in Figure 4, PG64-22 increased slightly according to the addition of its recycled binder due to its marginal effect from aging. In the case of the CRM asphalt binder, using 15% and 30% recycled binders made no change, resulting in about 2.3 kPa. For the SBS asphalt binder, the decreasing trend of the value was generally shown in both contents of recycled binders, indicating from 6 kPa in 0% recycled binders to 4 kPa in 15% recycled binders, and this value increased slightly to about 4.8 kPa in 30% recycled binders. On the other hand, the value of the SIS binder steadily increased with the addition of its recycled binders from 3 kPa in 0% recycled binders and 4.8 kPa in 30% recycled binders. In general, it was observed that the properties of the modifier appeared in the binder when the modified binder was reused. This proves that the properties of the modifier remained intact even after the binder was reused, indicating that the effects of the modifier were retained throughout the recycling process.
The statistical significance of the change in the G*/sin δ value was evaluated in Table 5, comparing modified asphalt binders depending on recycling content. The statistical difference among recycled binders for the original condition was generally observed. All values in each modified binder between 15% and 30% recycled binders revealed an insignificant difference. However, it was observed that all modified binders, except for CRM binders, exhibited significance in their properties between 0% and 30% of the recycled binders. This finding supports the information presented in the bar chart depicted in Figure 4, additionally meaning that the properties of each modifier remained undamaged even though the modifiers were reused in asphalt binders.
3.2.2. RTFO Condition
In the RTFO condition, all values increased slightly compared to those in the original condition, shown in Figure 5. This is because the addition of aged binders causes increased brittleness due to the aging process. From the data, it can be seen that there was a decreasing trend of CRM and SBS binders with the addition of aged binders. However, the value of the SIS binder remained stable among each recycling binder, showing a result of about 6 kPa. The properties of each modified binder in the RTFO condition were shown to have a similar trend as those in the original condition, so the additives are still effective even after the RTFO aging process. Therefore, it is required to conduct the MSCR test to measure accurate rutting resistance based on elastic polymer modifiers. Overall, the tendency for using each modified binder showed their properties when recycling them. In addition, the property of modifiers appears even though these are used as a reusable resource.
The statistical significance of the change in the G*/sin δ value for RTFO condition was also analyzed in Table 6, comparing modified asphalt binders to recycled modified asphalt binders. The statistical analysis remained at a similar level compared to the statistical results of the original condition. However, the addition of a reused binder resulted in a notable difference among the CRM binders, whereas the results among SIS binders did not show a significant difference. These findings align with the observations depicted in the bar chart illustrated in Figure 5. Thus, even in the results of the statistical analysis, it was confirmed that the properties of the modifiers are evident when the modified binder is reused.
3.3. Multiple Stress Creep Recovery (MSCR) Test
3.3.1. Jnr for the Original Condition
In order to identify the extended viscoelastic properties of asphalt binders, the MSCR test was conducted, figuring out two factors of creep and recovery in both original and RTFO conditions. Based on the creep and recovery, Jnr and %rec were measured at the 3.2 kPa load at 76 °C.
In general, a decreasing trend for Jnr was seen for each modified binder with the addition of a recycled binder in the original condition. The Jnr of PG64-22 and CRM binders saw by far the highest value of about 12 kPa−1, then dropped steadily to a low of around 5.8 kPa−1 in the PG64-22 binder and 4.2 kPa−1 in CRM binders by increasing the recycled binder up to 30%. On the other hand, the Jnr value of the SBS binder remained at its lowest point of under 1 kPa−1. In the case of SIS, with the addition of a recycled binder, the value decreased from 3 kPa−1 to 1 kPa−1. These findings support the argument that the property of modifiers is kept after reusing them. In addition, this result conveys that styrene block copolymer can be mainly confirmed on the MSCR test rather than other modifiers.
The statistical significance of the change in the Jnr was evaluated by the one-way analysis of variance (Table 7). Overall, each value significantly differed depending on using recycled binders in the original condition. However, no significant differences were observed when using only SBS asphalt binders, even with the addition of recycled binders. The low Jnr value observed in all recycling binders during the MSCR test can be attributed solely to the asphalt binder modified with SBS. These findings align with the information presented in Figure 6, which illustrates the corresponding bar chart.
3.3.2. Jnr for the RTFO Condition
For the data of the RTFO condition, the tendency for the value was similar to the original condition, but the data were respectively lower due to the aging from the RTFO procedure. As shown in Figure 7, the addition of aged binder resulted in a slight decrease in the Jnr value of the PG 64-22 binder from 5.0 kPa−1 to 4.0 kPa−1. In contrast, the CRM binder exhibited a significant decrease in value from approximately 7.5 kPa−1 to 2.3 kPa−1. This is likely due to the tendency of CRM asphalt binder to become stiffer with aging. On the other hand, the SIS modifier showed consistent results even with the use of reused asphalt binders, indicating that it has a relatively high resistance to aging. The SBS-modified binder consistently showed the lowest value, shown in the results of the original condition when the reused binder was added. This confirms that the MSCR test has limitations in involving all modified asphalt binders because evaluating the performance of styrene block copolymer modifiers is mainly effective on the test.
The statistical significance of the Jnr change was assessed using one-way analysis of variance (ANOVA), as shown in Table 8. The results indicated that there were significant differences in each value when recycled binders were utilized under the RTFO condition. However, unlike the other binders, the one using the styrene block copolymer modifier did not consistently exhibit significant differences even though the reused modified binder was used. This indicates the fact that, similar to the results in the original condition, the MSCR test mainly demonstrated an effect on the Jnr value for the asphalt binder utilizing the styrene block copolymer modifier.
3.3.3. Percentage Rec for the Original Condition
For the %rec, contrary to the Jnr value, the results show a rising trend (Figure 8). The results of the SBS binder were the highest, peaking at over 70%. Moreover, there was an observed trend of increasing %rec in the SIS binder as this binder was reused, showing that %rec rose from approximately 10% to 15%. On the other hand, other data remained relatively low, revealing a limit to analyzing each data among binders, but each property of modifiers kept its inherent characteristics, such as results of the viscosity and DSR test. In the overall results of the MSCR test, a potential limit was seen that the binder used with a styrene block copolymer was mainly effective on this test method, indicating that MSCR might not provide a comprehensive analysis with various modifiers and additives.
The statistical significance of the %rec change was assessed using one-way analysis of variance (ANOVA), and the findings are displayed in Table 9. In general, significant differences were observed when the binder was reused by 15% and 30% across all modified binders. However, in the case of CRM asphalt, since the %rec was low at 1.0 when not reused, a significant difference was observed by adding the reused binder. Therefore, it can be concluded that the MSCR test was practical for asphalt binders using styrene block copolymer modifiers.
3.3.4. Percentage Rec for the RTFO Condition
Overall, the %rec after RTFO exhibited similar trends to those observed in the original condition, as shown in Figure 9. The SBS asphalt binder demonstrated a high recovery rate of over 70% across all ranges among reused binders. In contrast, the CRM asphalt binder showed a relatively lower %rec, increasing to around 15% when reusing the binder, but still lower compared to the SBS asphalt binder. On the other hand, the SIS asphalt binder exhibited a decreasing trend in %rec from around 20% to approximately 15% when using the reused binder, contrary to the results observed in the original condition. The observed trend can be attributed to the high elongation and aging resistance of the SIS asphalt binder, which is a similar trend to the results obtained from the DSR test. Likewise, in this study, the MSCR experiments proved to be effective only for asphalt binders that were modified with styrene block copolymers.
The statistical significance of the change in %rec for RTFO condition was evaluated using one-way analysis of variance (ANOVA), shown in Table 10. Overall, each value significantly differed depending on using recycled binders in the original and RTFO conditions. However, a couple of values showed insignificant effects between using 0% and 15%, or 15% and 30% recycled binders as shown in the above bar chart, but between data of 0% and 30% recycled binders, as shown in the above bar chart, the significant difference was distinct. In general, compared with the bar chart, it was confirmed that the difference between the data was shown depending on the tendency of the bar chart. This can be determined to support the results and proof analyzed in the bar chart, establishing that modifiers in asphalt binders are observable even after reusing recycled binders and that the limit of the MSCR test to evaluate various types of modifiers and additives was found.
4. Conclusions and Recommendations
To investigate the effect of additives in recycled modified binders, each test depending on asphalt binders was conducted with the addition of 0%, 15%, and 30% recycled binders. As a test method to evaluate asphalt binders, the rotational viscosity, and G*/sin δ are measured to assess viscoelastic properties at high temperatures. In addition, the short-term aging procedure using RTFO was applied to produce artificially aged asphalt samples, and the MSCR test was conducted. From these results, the following conclusions are drawn.
- (1)
- An increasing trend for the viscosity of all asphalt binders was seen as the recycled binder was added. Even though polymer additives in recycled binders are aged and reused in fresh binders, each binder used with modifiers was shown to have its characteristics depending on modifiers. This result means that modifiers in asphalt mixtures appear to have their unique properties even after reusing them in recycled asphalt mixtures.
- (2)
- Based on the DSR test results, the tendency for using each modified binder in the original condition showed their properties when reusing them. Moreover, the properties of each modified binder in the RTFO condition were shown to have the same trend compared to those in the original condition. Therefore, the modifier in asphalt binders can still be effective even after RTFO conditioning.
- (3)
- From Jnr and %rec, although the individual properties of modifiers are retained, such as the outcomes of viscosity and DSR tests, there is a potential limitation to using the MSCR test. This is because the styrene block copolymer is predominantly effective in this test method, while the CRM binder is not adequately measured to evaluate its properties. Consequently, it suggests that the MSCR test may not provide a comprehensive analysis when considering different modifiers and additives.
- (4)
- The results of the bar chart and statistical analysis demonstrated a notable and consistent positive correlation for each test. This finding indicates that the properties of modifiers can persist even when these materials are recycled and reused as RAP. Therefore, it is recommended that modifiers in asphalt mixtures should be considered a potential factor in utilizing RAP.
- (5)
- Consequently, it is recommended to maintain a record of the type of modifier used when storing or utilizing RAP. Additionally, before recycling it as a pavement material, it is essential to reassess and consider the properties of the asphalt mixture to ensure its suitability for the intended purpose.
- (6)
- Overall, these results are based on the viscosity and viscoelastic properties of asphalt binders at high temperatures. Therefore, further studies are recommended to expand the evaluation of binder properties at low temperatures, which should include assessing the performance of the asphalt mixture as a whole.
Author Contributions
Conceptualization, I.-H.N. and H.K.; Methodology, J.Y.; Resources, P.C.; Data curation, J.Y.; Writing—original draft, B.J.; Writing—review & editing, H.K. All authors have read and agreed to the published version of the manuscript.
Funding
This research received no external funding.
Data Availability Statement
Not applicable.
Conflicts of Interest
The authors declare no conflict of interest.
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Figure 1.
Flow chart of experimental design procedures.
Figure 2.
Ten cycles of creep and recovery at two stress levels of 0.1 kPa and 3.2 kPa [21].
Figure 2.
Ten cycles of creep and recovery at two stress levels of 0.1 kPa and 3.2 kPa [21].
Figure 3.
The viscosity of each modified binder based on recycling content at 135 °C.
Figure 4.
G*/sin δ of each modified binder based on recycling content for the original condition at 76 °C.
Figure 4.
G*/sin δ of each modified binder based on recycling content for the original condition at 76 °C.
Figure 5.
G*/sin δ of each modified binder based on recycling content for RTFO at 76 °C.
Figure 6.
Jnr of each modified binder based on recycling content for the original condition at 76 °C.
Figure 6.
Jnr of each modified binder based on recycling content for the original condition at 76 °C.
Figure 7.
Jnr of each modified binder based on recycling content for the RTFO condition at 76 °C.
Figure 8.
%rec of each modified binder based on recycling content for the original condition at 76 °C.
Figure 8.
%rec of each modified binder based on recycling content for the original condition at 76 °C.
Figure 9.
%rec of each modified binder based on recycling content for the RTFO condition at 76 °C.
Table 1.
Properties of asphalt binders.
| Aging States | Test Properties | PG64-22 | SBS-Modified Binder (PG76-22) |
|---|---|---|---|
| Unaged binder | Viscosity @ 135 °C (Pa-s) | 531 | 3244 |
| G*/sin δ (kPa) | 1.415 @ 64 °C | 1.9 @ 76 °C | |
| RTFO aged residual | G*/sin δ (kPa) | 2.531 @ 64 °C | 3.3 @ 76 °C |
| RTFO + PAV aged residual | G*sin δ @ 25 °C (kPa) | 2558 | 3650 |
| Stiffness @ −12 °C (MPa) | 287 | 285 | |
| m-value @ −12 °C | 0.307 | 0.302 |
Table 2.
The gradation of crumb rubber used in this study.
| Sieve No. (μm) | Ambient CRM | |
|---|---|---|
| % Retained | % Cumulative Retained | |
| 30 (600) | 0 | 0 |
| 40 (425) | 9.0 | 9.0 |
| 50 (300) | 31.9 | 40.9 |
| 80 (180) | 32.9 | 73.8 |
| 100 (150) | 7.6 | 81.4 |
| 200 (75) | 18.6 | 100.0 |
Table 3.
Properties of SIS.
| Properties | Test Method | Units | Typical Value |
|---|---|---|---|
| Styrene | TSRC/DEXO Method | wt% | 15 |
| Diblock content | TSRC/DEXO Method | wt% | 18 |
| Melt Flow Rate (200 °C/5 kg) | ASTM D1238 | g/10 min | 11 |
| Solution viscosity | ASTM D2196 | cps | 1240 |
| Ash | ASTM D5630 | wt% | 0.3 |
| Tensile strength | TSRC/DEXO Method | MPa | 25 |
| 300% modulus | TSRC/DEXO Method | MPa | 1.1 |
| Elongation | TSRC/DEXO Method | % | 1250 |
| Hardness | ASTM D2240 | Shore A | 33 |
| Bulk density | ASTM D1895 | g/cm3 | 0.55 (4113A) |
| Specific gravity | ASTM D792 | - | 0.92 |
Table 4.
Statistical analysis results of the viscosity as a function of recycling content and modified binders.
Table 4.
Statistical analysis results of the viscosity as a function of recycling content and modified binders.
| Viscosity | Recycling Content | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 0% | 15% | 30% | ||||||||||||
| P | C | S | I | P | C | S | I | P | C | S | I | |||
| Recycling content | 0% | P | - | S | S | S | N | S | S | S | S | S | S | S |
| C | - | S | S | S | S | S | S | S | S | S | S | |||
| S | - | S | S | S | S | S | S | S | S | S | ||||
| I | - | S | S | S | S | S | S | S | S | |||||
| 15% | P | - | S | S | S | S | S | S | S | |||||
| C | - | S | S | S | S | S | S | |||||||
| S | - | S | S | S | S | S | ||||||||
| I | - | S | S | S | S | |||||||||
| 30% | P | - | S | S | S | |||||||||
| C | - | S | S | |||||||||||
| S | - | S | ||||||||||||
| I | - | |||||||||||||
P: PG64-22 (Control), C: CRM, S: SBS, I: SIS, N: nonsignificant, S: significant.
Table 5.
Statistical analysis results of the G*/sin δ as a function of recycling content for the original condition (α = 0.05).
Table 5.
Statistical analysis results of the G*/sin δ as a function of recycling content for the original condition (α = 0.05).
| G*/sin δ (Original) | Recycling Content | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 0% | 15% | 30% | ||||||||||||
| P | C | S | I | P | C | S | I | P | C | S | I | |||
| Recycling content | 0% | P | - | S | S | S | N | S | S | S | N | S | S | S |
| C | - | S | N | S | N | S | S | S | N | S | S | |||
| S | - | S | S | S | S | S | S | S | S | S | ||||
| I | - | S | S | S | N | S | N | S | S | |||||
| 15% | P | - | S | S | S | N | S | S | S | |||||
| C | - | S | S | N | N | S | S | |||||||
| S | - | N | S | S | N | N | ||||||||
| I | - | S | S | N | N | |||||||||
| 30% | P | - | N | S | S | |||||||||
| C | - | S | S | |||||||||||
| S | - | N | ||||||||||||
| I | - | |||||||||||||
P: PG64-22 (Control), C: CRM, S: SBS, I: SIS, N: nonsignificant, S: significant.
Table 6.
Statistical analysis results of the G*/sin δ as a function of recycling content for the RTFO condition (α = 0.05).
Table 6.
Statistical analysis results of the G*/sin δ as a function of recycling content for the RTFO condition (α = 0.05).
| G*/sin δ (RTFO) | Recycling Content | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 0% | 15% | 30% | ||||||||||||
| P | C | S | I | P | C | S | I | P | C | S | I | |||
| Recycling content | 0% | P | - | S | S | S | N | N | S | S | N | N | S | S |
| C | - | S | N | S | S | N | N | S | S | N | N | |||
| S | - | S | S | S | S | S | S | S | S | S | ||||
| I | - | S | S | N | N | S | S | N | N | |||||
| 15% | P | - | N | S | S | N | N | S | S | |||||
| C | - | S | S | N | N | S | S | |||||||
| S | - | N | S | S | N | N | ||||||||
| I | - | S | S | N | N | |||||||||
| 30% | P | - | N | S | S | |||||||||
| C | - | S | S | |||||||||||
| S | - | N | ||||||||||||
| I | - | |||||||||||||
P: PG64-22 (Control), C: CRM, S: SBS, I: SIS, N: nonsignificant, S: significant.
Table 7.
Statistical analysis results of the Jnr as a function of recycling contents for the original condition (α = 0.05).
Table 7.
Statistical analysis results of the Jnr as a function of recycling contents for the original condition (α = 0.05).
| Jnr (Original) | Recycling Content | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 0% | 15% | 30% | ||||||||||||
| P | C | S | I | P | C | S | I | P | C | S | I | |||
| Recycling content | 0% | P | - | N | S | S | S | S | S | S | S | S | S | S |
| C | - | S | S | S | S | S | S | S | S | S | S | |||
| S | - | S | S | S | N | S | S | S | N | S | ||||
| I | - | S | S | S | S | S | S | S | S | |||||
| 15% | P | - | S | S | S | S | S | S | S | |||||
| C | - | S | S | N | S | S | S | |||||||
| S | - | S | S | S | N | S | ||||||||
| I | - | S | S | S | N | |||||||||
| 30% | P | - | S | S | S | |||||||||
| C | - | S | S | |||||||||||
| S | - | S | ||||||||||||
| I | - | |||||||||||||
P: PG64-22 (Control), C: CRM, S: SBS, I: SIS, N: nonsignificant, S: significant.
Table 8.
Statistical analysis results of the Jnr as a function of recycling content for the RTFO condition (α = 0.05).
Table 8.
Statistical analysis results of the Jnr as a function of recycling content for the RTFO condition (α = 0.05).
| Jnr (RTFO) | Recycling Content | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 0% | 15% | 30% | ||||||||||||
| P | C | S | I | P | C | S | I | P | C | S | I | |||
| Recycling content | 0% | P | - | S | S | S | N | S | S | S | N | S | S | S |
| C | - | S | S | S | S | S | S | S | S | S | S | |||
| S | - | S | S | S | N | S | S | S | N | N | ||||
| I | - | S | S | S | N | S | S | S | N | |||||
| 15% | P | - | S | S | S | S | S | S | S | |||||
| C | - | S | S | S | N | S | S | |||||||
| S | - | S | S | S | N | S | ||||||||
| I | - | S | N | S | N | |||||||||
| 30% | P | - | S | S | S | |||||||||
| C | - | S | S | |||||||||||
| S | - | S | ||||||||||||
| I | - | |||||||||||||
P: PG64-22 (Control), C: CRM, S: SBS, I: SIS, N: nonsignificant, S: significant.
Table 9.
Statistical analysis results of the %rec as a function of recycling contents for the original condition (α = 0.05).
Table 9.
Statistical analysis results of the %rec as a function of recycling contents for the original condition (α = 0.05).
| %Rec (Original) | Recycling Content | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 0% | 15% | 30% | ||||||||||||
| P | C | S | I | P | C | S | I | P | C | S | I | |||
| Recycling content | 0% | P | - | N | S | S | N | S | S | S | N | S | S | S |
| C | - | S | S | N | S | S | S | N | S | S | S | |||
| S | - | S | S | S | S | S | S | S | S | S | ||||
| I | - | S | S | S | S | S | S | S | S | |||||
| 15% | P | - | S | S | S | N | S | S | S | |||||
| C | - | S | S | S | S | S | S | |||||||
| S | - | S | S | S | N | S | ||||||||
| I | - | S | S | S | N | |||||||||
| 30% | P | - | S | S | S | |||||||||
| C | - | S | S | |||||||||||
| S | - | S | ||||||||||||
| I | - | |||||||||||||
P: PG64-22 (Control), C: CRM, S: SBS, I: SIS, N: nonsignificant, S: significant.
Table 10.
Statistical analysis results of the %rec as a function of recycling contents for the RTFO condition (α = 0.05).
Table 10.
Statistical analysis results of the %rec as a function of recycling contents for the RTFO condition (α = 0.05).
| %Rec (RTFO) | Recycling Content | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 0% | 15% | 30% | ||||||||||||
| P | C | S | I | P | C | S | I | P | C | S | I | |||
| Recycling content | 0% | P | - | N | S | S | N | S | S | S | N | S | S | S |
| C | - | S | S | N | S | S | S | N | S | S | S | |||
| S | - | S | S | S | N | S | S | S | S | S | ||||
| I | - | S | S | S | S | S | S | S | S | |||||
| 15% | P | - | S | S | S | N | S | S | S | |||||
| C | - | S | N | S | N | S | S | |||||||
| S | - | S | S | S | N | S | ||||||||
| I | - | S | S | S | S | |||||||||
| 30% | P | - | S | S | S | |||||||||
| C | - | S | S | |||||||||||
| S | - | S | ||||||||||||
| I | - | |||||||||||||
P: PG64-22 (Control), C: CRM, S: SBS, I: SIS, N: nonsignificant, S: significant.
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Yun, J.; Na, I.-H.; Choi, P.; Ji, B.; Kim, H. Laboratory Evaluation of High-Temperature Properties of Recycled PMA Binders. Sustainability 2023, 15, 12744. https://doi.org/10.3390/su151712744
AMA Style
Yun J, Na I-H, Choi P, Ji B, Kim H. Laboratory Evaluation of High-Temperature Properties of Recycled PMA Binders. Sustainability. 2023; 15(17):12744. https://doi.org/10.3390/su151712744
Chicago/Turabian StyleYun, Jihyeon, Il-Ho Na, Pangil Choi, Bongjun Ji, and Hyunhwan Kim. 2023. "Laboratory Evaluation of High-Temperature Properties of Recycled PMA Binders" Sustainability 15, no. 17: 12744. https://doi.org/10.3390/su151712744
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