High-temperature Performance Grade Research Articles

Functional and rheological investigations on hydrophilic nanoclay blended bitumen

Functional and rheological characteristics are two essential criteria for the success of any modifiers for the modification of bitumen. Recently, nanoclay has grabbed extensive attention as a key solution for enhancing the performance of bitumen. This study focuses on evaluating the dispersion, storage stability, high-temperature performance, and aging resistance potential properties of bitumen VG-30 modified with montmorillonite bentonite hydrophilic nanoclay (NC). Various proportions (0, 2, 4, 6, and 8% by weight of bitumen) of NC were blended with VG-30 using a high shear mixer (HSM). Various performance assessments, including kinematic viscosity by Brookfield Rotational Viscometer (BRV), multiple stress creep recovery (MSCR), high-temperature performance grade (PG), frequency sweep along with scanning electron microscopy (SEM) were conducted. SEM images and viscosity data analysis show that dispersion problem arises beyond 6% of NC addition while phase separation is in the acceptable range. Further, considerable increment in Superpave rutting parameter (G*/Sinδ) and recovery percentage (%R), and decrease in non-recoverable compliance (Jnr) was seen, resulted up to 30% improvement in rutting performance of the bitumen. Furthermore, the potential for aging resistivity resulted a significant drop in aging index (AI) values, suggesting that introducing NC to bitumen could significantly improve aging resistivity. Moreover, rheological approaches can be helpful to understand temperatures and frequency dependent aging behaviours of bitumen.

Evaluating the Effects of RA on the Rheological Properties and Aging Susceptibility of RAM Asphalt

Recycling agents (RAs) can mitigate the adverse effects of reclaimed asphalt pavement (RAP) on recycled asphalt, which can result in more RAP being added. To explore the effects of four RAs on recycled asphalt, this study used asphalt rheological performance experiments, including the bending beam rheometer (BBR) test, the dynamic shear rheological (DSR) test, and the indirect tensile asphalt cracking test (IDEAL-CT), to study the performance grade (PG), cracking resistance, and cracking susceptibility of recycled asphalt. In addition, an aging model for asphalt was used, and short-term and long-term aging sensitivities were evaluated according to this model. Results showed that US Soybean significantly enhanced the high-temperature and low-temperature performance grade (PGLT) and cracking resistance and reduced cracking sensitivity of the recycled asphalt. In addition, the short-term aging sensitivity was the lowest. It showed the best regeneration effect. However, the recycled asphalt with US Soybean showed the highest long-term aging sensitivity, suggesting that longer aging time results in poorer performance. Ingevity’s PG, cracking resistance, and cracking sensitivity are slightly lower than that of US Soybean, and Ingevity demonstrated the second lowest short-term aging sensitivity. However, its prolonged aging sensitivity was much lower than that of US Soybean. Asphalt and Wax Innovations and Georgia Pacific agents slightly improved recycled asphalt properties. The long-term aging sensitivity of recycled asphalt with four Ras was higher than that of recycled asphalt without Ras. These results indicated that the recycled asphalt’s performance with Ras worsened as aging time increased compared to the original recycled asphalt.

Effect of Sasobit/Waste Cooking Oil Composite on the Physical, Rheological, and Aging Properties of Styrene–Butadiene Rubber (SBR)-Modified Bitumen Binders

The modifying effects of polymer on bitumen low-temperature performance are substantially compromised by the thermal breakdown of styrene–butadiene rubber (SBR) polymer during bitumen mixture production operations. The efficacy of the utilization of Sasobit/waste cooking oil (Sasobit/WCO) as a warm-mix additive has been demonstrated in mitigating the adverse consequences of thermal aging on SBR-modified bitumen binder (SB) while preserving the binder’s original performance characteristics. However, few studies have been conducted to further investigate the rheological properties and aging resistance of SB modified with Sasobit/WCO compounds. In this work, three additives—Sasobit, WCO, and Sasobit/WCO composite—were selected, and their effects on the physical and rheological characteristics of SB as well as the temperatures at which the mixtures were prepared were assessed. In addition, by using dynamic shear rheometers (DSR) and bending beam rheometers (BBR), the effects of this innovative warm-mix addition on the performance grade (PG) and aging resistances of SB were evaluated. According to the results, Sasobit/WCO composites outperform Sasobit and WCO in lowering the mixture preparation temperature. Sasobit/WCO also improves both the high- and low-temperature performance of SB simultaneously. Compared to hot-mix asphalt mixtures, the addition of Sasobit/WCO reduces the preparation temperature of the bitumen mixtures by 19 °C, which in turn helps to minimize the negative effects of temperature aging on the functioning of the SB. Additionally, the Sasobit/WCO composite addition can improve the SB mixture’s resistance to thermal cracking. After the introduction of Sasobit/WCO, the high-temperature PG of SB was raised by two levels, regardless of whether the warm-mix impact was taken into account. With the addition of Sasobit/WCO, SB’s resilience to short-term aging was enhanced.

Synthesis of organic layered double hydroxide from waste bischofite and its application on ageing resistance of asphalt

For the utilization of waste bischofite from salt lakes, the waste bischofite was utilized to synthesize layered double hydroxide (LDH) by hydrothermal method, and the synthesized LDH was further organically intercalated with 3,5-Di-tert-butyl-4-hydroxyphenylpropionic acid (antioxidant, DPA) by anion exchange methods. Then, the synthesized LDH and DPA intercalated LDH (DPA-LDH) were applied to improve the ageing resistance of asphalt. X-ray diffraction and Fourier transform infrared spectroscopy manifested that LDH and DPA-LDH had been successfully synthesized. After DPA intercalation, the adhesive aggregation among LDH particles was obviously ameliorated, and the contact angle of LDH increased from 31.3° to 77.9°, the hydrophilicity of LDH was significantly decreased. The effect of LDH and DPA-LDH (3 % by weight of asphalt) on rheological properties, chemical constituents and molecular weight of asphalt before and after ageing were comprehensively studied. The high-temperature performance grade of asphalt increased from PG64 to PG70 with the addition of LDH and DPA-LDH, which indicated that LDH and DPA-LDH could enhance the high-temperature performance of asphalt. After ageing, the high and low- temperature performance of asphalt worsened, the colloidal stability index (CI) decreased from 3.548 to 1.844, the gel index (GI) was 48 %, the colloidal structure tended to gel structure, the molecular weight (Mw) enlarged from 3387 to 4101 (the Mw growth rate of 21 %). LDH could restrain the destruction of ageing on rheological properties, the colloidal structure gel of asphalt (the GI of 37.4 %) and molecular weight (the Mw growth rate of 13 %) of asphalt, and strengthen the ageing resistance of asphalt. Furthermore, the enhancement of DPA-LDH (the GI of 16.7 % and the Mw growth rate of 6 %) on the ageing resistance of asphalt was more superior than LDH. The result showed that the synthesized DPA-LDH exhibited outstanding performance in improving the ageing resistance of asphalt, which was beneficial to the long-life pavement and the utilization of abandoned bischofite from salt lakes.

Rheological and Aging Characteristics of Polymer-Modified Asphalt with the Addition of Sulfur

Crosslinking agents, notably sulfur, are used in asphalt binder modification to facilitate chemical bonding between polymer chains and the asphalt binder. Despite some prior research indicating the benefits of sulfur crosslinking in enhancing polymer-modified asphalt’s (PMA) stability, there is a lack of comprehensive understanding regarding its impact on rheological properties and its anti-aging potential. This study addresses these gaps by thoroughly investigating the effects of varying the sulfur content (ranging from 0.03% to 0.5% by total weight of binder) on PMA’s rheological properties. The research assesses the effectiveness of sulfur in enhancing PMA’s resistance to aging using various methods, including the Glover-Rowe parameter, FTIR analysis, and the examination of the dynamic modulus and phase angle master curves. The results indicated that the addition of sulfur, particularly up to 0.3%, bumps the high-temperature performance grade by one level, and significantly improves elasticity, allowing the PMA to support heavier traffic without experiencing rutting, all while maintaining resistance to low-temperature cracking. Furthermore, PMA with sulfur demonstrated an increase in resistance to aging, reducing the aging potential by approximately 15% with the best sulfur formulation. This enhanced durability can reduce the frequency of maintenance activities, leading to cost savings, reduced roadwork emissions, and prolonged pavement life.

Effects of multiple recycling on the performance characteristics of asphalt binder using different recycling agents

The process of reclaimed asphalt pavement (RAP) recycling may occur multiple times during the life of the pavement. This study investigates the effect of multiple recycling on binder properties by employing a virgin 3045 PEN grade binder that was aged in the laboratory intended to simulate aging of binders in RAP. The aged binder was rejuvenated using two bio-oils and one softer binder. The doses of the bio-oils and softer binder were determined by matching the continuous high-temperature performance grade (PGH) of the rejuvenated RAP binder to that of the virgin binder. This aging and rejuvenation cycle was repeated three times. Finally, fatigue and rutting performance of the binder was evaluated for the three reuse levels. Results indicate that the material can be reused up to three cycles keeping good performance on fatigue or rutting. However, care should be taken regarding the cumulative effect of bio-oils causing an over-softening effect on the of the RAP.

Influence of climate change on asphalt binder selection in China

ABSTRACT The impact of climate change on asphalt pavement infrastructure has become increasingly apparent. This paper investigated how climate change impacts the selection of asphalt binder for freeway pavement in China. The climate data predicted by the Global Climate Model were employed to select the appropriate performance grade for asphalt binder. The predicted air temperature converted pavement temperature, and performance grade distribution of the country was analysed. It is suggested that the performance grade of asphalt binder for freeways’ pavement should be determined based on ten years’ predicted climate data. This study concluded the following four major findings. Firstly, the selection of the appropriate asphalt binder performance grade needs to take into account the effects of future climate change. Secondly, the change in the standard deviation of temperature has a greater impact on the change in asphalt performance grade, as compared to the change in average air temperature. Thirdly, climate change affects the low-temperature performance grade more than the high-temperature performance grade in China. Finally, by 2050s, 15.2% of freeway asphalt pavement needs to upgrade high-temperature performance grade limit, and 17.3% of freeway asphalt pavement needs to upgrade to low-temperature performance grade limit.

Rheological performance of bitumen mixed with laboratory simulated polymerized RAP binders

Researchers have mostly used three artificial aging techniques, namely pressure aging vessel (PAV) binder aging, compacted mix aging (CMA), and loose mix aging (LMA) to simulate recycled asphalt pavement (RAP) binder in the laboratory. RAP binder (RAPB) simulated using different techniques will differ in characteristics and may affect the performance of the base binder differently. Which may affect the parameters used for blending and recycling, such as the selection of base binder, rejuvenator dosage, etc. Therefore, in this study, three RAP binders, namely RAPB-P, RAPB-C, and RAPB-L, were simulated from a polymer modified binder (PMB) with 3.5% SBS content, using PAV aging (100 °C, 20 hrs, 2.1 MPa), CMA (85 °C, 5 days) and LMA (85 °C, 8 days), respectively. These polymerized RAPBs were added to an unmodified binder (AC 30) at three proportions: 15 %, 25 %, and 40 %. These RAPB and AC 30 blends were characterized in terms of their dynamic viscosity, mixing and compaction temperature, and high temperature performance grade (PG). Superpave rutting factor (|G*|/sin δ) and multiple stress creep and recovery (MSCR) test parameters were used to evaluate the rutting performance of the RAPB blended AC 30 binders. Further, resistance to yielding and elastic recovery values were evaluated using the binder yield energy test (BYET). The test results suggested that all three RAP binders affect the performance of the AC 30 binder differently, which was also confirmed by statistical analysis using one-way ANOVA. From MSCR and BYET test results, it may be stated that RAP binder simulated from standard PAV aging may mislead in predicting the high and intermediate temperature performance of AC 30 binder with RAPB. Overall, the present study is helpful for asphalt researchers and practitioners to understand how the selection of different defined aging strategies affects the performance of aged recycled PMB with unmodified base binder.

Characteristics of Waste Oil-rejuvenated RAP Bitumen: An Experimental Study

In recent years, Reclaimed Asphalt Pavement (RAP) has become very popular in pavement construction due to its benefits to the economy and the environment. The present study investigates the feasibility of employing Waste Cooking Oil (WCO) and Waste Engine Oil (WEO) as rejuvenators blended with reusable asphalt binder through physical and rheological properties at high and intermediate temperatures. Examined conventional properties of WCO-and WEO-modified bitumen include softening point, penetration, ductility and viscosity. In addition to these rheological properties, they also include Amplitude Sweep, Frequency Sweep, Multiple Stress Creep Recovery (MSCR), Linear Amplitude Sweep (LAS) and High-temperature Performance Grading (HTPG) tests carried out by Dynamic Shear Rheometer (DSR). The experimental outcomes revealed that both WCO and WEO could reduce deformation resistance and improve stiffness, workability and viscous behavior of aged bitumen. Moreover, the addition of waste oils improves the fatigue lives of rejuvenated bitumen and enhance fatigue cracking resistance, but at the cost of rutting resistance. Overall, WCO performs better in restoring stiff binder properties than WEO as per rheological testing. KEYWORDS: Dynamic shear rheometer (DSR), Reclaimed asphalt pavement (RAP), Rejuvenators, Waste cooking oil (WCO), Waste engine oil (WEO).

Benchmarking Recycled Binder Blends Using Statistical Analysis: A Case Study of Virginia and North Carolina

Recycling agents (RAs) are added to asphalt binder blends containing recycled materials to mitigate the negative effects of adding oxidized material to asphalt mixtures. Several methods exist to select a particular RA dosage to restore a specific Superpave performance parameter. However, the rheological similarities between the RA-modified systems and typical virgin binders across the complete range of temperatures remain to be ascertained. In this study, two RA dosage selection procedures, one aiming to restore high-temperature performance grade and the other aiming to restore low-temperature performance grade were statistically compared. Quality assurance datasets from Virginia and North Carolina were used to benchmark the typical virgin binder properties, and 17 recycled binder blends using constituent materials from the two states were studied with respect to Superpave binder properties. Both univariate and bivariate statistical analyses were applied to compare and contrast the rheological properties of these blends with the benchmarked virgin binder properties for the two states. Then, a statistical similarity analysis was done using the Mahalanobis distance to evaluate the rheological properties of these blends with those of the reference binders. The study found that both dosage selection procedures were successful in achieving rheological similarity at target-specific temperatures and for specific binder properties but might not necessarily yield similar properties at other temperatures. Finally, an example application is presented using statistical analysis to select an RA dosage that yields a rheological fingerprint more similar to that of virgin binder systems.

Multiple Stress Creep Recovery Test to Differentiate Polymer Modified Bitumen at High Temperature

Abstract The constant demand for high-performing and more reliable roads has led to an increasing use of complex bituminous binders such as polymer-modified bituminous binders, which has become a widespread practice for asphalt pavement. As a result, specification and testing have evolved to better distinguish between quality materials. In recent years, more focus has been devoted to better evaluating the rutting resistance of bituminous binders. The multiple stress creep recovery (MSCR) test has gained popularity over the last decade, especially for polymer-modified binders, bringing more advantages in discriminating amongst quality binders such as polymer-modified bitumen. Within the International Union of Laboratories and Experts in Construction Materials, Systems and Structures technical committee 272, Phase and Interphase of Behavior of Innovative bituminous Materials, and its TG1 task group, several binders were thoroughly evaluated, including two non-modified and two polymer-modified bituminous binders, under various testing conditions to address the high-temperature behavior. Five laboratories performed MSCR on short-term aged binders after performing the rolling thin film oven test, in the same temperature conditions for all binders. Despite the limited data set, the variability between laboratories was reasonable. The MSCR results were compared with softening point temperature, high-temperature performance grade criteria, |G*| / sinδ, and equi-modulus temperature. MSCR was able to distinguish between complex binders better as compared with conventional parameters. It generates multiple useful parameters, amongst which percent recovery and non-recoverable creep compliance are the most relevant. This paper presents the analysis of MSCR results and comparison with other test methods.

High-Temperature Rheological Properties and Storage Stability of Bitumen Modified with the Char Produced from Co-Pyrolysis of Different Wastes

By enhancing the bitumen properties with the additives produced from waste, not only can the performance of flexible pavements be improved, but it can also contribute to the environment. This research aims to produce a novel pyrolytic char from different wastes and to investigate the usability of this char as an additive in bitumen. In this study, first, the pyrolytic char was produced from the co-pyrolysis of three different wastes, including waste paper cups, polypropylene (PP), and polyethylene terephthalate (PET) waste. Properties of the char were determined by using CHN (carbon, hydrogen, and nitrogen) and Fourier transform infrared spectroscopy (FTIR) analyses. The high-temperature rheological properties of binders were evaluated by using DSR (dynamic shear rheometer), RV (rotational viscometer), softening point, and penetration tests. Additionally, specific gravity, storage stability, high-temperature performance grades (PGs), and temperature susceptibilities of binders were determined. Test results showed that this pyrolytic char enhanced the high-temperature properties of neat bitumen by increasing softening point, viscosity, rutting resistance, and high-temperature PG of pure bitumen. Additionally, it can be said that the bituminous binder modified with this pyrolytic char had good storage stability when it was used at an 8% ratio in neat bitumen.

Rheological Characterization of Reclaimed Asphalt Binder Blended with The Neat And Sbs-pma Binders

Reusing reclaimed asphalt pavement material guarantees a substantial optimization of non-renewable material resources, emissions reduction, and decreasing landfill space, along with the economic benefits associated with saving the costs of purchasing and transporting new aggregate and asphalt binder for asphalt concrete mixture production. This study aims to investigate the influence of aged asphalt binder from reclaimed asphalt pavement on the virgin asphalt binder’s rheological properties. Therefore, different dosages of RAP binder (20%, 30%, and 40% by weight of the total mix) were blended with neat asphalt binder (40-50), penetration grade (P40), and SBS polymer asphalt (SBS-PMA) binder. Using both traditional and Superpave performance testing methods, the effects of RAP on the blend's consistency, viscosity, softening, elastic recovery, rutting (permanent deformation), fatigue cracking, and low temperature cracking were evaluated. The results revealed that the RAP binder decreased the penetration value of both neat and SBS-PMA binders. The neat asphalt binder’s viscosity and softening point increased with the increase in RAP content, whereas they decreased for SBS-PMA. The RAP binder decreases the SBS-PMA elastic recovery. where the neat asphalt experienced a little improvement in elastic recovery when blended with the RAP binder. The Superpave test results revealed that the RAP binder deteriorates the performance of the SBS-PMA binder at high, intermediate, and low testing temperatures. With the addition of 20%, 30%, and 40% RAP, the high-temperature PG grade of SBS-PMA blends decreased by 0.64%, 0.95%, and 1.10%, respectively, while the low-temperature PG grade increased by 23%, 31%, and 32%, respectively. In contrast, the RAP improves the neat asphalt blend's high-temperature performance grade and deteriorates intermediate and low-temperature performance grades. The addition of 20%, 30%, and 40% RAP increased the neat asphalt blends' high-temperature properties by 1.5%, 3.3%, and 4.5%, respectively. whereas the neat asphalt low-temperature PG grade increased by 5%, 11%, and 15% with the addition of 20%, 30%, and 40% RAP, respectively. In summary, the performance of virgin and RAP binder blends depends on the individual characteristics of the blended asphalt binders

Investigation on rheological characteristics of low-emissions crumb rubber modified asphalt

ABSTRACT Asphalt modified by microwave-treatment crumb rubber (CR-microwave) and that of deodorant-addition crumb rubber (CR-deodorant) have low unfavorable or detrimental emissions, but their high- and low-temperature performances have been insufficiently researched, potentially limiting their application and promotion. In order to investigate high-temperature performances of the two low-emissions crumb rubber modified asphalt (CRMA), viscosity, temperature ramp, creep and creep recovery and amplitude sweep tests were conducted using Brookfield Viscometer and dynamic shear rheometer (DSR). Also, low-temperature performances of CMRA were characterised by bending beam rheometer (BBR) tests. Results showed that deodorant-addition CR with a high dosage is not allowed considering asphalt workability, but microwave-treatment CR with various dosages can still meet workability requirements. Moreover, the introduction of microwave-treatment CR or deodorant-addition CR into asphalt improved high-temperature performances of asphalt, while the former had lower positive effects on high-temperature performance grades, elastic recovery and deformation resistance of asphalt. Furthermore, like common CRMA, the two low-emissions CRMA had different viscoelastic behaviour from styrene–butadiene-styrene copolymer (SBS) modified asphalt. Additionally, 18% CR-microwave or CR-deodorant can basically improve the low-temperature performance grades of asphalt. Comprehensively considering the workability and high- and low-temperature performances of the two low-emissions CRMA, 18% CR-microwave is recommended for low-emissions CRMA manufacture.

Development of mechanical properties predictive model of extracted asphalt binder based on long-term field asphalt pavements

This paper was to develop a prediction framework for obtaining the rheological properties of extracted and recovered asphalt binders utilizing mixture performance and other factors such as in-place air voids, pavement structure, traffic level, and aging duration. A total of 21 field projects consisting of 66 pavement sections were included in the analysis, which were located in different climatic zones with various RAP contents, traffic levels, pavement structures, pavement age, and material properties. Results indicate that the neural network can be successfully adopted to predict cracking-related binder properties consisting of effective asphalt binder, G*sin(δ) and binder fracture energy, and rutting-related binder properties including high temperature performance grade (PG), MSCR Jnr3.2, and R3.2. Both prediction and validation models worked well for pavement sections with varied contents of RAP when new data was introduced.

Effects of Field Aging on Material Properties and Rutting Performance of Asphalt Pavement

This study evaluates field asphalt aging based on material property changes in pavement with time, and investigates if such changes could have an impact on field rutting performance. Four projects from three different climate zones were monitored as part of the NCHRP 9-49A project at two stages: during pavement construction and two to three years after opening it to traffic. Construction information were collected, and field cores were drilled at both stages to evaluate the material properties of recovered asphalt binder and asphalt mixture. Field rut depth was also measured. In addition, pavement structure, climate and base/subgrade modulus information were also obtained. Results indicate that the asphalt mixture stiffening is caused in major part by asphalt aging. However, the effect of asphalt aging on pavement mixture property may not follow a proportional liner trend. The parameters that are most sensitive to field ageing are MSCR R3.2 and dynamic modulus. It is also found that the variables which showed a good ranking trend with the field rut depth are climate condition (relative humidity, high temperature hour, solar radiation), material properties (Hamburg rut depth, rutting resistance index, high temperature performance grade, MSCR, and dynamic modulus, base and subgrade moduli), as well as air voids.

Investigation of self-healing properties of nanoclay-modified asphalt binder using two-piece healing test

Asphalt's self-healing properties demonstrate the capability to partially or even fully restore the damage caused by external loads, which could be improved using innovative modifying materials. In this study, the impact of nanoclays on asphalt performance grading (PG), complex shear modulus, and self-healing properties are investigated on a laboratory scale. The intrinsic healing phenomenon of the analyzed binders is measured using a two-piece healing test. Prepared by high shear mixing, the modified binders containing different dosages of two types of organo-modified montmorillonites were evaluated in this paper. In addition to the Superpave PG, the dispersion method's effectiveness was analyzed using a scanning electron microscope. This study indicates that nanoclays improve the high-temperature performance grade of the binder, while they do not hinder the low-temperature performance. Finally, nanoclay-modified binders showed higher shear strength and improved self-healing properties compared to the unmodified binder.

Experimental characterization of the oxidative kinetic aging behavior of rejuvenated asphalt binder

• Rejuvenated binders were subjected to over-aging at various temperature and time. • The effect of temperature, duration and rejuvenator dosage on the oxidative aging mechanisms of rejuvenated binders were revealed. • Oxidative aging increased the viscoelastic behavior of rejuvenated binders while rejuvenator reduced. • The effect of rejuvenator on viscoelastic behavior of rejuvenated binders weakened gradually during oxidative aging. Rejuvenator is commonly used in reclaimed asphalt pavement (RAP) to improve the properties of the blended binder. However, the rejuvenated binder would experience aging again and cause the rejuvenated asphalt mixture prone to durability issues. This study focused on evaluating the impact of oxidative aging on the chemical and rheological properties of rejuvenated binder (RB) by means of Fourier Transform Infrared Spectroscopy and Dynamic Shear Rheometer. First, the aged binders blended with waste engine oil used as the rejuvenator at 0%, 3%, 6%, and 9% by total weight of binder. Then, laboratory oven aging procedures were employed to the RB binders at different aging temperatures and periods. Carbonyl content were determined to understand the effect of temperature and duration on the oxidative aging mechanisms of RB binders. Each RB binder had its specific fast and constant oxidative rates. With the increase of rejuvenator dosage, the temperature sensitivity of RB binders decreased in the constant rate stage and increased in the fast rate stage. The high-temperature true performance grade (HTPG) of RB binders increased with the aging time and temperature, and the effect of rejuvenator dosage on HTPG decreased gradually with aging duration. Based on the master curves of complex modulus and phase angle, the aging time and aging temperature increased the viscoelastic behavior of RB binders, and rejuvenator reduced the viscoelastic behavior, but the effect of rejuvenator lowered gradually during oxidative aging. The crossover frequency, rheological index and Cole-Cole plot demonstrated the aging decreased the viscous components and increased the elastic behavior of the RB binders. As the rejuvenator dosage increased, the viscous component of the aged RB binders increased, and the elastic behavior decreased as well as more transition behavior from viscous to elastic.

Improving the Performance Grade and Traffic Loading of Egyptian Asphalt Binders by Recycled Polyethylene Modification

Recent SUPERPAVE technology allows assessment and performance grading (PG) of modified asphalts according to AASHTO T 350–14 and ASTM D7405-15 standards. These testing protocols use modified - multiple stress creep recovery (MSCR) test, to yield the high temperature PG and the traffic level of the asphalt binder. Latest AASHTO T 350–14 test protocol is used to assess two major Egyptian bitumen products, Alex and Suez (pen 60/70) before and after polymer modification. These standard products have different fractional composition since they are obtained from different local origins. Low density polyethylene modification (LDPE) of such products leads to a major enhancement in their PGs and decreases their high temperature rutting potential. A characteristic comparison between virgin a and LDPE modified bitumen samples is provided to achieve the desired PG and traffic level for high reliability projects deployed in Egyptian hot climate regions. it was found that a 2% wt recycled LDPE modification, enhances the high temperature performance grade and the traffic grade from PG 58S-XX to PG 64S-XX for the bitumen produced by Alexandria Oil Company, and from PG 58S-XX to PG 70S-XX for the bitumen produced by Suez Oil Company.

Performance evaluation of bitumen modified with styrene–isoprene-styrene and crumb rubber compound

Modifying bitumen with polymers has become inevitable to achieve resistance to severe traffic and environmental conditions. Researchers have focused on using modifiers with low-cost additives, such as crumb rubber (CR) obtained from waste vehicle tires, to enhance the efficiency of polymer modification. The present study investigated the effects of using styrene–isoprene-styrene (SIS) alone and in combination with CR on conventional and rheological properties of bitumen. To this end, viscosity, softening point, penetration, bending beam rheometer (BBR), and dynamic shear rheometer (DSR) tests were conducted. Elastic properties and performance grading were evaluated by the multi-stress creep recovery (MSCR) test. The use of 3% SIS with 7% CR gave one degree higher high-temperature performance level and 15% lower low-temperature stiffness than 6% SIS modification. It also provided 2.5 times lower non recoverable creep compliance and 1.5 times higher percent recovery than 6% SIS modification at 64 °C. The combined use of SIS and CR provided satisfactory performance under low- and high-temperature conditions and ensured a cost-effective solution when compared to the use of SIS polymer alone. Although SIS and CR modified binders exhibited satisfactory rutting resistance and elastic properties, the percent-difference criterion significantly restricted their high-temperature performance grade. According to this criterion, modification makes the binders suitable for extremely heavy traffic conditions without changing the resistance against temperature. Furthermore, it was determined that the estimated softening point, viscosity and rutting parameter values as a function of SIS and CR contents are highly compatible with the experimental results.