Polymer-modified Binders Research Articles

The role of polymer modification in mitigating ‘sunburn’ damage on asphalt roads

Asphalt roads suffer from ageing throughout their service life due to exposure to ultraviolet light (UV). The aim of this study is to determine the role of polymers such as ethylene vinyl acetate (EVA), styrene butadiene styrene (SBS) and crumb rubber from end-of-life tyres (CR) in protecting bitumen against the damage caused by UV radiations when roads are exposed to sunlight. One unmodified bitumen and four polymer-modified commercial binders were exposed to a filtered xenon-arc light for 10, 20 and 30 days before being tested. Overall, SBS modified binders were less damaged by UV exposure, followed by CR and EVA modified binders. More specifically, SBS provided the best cracking resistance to the binder after ageing compared to conventional unmodified bitumen, followed by CR. EVA did not improve the cracking resistance of the binder. A deep chemical analysis of the photo-oxidation mechanism of polymer-modified binders revealed that SBS is more effective in reducing the formation of carbonyls and aromatics in aged bitumen compared to CR and EVA. The 3D network formed by SBS polymer chains in bitumen was found to be more resistant to oxidation than CR and EVA chains, hence providing a superior UV resistance to SBS-modified binders. Overall, CR seems to provide a sustainable alternative to conventional polymers since using CR for bitumen modification would reduce landfilling of tyres while increasing roads service life and reducing maintenance costs.

Effects of waste high-density polyethylene (HDPE) on asphalt binder and airfield mixes

ABSTRACT Flexible airport pavements may require polymer-modified asphalt binder for their asphalt concrete (AC) mixes to withstand heavy gear loading and slow traffic moving in taxiways and aprons. Waste plastics could be repurposed as a possible alternative to Styrene–butadiene-styrene (SBS) modifiers. In this study, the feasibility of using granulated recycled high-density polyethylene (HDPE) waste was evaluated as an asphalt binder modifier for airfield pavements. A base asphalt binder was modified with waste HDPE to obtain a Superpave performance grade (PG) of 70-22. Adding waste HDPE would increase binder’s stiffness and bond to aggregate, it slightly improved ductility and elasticity; but less than SBS polymer-modified binders. The AC mixes prepared with waste HDPE-modified binder showed less potential for rutting and cracking compared control AC mixes with PG 64-22. However, the rutting and cracking potential was higher when compared to their SBS-modified PG 70–22 counterparts. On the other hand, AC mixes containing waste HDPE-modified binder were less susceptible to moisture-induced damage. It appears that using waste HDPE-modified binder is feasible where improving adhesion and resistance to moisture-induced damage AC mixes are needed and embrittlement and elastic recovery are not critical, while meeting rutting and cracking potential regional thresholds.

Assessment of microbial degradation of various types of bitumen using FTIR

ABSTRACT Pseudomonas aeruginosa (P. aeruginosa), a common bacterium found in the environment, is known to be a potential cause of bitumen degradation. Hence, the effect of P. aeruginosa on bitumen is to be evaluated. For this purpose, Reclaimed Asphalt Pavement (RAP) is collected from the pavement surface and it is tested for the presence of P. aeruginosa. Subsequently, this isolated P. aeruginosa strain is employed in experiments to evaluate its effect on three types of bitumen, namely: Viscosity Grade-30 (VG-30), and two types of Polymer Modified Binders (PMBs) viz., PMB-K and PMB-T. Bitumen degradation, Fourier Transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscope (SEM) studies show that P. aeruginosa has degraded PMB-T more than PMB-K and VG-30. Degradation occurs due to the breakage of bonds between polymer and bitumen and confirmed that P. aeruginosa has the ability to degrade PMBs, which may alter their physical properties. The degradation test results presented that PMB-T has 12.5% degradation compared to the control sample. The FTIR findings indicate that P. aeruginosa has modified the chemical composition of PMBs, and has converted them into base bitumen. It is recommended to study, molecular analyses (i.e. metagenomic and transcriptomic) of P. aeruginosa on PMBs.

Incorporating Environmental Impact Analysis into Louisiana’s Balanced Asphalt Mixture Design

To meet the asphalt pavement industry’s net zero carbon emission goals, increasing reclaimed asphalt pavement (RAP) levels to greater than 25% is considered a critical tactic. However, many state departments of transportation are cautious in adopting high RAP content into their designs because of durability issues resulting from aged RAP binders. This paper assesses the effectiveness of using the Lewis acid catalyst, FeCl3, in improving the cracking resistance of high-RAP asphalt mixtures to meet Louisiana’s balanced mixture design (BMD) criteria, and lower embodied carbon of asphalt mixtures. Four asphalt mixtures were designed and tested against permanent deformation, intermediate- and low-temperature cracking, and durability. Mixture 1 is conventional, which contains performance grade (PG) 76-22 polymer-modified asphalt binder with no RAP. Mixture 2 is unmodified PG 67-22 and 30% RAP without catalyst. Mixtures 3 and 4 incorporated an unmodified asphalt binder PG 67-22, a catalyst, and 30% and 50% RAP, respectively. A life cycle assessment (LCA) analysis was conducted on asphalt mixtures that complied with Louisiana’s BMD specifications to quantify global warming potential improvements. Because the performance of both mixtures is expected to be similar, the scope of the LCA analysis was limited to only those life cycle stages that are expected to be different, modules A1–A3 (i.e., cradle-to-gate stages). Results showed that the use of FeCl3 can improve asphalt mixtures’ cracking resistance containing high RAP contents, whilst it did not have a negative impact on permanent deformation resistance. Further, the addition of FeCl3 to asphalt mixtures with 30% and 50% RAP levels showed a reduction in greenhouse gas emissions by 28% and 43.4%, respectively.

The Influence of Single-Walled Carbon Nanotubes on the Aging Performance of Polymer-Modified Binders.

The use of polymer-modified binders in asphalt concrete makes it possible to increase the efficiency and durability of highways. However, at present, there is an important and unresolved problem in this area, making it impossible to fully exploit the potential of modified binders. This is a tendency of aging processes that leads to the premature destruction of the pavement. In many literary sources, it is reported that reasons are related to the peculiarity of the chemical composition and occur at the submicron level. Therefore, the influence of single-walled carbon nanotubes has been studied for a better understanding of aging processes. The aging processes of the RTFOT (rolling thin film oven test) and PAV (pressure aging vessel) modified with SBS (styrene-butadiene-styrene) polymer, single-walled carbon nanotubes, and waste industrial oil were simulated in a laboratory furnace. Microstructural features were studied using the method of infrared spectral analysis. The dependences of viscoelastic properties on the component composition of binders were investigated. The optimal content of single-walled carbon nanotubes (0.001%), SBS (styrene-butadiene-styrene) polymer (3.5%), and waste industrial oil (4%) in the binder composition was established, which synergistically improved the performance of the modified binder from PG (52-22) (performance grade) to PG (64-34). It was established that single-walled carbon nanotubes provide improvement in the durability parameter ∆Tc binder by 150%, improved relaxation properties at low temperatures, and resistance to fatigue damage.

Effect of Different Long-Term Aging Conditions on Cracking Resistance of Polymer-Modified Asphalt Binder and Mixes

Effect of Different Long-Term Aging Conditions on Cracking Resistance of Polymer-Modified Asphalt Binder and Mixes

Development of improved porous asphalt mixtures with high porosity levels

Porous asphalt (PA) mixtures are gaining wider acceptance in pavement construction due to their benefits in terms of road safety, noise mitigation and stormwater management. Increasing demands, such as those imposed by climate change, require the design of mixtures that provide enhanced functional properties, while keeping the same durability of conventional porous asphalt mixtures. This study proposes different experimental PA mixes with higher air voids content and suitable structural capability than a conventional PA mixture. The functionality of the mixtures was evaluated in accordance with total and interconnected air voids, while the mechanical performance was assessed in terms of raveling resistance both in dry and wet conditions, tensile strength, and moisture sensitivity. The binder drain down was also verified. In a first stage, the experimental results were analyzed through descriptive and inferential statistics tests. As multiple responses were obtained, principal component analysis (PCA) and agglomerative hierarchical clustering (AHC) were applied to explore the association pattern among the test results and experimental designs. The study concluded that PA mixes with air voids content of up to approximately 28% and admissible values of resistance can be designed. The use of polymer modified binder (PMB) and the inclusion of fibers and hydrated lime (HL) was essential for the formulation of the mixes.

Prediction of asphalt binder elastic recovery using tree-based ensemble bagging and boosting models

The Multiple Stress Creep Recovery (MSCR) test has been proposed and implemented over the last two decades as an alternative to traditional tests, especially the elastic recovery (ER) test, to better capture rutting resistance. This paper presents a study on predicting asphalt binder ER using MSCR test results through ensemble learning methods, based on a database of more than 700 points for mostly polymer-modified binders. The ensemble approach involved tree-based Bagging (Random Forest and Extra Trees) and Boosting (Adaboost, gradient boosted decision tree, XGBoost, LightGBM, and CatBoost). The findings revealed the effectiveness of ensemble learning methods in capturing complex relationships within the data. Extra Trees and XGBoost emerged as the most accurate models based on coefficient of determination, mean absolute error, and root-mean-square error, compared to the other mentioned models and Neural Networks. These models offer precise predictions of asphalt binder ER from MSCR test results, surpassing the ER-DSR test proposed in the literature. Recovery at stress levels of 0.1 and 3.2 kPa were identified as the top influential features. In addition, clustering methods were employed to detect patterns within the dataset. The outcomes highlighted difficulties in discerning binders based on existing MSCR parameters, suggesting opportunities for refining MSCR analysis, and exploring additional tests to improve the distinction among asphalt binders. This investigation provides practical implications for states still utilizing PG-Plus, promoting the adoption of MSCR specifications for asphalt binder characterization.

Mechanism of physical hardening on the fracture characteristics of polymer-modified asphalt binder

This article aims to reveal the physical hardening mechanism of polymer-modified asphalt binder (PMA) and accurately assess its impact on the low-temperature fracture properties of asphalt binders. Base asphalt binder (BA), styrene–butadiene–styrene modified asphalt binder (SBSMA), and crumb rubber modified asphalt binder (CRMA) were used as the research objects. Molecular dynamics (MD) simulation and differential scanning calorimetry (DSC) test were used to investigate the physical hardening mechanism of PMA at the microscopic level. The fracture characteristics of PMA under physical hardening were analyzed based on the single-edge notched beam (SENB) test. The results show that under prolonged cold service conditions, the asphalt molecular mobility is weakened, the non-bond energy and the free volume are reduced, and the molecules undergo aggregation state transformation, leading to the physical hardening of asphalt materials. In the process of physical hardening of asphalt molecules in the micro-Brownian motion of the main active force from the aromatic and saturate fractions. Considering the effect of physical hardening, it is recommended that the method used to test the low temperature properties of asphalt binders should ensure a constant temperature for at least 24 h. The crack tolerance (Ct) is recommended as the evaluation index of low-temperature cracking resistance of PMA in cold regions. The Ct of BA, SBSMA, and CRMA are reduced by 52.88 %, 12.04 %, and 35.24 %, respectively, after 24 h of constant low temperature. This indicating that the polymer modifiers can improve the fluidity of asphalt molecules, inhibit molecular aggregation, and reduce the effect of physical hardening on asphalt binders. Thermo-oxidative aging can aggravate the physical hardening phenomenon of asphalt binder, and the higher the degree of thermo-oxidative aging, the more severe the physical hardening of asphalt binder. The related research results provide the theoretical basis and technical support for the accurate design and development of the low-temperature performance of asphalt binders for roads in cold regions.

Development of Plug Joint with Polymer-Modified Rubber Asphalt as Filling Material

Rising traffic volume, heavy loads, and construction activities have raised concerns about expansion joint device damage. This study focuses on developing an innovative expansion joint using polymer-modified rubber asphalt as the filling material to enhance its service life. Styrene–butadiene–styrene (SBS) emerged as a suitable modifier for rubber-modified asphalt, significantly improving elasticity and adhesion. Through the strategic combination of 3- and 2-block linear SBS, the elasticity and adhesion properties were significantly improved, resulting in the formulation of a well-suited polymer-modified rubber asphalt binder. The developed asphalt binder exhibits impressive elastic recovery (61.1% to 66.1%), surpassing commercial products, with enhanced constructability and workability (15% to 21% viscosity reduction). The carefully engineered mastic asphalt mixture showcases self-leveling characteristics at a moderate 210 °C, addressing historical constructability challenges. Settlement is 40% less than traditional hot mix asphalt for surface layers, with improved moisture and stripping resistance, enhancing existing asphalt plug joint durability and workability. Collectively, this novel mixture, comprising polymer-modified rubber and mastic asphalt, showcases the potential to enhance the durability of existing asphalt plug joints while ensuring superior constructability and workability.

Mechanical, thermodynamical, and microstructural characterization of adhesion evolution in asphalt binder-aggregate interface subjected to calcium chloride deicer

Frigid weather and freezing road conditions in cold regions result in reduced pavement surface friction, compromised vehicle maneuverability, leading to deteriorated transportation safety. Given their effectiveness and low cost, using chloride-based deicing agents such as CaCl2 has become a standard winter maintenance strategy for many highway agencies. However, coupled with freeze–thaw (F-T) cycles, CaCl2 can adversely affect the durability of asphalt pavements and cause complex distresses such as moisture-induced damage, among others. Despite this fact, the mechanisms and the extent of the damage made to the asphalt binder-aggregate interface due to use of chloride salts are not well-understood. This study was undertaken to characterize the mechanisms by which different eutectic concentrations of aqueous CaCl2 solutions and F-T cycles affect the adhesion between asphalt binder and different aggregates through a multi-scale characterization and testing program. Given the rise in use of polymer-modified asphalt binder a PG 64–34 asphalt binder and aggregates of granite, quartzite, and limestone mineralogies were evaluated. More specifically, pull-off strength of the aggregate-binder systems subjected to different aqueous concentrations of CaCl2 and F-T cycles were determined. In addition, surface free energy method as a thermodynamic-based approach was employed to determine the effect of salt concentration on the adhesion and debonding energies, and the moisture-induced damage potential of the binder-aggregate interfaces. Furthermore, atomic force microscopy was employed to evaluate the effect of salt concentration and F-T cycles on surface morphology, nanostructure, and adhesion of the asphalt binder. The applied multi-scale characterization provided invaluable information about the physio-chemical phenomena responsible for the accelerated damage in asphalt binder-aggregate interface when subjected to different aqueous concentrations of CaCl2. Gaining an accurate understanding of the damage mechanism is necessary for developing new materials and methods for combatting salt-accelerated moisture-induced damage in cold regions as a result of winter maintenance operations.

Performance of SMA Mix modified with waste plastic and fiber

Waste materials are harmful to the environment when incinerated, dumped in open water, or landfilled. Present-day society faces a serious challenge from the growing amount of waste materials and the need for a sustainable solution. Due to the limited amount of natural raw materials, there is a global need to minimize the amount of waste. Using suitable waste materials, such as waste plastic, as additives in asphalt mixtures is a viable strategy, offering an alternative to virgin materials like polymer-modified asphalt binders. This research studied the influence of waste fibers as a stabilizer and recycled Polyethylene waste as an asphalt modifier in the Stone Mastic Asphalt mix (SMA). Two categories of the SMA mixes were produced, base and modified mixes, with three different mixes under each category. The rheological properties of the Recycled Polyethylene Modified Asphalt (RPMA) have been assessed using different Recycled Polyethylene (RP) dosages at the upper-performance temperature. In addition, two Recycled Fibers (RF), cellulose and jute, were used as stabilizing materials for SMA mixes. The impact of RP and RF on the SMA mixes was investigated using three tests: Drain-down resistance, moisture sensitivity, and rutting performance. Statistical analysis was conducted to assess the effect of the additives on the measured SMA properties. The results showed that adding RP and RF improved the SMA mixes' ability to hold the asphalt and fine material inside the mix and solved the drain-down problem by 81.43%. In addition, adding RP as an asphalt modifier greatly enhanced the moisture and rutting resistance by 47.5% and 93%, respectively.

Exploring potential of Marshall-RT as simple performance test to evaluate rutting resistance of asphalt mixtures

ABSTRACT This study explored a new simple monotonic Marshall rutting test (Marshall-RT) to evaluate the rutting resistance of asphalt mixtures. The Marshall-RT test setup combines the Marshall fixture (at the bottom) and the IDT fixture (at the top). The rutting resistance of asphalt mixtures was evaluated using peak load (Pmax) and work done for the deformation damage obtained from the load-displacement curve. Nine plant-produced asphalt mixtures having different types of binders (unmodified, crumb rubber modified binder (CRMB)), and polymer modified binder (PMB)) and gradations having different nominal maximum aggregate sizes (NMAS) were evaluated. The Marshall-RT test parameters (i.e. Pmax and W P m a x ) have shown a strong correlation with fundamental (i.e. Flow Number (FN)), simulative (i.e. Hamburg wheel tracking test (HWTT)), and simple monotonic (i.e. Ideal rutting test (IDEAL-RT)) rutting tests. Moreover, the Marshall-RT test has shown good repeatability, the highest differentiation potential, and consistent ranking with other rutting tests. Furthermore, for high traffic levels (i.e. 100 MSA (Million Standard Axle)), at 50°C preliminary minimum threshold criteria were proposed for Marshall-RT (Pmax and W P m a x ), and IDEAL-RT (RTIndex) as 5 kN, 14 kN-mm, and 90, respectively, to avoid premature rutting failure. Thus, the newly developed monotonic Marshall-RT test can also be used as a surrogate simple performance test to estimate the rutting potential of asphalt mixtures during the mix design and plant production phases as quality control (QC)/quality assurance (QA).

Properties of recycled facemask fiber modified asphalt binder: Comparative analysis of surface modification and composite modification method

Polymer-modified asphalt binders had been developed as a novel strategy for road and building materials. People generally use disposable facemasks to reduce the risk of respiratory diseases during travel and commuting. These discarded masks will become a serious environmental problem. Recycled facemask has great potential application in the modified asphalt, but its modification effect of modified asphalt needs to be studied. In this work, different kinds of fibers and their modified asphalts had been successfully prepared and comparatively analyzed after the surface of fibers treated by butyl acrylate (BA) and further modified by copper oxalate (CO) nanoparticles. From the test results, the activation energies of polypropylene fiber extracted from recycled facemask (RPF) modified asphalt (RPA), treated RPF (MRP) modified asphalt (MRPA), and MRP further decorated with CO (MRPCO) modified asphalt (MRPCOA) were 64.08 kJ/mol, 59.09 kJ/mol, and 62.32 kJ/mol, respectively. MRP and MRPCO were better dispersed in asphalt than RPF. MRPA performed a lower value of the viscoelastic than RPFA, but MRPCOA performed the higher value of viscoelastic than MRPA. Compared with RPA, the short-term aging factors of MRPA and MRPCOA decreased by 31.73% and 53.18%, while long-term aging factors of MRPA and MRPCOA decreased by 11.34% and 12.31%. From the nanoindentation data, the maximum depth of MRPA increased by 5.23% and the hardness decreased by 2.55% than RPA. The maximum depth of MRPCOA also decreased by 6.68% and its hardness also decreased by 4.45% than MRPA. These results indicated composite modification of RPF performed better than only surface modification based on the viscoelastic and aging properties of modified asphalts. It provided a meaningful study for the potential applications of various recycled polymeric fibers in modified asphalt binder in the future.

Linear viscoelastic properties and fatigue S-VECD based evaluation of polymer-modified asphalt mixtures

Direct tensile fatigue tests associated with the simplified continuous damage viscoelastic model (S-VECD) have proven to be an effective tool for evaluating fatigue in asphalt materials. Thus, this study evaluated the fatigue damage of asphalt mixtures modified by the addition of polymer based on the results of the direct tensile fatigue test using the S-VECD model. Three asphalt mixtures were produced: a control asphalt binder with 50/70 penetration, a polymer-modified styrene-butadiene-styrene (SBS) asphalt binder, and a mixture produced with a modified asphalt binder (composed of 98.38% control + 1.26% Ethylene Methyl Acrylate and Glycidyl Methacrylate (EMA-GMA) + 0.21% High-Density Polyethylene (HDPE) + 0.15% Polyphosphoric Acid (PPA116%)). The binders were evaluated for physical and rheological properties, and fatigue using the Linear Amplitude Sweep (LAS) test, applying the S-VECD model. Asphalt mixtures were evaluated for stiffness using tensile strength, resilient modulus and flow number tests. The viscoelastic linear behaviour (LVE) was characterized based on the dynamic modulus test and the fatigue performance was evaluated from the uniaxial direct traction test with the application of the S-VECD viscoelastic damage model. The results of the LAS test indicated that the modified binder presented the best fatigue performance, being classified according to the binder fatigue factor (FFB) as excellent. Mixtures with binders modified by polymers showed the highest values in mechanical performance tests. As for the LVE behaviour, the mixture with the modified binder showed the expected behaviour, with higher dynamic modulus values at high temperatures (low reduced frequencies), and the lowest modulus values at lower temperatures (high reduced frequencies). In addition, for the entire spectrum of frequencies and temperatures, the modified mixture presented the lowest values of phase angle, indicating more elastic and less viscous behaviour. From the direct tensile test, based on the GR failure criterion, the modified mixture showed better fatigue performance, with a higher value of the Fatigue Factor of the Mixture (FFM). Based on the DR failure criterion, from the Sapp damage capacity, mixtures with polymers were classified with the best performances concerning fatigue. Therefore, the use of polymer-modified binders promoted asphalt mixtures with better fatigue damage performance.

Investigation of factors affecting modified asphalt binder development and performance using the poker chip test

With the surge in the use of modified asphalt binders throughout the world, it is important to examine these materials for performance outside of their linear viscoelastic (LVE) range. Modified asphalt binders, which are usually costlier, are expected to increase the service life of asphalt pavements. The current paper utilizes two approaches to evaluate the nonlinear viscoelastic and failure performance of eight binders including six novel modified asphalt binders. First, the poker chip test for cracking performance evaluation was conducted at different loading rates and aging levels. The results conclude the efficacy of the poker chip test to differentiate and rank the best performing modified asphalt binders. Furthermore, the impact of varying the loading rates, aging levels, modifications, and performance grades was also studied. These results indicated that loading rates ranging from 1 to 4 N/s can be used to differentiate modified binder performance with similar ranking, which allows a wider range of machines to be used to do this test. In addition, the impacts of aging were studied to introduce differentiation between modifiers which are sensitive to aging. Apart from this, the Multiple Stress Creep Recovery (MSCR) test was conducted to evaluate the rutting performance. MSCR results further augmented the confidence in initial rankings as polymer-modified binders showed superior performance to other modifier types. It was observed that the top two binders in terms of poker chip results also had the best MSCR performance. Hence, instead of balancing the performance, like is done for mixtures, between rutting and cracking, an optimum binder can be synthesized which has excellent performance against load-related cracking and permanent deformation. This sets the stage for a balanced binder selection and design process to be implemented into future specifications and research efforts.

A Comprehensive Literature Review on Polymer-Modified Asphalt Binder

Due to periodic variations in temperature and heavy traffic loading, hot-mix asphalt (HMA) pavements undergo considerable distress during their service life. The rheological properties of asphalt binder, when subjected to complex physical and chemical processes, make it stiff and sometimes brittle, which ultimately plays a huge part in pavement deterioration. This phenomenon is commonly known as asphalt aging. Incorporating polymer modifiers with virgin asphalt can work as an effective means to change the binder properties and alleviate the issues related to asphalt aging. Different types of polymers, including elastomers, plastomers, and reactive polymers, can mixed in different combinations with the virgin asphalt to create polymer-modified binders (PMBs). In general, polymers are typically added to the virgin asphalt binder in PMB manufacturing at weight percentages ranging from 3% to 7%. Previous research suggests that many polymer-modified binders (PMBs) show great resiliency and perform extremely well during field and laboratory testing, although the complex nature of asphalt itself makes it significantly difficult to understand the relationship and compatibility of the asphalt–polymer system. This paper aims to develop a comprehensive literature review on the chemical aspects, microscopic structure, and compatibility of polymers with virgin asphalt. It was found that swelling, storage stability, blend morphology, and the polymer mixing technique play a great role in the compatibility of asphalt–polymer systems. Thermoplastic elastomers (e.g., styrene–butadiene–styrene) and plastomers (e.g., ethylene–vinyl acetate) are the most used polymer modifiers for asphalt binders. The compatibility of the polymer–asphalt system can be improved by sulfur vulcanization, antioxidants, hydrophobic clay minerals, functionalization, and reactive polymers, among other techniques.

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.

Rutting Resistance Evaluation of Highly Polymer-Modified Asphalt Binder and Mixes Using Different Performance Parameters

This study focused on evaluating the rutting performance of three different highly polymer-modified asphalt (HiMA) binders (i.e., O, T and B) using binder-based [i.e., multiple stress creep recovery (MSCR) and force ductility (FD)] and mix-based [flow number (FN) and Hamburg wheel tracking test (HWTT)] rutting performance tests. The binder-based rutting indicators were compared with mix rutting performance to determine a parameter that can help in the correct prediction of HiMA rutting resistance. In addition, the study looked into application of a simple performance test, the indirect rutting tolerance index (IDEAL-RT), for HiMA mix rutting prediction. The MSCR test revealed different rankings of recovery at 0.1- and 3.2-kPa stress levels. Moreover, the T and B binders did not satisfy the stress sensitivity criteria (Jnr_difference) of Max 75%. The force ductility tests revealed that the peak force observed for polymer network phase in HiMA was significantly higher than base binder stiffness, which is in contrast with force distribution in polymer-modified binders (PMBs). The mix rutting resistance ranking (O>T>B) was similar in all the tests (i.e., FN, HWTT, and IDEAL-RT). Although IDEAL-RT can be used to compare the rutting resistances of HiMA mixes, detailed future work is required to establish its acceptability in comparing various types of mixes and the minimum requirements of RTIndex. The comparison between binder and mix rutting indicators demonstrated that MSCR testing on binder at stress levels of 6.4 kPa and higher can be used to predict the rutting resistance of HiMA binders. Parameters like slope and cohesion energy and a newly introduced parameter—work done for polymer activation (WPA)—from FD tests can be used to determine the polymeric phase dominance in HiMA binders. Overall, this study provides pavement stakeholders with a framework for rightly predicting the rutting resistance and polymeric phase dominance of HiMA binders and mixes using MSCR, FD, and IDEAL-RT tests.

Investigating the properties of asphalt binder modified by high- and low-density polyethylene polymer and nano-silica

This paper describes nano-silica (NS) reinforcement effects on the properties of an asphalt binder modified by 5% of low density polyethylene (LDPE) and high density polyethylene (HDPE) polymers. NS was added at 0, 2, 4 and 6% of modified asphalt weight and some physical, rheological, chemical and microstructure of the binders were evaluated. Results show adding NS into the polymer modified binder (PMB) results in better dispersion of polymer in the binder, improvement of elastic recovery and storage stability, decrease of temperature susceptibility, decrease of ductility, and slightly improvement in rutting resistance. Statistical analysis revealed that the polymer type has significant effect on SHRP rutting parameter at 76°C, elastic recovery and storage stability. It was also found that the effect of NS content is significant on the penetration, penetration index, viscosity temperature sensitivity (VTS) and storage stability.