Polymer Modified Asphalt Binders Research Articles

Improving hydrophobicity of asphalt surfaces using pulverized recycled polyethylene terephthalate: Towards efficient roofing/waterproofing

Hydrophobic surfaces exhibit low wettability, low water and ice adhesion, etc. with an enhanced water resistance overall. Asphalt binder is popularly employed for roofing and waterproofing due to its intrinsic hydrophobicity. Yet, both unmodified and conventionally polymer-modified asphalt binders exhibit water contact angle (WCA) within the lower hydrophobic range (≤ 121°). Recent studies have shown that the hydrophobicity of asphalt binder can be enhanced via surface treatment using carefully selected materials. In this current study, the use of recycled polyethylene terephthalate (rPET) to improve the hydrophobicity of asphalt-binder was explored. The rPET was processed into micro-sizes and utilized to thermally treat the asphalt-binder at 100 °C. The morphology of the processed rPET and the treated-asphalt surfaces was examined using scanning electron microscopy (SEM). An optical surface profilometer was employed to quantify the roughness of the treated-asphalts. A video contact angle measurement system was used to measure the WCA of the unprocessed/untreated materials and the treated asphalt surfaces. The treated-asphalt showed average and maximum WCA of up to 144° and 148° respectively. This indicates that the rPET-treated asphalt surface could exhibit super-hydrophobicity (WCA ≥ 145°). The improvement in the WCA was due to the increase in surface roughness as a result of the embedment of rPET-particles onto the asphalt surface. The embedment resulted in the stretching of the asphalt surface, forming micro-valleys and -ridges of multiple hierarchies. Higher curing duration was found to yield treated-asphalts with hydrophobicity that last longer. It is found that micronized rPET with sizes smaller than 149 µm can be employed to successfully improve the hydrophobicity of asphalt binder surfaces.

Investigating the influence of polyethylene terephthalate fibres with different lengths on the cracking resistance of high-performance asphalt concrete

High-performance asphalt concrete is an innovative paving material that typically relies on the properties of polymer-modified asphalt binders. However, the application is limited due to their high cost and phase separation issues. A solution is explored in the present study by blending 12% asphaltenes and a straight-run asphalt binder with a true performance grade of 70.2–25.9, resulting in a true performance grade of 82.9–21.8, which elevates the binder’s stiffness. Three lengths of polyethylene terephthalate fibres are used to improve the cracking resistance of these asphaltenes-modified mixes. An indirect tensile cracking test is conducted at 25 and 37 °C, revealing a significant improvement in cracking tolerance and failure energy, particularly at 37 °C. The cracking tolerance index value peaked at 105 for 12 mm polyethylene terephthalate fabricated sample, while control asphaltenes-modified, 6 mm, and 18 mm polyethylene terephthalate fabricated samples achieved 61, 87, and 99, respectively, with failure energy increasing with longer fibres.

RMPD-22-12-09.R3 - Improvement in rheological properties of polymer-modified asphalt binder through sulfur addition using traditional and advanced analyses

The use of crosslinking agents, particularly sulfur, addresses compatibility issues in Polymer-modified binders (PmB), impacting storage stability and rheological properties. Through comprehensive rheological assessments, including Superpave grading and advanced techniques such as Glover-Rowe, master curves, Arrhenius and Power-law models, this study aimed to provide a deeper understanding of the role of sulfur as a crosslinking agent between asphalt and styrene-butadiene copolymer (SB), investigating its influence on the durability and performance of the asphalt binder. Results show sulfur levels up to 0.3%, enhanced PmB's elasticity, resistance to shear deformation, rutting, low-temperature cracking, and fatigue, making it suitable for a wider range of climatic conditions and heavier traffic levels. Beyond this threshold, the binder became very stiff and less workable, suggesting the potential onset of gelation. An optimal sulfur content in PmB enhanced compatibility, rheological properties, and overall efficiency of binder modification, potentially reducing polymer modification costs.

Investigation of LAS-based fatigue evaluation methods for high-viscosity modified asphalt binders with high-content polymers

The objective of this paper is to investigate the microstructure of high-viscosity modified asphalt binder (HVA) containing high-content polymers and its effect on fatigue performance, as well as the applicability of different analytical methods and failure criteria of linear amplitude sweep (LAS) test to HVA. In this paper, two types of HVAs with different polymer contents, a commercial HVA, a conventional polymer-modified asphalt binder, and a base asphalt binder were first prepared or selected. Fluorescence microscopy tests, time sweep tests, and LAS fatigue tests were then performed on these binders. Finally, the fatigue properties of the different binders were analyzed in depth using different analytical methods and failure criteria. The results show that the polymers in HVA crosslink with each other to form a strong cross-linking structure, and the phase inversion of the polymers renders them into a continuous phase, which significantly improves the fatigue damage resistance of the HVA; moreover, the evolutions of stress with shear strain for the fatigue process of HVAs is related to the polymer network. Besides, the two-dimensional damage characteristic curve (DCC) cannot accurately reflect the evolution of the fatigue performance of HVA, and this paper suggests the use of a three-dimensional DCC curve with strain information. Furthermore, the 35% reduction in C0 in the dissipative energy method is not a suitable failure criterion, a more accurate fatigue performance ranking can be obtained by using the yield stress as the failure criterion. Although the fatigue resistance of HVA after yield stress is theoretically considered using the pseudo-strain energy approach, HVA does not show a peak of stored pseudo-strain energy even when the strain is increased to 60% in the LAS test. Therefore, the maximum strain value (30%) in the standard LAS test is not sufficient in characterizing high-polymer HVAs because there is not enough fatigue accumulation of HVAs in this range, consequently, the maximum shear strain parameter in the LAS experiment needs to be reconsidered.

Evaluation of Rheological Properties of Polymer-Modified Asphalt Binders and Mastics with Organic Additive—Imidazoline

The article presents the results of testing the asphalt binder modified with SBS copolymer (5%) and its mixture with mineral fillers called asphalt mastics. The aim of the research and analysis was to check the possibility of using an organic additive in the form of imidazolines and to assess their impact on the viscoelastic properties of the obtained asphalt mastics. The main advantage of using imidazoline is the increased resistance of asphalt mixtures to low-temperature cracking at the top of the road route and reducing its maintenance costs. Based on the examination of the adhesion of the binder with the addition of various imidazolines to the aggregate, a selection was made from six analyzed subtypes. One of them was selected for further research. The tests were carried out in a dynamic shear rheometer in a wide temperature range from −36 °C to 82 °C, determining the most important parameters of the tested materials, i.e., dynamic shear modulus (|G*|), phase angle (δ) and the non-recoverable creep compliance (Jnr). The test results and their analysis confirmed the beneficial effect of imidazoline on the viscoelastic properties of mastics in the low-temperature range, even at the lowest content of 0.2%. Based on the results of the determination of Jnr and |G*|/sinδ in the range of high operating temperatures, no significant deterioration in permanent deformation parameters was observed. Moreover, the use of imidazoline reduces technological temperatures during the production of HMA used in the pavement and, therefore, reduces CO2 emissions into the atmosphere.

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.

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.

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

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.

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.

Laboratory Evaluation of High-Temperature Properties of Recycled PMA Binders

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).

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.

INVESTIGATION OF THE MECHANICAL PERFORMANCE OF STONE MASTIC ASPHALT MIXTURES MODIFIED BY RECYCLED WASTE POLYMERS

The usage of polymer-modified asphalt binders has increased as a result of the significant increase in the number of conventional cars operating on Iraqi roads in recent years. This has resulted in increased strains being placed on pavement structures and materials. Global exploration has focused on the development of stabilizing Stone Mastic Asphalt mixtures for improved pavement behavior. Numerous effective efforts were made to stabilize stone mastic asphalt mixes with polymers and fibers. Iraq produces a considerable amount of waste polymer materials each year. Usually, they are sent to landfills for disposal. These wastes are dumped, occupying a sizable portion of landfill space and creating various serious environmental issues. The study focuses on how waste polymer additions, such as recycled plastic bottles, shopping boxes, and tire crumb rubber, affect the mechanical performance and durability of stone mastic asphalt mixtures. The mechanical performance attributes were assessed. It is evident from the findings that the drain-down amounts were within the permissible requirement range. The findings also showed that the indirect tensile strength, Marshall Stability, moisture damage resistance, and resistance for permanent deformation of stone mastic asphalt mixtures have all increased as a result of the use of waste polymer components. The recycled polymer-modified mixes are the combinations that are most resistant to rutting, according to the results of the repeated load axial creep tests. Iraq may have new options to employ the significant volumes of recycled polymers that are becoming accessible as a result of recycling waste polymers.

Experimental Investigation of LDPE and EVA on Asphalt Binder

Abstract: This research study aims to investigate the impact of incorporating Ethylene Vinyl Acetate (EVA) and Low-Density Polyethylene (LDPE) on the properties of asphalt binder. The use of polymer-modified asphalt binders has gained significant attention in recent years due to their potential to improve the performance and durability of asphalt pavements. EVA and LDPE are two commonly used polymers that have shown promise in enhancing the rheological and mechanical properties of asphalt binders. The experimental investigation involved the preparation of asphalt binder samples with varying percentages of EVA and LDPE, ranging from 0% to 8% by weight. A series of laboratory tests were conducted to evaluate the effects of polymer modification on the fundamental properties of asphalt binder. These tests included penetration, softening point, ductility, viscosity, and dynamic shear rheometer (DSR) tests.The results of the study indicated that the addition of EVA and LDPE led to notable improvements in the rheological and mechanical properties of asphalt binder. Increased polymer content resulted in reduced penetration values, higher softening points, and improved resistance to rutting and deformation. Additionally, the modified binders exhibited enhanced viscosity and elastic behavior, as indicated by the DSR tests. The study also investigated the compatibility between EVA/LDPE and asphalt binder through microscopy and chemical analysis techniques. The findings of this experimental investigation contribute to the understanding of the effects of EVA and LDPE on asphalt binder performance. The results highlight the potential of these polymers in enhancing the resistance to rutting and deformation of asphalt pavements. This research can serve as a basis for further studies on polymer modification of asphalt binders and aid in the development of improved asphalt pavement materials with enhanced durability and longevity.

Rheological analyses of binders modified with triple combinations of Crumb-Rubber, Sasobit and Styrene-Butadiene-Styrene

The development of polymer-modified asphalt (PMA) has been a widely used technique by many researchers. Moreover, further modification of PMA binders has generated interest due to possible improvements in performance and cost. In this regard, Sasobit wax has been an alternative to reduce costs in Crumb-Rubber (CR) and Styrene-Butadiene-Styrene Copolymer (SBS) binders. However, there is little detail on the rheological behaviour of CR-SBS-Sasobit triple-modified samples for failure and damage resistance properties. Therefore, this study shows various properties of binders with triple modification of CR-SBS-Sasobit at different dosages. For this purpose, the development of single, double and triple modifications has been proposed to be tested by Multiple Stress Creep Recovery (MSCR) for permanent deformation. In the case of radial cracking and thermal cracking, it is evaluated by linear amplitude sweep test (LAS) and binder creep energy test (BYET). The results indicate that a CR-SBS combination in single or double addition achieves good thermal stability and behaviour. However, a higher elasticity is achieved in the case of a triple modification with CR-SBS-Sasobit. Specifically, Sasobit achieves 67% and 28% reduction in the cumulative deformation of MSCR for a variation of 40–80 °C, respectively. Concerning fatigue life (Nf), it is shown that CR-SBS modifications do not always acquire higher Nf than single modifications. However, adding Sasobit in triple modifications increases these values, generating bitumen with higher strength. It is also shown that adding Sasobit is a viable modifier in yield, even increasing the yield energy (Er) for samples with equal CR-SBS and reducing the percentage of SBS in the sample.

Identification of undisclosed modifiers and their effects on chemical, thermal, and microstructural properties of unaged and aged industrial high polymer-modified asphalt binders

This study employs thermo-chemical and microstructural analyses to identify undisclosed crystalline modifiers (UMs) in industrial high polymer-modified binders (HiPMBs) and evaluate their effects on aging phenomena. Chemical, thermal, and microstructural properties of several industrial HiPMBs were evaluated via Fourier-transformed infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), fluorescence microscopy (FM), and atomic force microscopy (AFM). Results indicate that crystalline UMs, contained in most binders, can be readily identified by calorimetric analysis. In contrast to styrene–butadienestyrene (SBS) thermoplastic elastomers, UMs drastically alter the surface microstructure of all binders. Typical bee-like structures disappear, and undefined topographies emerge due to the interactions between UMs and bituminous waxes. No significant effects were noticed concerning the homogeneity of the binders’ amorphous phases. Aging processes affect the characteristics of base bitumen, SBS, and UMs. Oxidation of bitumen and degradation of SBS can be evaluated by semi-quantitative analysis of FT-IR absorption bands and glass transition temperature (Tg) values. At the same time, variations of DSC endotherms reflect the influence on the crystallinity of UMs.

Properties of polymer modified asphalt by polyphosphoric acid through molecular dynamics simulation and experimental analysis

Polyphosphoric acid (PPA) plays an important role in improving the performance of polymer modified asphalt binders. This study aims to understand the modification mechanism of PPA in styrene-butadiene rubber (SBR) modified asphalt and investigate the rheological and chemical properties after modification based on molecular dynamics (MD) simulation and experimental analysis. Unaged and aged SBR asphalt binders with six PPA contents (0, 0.3%, 0.6%, 0.9%, 1.2%, and 1.5%) were prepared and tested. Four modified asphalt system models in different modifying and aging states were constructed in the molecular dynamics process. The calculated molecular dynamics parameters were used to observe intermolecular behaviors and system phenomena. Dynamic shear rheometry (DSR) and Fourier transform infrared (FTIR) spectroscopy were used to characterize rheological and chemical properties respectively. The results showed that the addition of PPA increased the complex modulus (G*) to promote elasticity and stiffness, and then enhanced the rutting resistance of the SBR asphalt binder. Multiple stress creep recovery (MSCR) results revealed that PPA/SBR asphalt had a better high-temperature performance than SBR asphalt due to its excellent creep recovery capability. Besides, the interaction between PPA and asphalt introduced phosphorus-containing functional groups into asphalt. In addition, analysis of the free volume and mean square displacement (MSD) displayed larger and higher molecular weight in PPA/SBR asphalt hindered the diffusion and mobility of the system. The radial distribution function (RDF) and radius of gyration (Rg) were calculated to observe that PPA provided a more ordered and more stable molecular structure. The electron density and potential were estimated to explore the adsorption mechanism of PPA to asphalt or SBR molecules and explain the source of stability and orderliness of the unaged and aged PPA/SBR/asphalt system.