Polymer-modified Bitumen Research Articles

The Basic Rheological Properties of LDPE Modified Bitumen

Various polymers have widely known in its capability in enhancing rheological properties of bitumen for various pavement applications. Many polymer types have been used in studies, where the properties of the final product of the polymer modified bitumen (PMB) are different, depending on the used polymers. LDPE or Low-Density Polyethylene are one of widely studied polymers in bitumen modification that exhibit higher bitumen's viscosity, perform better in resisting deformation under heavy loads, and tend to show better integrity in high temperatures. LDPE-modified bitumen also believed to enhance elasticity, allowing a potentially better resistance to cracking due to ability to recover at low strain. Many studies also stated the improvement of LDPE-modified bitumen against thermal and mechanical stress, better adhesion to aggregates in asphalt mixtures, and various promising result for overall durability and longevity of pavement. This study explains basic rheological properties of LDPE-modified bitumen prepared by high shear mixing and specified preparing methodologies. Five variables of %modifications were used: 2%, 4%, 6%, 8% and 10% of bitumen weight. Ring and Ball softening point, Penetration test and rotating spindle viscometry were done to understand the rheological changes of the modified bitumen compared to unmodified bitumen control. For further understanding the behaviour, two types of LDPE were used: virgin LDPE and recycled LDPE. The study shows interesting noticeable differences between the two used LDPE polymers, allowing further proposed studies in this field.

Rheological and mechanical evaluation of a novel fast curing cold asphalt concrete made with asphalt emulsion, by-products and magnetic induction

This work studies the feasibility of a new cold asphalt concrete with 5 % voids with fast curing, developed with asphalt emulsion and magnetic induction. Until now, it was impossible to produce fast curing cold asphalt concretes due to the impossibility of compacting and evaporating the water in the asphalt emulsion quickly. Therefore, the aim of this work is to solve the impossibility of compacting the cold asphalt concrete and thus reduce the long curing times. For this purpose, at laboratory level, an experimental cold asphalt concrete was designed with magnetic induction and compared with two reference hot asphalt concretes manufactured according to Spanish standards without magnetic induction (one with 50–70 grade bitumen and another with a PMB45/80–65 type polymer-modified bitumen). The research was carried out in two stages. First, the new cold asphalt concrete was rheologically characterized, the binder recovered from the asphalt concrete was analyzed according to the tests of ring and ball, penetration, dynamic shear rheometer (DSR) and multiple stress creep and recovery (MSCR). Secondly, the new cold concrete asphalt was mechanically characterized, the mechanical performance of the cold asphalt concrete was analyzed by evaluating stability and deformation, dry and wet indirect tensile strengths (ITS), wheel tracking test, stiffness modulus and resistance to raveling dry and wet conditions. Based on the rheological analysis results, the asphalt emulsion recovered from the cold asphalt concrete is extremely soft with a low softening point and a high penetration rate. On the other hand, the values of viscosity, phase angle, stiffness and non-recoverable creep compliance are between those of the bitumen 50/70 and the PMB45/80–65, but closer to bitumen 50/70. As for their mechanical performance, the novel cold asphalt concrete studied presents better resistance to water damage and particle loss, both in dry and wet conditions, but also high permanent deformations and low ITS, probably due to the fact that the residual binder of the emulsion used is softer than the others.

Proposal for a New Method for Evaluating Polymer-Modified Bitumen Fatigue and Self-Restoration Performances Considering the Whole Damage Characteristic Curve

Fatigue performance and self-repairing activity of asphalt binders are two properties that highly influence the fatigue cracking response of asphalt pavement. There are still numerous gaps in knowledge to fill linked with these two characteristics. For instance, current parameters fail to accommodate these two bitumen phenomena fully. This study aims to propose a new procedure to address this issue utilizing the linear amplitude sweep (LAS) test, LAS with rest period (RP) (LASH) test, and simplified viscoelastic continuum damage (S-VECD) model. This research work used four different types of asphalt binders: neat asphalt (NA), self-healing thermoplastic polyurethane (STPU)-modified bitumen (STPB), self-healing poly (dimethyl siloxane) crosslinked with urea bond (IPA1w)-modified bitumen (IPAB), and styrene–butadiene–styrene (SBS)-modified bitumen (SBSB). Before the testing process, all the materials were subjected to short-term and long-term aging. The new procedure showed a superior capacity to analyze and accommodate all bitumen fatigue performances and self-repairing activities compared to the current method. Another finding proved that asphalt binders with a higher self-restoration behavior failed to show a better fatigue performance. Moreover, the higher fatigue performance increments produced by STPU and IPA1w in NA concerning the control bitumen were 123.7% and 143.7%, respectively. Those values were obtained with 1.0% STPU and 0.5% IPA1w in NA. A breakthrough finding demonstrated that asphalt binder fatigue response is augmented when the RP was applied at a higher damage intensity (S) value. STPB and IPAB reached their highest increments of fatigue response, containing 1.0% of STPU and 0.5% of IPA1w, respectively. Those augmentations were 207.54% and 232.64%, respectively.

The Use of Waste Low-Density Polyethylene for the Modification of Asphalt Mixture

In this study, a critical evaluation and the benefits of using a waste and a virgin polymer in an asphalt mixture are presented. The present paper is the result of a three-year research effort to find a suitable recyclate compatible with asphalt binder and setting reaction conditions in the preparation of asphalt mixtures with the mentioned recyclate. This suitable candidate was recycled low-density polyethylene (LDPE), which was produced by recycling old, worn-out bags and films. An amount of 6% of LDPE by the weight of the binder content was suggested as the best amount of the modifier. Physical tests, including penetration, softening point, and kinematic viscosity have been carried out to prove the effectiveness of the modification on the binder properties. The effectiveness of the blending process and the appropriate concentration of additives led to a homogeneous polymer-modified bitumen without any imperfections in the structure. After successful preparation under laboratory conditions, this paper describes the preparation of asphalt mixtures directly in an asphalt-mixing plant and the subsequent implementation of a verification section. The overall composition of prepared polymer-modified asphalt mixtures has been studied. An important result of this study is the preparation of the asphalt mixture with waste LDPE that meets all the technical requirements. Moreover, it has been proven that this type of waste PE is fully applicable in asphalt-mixing plants in Slovakia, with zero or minimal financial burden on construction companies to complete the construction of their production facilities. Using such a technology, we can reduce the amount of waste plastics that otherwise end up in landfill.

Effects of Laboratory Ageing on the Chemical Composition and High-Temperature Performance of Warm Mix Asphalt Binders

Warm asphalt mixtures can suffer from decreased short-term high-temperature performance; therefore, introducing additional modifiers can mitigate this risk. This study investigates the effects of a liquid organosilane warm mix additive (WMAd) and grade-bumping polyethylene-based additive added simultaneously to asphalt binders on their chemical composition and its relationship with performance characteristics. Previous studies found relationships between the formation of certain chemical species during bitumen ageing and the increase in their viscosity, stiffness and other performance characteristics—the present work intended to verify these relationships when the two mentioned additives are used. Two asphalt binders were investigated—a paving-grade 50/70 binder and a 45/80-55 polymer-modified bitumen. The chemical analysis was performed using Fourier-transform infrared (FTIR) spectroscopy in attenuated total reflectance mode and focused on the quantification of carbonyl, sulfoxide, polybutadiene and polystyrene structures in the asphalt binders subjected to laboratory short- and long-term ageing. Additionally, the relationships between asphalt binder performance and selected FTIR indices were evaluated using a dynamic shear rheometer. It was found that the investigated additives significantly affected the apparent contents of all evaluated chemical structures in the asphalt binders; however, these changes were not reflected in their performance evaluation.

Use of modified chitosan as bitumen modifier and its impact on rheological properties in bitumen modification.

Conventional bitumen is a viscoelastic material composed of asphaltene and maltene. It is prepared by air-blowing, but this approach makes the bitumen more brittle and susceptible to temperatures. To decrease the temperature susceptibility, synthetic polymers or additives are used to make polymer-modified bitumens. Polymer-modified bitumens have poor storage stability and phase separation and are costly. Chitosan has free amino and hydroxyl groups. Some studies showed that chitosan can be used as a bitumen emulsifier, increasing emulsion viscosity. This study describes the synthesis of O-carboxymethyl chitosan (OCMC) from chitosan, and the same was blended in base bitumen VG10 and VG30 to improve its constitutive properties. VG10 and VG30 grade bitumen were characterized for penetration, softening point, kinematic and absolute viscosity, and ductility. OCMC-modified bitumens were also characterized by their rheological and mechanical properties. OCMC was used in the concentration range of 0.5 to 4.5 wt%. The study revealed that using sulfur increases the ductility and penetration of modified bitumen with 1.5 wt% of OCMC and meets the specification of VG40-modified bitumen as per BIS specification IS:73:2013. The study showed that blending 1.5 wt% of OCMC in VG30 base bitumen enhances the complex modulus to 76,517Pa (at 42°C) with a minimum phase angle of 68.58° and meets the VG40 bitumen specification. Simultaneously, blending 1.5 wt% of OCMC in VG10 base bitumen enhances the complex modulus to 64,454Pa with a minimum phase angle of 77.39° (at 42°C) and meets the VG30 bitumen specification. Studies showed that using SBS in a small amount of 0.25 wt% along with modified chitosan improves the rutting resistance and shear modulus by more than 67°C at 1.1kPa.

Development of an Energy-Efficient Method of Obtaining Polymer-Modified Bitumen with High Operational Characteristics via Polymer–Bitumen Concentrate Application

New requirements for the operational reliability of roads make the utilization of polymer-modified bitumen (PMB) more common in road construction. The application of polymer-modified bitumen based on traditional technology for the production of asphalt mixtures is associated with technological and economic difficulties and does not provide proper adhesion to the mixture’s mineral components. In addition, the method of producing a binder over a long time at high process temperatures leads to increased aging, which significantly reduces the service life of the material in the pavement. This paper presents the results of studies on the effect of polymer–bitumen concentrate (PBC) consisting of styrene–butadiene–styrene, plasticizer, and surfactant on the bitumen characteristics. It has been established that the use of PBC in the bitumen binder leads to an increase in the temperature range of plasticity, softening temperature, elasticity, and cohesive strength with a decrease in the viscosity of the modified bitumen. With a complex modifier rational content of 8% by weight of bitumen, the temperature range of plasticity is 79 °C, and elasticity is 82%, which exceeds the parameters of the factory PMB-60 based on SBS polymer. Tests of binders using the Superpave method allow classifying the modified binder to the PG 64-28, which shows an increase in the temperature range of viscoelastic properties by 6 °C compared with the binder produced by traditional methods. Thus, the expediency of using a complex additive containing a polymer and surface-active substances (surfactants) that can be distributed in bitumen without the use of a colloid agitator and plasticizer has been proven to improve the quality of an organic binder.

Enhancement of porous asphalt mixtures modified with various fibers and ethylene–vinyl acetate polymer

Porous asphalt mixture is conventional hot mix asphalt (HMA) with substantially decreased fines, which produces an open-graded mixture that enables the water to flow through an interconnected void space. Porous asphalt is a permeable system that has a lot of benefits. However, because of its open structure, the durability of this mixture decreases, and both its stability and resilient modulus are much lower compared to the dense conventional asphalt mixtures. Also, the high void percentage may lead to an increase in the draindown proportion. Fibers (cellulose or mineral) and polymer-modified binders are recommended for porous asphalt mixtures, especially in hot and moderate climates. The objective of this study is to improve the porous asphalt mixture's performance by using ethylene–vinyl acetate (EVA) polymer-modified bitumen. Two types of fibers (cellulose fibers and glass wool fibers) were used, separately to determine the control mixture. Four different proportions of EVA polymer were added to the bitumen (1%, 2%, 3%, and 4%) and Scanning Electron Microscopy (SEM) was used for better investigating of the bitumen microstructure, then The Marshall mix design was used to determine the optimum EVA content (OEC) for the porous asphalt mixture. Several performance tests were conducted to investigate the characteristics of the porous asphalt mixture, such as the infiltration rate, binder draindown, the wheel track and the cantabro abrasion tests. The findings of the study conclude that the addition of EVA polymer to the porous asphalt mixtures enhances the performance as it increases stability by 20.8% and the infiltration rate by 20.6%. It decreases binder draindown proportion by 33.3%, cantabro abrasion loss by 25.1% and the rut depth at 5,000 cycles and 10,000 cycles by 29.8% and 19.7%, respectively.

Integrating Mechanistic-Empirical Pavement Analysis in the Life Cycle Assessment Use Phase and Monetization of Environmental Impacts to Promote Low Carbon Transportation Materials

This study attempted to integrate the Mechanistic-Empirical Pavement Design Guide (MEPDG) analysis into the life cycle assessment (LCA) framework to explore the potential of terminal blend rubberized bitumen (TBRB) technology as a sustainable alternative to traditional paving materials in the United Arab Emirates (UAE). In addition, the concept of environmental impact monetization is introduced for quantifying shadow prices to be used in cost–benefit analyses and encourage the adoption of sustainable technologies in pavement construction. The findings demonstrate that hot mixed asphalt (HMA) with TBRB outperforms asphalt mixtures with neat bitumen (NB) and polymer-modified bitumen (PMB) containing 7% linear styrene–butadiene–styrene, with respect to durability and environmental impacts. The cradle-to-grave analysis, which includes maintenance and rehabilitation cycles based on the MEPDG results, alters the hierarchy among scenarios compared to conventional cradle-to-gate analyses, highlighting the importance of the use phase in LCA. Overall, the asphalt mixture with TBRB exhibits 83% and 63% less global warming potential than mixtures with NB and PMB, respectively. The monetization process through the distance-to-target approach returned the shadow price of US$157 per metric ton of CO2eq in the UAE. Based on this value, the HMA with TBRB, if selected over those with NB and PMB, offers environmental savings of US$47,186/km-lane and US$15,852/km-lane for the case study investigated.

ABCD method for determination of low-temperature properties of ordinary and modified binders

Introduction. The active introduction into practice of the system of volumetric and functional design (OFP) is aimed at the large-scale development by the Russian road construction industry of advanced foreign approaches to the technology of designing asphalt concrete pavements (Superpave). One of the fundamental differences between the OFP methodology and the previously established practice of evaluating technical, technological and operational indicators of road construction materials is the introduction of new methods that characterize quantitative indicators with a high degree of accuracy, based on the actual physical, chemical and mechanical properties of the components used. Thus, as methods for assessing the low-temperature properties of bitumen binders, it is proposed to use the bending beam method (BBR), which has proven itself quite well when working with traditional (ordinary) bitumen. However, the natural and climatic conditions of operation of highways in Russia clearly require the use of binders modified with high- and low-molecular compounds, including polymers. In this study, the task of applying the ABCD method to evaluate the low-temperature parameters of ordinary bitumen and polymer-bitumen binders was realized.Materials and methods. Samples of industrial batches of petroleum road viscous bitumen (GOST 33133-2014) and polymer-modified bitumen (GOST R 52056-2003) were used as objects of research. To determine the lowtemperature parameters, an ABCD 8.0 device and an air-cooled climate chamber were used. The study of bitumen binders according to the parameters laid down in the technical requirements of GOST R 58400.11–2019 ‘Automobile roads of general use. Petroleum-based bitumen binders. Method of determining the temperature of cracking using the device ABCD’ was carried out.Results. The values of the cracking temperature for ordinary and modified bitumen binders were determined. It is shown that the low-temperature parameters of polymer-bitumen binders significantly exceed similar properties of oxidized road bitumen.Discussion and conclusions. A comparative analysis of the low-temperature properties of ordinary and modified binders obtained during their determination by the direct method enables to confirm the effectiveness of the methodology developed in GOST R 58400.11-2019 for assessing the performance of binders of various component composition in difficult climatic conditions of Russia. The effectiveness of the domestic second-generation ABCD 8.0 device for direct assessment of the cracking temperature of bitumen binders of variable composition has been confirmed.

Rheological and microstructural properties of nano-composite bitumen modified by nano-alumina and low-SBS content

This study explores a new nanocomposite-modified bitumen (NCMB) that could be more cost-effective and environmentally friendly than current options. It achieves this by combining a lower amount of styrene butadiene styrene (SBS) polymer with nano-alumina, aiming to improve performance at high and moderate temperatures. This innovative material aims to overcome the performance limitations of traditional polymer-modified bitumen (PMB). Moreover, this NCMB, which uses less modifier (SBS) and nano-alumina, paves the way for more economical and eco-friendly roads, leading to significant fuel savings. The new NCMB was prepared by mixing various nano-alumina contents (2, 3, 4, and 5 % by weight of bitumen) with low-SBS content (2.5 % by weight of bitumen) PMB. Multiple stress creep recovery (MSCR) and linear amplitude sweep (LAS) tests, further the Superpave standard method, were used to assess the rutting and fatigue cracking resistance of PMB and NCMBs. Field emission scanning electron microscopy (FESEM) with elemental analysis by energy dispersive X-ray spectroscopy map (EDS) techniques and Fourier-transform infrared spectroscopy (FTIR) was used to investigate the microstructural and elemental characteristics of NCBBs. The results demonstrated that adding nano-alumina to low-SBS content PMB significantly enhanced both the storage stability and its durability over time (i.e. aging resistance) of the NCMBs. The MSCR test results showed that samples with 5 % nano-alumina had a rutting resistance higher than the PMB, up to 31 %. The NCMB samples with 4 % nano-alumina demonstrated a significant improvement in fatigue resistance of up to 67 %. The FTIR results revealed a 64 % improvement in aging resistance for NCMBs containing 3 % nano-alumina compared to the PMB. The storage stability values increased for all NCMB types and reached 62 % for the samples with 5 % nano-alumina. Overall, adding nano-alumina to low-SBS content PMB led to a remarkable improvement of rheological properties at intermediate and high temperatures and a stable system under storage conditions with high anti-aging resistance.

Multi-criteria analysis of porous asphalt mixtures with aramid fiber under adverse conditions

This study the functional performance of super porous asphalt mixtures with two types of aramid fibers against adverse events during their service life. This research was organized in 4 phases: first, particle loss after extreme weather conditions was evaluated. Second, the permeability and clogging resistance was assessed. Third, its resistance to fuel spillage was studied. Fourth, a multi-criteria analysis was performed to determine the best performing mixture considering all the studied variables.Regarding the results, mixture with aramid and polyolefin was the best performing blend according to the multi-criteria analysis. The fiber content allowed for acceptable performance in terms of particle loss despite having a higher void content than the reference mixtures. In addition, a higher permeability and clogging resistance was found, so the use of such fibers did not negatively affect the internal structure of the mixture. Finally, it had a higher resistance to fuel spillage due to the use of polymer-modified bitumen.

Laboratory evaluation of the effect of cement concrete overlays on the existing asphalt concrete pavement with different degrees of bonding

ABSTRACT The utilisation of cement concrete overlays has been on the rise owing to the growing demand for the repair and enhancement of existing pavements, emphasising cost-effectiveness and prolonged overlay lifespan. The primary objective of this study is to ascertain the performance and scrutinise the impact of various types of separating layers on the mechanical parameters of cement concrete overlays. Upon the acquisition of requisite materials and the preliminary testing pertaining to the design of mixtures utilised in both asphalt concrete and cement concrete, three-layer samples were employed in pull-off tests and bending beam tests. These samples incorporated separating layers of different material types, namely AC60/70 neat bitumen (neat bitumen with Pen 60/70), AC85/100 neat bitumen (neat bitumen with Pen 85/100), bitumen emulsion (tack coat), polymer-modified bitumen, bituminous thin layer mixture, and a control sample without a separating layer. Subsequently, through a comparative analysis of the tensile strength and flexural strength results derived from the three-layer samples, the separating material demonstrating the highest and lowest potential for bonding was identified and compared through diverse diagrams. Furthermore, to ensure the reliability of the obtained results, a comparative analysis was conducted against the Darter and Barenberg criterion, along with average stress (mean fatigue).

Assessment of indirect tensile stress and tensile–strength ratio and creep compliance in HMA mixes with micro-silica and PMB

Abstract This study aims to ascertain the effects of polymer-modified bitumen (PMB) and to utilize mineral filler with micro-silica (MS) on various properties of hot-mix asphalt (HMA). In this work, three specimens of an asphalt-concrete mixture were prepared. The first specimen represents a control mixture, the second specimen contains MS at rates 15, 30, and 45% by the total weight of the total aggregate as filler, and the third specimen contains MS and PMB with 4% novolac by the weight of bitumen and 15% hexamine by the weight of the novolac. The properties of designed mixes were evaluated using the indirect tensile strength test, tensile–strength ratio, and creep compliance. The test results showed an increase in the resistance of asphalt concrete to moisture damage, a reduction influence of water on asphalt concrete properties, creep compliance values indicating growing stiffness for asphalt mixture, and enhanced fatigue life. In conclusion, using 45% MS and PMB improved the properties of HMA and provided long-lasting mixtures for highway construction.

Utilization of Distilled Water to Observe Surface Contact Angle of Polymer-Modified Bitumen

Utilization of Distilled Water to Observe Surface Contact Angle of Polymer-Modified Bitumen

Performance and Lifecycle of Hot Asphalt Mix Modified with Low-Percentage Polystyrene and Polybutadiene Compounds

The paper investigates the improvement of bitumen mixture fatigue resistance and the rutting performance by using a specific low percentage of a styrene–butadiene–styrene (SBS) polymer, which contains polystyrene and polybutadiene compounds. A Fourier transform infrared (IR-FT) spectroscopy of the SBS polymer used in following test was carried out to ascertain the polybutadiene and polystyrene compound ratio, which may affect the modificant properties. Unmodified, low-percentage modified SBS, and common polymer-modified bitumen (PMB) as a reference were tested to ascertain the properties, fatigue resistance, and the rutting performance. The test results of the low-percentage modification with SBS are compared against unmodified mixtures and standard PMB mixtures. Finally, a simulation of the practical application was performed using the HDM-4 software (version 2.0), where the material research findings, with an emphasis on the rutting performance, were translated into the pavement performance with a varying binder course layer under simulated traffic conditions. Lifecycle analysis, with a focus on emissions production (CO2, SO2, and NOx) during pavement operation, was conducted for pavements with unmodified, low-percentage modified SBS, and standard PMB binder courses. The lifecycle analysis showed that a 3% modification of the binder course with the SBS polymer can extend the rutting parameter pavement lifecycle by approximately 34.5%, which is about half of the extension provided by the standard PMB modification. The resulting improvement in the pavement serviceability translated to a 9% reduction in CO2 and SO2 emissions and a 7.2% reduction in NOx emissions over a 20-year period.

Effect of Polymer-Modified Bitumen and Reclaimed Asphalt Pavement on The Physical Properties of Bitumen

The high cost of road construction due to the energy required for new material production and the environmental impact necessitates the use of reclaimed asphalt pavement (RAP) and other waste materials. This paper examined the effect of using RAP with a PET additive as a rejuvenator. PET additive (2%) was added to the virgin binder (VB) of 60/70 penetration grade to form a Polymer modified bitumen (PMB). RAP percentages used were 30, 40, and 50%, respectively. The physical properties were examined using the penetration, softening point, and ductility. The results show that the physical properties of RAP were improved by utilizing Rap binder (RB) and PMB mix ratio. The penetration and ductility values increased by 46.4% and 66.7%, respectively, with the PMB (30): RB (70) ratio blend, compared to RB: VB blend. This suggests a reduction in brittle behavior and less stiffness with the addition of PMB in the blend, enhancing the flexibility of the RAP. Although both mixtures blended with RB exhibited softening points within the acceptable range, improved performance was observed with RB/PMB mix blend over RB/VB blend when used in hot asphalt mixture.

Investigating the unique entropy-elasticity of polymer modified asphalt

Crafting Styrene-Butadiene-Styrene (SBS) polymer into the bitumen can notably improve the elastic response of the polymer modified bitumen (PMB), which will significantly enhance the overall performance of bituminous pavement. But the molecular mechanism of the PMB’s unique entropy elasticity has not been fully understood yet. The prominent entropy-elasticity of SBS polymer modified asphalt was investigated in this study. To do so, Fourier Transform Infrared (FTIR), Gel Permeation Chromatography (GPC) and Dynamic Mechanical Analysis (DMA) were conducted to investigate the molecular modification mechanism of PMB. Afterwards, polymer molecular model with a polymerization degree over 2000 is constructed and dynamic simulation is conducted to reveal the mesoscopic mechanism of SBS polymer’s entropy elasticity. As for macroscopic evaluation, a series of creep and recovery tests associated with different testing temperatures (10 °C to 100 °C with a 6 °C gap), recovery times (0.01 s, 0.1 s, 1 s, 4 s and 9 s) and SBS dosages (0 %, 2.5 %, 4.2 %, 7.5 %) were carried out to characterize the elasticity of various PMBs. The results show that plain bitumen mainly shows energy-elasticity, which is small, instantaneous and highly temperature-dependent, while PMB mainly shows entropy-elasticity, which is strong, delayed and less temperature-dependent. Under the condition of low temperature and short recovery time, the bitumen molecules freeze and prevent the SBS polymer to demonstrate its entropy-elasticity, hence the energy-elasticity dominates. Higher temperatures and long recovery time render the SBS molecule more time to relax and thus the entropy-elasticity dominates. The predominant influence of entropy-elasticity in PMA leads to a unique increasing recovery rate within a specific high-temperature range. This phenomenon can be utilized as a fingerprint approach for the identification of the entropy-elasticity and polymer modification.

An evaluation proposal for the fatigue and healing performances of high-viscosity polymer-modified bitumen based on continuous multiple linear amplitude sweep

Due to the excellent shear deformation resistance of high-viscosity polymer-modified bitumen (HVPMB), the traditional methods based on time sweep and linear amplitude sweep (LAS) had problems with insufficient damage accumulation and inability to disrupt the integrity of HVPMB, making it difficult to accurately evaluate its fatigue and healing characteristics. To solve this problem, this study developed an effective evaluation proposal called continuous multiple LAS (MLAS) test and MLAS-based healing (MLASH) test. One base bitumen and three HVPMBs were selected for related experiments. MLAS test results confirmed that the percentage of strain energy attenuation (PSEA) can be used to evaluate the fatigue damage degree of HVPMBs. The lower the PSEA, the lesser damage. Combined with the fluorescence microscope and direct photography observation, the fatigue hairline cracks during MLAS test gradually expanded from the sample periphery to center until completely destroyed. Further, the MLASH test was developed to evaluate the healing performance of HVPMB by introducing intermittent duration into MLAS test. The variation of PSEA after tenth LAS loading (i.e. ΔPSEA) was proposed to evaluate the healing performance of HVPMB. The larger the ΔPSEA, the better the healing performance of HVPMB. All HVPMBs showed satisfactory healing performance once there was sufficient healing intermittent time (e.g. 180 s), and the healing performance was negatively correlated with the damage degree. Notably, the polymer structures had a dual effect on the healing performance of HVPMB, that is, they promoted the elastic healing recovery of HVPMB at lower temperature, while hindering the flow healing recovery at higher temperatures. Moreover, different temperatures caused a shift in the ranking of healing performance of various HVPMBs, thus the healing result at only single temperature cannot comprehensively represent the healing performance of HVPMB. Overall, the newly developed evaluation proposal can help to select HVPMB with excellent fatigue resistance and healing properties and provide a certain basis for accurately predicting HVPMB pavement life.

STUDY OF NON-FUEL APPLICATION OF BROWN COAL DERIVATIVES FOR BITUME MODIFICATION

The article shows research into the non-fuel use of brown coal derivatives for the modification of bitumen. The work used petroleum road grade bitumen BND 60/90 with a flash point in an open crucible of 260 °C, a softening temperature (using the ring and ball method) of 48 °C, resin after lignite thermal destruction and rubber waste. and powder. Based on the fact that the most relevant technologies for the non-fuel use of brown coal concern areas aimed at obtaining wax, humane preparations, adsorbents, obtaining valuable derivatives in the form of resins, GR, etc., an assessment was made of the non-fuel use of brown coal derivatives for modification bitumen. Analysis of the experimental results showed that the studied quality indicators of the composition samples, which include waste rubber powder, have an increased complex of both thermophysical and physical-mechanical characteristics. This is obviously due to the fact that, as a result of thermal destruction of rubber powder, the swelling process occurs faster compared to crumb rubber with a size of 2.5–4.5 mm. However, the process of destruction and dispersion in both cases does not occur completely, of course, and the volume of edematous rubber particles contains resins and polyaromatic components that affect the value of both thermophysical and physical-mechanical characteristics. Thus, it has been established that the optimal composition for creating effective polymer-modified bitumens with an increased complex of thermo-physical and physical-mechanical characteristics is 40 % by weight of rubber powder and 5 % by weight. brown coal resins after thermal destruction. It is shown that the results of laboratory studies have proven the prospects of using brown coal tar after thermal destruction for the modification of road bitumen. Summarizing research into the direction of non-fuel use of brown coal derivatives in the form of liquid products – tar resins of brown coal after thermal destruction for the modification of bitumen materials, it should be noted that the results obtained are moderate in comparison with existing directions for the production of polymer-modified bitumens. Modification of bitumen with primary and secondary polymers makes it possible to significantly improve their adhesion and performance characteristics compared to brown coal resins after thermal destruction. The use of brown coal resins after thermal destruction is much less effective in improving the elasticity, heat resistance and reducing the fragility of bitumen compositions compared to the use of thermoplastic and thermoelastomer modifiers in the production of polymer-modified bitumens.