Polymer-modified Bitumen Research Articles

THE INFLUENCE OF POLYMER ON RHEOLOGICAL AND THERMO OXIDATIVE AGING PROPERTIES OF MODIFIED BITUMEN BINDERS

Polymer modified bitumen (PMB) has been used for many years to improve the performance of asphalt concretes against premature pavement defects. In this research, modified samples were prepared with 2%, 3%, 4%, 5% and 6% Linear Low Density Polyethylene (LLDPE) polymer by weight of bitumen binder. The influence of LLDPE polymer was evaluated through binder properties test which includes penetration, softening point, storage stability, temperature susceptibility, rutting, fatigue and thermal oxidative aging resistance from a dynamic shear rheometer (DSR) measurements at a temperature of 20 OC to 60 OC. Results show that LLDPE polymer has a significant effect on binder properties. Penetration decreases and softening point increases with increasing LLDPE content on the modified binder after aging, which implies LLDPE improves the thermo oxidative aging resistance of the binder. Furthermore, the storage stability test shows that at higher LLDPE concentrations phase separation may occur. DSR analysis shows that modified binders have lower temperature susceptibility and higher aging resistance with increased stiffness and elastic behavior compared with unmodified binders. In addition, modified binders show enhanced resistance against high temperature rutting and at low temperature fatigue performance. It was found that the optimum LLDPE content is 6%.

Use of Fourier transform infrared spectroscopy to study ageing characteristics of asphalt binders

ABSTRACTThe present study aims at studying ageing characteristics of conventional bitumen, polymer modified bitumen (PMB) and warm mix asphalt (WMA) by using FTIR. Results of obtained FTIR spectrum were quantified by calculating different indices and finally based on these indices ageing index of the binders for short- and long-term ageing were calculated. Results showed ageing increased amount of complex and high molecular weight components of the binders. PMB was found to have greater ageing resistance than conventional asphalt binders. In case of WMA, results found to be inconclusive, requiring further investigation.

Improvement of polypropylene (PP)-modified bitumen through lignin addition

Polypropylene (PP) is usually added to bitumen to improve its mechanical properties, however, both of them have different chemical properties. To achieve best mechanical properties of the mixture, coupling agent such as lignin is importantly required. Lignin is an amorphous biopolymer, has bipolar characteristic due to its distinct chemical function which has carbonyl, carboxyl, hydroxyl and phenol chemical function. Otherwise, bitumen and PP have polar and non-polar characteristic, respectively. In the previous research, it is found that lignin is potential to be used as coupling agent. In order to confirm the potential of lignin as a coupling agent, there are various compounds of lignin on PP-bitumen mixtures used in this research. This experiment consists of several stages, ranging from sample preparation, characterization of raw materials, mixing, and characterization of the PP-Modified Bitumen. This experiment used hot melt mixing to mix lignin, PP, and bitumen. The result of this experimental was analyzed by using FTIR and FESEM. The addition of lignin make Polymer Modified Bitumen (PMB) getting better mixing and increase mechanical properties. Furthermore, FESEM characterization indicated that the addition of lignin gave better mixing of PP-Bitumen. FTIR showed a new chemical structure due to the addition of lignin. From this experiment, the addition of lignin can improve mixing between PP and Bitumen. So, we can use lignin as coupling agent.

Ageing and temperature effect on the fatigue performance of bituminous mixtures

The ageing of asphalt mixes, together with their exposure to low temperatures, causes a progressive increase of cracking. In this paper, the effect of ageing and temperature on the fatigue of asphalt concretes made with two types of binders, conventional (50/70) and polymer modified bitumen (PMB), is studied. For this purpose, specimens previously subjected to an accelerated laboratory ageing process were tested by a strain sweep test at different temperatures (-5ºC, 5ºC and 20°C). Results were compared with the obtained from the unaged specimens showing the relative importance of ageing, temperature and type of bitumen on the parameters that determine the fatigue life of the mixture. The mixtures behaviour becomes more brittle with ageing and the decrease of temperature. However, ageing hardly has an effect on fatigue at lower temperatures. In general, mixtures made with polymer modified bitumen have a better fatigue performance to ageing and temperature.

Identifying the rheological properties of polymer-modified bitumen based on its morphology

This paper is an attempt to identify the relationship between morphology and performance of polymer-modified bitumen (PmB) containing styrene–butadiene–styrene (SBS) copolymer and carbon nanotubes (CNTs). Morphology is defined as the partition of polymer-rich and bitumen-rich phases, which is obtained by fluorescence microscopy and atomic force microscopy. Rheological properties of PmB are captured by Master curve, Han curve, and Cole–Cole curve. Three different bitumen samples with same polymer amount were selected in this paper. The results showed that a dense network and the interlocked structure in SBS phase provided a better anti-rutting property of PmB. Han curve demonstrated that the elastic modulus improvement of PmB had a close relationship with the size of SBS phase. Cole–Cole curve illustrated that the smaller size and interlocked structure of SBS phase prevented the movement of SBS phase and presented a higher loss viscosity at low-driving speed condition. Furthermore, CNTs played a positive role on the anti-aging property, storage stability, and anti-cracking performance of SBS-modified bitumen.

The modification of bitumen with styrene–butadiene–styrene, ethylene vinyl acetate and varying the amount of reactive ethylene terpolymer

In this article, 50/70 penetration grade TUPRAS bitumen was modified. Reactive elastomeric terpolymer (Elvaloy RET; DuPont Company), ethylene vinyl acetate (EVA) and styrene–butadiene–styrene (SBS) polymers were used in bitumen modification. Set hours of the tests were applied to samples taken from the obtained modified bitumen mixture. Varying amount of reactive ethylene terpolymer with weight ratios of 0.5%, 1.0%, 1.5%, 2.0% and 2.5% were introduced to the mixture of raw bitumen with 1.0% SBS and 1.0% EVA. Penetration, penetration index, softening point, ductility and elastic recovery tests were performed with these modified bitumen and raw bitumen. The samples of raw bitumen and modified bitumens of 2.0% Elvaloy RET, 1.0% SBS and 1.0% EVA were investigated by means of IR spectroscopy. The raw bitumen was modified with SBS, EVA and RET, and it was determined that penetration and ductility values were decreased while penetration index, softening point and elastic recovery were increased. The purpose of this study is to research the improving properties of 50/70 penetration grade–modified bitumen used in highways of Turkey. The most important characteristics (such as softening point, penetration and % elastic recovery) of new polymer-modified bitumen (NPMB) containing 2.5% EVA, 1% RET and 1% SBS were compared with eight different types of polymer-modified bitumens in Turkey (TPMB). NPMB provided all required parameters (softening point, penetration and % elastic recovery) for five different types of TPMBs (TPMB 70-16, TPMB 70-22, TPMB 76-16, TPMB 76-22 and TPMB 82-16).

Protocol for the morphology analysis of SBS polymer modified bitumen images obtained by using fluorescent microscopy

ABSTRACTFluorescent technique has been used to characterise the morphology of polymer modified bitumen for years. However, the main problem of this technique is a missing standardised protocol for image capture factors and processing algorithms (CF&PA). The purpose of this study was to find out the effects of CF&PA on morphology and set up a protocol for morphological analysis of SBS polymer-modified bitumen (PMB) using the fluorescent microscopy technique. In order to set up this protocol, fluorescent images were captured and processed with different CF&PA. Capture factors mainly include magnification, exposure time and storage format while processing algorithms include noise reduction, enhancement and segmentation. Morphological and parametric analysis indicated that all images must be captured under the same exposure time and should not be processed by white balance. Besides, four principles should be followed to determine the optimal magnification. As to the image storage format, JPEG 2000 was selected to retain the most details. The proper neighbourhood level was obtained from the particle number curve to realise noise reduction. Compared with other complicated segmentation algorithms, threshold methods are more suitable because of the typical two-phase characteristic of PMB. Because of potential change in detailed information of original images, enhancement was not recommended. Finally, the image capturing and processing steps and their levels were given based on the discussion above.

Study on High-Temperature Property Parameters of Polymer Modified Bitumen Based on Rheology

This paper investigates the evaluating parameters on high temperature performance of polymer modified bitumen (PmB). Six bitumen were adopted in this paper and its high temperature performance was researched by rheology method and phenomenology method. Softening point, rutting factor G*/sin () and non-recovery creep compliance Jnr are tested and the mutual relationship is analyzed. Results indicated Jnr is better than rutting factor for evaluating high temperature performance of PmB.

Numerical investigation on phase separation in polymer-modified bitumen: effect of thermal condition

With the aim to understand the effect of thermal condition on phase separation in polymer-modified bitumen (PMB), this paper numerically investigates four PMB binders under five thermal conditions between 140 and 180 °C. Based on a phase-field model previously developed by the authors for PMB phase separation, the updated model presented in this paper uses temperature-dependent parameters in order to approach the concerned temperature range, including mobility coefficients, interaction and dilution parameters. The model is implemented in a finite element software package and calibrated with the experimental observations of the four PMBs. The experimental results are well reproduced by the model, and it is thus believed that the calibrated parameters can represent the four PMBs. The simulation results indicate that the model proposed in this paper is capable of capturing the stability differences among the four PMBs and their distinct microstructures at different temperatures. Due to the transition of some PMBs from the thermodynamically stable state at 180 °C to the unstable state at 140 °C, a homogenization process may occur during the cooling applied numerically. After the transition, the PMBs start to separate into two phases and gradually form the binary structures controlled by the temperature. It is indicated that the cooling rate slightly affects the final pattern of the PMB binary microstructure, although the process can be more complicated in reality due to the potential dynamic reasons.

Multi-fractal morphology of un-aged and aged SBS polymer-modified bitumen

ABSTRACTPolymer-modified bitumen (PmBs) has been characterised by fluorescence microscopy, conventional performance tests and by the rheological measurements, before and after the Rolling Thin Film Oven Test (RTFOT), and by multi-fractal analysis. The addition of 2–7 wt-% of linear styrene-butadiene-styrene block copolymer (SBS-L) or radial block copolymer (SBS-R) increased viscosity, softening point and complex modulus of PmBs. Hardening of PmBs occurred and the elastic response decreased after RTFOT aging. SBS-L PmBs are more susceptible to RTFOT aging. Digital fluorescence micrographs of sections of PmBs qualitatively exhibit different morphological structures which can be quantitatively probed by multi-fractal analysis: differences are reflected in the f (α) spectrum. The PmBs which appear less multi-fractal have the best rheological properties. In another approach, the focal fractal dimensions’ distributions for the SBS-modified bitumen have peak around 2.35 (which corresponds to the bitumen-rich phase) and around 2.7 (which corresponds to the noncontinuous SBS-rich phase).

Effect of shear processing on the linear viscoelastic behaviour and microstructure of bitumen/montmorillonite/MDI ternary composites

Abstract Polymer modified bitumens (PMBs) have largely been utilized as a construction material. However, lack of affinity between bitumen and polymer leads to phase separation, and eventually, performance depletion. In this paper, alternative formulations of bitumen with an organically-modified montmorillonite (OMMT) Cloisite 20A ® and polymeric methylene diphenyl diisocyanate (MDI) were prepared by melt blending. Their comprehensive rheological characterisation evidenced improved linear viscoelastic properties when OMMT is added, revealing a noticeable structural reinforcement and thermal stability. Rheological data also showed that MDI-involved reactions control the composite end properties, being greatly influenced by the shear conditions applied.

Numerical Prediction of Storage Stability of Polymer-Modified Bitumen: A Coupled Model of Gravity-Driven Flow and Diffusion

A coupled diffusion–flow model by phase-field method is proposed in this paper with the goal of predicting the storage stability of polymer-modified bitumen (PMB). In this study, the incompressible Navier–Stokes equations were coupled with a previously developed phase-field model for PMB phase separation. The coupled model was implemented in a finite element software package with experimentally calibrated parameters and reported data in the literature. Effects of the parameters (bitumen density and dynamic viscosity) that affected the gravity-driven flow and phase separation in PMB were evaluated at 180°C with the simulation results. The results indicate that the coupled diffusion–flow model can predict the storage stability (and instability) of PMBs. A good correlation between the simulation results and the previously reported experimental results (storage stability tube test) was observed. The different gravity-driven phase separation behaviors of PMBs might have resulted from the different composition of the equilibrium phases in the PMBs as well as the different densities and dynamic viscosities of the individual components (polymer and bitumen). A bigger polymer–bitumen density difference, a lower bitumen dynamic viscosity, or both caused a faster flow and separation in the PMB at storage temperature. The investigated variation of bitumen dynamic viscosity had a more significant influence than the investigated variation of bitumen density in this study, but this finding might depend on the specific values of the model parameters. With this study as a foundation, further experimental and numerical studies will be conducted to increase understanding of storage-stable PMB binders and to develop a more efficient test method for determining PMB storage stability.

Viscoelastic Properties of Polymer Modified Bitumen in Warm Mix Asphalt Technology in Terms of Ageing

The paper presents the influence of ageing on the viscoelastic properties of the polymer modified bitumen (PMB) in WMA technology. The base bitumen was PMB 45/80-65. Fischer-Tropsch synthetic wax (SW) and the liquid surface active agent (FA) ware used as a bitumen viscosity-reducing modifiers. All properties of binders have been determined before ageing (NEAT) and after long-term ageing (RTFOT+PAV). The research area includes the study basic properties (softening point and Fraass breaking point) and rheological characteristics (zero shear viscosity ZSV, complex viscosity η0 and rutting factor G*/sinδ). It was found that fatty amine additive works as a ageing inhibitor. The ageing process revealed degradation process in polymer. This phenomenon is more explicit in the bitumen modified with wax than the fatty amine.

Influence of Moisture Conditioning on Linear Viscoelastic Behaviour of Bituminous Mixtures Used For Railway Trackbeds

Abstract The influence of moisture on the linear-viscoelastic properties of bituminous mixtures with and without polymer modified bitumen (PMB) to be used for railway trackbeds was addressed in this paper. Nowadays, the use of bituminous mixtures in railway trackbeds, particularly for new high-speed lines, is a common practice. The variation of the thermomechanical properties of bituminous mixtures needs to be characterized considering railway loading, circulation speed, and environmental exposure conditions. For this purpose, improved 3D complex modulus tests were performed on base-course type mixtures. A tri-dimensional constitutive model, called 2S2P1D (2 Springs, 2 Parabolic creep elements and 1 Dashpot), was used to model the viscoelastic behavior of the materials. A moisture conditioning procedure was used to induce moisture damage to the mixtures. The thermomechanical properties of the materials are compared for the conditioned and non-conditioned states. Low variation of the linear viscoelastic behavior of the studied materials after moisture conditioning was observed. The results allowed assessing the interest of using polymer modified bitumen for bituminous mixtures to be used in railway trackbeds.

Low-temperature adhesion performance of polymer-modified Bitumen emulsion in chip seals using different SBR latexes

ABSTRACTDue to increasing use of styrene-butadiene rubber (SBR) latex in the preparation of polymer-modified bitumen emulsions (PMBE) to improve bitumen-aggregate adhesion of chip seal surface treatments and lack of scientific data on the effect of SBR micro-structure on the performance of the resulting treatment at low temperatures, the Vialit test was conducted. The conventional tests showed that addition of SBR and X-SBR to PMBE reduces bituminous residue (BR) penetration and enhances its penetration index (PI) and softening point. Also, addition of linear SBR latex to bitumen results in an increase in BR ductility and recovery at low temperatures. Meanwhile, addition of the branched carboxylated styrene-butadiene rubber (X-SBR) latex reduces ductility of the corresponding BR. The effect of the performance of bitumen emulsions on aggregate bitumen adhesion in chip seals was investigated using Vialit test. It was found that an increase in SBR latex content in bitumen emulsion leads to an increased aggregate retention; this effect is more pronounced at low temperatures. Comparatively, the addition of X-SBR latex results in a lower bitumen-aggregate adhesion at low temperatures.

Effect of granular polymers on rutting performance of SMA with respect to modification process

The aim of this research is to investigate the effect of two types of modification processes for granular polymers, Polymer Modified Bitumen and direct addition of polymer into mix, on rutting performance of Stone Matrix Asphalt (SMA). In this research, granular polymers including Rheofalt and Ethylene-Copolymer-Bitumen (ECB), namely Lucobit, were used and their impact on rutting resistance improvement were compared with SBS modified and unmodified mixtures. Results of performing dynamic creep test revealed that, with respect to both modification types, Rheofalt modified mixtures resulted in significantly greater rutting resistance than ECB modified ones. Moreover, it was found that although ECB modified bitumen is effective to rutting enhancement, there is no improvement as a result of direct addition of it into mixtures. On the other hand, results showed that Rhefalt is influential in direct addition into mixtures but not as efficient as introduction of Rheofalt modified bitumen into mixes. Finally, investigating resilient modulus vs. cycle curves, it was revealed that SBS with elastomeric property predominance resulted in resilient modulus reduction as the content increases while Rheofalt and ECB showed reverse trend with their content increase.

Use of waste plastic materials for road construction in Ghana

This paper forms part of research to solve two main problems in Ghana: firstly, the management of municipal solid waste (MSW), particularly with regards to used plastics which have overwhelmed major cities and towns; secondly, the formation of potholes onroads due to excessive traffic and axle weight. This study examines the effect of blending waste thermoplastic polymers, namely High density polyethylene (HDPE) and Polypropylene (PP) in Conventional AC-20 graded bitumen, at various plastic compositions. The plastics were shredded and blended with the bitumen ‘in-situ’, with a shear mixer at a temperature range of 160°C–170°C. Basic rheological parameters such as penetration, ring & ball softening point and viscosity tests were employed to determine the resulting changes from base bitumen.FTIR spectroscopy was also employed to study the chemical functionalities present in the bitumen composite. The properties of the unmodified bitumen were found to be enhanced with the changes recorded in the rheological properties of the polymer modified bitumen (PMB). It was observed that polypropylene polymer, showed profound effect on homogeneity and compatibility with slight linear increment in the viscosity, softening and penetration values as against relatively high changes for HDPE modified bitumen.The viscosity of unmodified bitumen was enhanced with the addition of the polymers and thixotropic effect was observed for both HDPE and PP at 60°C. For all modified binders prepared, the penetration values decrease as polymer-bitumen ratio increases whiles softening temperature generally increases as polymer ratio increases. The most compatible and incompatible blends for HDPE were respectively observed at 2% and 3% polymer loading. The most enhanced, homogenous blend is achieved with PP at 3% polymer loading. Three prominent peaks were identified in the spectrum of the unmodified bitumen, occurring at the 3000–2850cm−1 IR frequency range, typical of aliphatic CH symmetrical and asymmetrical stretches in alkanes. CH2 and CH3 bends were also observed at the characteristic frequencies of 1465cm−1 and 1375cm−1 respectively. A low intensity peak was observed within the 2400cm−1–2100cm−1 range, indicating the presence of a very weak −CC- or −CN group with an absorbance of precisely 0.12.The use of waste commodity plastics in binder modification carries the advantage of a cheap and effective means of enhancing conventional bitumen binder performance characteristics and is an alternative way to utilise plastic waste.

Linear rheology of bituminous mastics modified with various polyolefins: a comparative study with their source binders

The effect of bituminous mastics on controlling the mechanical properties of the asphalt mixtures has been largely claimed. Theoretical models often fail to predict the rheological behavior of highly concentrated mastics because of the various interaction forces involved. This situation becomes much more complex when dealing with biphasic polymer modified bitumens (PMBs). This investigation explores the influence of various recycled polyolefins (LDPE, HDPE and PP) on the linear rheological behavior of modified mastics with a fixed filler/binder ratio of 65/35 (by weight). The filler was of siliceous-type, and all the PMBs contained 4 wt.% polymer. Oscillatory torsion/shear tests were carried out between 25 and 65 °C. It was found that the rheology of the HDPE-binder very much resembles its polymer-rich phase (PRP), which behaves like a concentrated polymer solution. In contrast, the LDPE-binder proved to have a bitumen-rich phase (BRP) still playing a large part in the PMB rheology. This result had a strong effect on the mastic rheology, as the filler shows more affinity for the bitumen. In consequence, the G′ plateau observed in the HDPE-mastic was similar to that found in its parent PMB. In contrast, if compared to its source binder, the LDPE-mastic manifested a rheological behavior better described by the filler acting as bridging points of PRP domains.

Modeling the linear viscoelastic behavior of asphaltite-modified bitumens

A modeling approach which allows predicting the linear viscoelastic behavior of bitumen blends from the linear viscoelastic properties of individual constituents is presented in this paper. This approach consists in a combination of the Tsenoglou rule for miscible viscoelastic materials with the Palierne model for viscoelastic emulsions. Based on some simple assumptions, this combination predicts satisfactorily the rheological behavior of asphaltite-modified bitumens and, consequently, it can be used for dosage purposes. Beyond asphaltite-modified bitumens, the modeling approach developed here can be applied on reclaimed asphalt-modified bitumens, polymer-modified bitumens, and on blends of partially miscible polymers presenting a suspended droplet morphology.

Rutting resistance and resilient modulus evaluation of polymer-modified SMA mixtures

ABSTRACTEthylene copolymer bitumen (ECB), namely Lucobit, as a thermoplastic polymer, SBS as a thermoplastic-elastomer polymer, and ethylene-vinyl-acetate (EVA) combined with Fischer-Tropsch wax and resin additives, namely Rheofalt WKR-2, as a modified thermoplastic polymer were used for stone matrix asphalt modification. Two types of asphalt modification processes including polymer-modified bitumen (PMB) and direct addition of polymer into mixture were employed and the effect of each one on resilient modulus and rutting resistance was evaluated by performing Indirect Tensile Resilient Modulus and Hamburg Wheel Tracking tests. PMB, SBS, and Rheofalt-modified mixtures resulted in lower rut depth and higher resilient modulus than did those modified by ECB. In direct addition of the polymer into mixture process, there is reduction in rutting resistance and resilient modulus of Rheofalt-modified mixtures in comparison with PMB. Furthermore, there was no improvement for ECB-modified mixtures by direct addition modification.