Polymer-modified Bitumen Research Articles

Modelling the rheological properties of bituminous binders using the 2S2P1D Model

This study evaluates the suitability of the 2S2P1D Model to describe the rheological properties of a large database of bituminous binders held by the Nottingham Transportation Engineering Centre. This database includes more than 60 different combinations of unmodified bitumen, polymer-modified bitumen and bitumen–filler mastics, unaged and aged samples. The 2S2P1D Model is found to be able to satisfactorily describe the linear viscoelastic rheological (LVE) properties of binders over a wide range of temperatures and frequencies. A comparison between measured and descriptive complex modulus and phase angle data was done using a graphical method and goodness-of-fit statistics. Except for the unaged polymer-modified bitumens, all tested samples show good agreement between the measured and descriptive data.

Influence of hindered phenol additives on the rheology of aged polymer-modified bitumen

Oxidation (aging) in polymer-modified bitumen occurs due to exposure in air at high temperatures. The aging mechanism tends to alter the physical and chemical properties of bitumen as reflected by the change in their rheological properties. In this study, a blend of SBR and hindered phenols (HPs) was used to improve the rheological characteristics of base (unmodified) and polymer-modified bitumen. Rheological properties were measured using a Rotational Viscometer, a Dynamic Shear Rheometer and a Bending Beam Rheometer. Stiffening indices and complex modulus indices were used to assess the effectiveness of the additives in the bitumen and its thermal stability, respectively. It was found that the additives were capable of increasing the stiffness at high temperature and reducing the hardening propensity of aged bitumen at intermediate and low temperatures. Bitumen morphology suggests that the degree of polymer network chain break-down was less severe when the HP was used in the bitumen. Performance testing of bituminous mixtures indicated that the HP additives enhanced the stripping resistance, improved rutting performance and extended the mixture service life.

Flame retardancy of bitumen: A calorimetry study

The article investigates the flame retardancy of bitumen for roofing applications using the mass loss calorimeter. Screening of the solid flame retardants, including expandable graphite, boron-based compounds, and silsesquioxanes, shows that they can provide high fire performance. Nevertheless, the settling of these compounds during hot storage stability tests does not permit using them for large-scale application (transportation of bitumen at high temperature). On the contrary, the incorporation of the commercial liquid flame retardant OP 920 (phosphoric acid alkyl ester) in bitumen enhances the reaction to fire of the bitumen, and the mixture is stable during hot storage test. Nanoparticles (organoclay and multiwall carbon nanotubes) have not been found to be appropriate flame retardants for bitumen, but they can be used as synergist with OP 920. Nevertheless, they are not suitable for practical applications because organoclay settles during hot storage tests. Only OP 920 among the evaluated flame retardants can be considered for roofing applications. It provides a very promising fire performance in polymer-modified bitumen and in roofing felts.

Penetration testing and thermal behavior of bitumen 35/50 and modified bitumen 13/40

Physical properties of pure bitumen 35/50 and polymer-modified bitumen 13/40 are studied using needle penetration test and differential scanning calorimetry (DSC). In particular, the mechanical response under indentation conditions is achieved as a function of different loads and temperatures. Our results show that lower temperature susceptibility is associated to larger loads but its change is rather small for the tested bitumens. A pure bitumen 35/50 exhibits a single glass transition temperature for different heating rate whereas modified bitumen 13/40 presents two Tg for different heating rate.

A Comparative Study of Phase Angle Predictive Equations Using Bituminous Binder Data

This study investigates the validity of several phase angle (δ) predictive equations; the Kramers–Kronig relationship, Christensen and Anderson (CA), Christensen Anderson and Marasteanu (CAM), Al-Qadi and co-workers, fractional and arctan (G′′/G′) models on unmodified and polymer modified bitumens (PMBs), unaged and aged samples. The viscoelastic properties of these binders were determined by means of a dynamic shear rheometer covering a wide range of temperatures and frequencies. The results indicate that most of the models are able to predict the viscoelastic behaviours of unmodified bitumens reasonably well. However, some equations failed to predict the appearance of a plateau in the δ master curves of PMBs. The goodness-of-fit statistics between measured and predicted δ shows that the fractional model yielded the most outstanding correlation for all test samples, followed by the Al-Qadi and co-workers, CAM, CA, arctan (G′′/G′) and Kramers–Kronig relationships. As expected, an anomaly is observed between measured and predicted δ of the Kramers–Kronig relationship particularly at high frequencies. The fractional model is, however, not considered suitable for practical purposes due to the high number of coefficients that need to be solved even though this model is able to satisfactorily predict the viscoelastic properties of the unmodified bitumens and PMBs.

Morphology and Rheological Analysis of Nanoclay in Polymer Modified Bitumen

This paper investigated the influence of nanoclay on the properties of polymer modified bitumen(PMB). The nanoclay-polymer modified bitumen has been produced by mixing a standard 70/100 pen bitumen with polymer at a fixed proportion and then mixed with different amount of nanoclay. The rheological behaviour of the samples have been determined using dynamic shear rheometer. The morphology of the samples as well as the distribution of polymer and nanoclay throughout the bitumen have been characterized with a fluorescence microscopy. The result indicate that the rheological properties of nanoclay-polymer modified bitumens dependent on the percentage nanoclay. The morphology result shows that dispersed polymer particles existed in continuous bitumen phase and the addition of nanoclay does not seem to change the particle size of the polymer.

Polymer modified bitumen

Standard methods of characterisation of bitumen (BIT) and polymer modified bitumen (PMB) do not provide sufficient information. We propose to rely on determination of rheological properties which are much more informative. Along theses lines, we have determined rheology before and after the rolling thin film oven test. The materials studied were BIT, BIT+linear (L), styrene–butadiene–styrene (SBS), block copolymer, BIT+radial (R) and SBS copolymer. The rheological properties of the modified binders are characterised using a dynamic shear rheometer, over wide ranges of temperatures at a fixed traffic frequency of 10 rad s−1. The SBS block copolymers increase the elasticity of the BIT at high temperatures and contribute to a better flexibility at low temperatures. Polymer modified bitumens have higher resistance to permanent deformation. After aging, the hardening of BIT and PMBs occurred and the elastic response decreases as a consequence of degradation. The determined rheological properties are in agreement with the results of conventional tests.

Analysis of Structural Compatibility at Interface between Asphalt Concrete Pavements and Orthotropic Steel Deck Surfaces

Orthotropic steel deck is the most suitable solution for long-span bridges by virtue of its low weight and good mechanical properties. However, this deck shows a lack of adhesion with ordinary paving materials; for this reason special bonding coats are usually applied on the steel surface. Polymer-modified bitumen, asphalt-based mastic, epoxy asphalt, and reinforced asphalt membrane have been used at the interface between the hot-mix asphalt (HMA) course and steel bridge decks. A description of these materials and their construction process is provided. In some extreme situations mechanical reinforcement is necessary to provide adequate bonding between the steel deck and the asphalt pavement. The aim of this study was the laboratory evaluation of the shear properties of smooth and reinforced steel interfaces, which were coated with a polymer-modified bitumen and placed between the steel deck and conventional HMA. A suitable specimen preparation procedure was first defined. Shear resistance was evaluated with the ASTRA shear test device to investigate the effects of temperature and normal stress on different types of HMA–steel interfaces. The results showed that reinforced steel interfaces guaranteed higher performance than did smooth interfaces, especially with increasing temperature. Reinforced steel interfaces can be considered as a reliable solution in cases of high-shear traffic-induced stresses.

A Novel Approach to Recycle the Waste Plastics by Bitumen Modification for Paving Application

Recycling of waste plastics (WP) denotes an effectual method to dispose the post-consumer products for possible alternative way to obtain new materials with good properties. With this aim the influences of WP and maleic anhydride (MA) grafted WPs (MA-g-WP) were investigated as the bitumen modifiers for paving applications. Fourier transform infrared (FTIR) spectroscopy analysis established the effective grafting of MA with the waste plastic (WP). Polymer modified bitumen (PMB) binders were analyzed under scanning electron microscopy (SEM) and optical microscopy (OP) in an effort to characterize the bitumen/modifier interphase morphology. The conventional rheological tests such as penetration test, softening point, and ductility results indicate that the degree of polymer modifications are function of the nature of modifier, bitumen–modifier compatibility, and modifier concentration. It has also been confirmed that the morphology observed by SEM and optical microscopy revealed the compatibility between MA-g-WP and bitumen, and the storage stability of binder was improved significantly compared with WP modified bitumen (WPMB) binders. Consequently, the use of grafted modifier with polar site can be considered as a suitable alternation for modification of binder in pavement by expecting their chances for better performance during service.

Evaluation of rheological and image properties of styrene‐butadiene‐styrene and ethylene‐vinyl acetate polymer modified bitumens

AbstractThis article presents a laboratory evaluation of conventional, fundamental, rheological, and morphological characteristics of styrene‐butadiene‐styrene (SBS) and ethylene vinyl acetate (EVA) polymer modified bitumens. Polymer modified bitumen (PMB) samples have been produced by mixing a 50/70 penetration grade unmodified (base) bitumen with SBS and EVA copolymer at different polymer contents. The fundamental viscoelastic properties of the PMBs were determined using dynamic (oscillatory) mechanical analysis and presented in the form of temperature and frequency‐dependent rheological parameters. The morphology of the samples as well as the percent area distribution of polymers throughout the base bitumen have been characterized and determined by means of fluorescent light optic microscopy and Qwin Plus image analysis software, respectively. The results indicated that polymer modification improved the conventional and rheological properties of the base bitumen. It was also concluded that the temperature and frequency had a significant effect on complex modulus of PMBs. The behavior of EVA and SBS PMBs had exhibited quite difference at 50°C. Moreover, it was found out that at low polymer contents, the samples revealed the existence of dispersed polymer particles in a continuous bitumen phase, whereas at high polymer contents a continuous polymer phase has been observed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Attenuated Total Reflection (ATR) Fourier Transform Infrared (FT-IR) Spectroscopy of Oxidized Polymer-Modified Bitumens

Oxidative age hardening of bitumen results in increasing fatigue susceptibility of bituminous mixtures, thus reducing the service life of asphalt pavements. Polymer additives to bitumen have been shown to improve its viscoelastic properties and, in some cases, reduce the level of bitumen hardening. Fourier transform infrared (FT-IR) spectroscopy enables evaluation of oxidation levels in bitumen by measuring the concentration of oxygen-containing chemical functionalities. This paper summarizes the results of the investigation of oxidative age hardening of polymer-modified bitumens (PMB) caused by accelerated aging in laboratory conditions. The PMB samples are prepared with different concentrations of styrene-butadiene-based co-polymers. Next, the PMB samples are aged using standard procedures that employ air blowing at 163 °C for 85 min followed by conditioning the samples at 100 °C and 2.1 MPa pressure for 20 to 48 hours. The resultant changes in their chemical composition are evaluated by portable attenuated total reflection (ATR) spectrometer. Measurements of ketone, sulfoxide, and hydroxyl content in PMB samples indicated similar oxidation pathways to those of non-modified bitumens. In addition, no evidence of polymer degradation due to accelerated aging of PMB was found in this study.

Thermal and dynamic mechanical properties of blends of bitumen with metallocene catalyzed polyolefins

A high penetration grade bitumen has been blended with up to 50 wt% of two different grades of metallocene catalyzed linear low density polyethylene (m-LLDPE) in order to investigate the potential of these and similar copolymers as a substitute for styrene butadiene styrene triblock copolymers in polymer-modified bitumens (PMB). A continuous polymer-rich phase was observed at m-LLDPE contents as low as 5–10 wt%, along with a significant decrease in the effective glass transition temperature of the PMBs with increasing polymer concentration, suggesting benefits for low temperature flexibility. The m-LLDPE-based PMBs also showed relatively low dynamic shear viscosities up to high polymer contents in the range of temperature and shear rate corresponding to typical PMB processing conditions. However, the presence of bitumen in the m-LLDPE-rich phase led to a significant reduction in the melting points of the m-LLDPE, and softening of the PMBs at temperatures as low as 40–50 °C, depending on the composition and the melting point of the pure polymer. PMBs based on the m-LLDPE with the higher melting point remained fully elastic in this temperature range, but at the expense of increased crystallinity and a higher glass transition temperature, which limit improvements in low temperature flexibility. On the other hand, the potentially broad composition and property windows associated with m-LLDPEs suggest considerable scope for the fine tuning of PMB properties by using combinations of different m-LLDPEs and/or other polyolefins as a means to optimize performance.

Texture analysis of polymer modified bitumen images

Abstract This study aims to analyze the textural features extracted from microscopic images of elastomeric and plastomeric type polymer modified bitumen (PMB) including five different types and contents of polymers. Fluorescence microscopy was used to capture microscopic images from thin films of PMB samples at different magnification scales (400×, 100×, and 40×). Gabor filters were utilized to extract the textural features of bitumen images. The features were used in three different query tests to quantify their representation capacity. The K nearest neighbor classifier was tested using leave-one-out cross validation. Textural analysis on the captured images provided numerical results that are in compliance with subjective visual tests.

French wheel tracking round robin test on a polymer modified bitumen mixture

In the framework of the RILEM TC 206-ATB TG3, a Round Robin Test (RRT) has been performed in order to evaluate the reproducibility of the French Wheel Tracking Test (FWTT) on a mix made with Polymer Modified Bitumen (PmB). For this mixture, some particular problems had been reported, such as heating of the sample due to friction and sticking of the binder to the wheel. Two procedures, called anti-overheating and anti-sticking procedures, have been proposed by the group in order to improve the reproducibility of the wheel tracking tests. These procedures are assessed. Causes of scattering are discussed. Differences between the tyres used during this RRT as a possible origin of scattering are discussed, as well as temperature peaks and over-compaction of specimens.

The Effect of Nanoclay on Rheological Properties and Storage Stability of SBS-Modified Bitumen

Linear and branched grades of styrene-butadiene-styrene (SBS) triblock copolymer are commonly used for modifying physical, mechanical, and rheological properties of bitumen. Because bitumen and SBS are incompatible, SBS-modified bitumen is not storage stable at elevated temperatures. Incompatibility of branched SBS is greater than linear SBS. To obtain greater compatibility between SBS and bitumen, organophilic montmorillonite/SBS-modified bitumen mixtures, prepared by melt intercalated blending, were used. Results showed that the presence of nanoclay could improve the storage stability, aging, and high-temperature performance of polymer-modified bitumen (PMB) significantly. Of course, this effect can be seen by proper dispersion of organophilic montmorillonite (OMMT) in SBS and obtaining a homogenous blend, which is calleed an exfoliated structure. The structure of OMMT/SBS/bitumen blend was characterized by X-ray diffraction (XRD).

Effect of pre-heating duration and temperature conditioning on the rheological properties of bitumen

It is well known that overheating asphalt bitumen can lead to oxidation and stiffening. While heating bitumen is an essential protocol in sample preparation, it is important to identify the oven setting time and temperature for lab testing. Current AASHTO standards do not specify exact oven settings for bitumen sample preparation prior to laboratory testing. This study is evaluating the effect of oven heating duration and pouring temperature during sample preparation in the rheological properties of neat and polymer-modified bitumen (PMB). Rheological properties are measured using Rotational Viscometer, Dynamic Shear Rheometer and Bending Beam Rheometer at grade-specific testing temperatures. A neat bitumen PG64-22 and two PMB PG70-22 and 76-22 in un-aged (original) and aged conditions were tested at two temperatures: 143°C and 185°C for 1/2, 2 and 4h. The effect of short-term aging by rolling thin film oven was also investigated. To investigate the rheological properties over a wide range of temperatures, temperature sweep testing was conducted from 35°C to 110°C at a 10rad/s frequency. The results suggest that there was no significant difference in the viscosity, complex modulus and creep stiffness for the tested bitumen. The RTFO aging index, absolute drop of complex viscosity and temperature aging indices were used to evaluate the bitumen preparation settings. The study recommends using the 143°C and 2-h heating for proper preparation prior to standard lab testing. The study also investigated the aging influence in rheological properties for neat and PMB using the black diagram, DSR function map, and critical-stiffness temperature.

Effect of Fine Aggregate Physical Properties on the Engineering Properties of Conventional and Polymer-Modified Bituminous Mixtures

Most studies on hot-mix asphalt have used crushed fine aggregate and gravel; research regarding the use of mining sand or marine sand as fine aggregate is limited. This work investigates the effects of fine aggregate physical properties on the engineering properties of hot-mix asphalt. Four types of sand (quarry, river, mining, and marine sand) with two conventional binders (PEN 50/60 and PEN 80/100) and four types of polymer-modified bitumen (PMB) (PM1_82, PM1_76, PM2_82, and PM2_76) were used. Electron microscopy scanning was performed along with sieve analysis and tests for specific gravity and angularity of the fine aggregate on the different types of sand to determine their properties and thereby examine the effects of these properties when the sands were incorporated into a bituminous mixture. Marshall test results showed that fine aggregate physical properties influenced the optimum bitumen contents and engineering properties. The study also revealed that angular and rougher particles of fine aggregate produced lower voids in mineral aggregate, lower optimum bitumen content, higher shear strength, and higher density, which consequently increased the stability of the resulting mixtures. Moreover, a polymer-modified bituminous mixture enhanced stability and stiffness, reduced density, and slightly increased the voids in mineral aggregate.

Preparation and properties of bitumen modified by EVA graft copolymer

This paper presents a laboratory study of modified bitumen containing ethylene vinyl acetate (EVA) and ethylene vinyl acetate grafted maleic anhydride (EVA-g-MAH) copolymers. When the different polymers were added, the physical properties of modified bitumens, such as softening point, ductility at low temperature and storage stability at high temperature are changed. The polymer modified bitumens (PMBs) were analyzed by thermogravimetry (TG), derivative thermogravimetry (DTG) and fourier transform infrared spectroscopy (FTIR). Thermal characterizations showed that the main decomposition stage refers to samples with modifiers exhibited a slight increase in thermal stability and the sample with the highest stability was EVA-g-MAH PMBs. FTIR analysis suggested that it is difficult to prove the EVA-g-MAH has reacted with the functional group in bitumen by FTIR spectrum. The dynamic shear rheometer (DSR) tests reported that added content of EVA-g-MAH has great effect on the rheological properties of the binder and its high temperature performance was improved while its temperature susceptibility was reduced in compare to EVA modified bitumens binder.

Investigation of complex modulus of base and EVA modified bitumen with Adaptive-Network-Based Fuzzy Inference System

This study aims to model the complex modulus of base and ethylene-vinyl-acetate (EVA) modified bitumen by using Adaptive-Network-Based Fuzzy Inference System (ANFIS). The complex modulus of base and EVA polymer modified bitumen (PMB) samples were determined using dynamic shear rheometer (DSR). PMB samples have been produced by mixing a 50/70 penetration grade base bitumen with EVA copolymer at five different polymer contents. In ANFIS modeling, the bitumen temperature, frequency and EVA content are the parameters for the input layer and the complex modulus is the parameter for the output layer. The hybrid learning algorithm related to the ANFIS has been used in this study. The variants of the algorithm used in the study are two input membership functions and three input membership functions for each of the all inputs. The input membership functions are triangular, gbell, gauss2, and gauss. The results showed that EVA polymer modified bitumens display reduced temperature susceptibility than base bitumens. In the light of analysis the Adaptive-Network-Based Fuzzy Inference System and statistical methods can be used for modeling the complex modulus of bitumen under varying temperature and frequency. The analysis indicated that the training accuracy is improved by decreasing the number of input membership functions and the utilization of the two gauss input membership functions appeared to be most optimal topology. Besides, it is realized that the predicted complex modulus is closely related with the measured (actual) complex modulus.

Utilization of Waste Polymers for Flexible Pavement and Easy Disposal of Waste Polymers

Solid waste management is the thrust area. Of this various waste materials, plastic waste, and municipal solid waste are of great concern. Use of disposed plastics waste is the need of the hour. On the other side, the road traffic is increasing. The traffic intensity is increasing. The load bearing capacities of the road are to be increased. The studies on the improvement of road strength using polymer modified bitumen (PMB) for flexible pavement are being carried out by different schools. Virgin and recycled polymers are being used for these studies. But when higher percentage of plastics waste was used, the polymer got separated from the blend. Hence a new innovative technique was developed by the author and the heated stone aggregate was first coated with plastics generated from wastes like carry bags, films, foams, and multi layers and the plastics waste coated aggregate (PCA) was used as the raw material for flexible pavement. PCA is then mixed with 60/70 or 80/100 bitumen and the mix is used for road construction. PCA + Bitumen mix showed better binding property. It had less wetting property. Its voids were much less. The sample showed higher Marshall Stability value. By this process a road of 1km length and 3.75m width of single lane can consumes 10,00,000 carry bags and the road strength is increased by 100% and there is no pothole formation. The roads laid using PCA + Bitumen mixes are performing well. Performance studies were carried out for plastic road of different ages and reported in this paper.