Rubber Binder Research Articles

Development of an Innovative Bio-Binder Using Asphalt-Rubber Technology

This research work evaluates several parameters that can affect Asphalt Rubber (AR) binder performance and applies the AR technology to the development of an innovative renewable bio-binder that can fully and cost-effectively replace asphaltic bitumen derived from petroleum in flexible pavement construction. The ”Binder Accelerated Separator” method was used to divide the constituents of the Asphalt Rubber and bio-binder (residual binder and swelled rubber). The physical and chemical changes in the Asphalt Rubber and bio-binder and in the residual binders (residual bitumen and residual bio-oil) were evaluated. The results demonstrate that the produced bio-binder is suitable for use in flexible pavements with properties comparable to those of conventional and Asphalt Rubber binders.

Investigating the effectiveness of Vacuum Tower Bottoms for Asphalt Rubber Binder based on performance properties and statistical analysis

Numerous studies reported crumb rubber modifier (CRM) as an environmentally friendly additive that is able to improve asphalt performance and helps reduce environment pollutions. However, addition of CRM leads to the viscosity increase and, consequently, increase in the asphalt mixture production temperature and the greenhouse gas emissions in the atmosphere. The objective of this study is to evaluate the effectiveness of Vacuum Tower Bottoms (VTB) in the laboratory performance of Asphalt Rubber Binder (ARB). In order to study mechanical and rheological properties of ARB containing VTB, rotational viscosity (RV), dynamic shear rheometer (DSR), bending beam rheometer (BBR) and Multiple Stress Creep and Recovery (MSCR) tests were performed. The results of viscosity test showed that adding 50% and 70% of the VTB into ARB decreases viscosity 32% and 45.6% averagely, respectively. Furthermore, the results of PG tests indicated that the VTB decreases HT continuous grade and increases LT continuous grade of ARB. The VTB was also found to be able to enhance the performance at intermediate temperatures, i.e. fatigue resistance of ARB. MSCR test results shows that addition of CRM leads to an increase of rutting resistance and elastic response, however, VTB lead to an increase of Jnr values of ARB. The results of ANOVA showed that, at the confidence level of 95%, the VTB and CRM have significant effect on HT, LT and PG temperature span of ARB. Finally, Tukey test results indicated that there is significant difference between the means of PG temperature spans at both CRM dosages (15 and 20%) while it is not significant for VTB dosages (50 and 70%).

Development of rubberized asphalt binder specification

The use of ground rubber from scrap tires has long been supported by environmental and government agencies to reduce the disposal problem associated with waste tires. In 2008, Louisiana turned to the use of crumb rubber in asphalt mixtures to address a shortage in polymer-modified asphalt binder. As a result, the state developed new specifications for rubberized asphalt binder, which was allowed as a substitute to polymer-modified asphalt binder. This study presents the research activities that led to the development of the Louisiana rubberized specifications. A laboratory experimental program was conducted to evaluate the performance of asphalt mixtures prepared with crumb rubber (CR) modified binder as compared to mixtures prepared with polymer-modified asphalt binder with and without reclaimed asphalt pavement. In addition, the field performance of test sections constructed with CR-modified binder was compared to a test section prepared with polymer-modified conventional mixtures under accelerated loading. Based on the results of the laboratory experimental program, it is concluded that the rutting and intermediate temperature fracture performances of CR-modified asphalt mixture were adequate and comparable to mixtures prepared with polymer-modified asphalt binder. Test results from the accelerated loading facility experiment showed that acceptable performance for asphalt mixtures can be achieved using either polymer-modified or CR-modified asphalt binders.

New eco-friendly low-cost binders for Li-ion anodes

In the production of commercial Li-ion batteries, the active materials slurries are generally prepared using polyvinylidene fluoride (PVdF) as binder because of its good adhesion properties and electrochemical stability. Unfortunately, there are some disadvantages related to the use of PVdF: the most important is the use of toxic and environmentally unfriendly solvents, such as N-methyl-pyrrolidone (NMP), and the second is the high costs. In the light of these considerations, it seemed straightforward to investigate the suitability of some water-soluble, inexpensive, and eco-friendly materials to test as alternative binders (sodium alginate, chitosan tragacanth gum, gelatin). The rheological properties of these materials have been investigated in addition to the electrochemical characterization. Furthermore, graphite electrodes with PVdF, carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) binders have been considered for sake of comparison. We found that some of these water-soluble binders, besides good electrochemical performances, showed a high adhesion to the current collector and a good electrochemical stability under the experimental conditions employed, which makes them interesting for the next generation of Li-ion batteries.

Synthesis and Characterization of Magnetic Elastomer based PEG-Coated Fe3O4 from Natural Iron Sand

Magnetic elastomer nanocomposite based PEG-coated Fe3O4 with silicone rubber binder have been prepared from natural iron-sand by using coprecipitation method. The samples were characterized by using X-ray Diffractometer, X-ray Fluorescence, Fourier Transform Infra-Red, tensile strength test, and Vibrating Sample Magnetometer to analyze the physical and magnetic properties. We observed that all samples were formed by single phase cubic spinel magnetite (Fe3O4) crystalline structure. The atomic bonding analysis by FTIR showed that the C-O-C and C-H ordering were understood as the PEG – Fe3O4 bonding characteristics. We have observed that the Young modulus of elastomer based PEG-coated Fe3O4 slightly decreased compared to the natural iron-sand based elastomer. The magnetic properties of PEG-coated Fe3O4 were known to be magnetically softer with the lowest coercivity without losing its magnetization saturation value. We propose that the PEG-coated Fe3O4 is a promising candidate to be applied as magnetorheological elastomer due to a good mechanical and magnetic characteristic and also promising as microwave absorbing materials.

Effect of various alcohols and reaction time on the properties of hydroxyl terminated natural rubber synthesized via oxidative degradation

The oxidative degradation of deproteinized natural rubber (DPNR) using cobalt bis(acetyl acetonate) in the presence of different alcohols and various reaction time; followed by reduction with sodium borohydride (NaBH4) for the synthesis of hydroxyl terminated liquid natural rubbers (HTNRs) was carried out. The synthesis of HTNRs from natural rubber is particularly important as an alternative to hydroxyl terminated polybutadiene (HTPB); one of the current leading synthetic rubber for the production of rubber binders for composite solid propellants. Four different alcohols (i.e. methanol, ethanol, propanol and hexanol) were investigated in order to achieve degraded DPNR with lowest molecular weight. The structure of the obtained HTNRs were analysed using gel permeation chromatography (GPC) and fourier transform infrared (FTIR). Based on GPC analysis, it was found that the use of ethanol at 1 h reaction time resulted in lowest molecular weight of approximately 6,690 g/mol. Analysis of chain scission of the HTNRs were consistent with the molecular weight attained. FTIR analysis, on the other hand confirmed the presence of hydroxyl functional group in the synthesized HTNRs with the highest amount of hydroxyl group presence in the HTNR prepared using ethanol. Overall, the properties of synthesized HTNRs (molecular weight and functional groups) displays a potential material for the production of propellant binder and are comparable to the properties of commercially available HTPB.

Production and performance of desulfurized rubber asphalt binder

Asphalt rubber binder typically exhibits disadvantages like segregation and high viscosity; however, this can be improved by the incorporation of desulfurized rubber powder. This study examined the swelling principle of desulfurized rubber asphalt (DRA). In addition, it evaluated the performance of DRA fabricated with various rubber powder contents under different shear conditions and development time. Superpave binders tests, including Brookfield viscosity, dynamic shear rheometer (DSR) and bending beam rheometer (BBR) tests, were applied on three control binders (i.e., neat, 20mesh asphalt rubber binder, 40mesh asphalt rubber binder) and a DRA binder. Binder testing results indicated that rubber powder swelled into the base binder and resulted in enhanced stability. Optimum performance of the DRA binder was achieved by adding 20% (by weight) of rubber powder into the base binder at shear rate, shear temperature, shear time and development time of 7000r/min, 170°C, 60min and 45min, respectively. Modified ranges of production conditions were also provided to widen the application of DRA in field construction. It appeared that DRA binder benefited from the recovered plasticity and viscosity of the rubber and consequently, exhibited superior performance over the neat and conventional asphalt rubber binders. Preliminary mixture evaluation was also conducted and the DRA binder was found to significantly improve the mixture resistance to permanent deformation and water damage. Overall, the DAR binder is encouraged to be used as a modified binder for flexible pavements.

Influence of Reclaimed Asphalt Pavement on Performance-Related Properties of Gap-Graded Rubberized Hot-Mix Asphalt

Rubberized hot-mix asphalt (RHMA) has been widely used in construction projects by the California Department of Transportation (Caltrans) for the environmental benefits of its recycled waste tires and for its improved fatigue and reflective cracking resistance. Currently, Caltrans does not permit the use of reclaimed asphalt pavement (RAP) in any gap- or open-graded rubberized asphalt mixes. However, given the cost and environmental benefits of RAP to replace portions of required virgin binder and aggregates in conventional mixes, interest is growing in the addition of some RAP to RHMA mixes as well. This study investigated concerns about this proposed practice. Three phases of laboratory testing (i.e., asphalt binder testing, fine aggregate matrix mix testing, and full-graded mix testing) were conducted to evaluate the effects of the addition of RAP into new RHMA mixes. The results indicated that the gap-graded aggregate structure of RHMA might limit the amount of RAP that could be used in the mix. Only 10% RAP by binder replacement could be achieved for the mix tested in this study, but the other specified volumetric requirements were still met. Replacement of a portion of asphalt rubber binder with age-hardened RAP binder increased the binder stiffness at low and high temperatures, which indicated enhanced rutting performance but diminished low-temperature cracking performance. Test results from full-graded mixes indicated similar trends, with improved rutting performance with the addition of RAP but also with significantly poorer fatigue and reflective cracking resistance.

Non-linear finite element modelling and analysis of the effect of gasket creep-relaxation on circular bolted flange connections

It is well known that gasket creep-relaxation results in a reduction of contact pressure between the surface of a gasket and the face of a flange over an extended period of time. This reduction may result in the subsequent failure of the circular bolted flange connection due to leakage. In this paper a pair of flat and raised face integral flanges, PN 10 DN 50 (in accordance with the European EN 1092-1 standard), with non-asbestos compressed fibre ring gaskets with aramid and a nitrile rubber binder were considered. Finite element modelling and analyses were done, for both the circular bolted flange configurations, during the seating condition. The results of the finite element analyses were experimentally validated. It was found that the number of bolt tightening increments as well as the time between the bolt tightening increments had a significant impact on the effect which gasket creep-relaxation had after the seating condition. An increase in either the number of bolting increments or the time between the bolting increments will reduce the effect which gasket creep-relaxation has once the bolts had been fastened. Based on these results it is possible to develop an optimisation scheme to minimize the effect which gasket creep-relaxation has on the contact pressure between the face of the flange and the gasket, after seating, by either increasing or decreasing the number of bolt tightening increments or the time between the bolt tightening increments.

Effect of Crumb Rubber Modifier on the Performance Properties of Rubberized Binders

AbstractBitumen as a main and efficient material in the behavior of hot mix asphalt (HMA) already has attracted the attention of various researchers. Bitumen modification with polymeric and nonpolymeric materials was considered one of the main research subjects relevant to increasing road life cycles. Crumb rubber is one of the appropriate bitumen modifiers due to its desired properties, and it also helps to reduce environmental pollution. In the current research, two types of mesh, crumb rubber (mesh of Nos. 14 and 50), with three different percentages (10, 15, and 20%), have been mixed with three types of bitumen, and the obtained results have been investigated on high-temperature (HT), intermediate-temperature (IT), low-temperature (LT), and viscosity properties. Also, in order to investigate the impact of aging on stated parameters, test results on bitumen samples modified by crumb rubber, before and after aging, have been studied.

Rheological and chemical characteristics of rubberized binders with non-foaming warm mix additives

This study aims to investigate the rheological and chemical characteristics of asphalt rubber (AR) binders modified with four non-foaming warm mix asphalt (WMA) additives: Evotherm-DAT, Sasobit, conventional paraffin wax, and combined Evotherm-DAT and Sasobit. The main findings of this study include that: (1) all selected WMA additives are effective in enhancing AR’s workability; (2) using combined Evotherm-DAT and Sasobit is not a viable option to reduce the construction temperature of AR mixture; (3) paraffin wax is a potential WMA additive for AR; and (4) WMA additives may affect the dissolution status of crumb rubber in base asphalt.

Low temperature performance of laboratory produced asphalt rubber (AR) mixes containing polyoctenamer

The use of the additive polyoctenamer (PO) in asphalt rubber (AR) binders helps to improve their storage stability and to reduce their stickiness and tackiness, while not affecting the low temperature performance of the AR binders and mixes. The objective of this paper was to determine if the use of PO had any impact over the low temperature performance of laboratory mixes produced with AR binders that were also laboratory produced. The low temperature performance of the laboratory produced asphalt rubber (AR) mixes were evaluated by means of the semicircular bend geometry test, utilizing two types of ground tire rubber (ambient and cryogenic) at two different percentages of polyoctenamer (PO). Stiffness, fracture toughness and fracture energy for the mixes were obtained in order to statistically evaluate how the variables influence their low temperature performance. Overall, the laboratory test results indicate that the use of PO at the dosage utilized and the rubber types at the percentage employed will not adversely impact the low temperature performance of AR mixes; furthermore the use of PO can increase the fracture toughness of AR mixes, making the pavements less brittle at lower temperatures.

Effect of Parallel Plate Gap Height on Repeatability in DSR Measurements of Crumb-Rubber Modified Binders

AbstractCurrent Superpave performance grade (PG) grading specification utilizes a dynamic shear rheometer (DSR) at a gap height of 1-mm to determine the high-temperature performance grade of asphalt binders. It has been anticipated that rubber particulates greater than 25% of the gap height may interfere with the measurements, resulting in properties that may not represent the actual crumb rubber binder. Therefore, this study tries to adjust the 1-mm gap height for measuring high-temperature performance properties of crumb rubber binders to minimize the effects of interaction between the asphalt binder and rubber particle on PG grading results. Trial gap heights of 2 and 3 mm were used to test five different crumb rubber modified (CRM) binders. The CRM binders were evaluated using the standard Superpave high-temperature grading test and multiple stress creep and recovery (MSCR) test. Results were analyzed using statistical analysis, and through the comparison with single operator precision statements, whe...

Effect of Rubberized Bitumen Blending Methods on Permanent Deformation of SMA Rubberized Asphalt Mixtures

This study aims at comparing the permanent deformation of Stone Mastic Asphalt (SMA) rubberized asphalt mixtures produced by the wet process. In this study, rubberized binders were prepared using two different blending methods, namely, continuous blend and terminal blend. To study the creep behaviour of control and rubberized asphalt mixtures, the dynamic creep test was performed using Universal Materials Testing Apparatus (UMATTA) at different temperatures and stress levels. Zhou three-stage creep model was utilized to evaluate the deformation characteristics of the mixtures. In all test conditions, the highest resistance to permanent deformation is showed by the rubberized mixtures produced with continuous blend binders. This study also reveals that the permanent deformation of rubberized mixtures cannot be predicted based on the characteristics of the rubberized binders.

Effect of Binder Modification on the Performance of an Ultra-Thin Overlay Pavement Preservation Strategy

The objective of this study was to determine whether asphalt rubber (AR) binders will provide similar or better performance compared with a polymer modified asphalt (PMA) binder when used in a high-performance, ultra-thin lift overlay pavement preservation strategy. Current specifications for these types of overlays normally require the use of a PMA binder, because it has the ability to make these overlays more elastic under traffic loading and is less sensitive to temperature fluctuations. However, several state agencies are looking into the feasibility of incorporating sustainable and environmentally friendly technologies, such as AR binders and warm mix asphalt (WMA) technologies, into their asphalt mixtures, including those used for high-performance, ultra-thin lift overlays. This study examined the effect of binder modification type (AR or PMA) and the influence of the use of WMA in high-performance, ultra-thin lift overlays. In general, the mixtures that were tested provided comparable rutting, moisture damage, and low-temperature cracking performance in the high-performance, ultra-thin lift overlay. However, the use of the AR binders indicated reduced performance compared with the PMA binder in mixture fatigue cracking via the beam fatigue test, and mixture reflective cracking in the overlay tester. The results from the beam fatigue test were not always supported by the fatigue life predictions from the simplified viscoelastic continuum damage model. The only detriment to mixture performance for mixtures incorporating WMA was a reduction in fatigue cracking performance when used with AR binders.

Effect of crumb rubber on viscosity of rubberized asphalt binders containing wax additives

Viscous properties of rubberized asphalt binders containing wax additive were evaluated through the rotational viscometer at 135°C and 120°C. Rubberized binders were produced with three percentages (10%, 15%, and 20% by the weight of binder), and then mixed with two commercial wax additives. Three different periods of 30, 120, and 240min were applied to the rotational viscosity test to evaluate the viscous properties depending on testing time. The viscosity changes by different time periods were drawn in time versus viscosity curve. From the results, it is concluded that (1) the addition of crumb rubber significantly increases the binder viscosity, (2) the wax additives are effective to reduce the binder viscosities at both testing temperatures, (3) all the viscosity values of rubberized binders are observed to increase after certain time, regardless of the addition of wax additives, (4) the higher the rubber contents, the steeper the viscosity change over time, and (5) the rubberized mixes with wax additive are expected to have a better haul management, based on the less viscosity increase over time.

Analysis of bitumen–crumb rubber affinity for the formulation of rubberized dry mixtures

Crumb rubber derived from end-of-life tires is nowadays considered as a valuable component to be employed for the production of high-performance bituminous binders and mixtures. Currently available technologies require such a material to be either pre-mixed with bitumen (“wet” method), with the consequent production of the so-called asphalt rubber binders, or to be added during the mixing of aggregates and bitumen (“dry” method), thereby leading to the preparation of rubberized dry mixtures. Depending upon the case, different interactions take place between bitumen and crumb rubber, resulting in mechanical properties of the final mixture which can increase its performance in the field under the effects of loading and environmental factors. The laboratory investigation presented in this paper focused on the issue of bitumen–crumb rubber affinity with the main purpose of developing a simple laboratory procedure which can be employed to support the formulation of rubberized dry mixtures. Affinity between bitumen and coarse crumb rubber, with particle sizes comprised between 1 and 4 mm, was evaluated by subjecting mortars of known composition to the volumetric expansion test (VET). Measured volumetric behavior was compared to that of reference blends prepared with the same base bitumen and inert silica sand. Obtained results were interpreted by taking into account phenomena which may occur during testing at bitumen-particle interfaces, allowing a quantitative comparison between crumb rubbers of different types. Moreover, an affinity parameter was defined, with the consequent possibility of assessing bitumen–crumb rubber affinity in absolute terms.

The Stress Relaxation Of Modified Bitumens

Abstract The Asphalt pavements in Central and Eastern Europe have to be resistant to high and very low temperatures and climatic changes. Especially emphasize influence of low temperatures seems to be critical parameter. That is why the modified bitumens with low temperature susceptibility and with high resistance to low temperature cracking are searched for. Dynamic Shear Rheometer (DSR) can be used as a quick method that can evaluate the modification system of bituminous binders. The advantage of DSR testing is also related to possibility of comparison of unaged and aged bitumen. The relaxations of shear stress of several asphalt rubber binders (containing 11 %, 13 %, 15 % and 17 % of crumb rubber) and paving bitumen were determined in DSR at the temperature of 0 °C and −10 °C. Relaxation tests were performed in the controlled strain regime. Total shear strain (rotation of upper geometry) was set to 1 % of the sample thickness and stress was applied for 60 s. Relaxation time was set to a period of 15 minutes. The shear stress relaxation behaviour of unaged bitumens and bitumens aged after 75 minutes and 225 minutes in Rolling Thin Film Oven Test (RTFOT) is presented and discussed.

Effect of FT Paraffin Wax Contents on Performance Properties of Crumb Rubber–Modified Asphalt Binders

AbstractThe performance properties of rubberized asphalt binders at high, intermediate, and low temperatures were evaluated as a function of Fischer–Tropsch (FT)–paraffin wax content. The rubberized binders were blended using five different wax content levels (0, 1.5, 2.5, 3.5, and 4.5% by binder weight) to produce warm rubberized binders. They were then artificially aged over the short term and long term through the rolling thin film oven (RTFO) and pressure aging vessel (PAV) procedures. Superpave binder tests were performed with the rotational viscometer, the dynamic shear rheometer (DSR), and the bending beam rheometer (BBR). In general, the results of this study suggested that (1) the viscosity of rubberized binders at 135°C can be reduced by the addition of a wax additive, as expected; (2) the rubberized binders with higher wax content can result in binder performance that meets current Superpave binder requirements, especially for cracking resistance parameters (i.e., G*sinδ and stiffness); and (3)...

Comparison of Concentric Cylinder and Parallel Plate Geometries for Asphalt Binder Testing with a Dynamic Shear Rheometer

In California, 35% of the asphalt concrete placed by the California Department of Transportation must, by law, contain recycled tire rubber. Asphalt rubber binder (produced in what is known as the wet process) is the main binder type used in rubberized hot-mix asphalt in California. The rubber particles vary in size, but 100% must pass the 2.36-mm No. 8 sieve. Because of the presence of these relatively large rubber particles in the binder, the current parallel plate testing system (with either 1- or 2-mm gaps specified in the Superpave® performance grading system) is not appropriate for use to measure the binder properties. These large rubber particles would be more likely to contact the plates, and the resulting measurement could be dominated by the rheology of the rubber particles rather than by the binder. Consequently, a modified dynamic shear rheometer testing geometry, a concentric cylinder, was investigated and compared with traditional parallel plates with a view toward the use of this new geometry for quality control on projects that used asphalt rubber binder. In the first phase of the investigation, summarized in this paper, the two geometries were compared by testing conventional and polymer-modified binders to determine the complex shear modulus (G*) and phase angle (d). The results indicated no statistically significant difference between the two geometries. On the basis of these results, testing has begun of asphalt rubber binders with a range of particle sizes with the use of the two geometries.