Rubber Modified Asphalt Binders Research Articles

Toughness, Tenacity and Maximum Initial Strength of Rubber Modified Asphalt Binders

The toughness and tenacity test method, which was developed in the 1980s, is popular for evaluating a polymer-modified binder. Several states like Nevada require performing this test to evaluate non-modified binder samples, as well as other types of modified binders. In this regard, a toughness and tenacity test was performed on rubber-modified samples produced from virgin binder PG58-28, PG64-16 and AC-20. In order to take the rubber size, type and content into account, two rubber sizes, mesh #20 and #40, two rubber types, ambient and cryogenic, and three rubber contents, 10%, 15%, and 20% were produced and tested. The results then were compared with polymer-modified and terminally blended rubber-modified samples. The results show improvement in the amount of initial maximum strength, and a decline in the magnitude of elongation, toughness and tenacity for the rubber-modified binder, compared to other types of binders.

Toughness, Tenacity and Maximum Initial Strength of Rubber Modified Asphalt Binders

Toughness, Tenacity and Maximum Initial Strength of Rubber Modified Asphalt Binders

Asphalt-rubber interaction and performance evaluation of rubberised asphalt binders containing non-foaming warm-mix additives

Warm mix asphalt (WMA) technology has been increasingly utilised in rubberised asphalt pavements to reduce the production and compaction temperatures and the incidental fumes and odours. This study aims to investigate the high, intermediate and low-temperature performance of crumb rubber modified asphalt binders containing WMA additives. The asphalt-rubber interactions under various mixing combinations of temperature and time were investigated through both microscopic and mechanical methods to obtain the optimum mixing procedure. The effects of WMA additives (wax-based and chemical-based products) on the binder performance were investigated by multiple stress creep and recovery (MSCR) test, linear amplitude sweep (LAS) test and low-temperature frequency sweep test. Results show that rubberised asphalt binders significantly improve the binder performance of base asphalt at different temperature ranges. The effects of WMA additives on binder performance varied with base asphalt and rubberised asphalt binder. In addition, the nonrecoverable compliance difference was found not suitable to characterise the stress sensitivity of rubberised binders and the difference in the nonrecoverable compliance for an incremental change in applied stress was proved to be a more accurate alternative. For the cyclic LAS test, the failure energy was found to have a strong correlation with the predicted fatigue life using simplified viscoelastic continuum damage analysis and therefore can be considered as a simple indicator for binder fatigue performance ranking. Relaxation modulus and rate derived from low-temperature frequency sweep tests produced comparable results for ranking the low-temperature performance of different binders. It is feasible and promising to use a unified DSR test methodology to characterise the binder performance covering the whole service temperature range.

Effect of APAO on the aging properties of waste tire rubber modified asphalt binder

Amorphous poly alpha olefin (APAO) was added into the waste tire rubber (WTR) modified asphalt and its effects on aging properties of WTR modified asphalt were investigated. Thin Film Oven Test (TFOT) and Pressure aging vessel (PAV) test were conducted to simulate the short-term and long-term aging respectively. Conventional properties including penetration, softening point, and viscosity were tested; Dynamic Shear Rheometer (DSR) test were conducted both to evaluate the properties of asphalt. The results showed that higher percentage retained penetration, lower softening point increment, and smaller viscosity aging index were gained after adding APAO to WTR modified asphalt. Closer G∗ and δ curves, smaller G∗ ratios due to the introduction of APAO confirmed the improved aging resistance. Higher G∗/sinδ at high temperature and smaller G∗·sinδ at intermediate temperature indicates WTR and APAO are beneficial to improving resistance to permanent deformation and fatigue cracking. Fourier Transform Infrared Spectroscopy (FTIR) measurements revealed that the double bonds in APAO and WTR were consumed for building a strengthened network in WTR modified asphalt and this may explain the better anti-aging properties of WTR + APAO compound modified asphalt.

Assessment of temperature susceptibility for rubber granulate modified road asphalt binders considering impact of aging

The article presents the results of research on temperature sensitivity of ground rubber modified asphalt binders. The tests were performed for 50/70 penetration grade road bitumen and two kinds of granulated rubber: activated and inactivated. Such parameters of asphalt binders as: penetration, softening point, dynamic shear modulus and phase angle have been determined and on this basis the temperature susceptibility of the reference bitumen and asphalt binders modified by activated and inactivated rubber have been determined. All the tests were carried out for three observation levels: without aging and after aging simulations carried out by RTFOT and PAV methods. The tests revealed that addition of granulated rubber has a positive influence on asphalt binder properties, even after the aging process, causing an increase in the softening point and a decrease in penetration and the phase angle of asphalt binder. Asphalt binders obtained in result of modification by addition of rubber show smaller temperature susceptibility than the reference bitumen (without addition of rubber). Also, a positive impact of aging on the temperature susceptibility was observed for the investigated binders.

Dynamic mechanical analysis of crumb rubber modified asphalt binder containing warm mix additives

Crumb rubber modified (CRM) binder has high working temperatures, which may be reduced with addition of warm mix additives (WMA). The dynamic mechanical analysis of CRM binder containing three different WMA additives, namely Fischer–Tropsch wax-based (FT), water-based (WB) and chemical surfactant-based (CS) additive, was undertaken in the present study. The CRM binder was blended with different percentages (by weight of asphalt binder) of WMA additives, i.e. FT (1, 2 and 3%), WB (4, 6 and 8%) and CS (1, 2 and 3%). The viscosity, rutting and fatigue performance of CRM binder with and without WMA additives were evaluated using Brookfield viscosity, multiple stress creep recovery and linear amplitude sweep tests, respectively. The FT modification effectively reduced the viscosity of CRM binder, while the inclusion of CS showed similar viscosity and WB increased the viscosity of CRM binder. The WB modification observed to create foaming effect in asphalt binder. The FT- and WB-modified CRM showed same High Superpave performance grade (PG), however, the addition of CS degraded high PG of CRM binder (from PG88 to PG82). The CRM binder showed reduced Jnr value and improved R-value after FT and WB modification, indicating improved rutting resistance. Whereas, CS-modified CRM indicating poor rutting performance (high Jnr and low R). Asphalt binder combinations showed significantly different rutting performance parameters (Jnr and R-value), whereas they were graded as E. Therefore grading of asphalt binders based on AASHTO MP 19 should be relooked. All WMAs improved the Nf i.e. fatigue resistance of CRM binder. The 2% FT dosage observed to be optimum for CRM binder. The study showed that selection of WMA additives should not only be based on viscosity criterion but also rheological performance parameters are to be looked into for making appropriate conclusions about their effectiveness.

Small and large strain rheological characterizations of polymer- and crumb rubber-modified asphalt binders

Nowadays, polymers and crumb rubber (CR) are extensively used modifiers in bituminous pavements. The objective of this paper is for characterizing the response of polymer- and CR-modified asphalt binders under small and large deformations to fully understand the behavior of such blends under various possible conditions. Under small strains, the complex modulus was measured and analyzed; while the large amplitude oscillatory shear (LAOS) test was carried out to characterize the non-linear behavior at strains beyond the linear viscoelastic region (LVER) of these materials. Styrene-butadiene-styrene (SBS) and ethylene vinyl acetate (EVA) as elastomeric and plastomeric polymers, respectively, and CR, at different concentrations were used to prepare the modified asphalt binders. For the large strain analysis, the waveforms for each material were collected for strain amplitudes of 0.5%, 10%, 20%, 30%, and 40% at 30°C and 1Hz. The small strain rheology was applied to discuss the linear properties, while the viscoelastic non-linearities of the studied asphalt binders were analyzed as a function of strain through the use of Lissajous-Bowditch plots and elastic and viscous non-linearities of an oscillatory shear cycle. The rheological measurements at small strain showed distinctive properties can be attained by the addition of polymers over CR, especially the EVA-modified binder. The analysis of Lissajous-Bowditch plots showed that higher deformations can dramatically change the behavior of the binder and it is worth be studied in conjunction with the small strain properties to capture the overall performance. Moreover, the polymer-modified binder showed higher ability to resist high strains and exhibited strong strain stiffening compared to the CR-modified binders. A continuous shear thinning was registered for the polymer- and CR-modified binders with the increase in strain amplitude.

Identification of the microstructural components of crumb rubber modified asphalt binder (CRMA) and the feasibility of using environmental scanning electron microscopy (ESEM) coupled with energy dispersive X-Ray spectroscopy (EDX)

Identification of the microstructural components of crumb rubber modified asphalt binder (CRMA) and the feasibility of using environmental scanning electron microscopy (ESEM) coupled with energy dispersive X-Ray spectroscopy (EDX)

Conceptualization of permanent deformation characteristics of rubber modified asphalt binders: Energy-based algorithm and rheological modeling

The objective of this study was to conceptualize and develop energy-based algorithm to characterize the comprehensive rheological behaviour of different asphalt binders with and without rubber modification. The scope included advanced asphalt binder characterization and analyses using viscoelastic parametric relationships. A total of thirteen different asphalt binders covering over 5000 data points were utilized, including: three virgin binders, one industrially available crumb rubber modified (CRM), and nine laboratory prepared CRM binders with varying dosages. Dissipated energy parameter tanδ was estimated, which helped in assessing the rutting resistance of asphalt binders. CRM binders produced flatter tanδ master curves and with lower magnitudes compared to the virgin binders indicative of higher rutting resistance with reduced energy dissipation-temperature susceptibility. Further, Weibull distribution function modeling on Multiple Stress Creep and Recovery (MSCR) test data quantified the contributions of various viscoelastic components of the asphalt binders. Rheological modeling and dissipated energy methodologies conceptualized as part of the study indicated that rubber inclusions in asphalt binder would aid in the improvement of the materials’ rutting resistance. Overall, it is envisaged that the algorithm developed in this research pertinent to asphalt binders’ advanced rheological characterization would further the state-of-the-art in designing rut-resistant asphalts.

Laboratory Investigation of Crumb Rubber Modified Asphalt Binder and Mixtures with Warm-Mix Additives

This study evaluated the effects of warm mix asphalt (WMA) additives on the compaction temperature and properties of crumb rubber modified (CRM) asphalt binder and mixture. Two different WMA additives (named as Sas and Evm) were used to prepare warm-mix CRM asphalt binder and mixture. The viscosity of different warm-mix CRM asphalt binders and mastics was measured at different temperatures. The rheological and mechanical properties of different warm-mix CRM asphalt binders were tested. At the mixture level, the volumetric properties of different warm-mix CRM asphalt mixtures were experimented by Gyratory compactor at different temperatures and the performance of different warm-mix CRM asphalt mixtures were evaluated. It was found that both of the two WMA additives could lower the compaction temperatures of CRM asphalt mixtures by 10–20 °C. However, they have different influences on rheological properties of CRM binder and performance of CRM mixture. The Sas warm-mix additive can improve the anti-rutting performance of CRM mixture but may degrade its low-temperature performance and moisture stability. The Evm warm-mix additive has no adverse effects on the high-temperature and low-temperature performance of CRM asphalt mixtures and can improve its moisture stability.

High temperature rheological properties of crumb rubber modified asphalt binders with various modifiers

This study aimed to analyze the rheological properties of the modified asphalt binders based on the effects of base binder type and other five polymers or acid combined with 7% dosage ground tire rubber (GTR) at the high temperature. The test results included viscosity, fail temperature, G∗/sinδ, phase angle, viscometry, amplitude sweep, frequency sweep, creep and creep recovery, and stress relaxation in this study. The results indicated that two of alternative polymers modified binders had noticeably lower viscosity values compared to SBS modified binders. Additionally, the addition of polyphosphoric acid could remarkably decrease the polymer dosage to produce PG76 binder. Meanwhile, asphalt source played a key role in determining the characteristics of all modified binders. The terminally and laboratory blended binders generally had approaching rheological properties in this study.

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)...

Investigation of the effect of rubber on rheological properties of asphalt binders using superpave DSR

The main objective of this study was to investigate the effect of the rubber additive on the rheological properties of asphalt binders including Superpave rutting parameter, fatigue parameter, storage modulus at six rubber percentages: 0.0, 2.5, 5.0, 7.25, 10, and 15%. The Superpave Dynamic Shear Rheometer (DSR) was used to measure the complex shear modules value and the phase angle for the fresh asphalt binder and the rubber-modified asphalt binders using DSR strain-controlled tests. The DSR tests were conducted at one loading frequency of 10 rad/sec (1.59 Hz) and five temperatures: 58, 64, 70, 76, and 82°C. A 12 percent constant strain was applied in these tests according to the Superpave specifications. The rubber additive improved the complex shear modulus value of asphalt binder at all temperatures. Findings of the study showed that the rubber additive resulted in an increase in each of: the complex shear modulus value, the rutting parameter, the fatigue parameter, and the storage modulus (|G*|, |G*|/sin δ, |G*|sin d, and |G*|cos δ, respectively) of the asphalt binder. In conclusion, the rubber additive improved the rutting resistance as well as the fatigue resistance of the asphalt binder by increasing the complex shear modulus value and the storage modulus, and decreasing the phase angle.

The Effects of Classifying CRM Sources on the Asphalt Cement Modification for Paving Roads

The improvement of Basrah asphalt cement that used in hot mix pavement can be achieved by using four influencing variables, which are the value of temperature needed for mixing, time of mixing, the amount of wasted car tire rubber (WCR) and the amount of wasted truck tire rubber (WTR). The main virtue of this study is to know the affecting of classifying the CRM sources, and how that will enhance the properties of tire rubber modified asphalt binder. The improvement is estimated through using the ranges (150-180 oC) of temperature, (20-60) minute of mixing time, (10-20) gm of WCR and (0-4) gm of WTR. The using of two different types of waste tires had shown clearly the affecting on the results of responses studied. The effect of independent variables was studied by using Box-Wilson technique of experimental design. Moreover, the regression coefficients for responses models equation and the optimum conditions were estimated by using STATISTICA software. The results had shown that the optimum values of the independent variables to submit the best responses of penetration test and softening point test was at temperature (180oC), mixing time (60 minute), WCR (20 gm), and WTR (4gm) and then found new mathematical models to estimate these responses at any values of independent variables. The Marshall stability result of the modified asphalt mixes was higher than of the unmodified asphalt mixes.

Laboratory Investigation of Different Standards of Phase Separation in Crumb Rubber Modified Asphalt Binders

AbstractThe phase separation between polymer additives and virgin asphalt binders during hot storage is an important issue in the asphalt industry. Traditionally, it has been customary to evaluate the degree of phase separations in polymerized asphalts by laboratory testing, such as the cigar tube test (CTB). However, the test circumstances, temperature, and storage time vary depending on different standards used in many countries. Based on a comprehensive literature review, the range of temperatures and oven storage times were selected to be 140–180°C and 2–7 days, respectively. The phase separation of 11 storage stability conditions selected from 12 different places using crumb rubber modified asphalts (CRMAs) were compared and evaluated in this study. The CRMAs produced in the laboratory were made with PG 64-22 virgin binder and ambient crumb rubber with various concentrations (10, 15, and 20% by weight of virgin binder). The CTB was used as the storage stability test method, and percent separation was...

Implementing viscoelastic rheological methods to evaluate low temperature performance of modified asphalt binders

In this research, the effects of four modifiers including crumb rubber, gilsonite, styrene–butadiene–styrene (SBS) and polyphosphoric acid (PPA) on the mechanical and rheological properties of asphalt binder at low service temperature are investigated. The main objective of this paper is to rank modifiers due to their effect on low service performance characteristics of asphalt binder for all type and extent of observed modified asphalt binders. For this purpose, the bending beam rheometer (BBR) test is performed on different extent of modifiers at five temperatures: −6°C, −12°C, −18°C, −24°C and −30°C. Asphalt binder is categorized as a viscoelastic material. Among several linear viscoelastic models, the Burgers model is selected for describing the mechanical behavior of modified asphalt binders. Four Burgers parameters are calculated by means of the principle of multiple non-linear regression and then these parameters are used for comparing the performance of asphalt binders by these three approaches: SuperPAVE Performance Grading (PG) protocol, dissipated energy ratio and derivation of creep compliance. Utilizing these three approaches, modified asphalt binders are ranked based on higher quantity of low temperature, dissipated energy ratio and derivation of creep compliance for all type and extent of modifiers alongside. Results show that each approach produces a particular grading which is not same as another one. In spite of variation of rankings, among the all evaluated modified asphalt binders, crumb rubber modified asphalt binder totally shows superior performance on low service temperature in all three methods.

Dynamic mechanical characterization of asphalt concrete mixes with modified asphalt binders

The primary objective of this work is to characterize and compare the dynamic mechanical behavior of asphalt concrete mixes with styrene butadiene styrene (SBS) polymer and crumb rubber modified asphalt binders with the behavior of mixes with unmodified viscosity grade asphalt binders. Asphalt binders are characterized for their physical and rheological properties. Simple performance tests like dynamic modulus, dynamic and static creep tests are carried out at varying temperatures and time. Dynamic modulus master curves constructed using numerical optimization technique is used to explain the time and temperature dependency of modified and unmodified asphalt binder mixes. Creep parameters estimated through regression analysis explained the permanent deformation characteristics of asphalt concrete mixes. From the dynamic mechanical characterization studies, it is found that asphalt concrete mixes with SBS polymer modified asphalt binder showed significantly higher values of dynamic modulus and reduced rate of deformation at higher temperatures when compared to asphalt concrete mixes with crumb rubber and unmodified asphalt binders. From the concept of energy dissipation, it is found that SBS polymer modification substantially reduces the energy loss at higher temperatures. Multi-factorial analysis of variance carried out using generalized liner model showed that temperature, frequency and asphalt binder type significant influences the mechanical response of asphalt concrete mixes. The mechanical response of SBS polymer modified asphalt binders are significantly correlated with the rutting resistance of asphalt concrete mixes.

Effect of blending time and crumb rubber content on properties of crumb rubber modified asphalt binder

The increasing use of crumb rubber modifier in flexible pavements justifies the necessity for a better understanding of its physical and rheological properties as well as its elasticity behaviour. Basically the performance and properties of rubberised asphalt binder are influenced by the blending conditions and crumb rubber content. In this study, the laboratory investigation was conducted on crumb rubber modified asphalt binder properties as a function of two blending times (30 minutes and 60 minutes) and five crumb rubber contents (4, 8, 12, 16 and 20% by weight of asphalt binder) at mixing temperature of 180˚C. Statistical analysis using two-way ANOVA was conducted on the results to evaluate the significance of rubber contents and blending times. The rubberised asphalt binder was evaluated in terms of binder elasticity and rutting resistance at high temperature. The results indicate that the crumb rubber content had a significant effect on G*/ sin (�) at 76˚C. The higher crumb rubber content appears to dramatically increase the elastic recovery and ductility. Statistical analysis showed significant effect of crumb rubber content in influencing the ductility, elastic recovery and G*/ sin (�) values. Whereas the blending time do not appears to significantly affect the ductility, elastic recovery and rutting factor (G*/ sin (�)) of the CRM asphalt binder. The asphalt binder with higher crumb rubber content and longer blending time of 60 minutes exhibited a higher value of elastic recovery. This indicates that crumb rubber modified asphalt binder has better resistance to rutting as compared to conventional asphalt binder.

Rheology investigation of crumb rubber modified asphalt binders

The incorporation of crumb rubber into asphalt pavement mixes is designed to enhance binder properties through reducing the binder’s inherent temperature susceptibility. During the interaction process, crumb rubber particles swell after absorbing a portion of the oils in the binder, resulting in the increase of binder viscosity. In this study, the Crumb Rubber Modified (CRM) asphalt binders were produced using virgin binder of Performance Grade (PG) 64-22 and ambient rubber with various concentrations (10%, 15%, and 20% by weight of virgin binder) in the laboratory. Rheological analyses (flow behavior, elasticity, loading dependence, and temperature dependence) of the control virgin binder and the CRM binders were conducted using a Bohlin Dynamic Shear Rheometer (DSR) II. The results indicated that (1) the use of crumb rubber as a modifier seemed to improve the penetration resistance of the asphalt binder because of the increased viscosity at 60oC, (2) its advantage was more apparent at lower frequencies of loading, and (3) the asphalt binder with higher crumb rubber contents was observed to have better resistance to permanent deformation at higher temperatures and elasticity at lower temperatures.

Advanced Rheological Characterization of Non-Reversible Deformation and Fatigue Behavior in Crumb Rubber Modified Asphalt Binders

ABSTRACT Starting from the assumption that the characterization of damage behavior associates specific mechanical properties to the materials' resistance in condition of incipient failure, this paper deals with the use of different rheometrical approaches to assess the resistance to fatigue and non-reversible deformation in crumb rubber modified (CRM) asphalt binders. Damage-related properties of CRM binders at high service temperatures were studied by analyzing the mechanical response and the viscous deformation mechanism in conditions of repetitive and static creep loading. Results shown that the accumulation of non-reversible deformations and the distribution of delayed elastic and viscous components in binders delayed mechanical response strongly depend on the presence of the rubber particles. At the intermediate service temperature, the development of the complex modulus (G*) in cyclic shear tests (time sweeps) was recorded under different loading conditions and the binders fatigue resistance was evaluated according to the available failure criteria. Using both stress-controlled and strain-controlled testing mode, the relations between the stress/strain amplitude and the number of cycle to failure (S-N curves) were established. Results allowed to define some dynamics related to the contribute of the crumb rubber modification in binder damage resistance with regard to the considered loading conditions.