Neat Bitumen Research Articles

Bitumen expanding using bio-oil product of rose pulp’s pyrolysis process

Within the study, the usability of rose pulp, which is the common waste of many industrial products produced by using rose, was examined as bitumen modification material. In order to investigate this possibility and potential benefits, waste rose pulp was subjected to the pyrolysis process to obtain the biochar, bio-oil and biogas. Since it has a viscous liquid form, the bio-oil product has been selected to modify the bitumen for this study. Supplied wet rose pulp was first dried until the water content decreases to around 10%. Afterwards, the dried rose pulp subjected to pyrolysis process for one hour at 450 °C after 30 min heating period. Used neat bitumen’s grade was PG 64–22. Bio-oil product has been mixed 2 and 4% by weight into the bitumen at 160 °C for 30 min. After the modification process, bitumen performance tests have been done. Because of the analysis, it was concluded that modification did not change the bitumen grade, reduced the mixing and compaction temperature up to 8⁰C and so saving energy. In addition, the modification increases the optimum bitumen ratio up to 5%, strength value up to 4.1%, tensile strength ratio (TSR) value up to 2.3%, and the wheel tracking depth up to 95.2% but still remains within the Hamburg wheel tracking test specification limits.

Effect of laboratory aging on chemistry and rheology of crumb rubber modified bitumen

Aging during construction and in-service substantially changes the chemical composition and physical properties of bitumen thereof influences the performance of asphalt pavements. The modification of bitumen by crumb rubber modifier (CRM) significantly increases the complexity of the aging mechanism and is expected to improve the aging resistance of bitumen. This study aims to investigate the effects of laboratory short-term and long-term aging on the chemistry and rheology of crumb rubber modified bitumen (CRMB). Neat bitumen and CRMB with four different CRM contents were studied. Fourier transform infrared spectroscopy and dynamic shear rheometer were employed to measure the change in the chemical composition and rheological properties of binders at different aging states. Bitumen hardening, which was rheologically revealed by the frequency sweep and multiple creep recovery test results, was also reflected in the growth of carbonyl and sulfoxide functional groups. In addition, the aliphaticity and aromaticity indices of binders before and after aging were also investigated. CRMB binders showed improved aging resistance compared to neat bitumen as reflected by the decreased carbonyl and sulfoxide indices as well as the lower change in rheological parameters. Higher resistance against aging was achieved when increasing the CRM content. The results also highlight the correlation between chemistry and rheology of bitumen. Among six selected mechanical parameters of binder, the non-recoverable creep compliance and percent recovery show better correlations with the combined chemical aging index (sum of carbonyl and sulfoxide indices) than the parameters derived from the linear viscoelastic region.

Are we correctly measuring the rotational viscosity of heterogeneous bituminous binders?

Modified bituminous binders allow asphalt technologists to design asphalt mixtures with superior performance. However, several recent studies highlighted that due to the complexity of these material, their characterisation can be challenging since common procedures used to characterise neat bitumen might not be adequate. For instance, during high temperature rotational viscosity testing of recycled tyre rubber modified binders (RTR-MB), a number of changes may occur to the sample leading to the here-defined sample stability which in turn provides misleading results. In this study the authors want to first provide a deeper understanding of this phenomenon by a numerical analysis using a bespoke Computational Fluid Dynamics (CFD) model to simulate the laboratory tests and use innovative visual aids to monitor the sample stability of heterogeneous bituminous binders during the rotational test. The numerical analysis was complemented by a laboratory campaign aiming at proving the occurring of sample stability during viscosity measurement of heterogeneous bituminous binders with a standard testing setup (SC-27). Furthermore, a dual helical ribbon (DHR) is here introduced as a solution to overcome the issue. Hence, laboratory tests were undertaken also with DHR and differences in viscosity measurements of neat bitumen, SBS-MB and RTR-MB were recorded. Results of this combined numerical and empirical approach proved that the standard setup for rotational viscosity measurements seems not be adequate for RTR-MB and depending on the level of modification and test temperatures, might not be best suited for SBS-MB either. The DHR seems to solve the issue and authors strongly recommend the adoption of this testing geometry to obtain more realistic high-temperature viscosity measurement of heterogeneous bituminous binders.

Micromechanical modelling of complex shear modulus of crumb rubber modified bitumen

Crumb rubber modified bitumen (CRMB) can be considered as a binary composite system where rubber particles are embedded in the bitumen matrix. The bitumen-rubber interaction process (mainly swelling) significantly changes the mechanical properties of both bitumen and rubber phases. This study aims to predict the complex moduli of CRMB binders with more representative constituent parameters using micromechanical models. To achieve this goal, frequency sweep tests using a dynamic shear rheometer were performed on the liquid phase of CRMB and swollen rubber samples to represent the essential properties of bitumen matrix and rubber inclusion. In addition, the numerical swelling model was developed to estimate the effective volume concentration of rubber after swelling. Results show that the liquid phases of CRMB are stiffer and more elastic than the neat bitumen while the swollen rubber is softer and more viscous than the dry rubber. The effective volume concentration of rubber can increase to 2.126 times as the blend percentage based on the finite element analysis. Using the liquid phase of CRMB binder and swollen rubber properties as the micromechanical model inputs yield more accurate predictions. The used four micromechanical models predict well at higher frequencies while underestimating the complex modulus at lower frequencies.

Rheological Properties Comparing Hot and Cold Bituminous Mastics Containing Jet Grouting Waste

The use of reclaimed asphalt pavement is a practice that is adding significant environmental value to road technologies, not only due to the reduction of materials sent to landfill but also because of the mechanical properties of the reclaimed asphalt (RA) that can be reused. This research focuses on the rheological properties of hot and cold bituminous mastics made up as follows: (1) hot mastics mixed with limestone filler (LF) and bitumen, (2) hot mastics, made from bitumen mixed with jet grouting waste (JW), a mixture of water, cement, and soil derived from land consolidation work in underground tunnels, and (3) hot mastics mixed with LF and JW as filler and bitumen. Three different ratios (0.3, 0.4, and 0.5) of filler per unit of neat bitumen (B50/70) were studied. The same number was used for mixing cold mastics, by using an appropriate laboratory protocol designed since the adoption of a cationic bituminous emulsion. A total of 18 mastics were prepared and investigated. The comparison was carried out using the frequency sweep (FS) test, analysing shear modulus G∗, applying the multistress creep and recovery (MSCR) test (40°C and 60°C) as well as the delta ring and ball (ΔR&B) test, focusing on two main issues: (1) the stiffening effect caused by the filler type used for mixing each mastic, and (2) a comparison, in terms of stiffening effects and nonrecoverable creep compliance (Jnr) of hot and cold mastic performance to highlight JW reuse in mastics. The results showed that the best G∗ performance at test temperatures higher than 30°C is given by cold mastic after 28 days of curing time when JW is added to LF and bitumen. The lowest Jnr value was 40°C and 60°C for the same mastic.

Durable poroelastic wearing course SEPOR with highly modified bitumen

International development of poroelastic pavements is still in the experimental stage. Insufficient durability is one of the most important issues to be solved. Currently, poroelastic road surface is typically composed of crushed stone aggregate, rubber (about 20% by weight) and polyurethane binder. Highly modified asphalt binders (HiMA), a relatively new product on the market, differ significantly in terms of mechanical properties when compared to neat bitumen, typical modified asphalt binders and even polyurethane binders. This paper presents first results obtained during initial stage of SEPOR research programme, which aim is to develop durable poroelastic wearing course based on selected bitumen binders and mixture compositions. Observations of the first short road sections constructed with different compositions of poroelastic SEPOR mixtures yielded promising results.

Fatigue performance of long-term aged crumb rubber modified bitumen containing warm-mix additives

Recently warm mix asphalt (WMA) technologies have been introduced to rubberized asphalt mixtures to decrease the required construction temperatures and to alleviate the hazardous gas emissions. Rubberized asphalt pavements combining with WMA have the potential to improve the long-term pavement performance. This study aims to investigate the fatigue performance of crumb rubber modified bitumen (CRMB) containing warm-mix additives using different characterization methods. The effects of crumb rubber modifier (CRM) content (5%, 10%, 15% and 22% by weight of base bitumen) and warm-mix additives on the binder fatigue performance were investigated. Various laboratory tests, including frequency sweep tests, time sweep (TS) tests and linear amplitude sweep (LAS) tests, were conducted on the long-term aged binders to obtain indicators of fatigue performance. Results show that there is a good correlation between the measured fatigue life determined by TS tests using the dissipated energy concept and the predicted fatigue life determined by LAS tests using the simplified viscoelastic continuum damage (S-VECD) theory. However, the traditional Superpave fatigue parameter and the G-R parameter cannot characterize accurate enough the fatigue performance of modified binders. CRMB binders exhibit superior fatigue performance compared to the neat bitumen. The effects of warm-mix additives on the fatigue performance are different for neat bitumen compared to CRMB binder. Based on the findings in this study, rubberized asphalt mixture combining with WMA additives is expected to have a promising long-term fatigue performance.

Effects of the addition of date palm fibers on the physical, rheological and thermal properties of bitumen

This paper investigated the contribution of plant fibers recovered from date palm waste to modify bitumen properties. Palm fibers were characterized to determine their chemical composition, structure, mass loss by heating and tensile strength and the properties of the bitumen-fiber mixtures were evaluated before and after aging using consistency (penetration, Ring and Ball softening point), rheological and thermal tests. The experiments were completed with binder drainage tests on asphalt mixtures to assess the ability for palm fibers to retain bitumen.The results pointed out that the addition of until 6 wt% fibers to neat bitumen conferred a slightly greater consistency, an increase in viscosity by 50% and complex modulus norm by 40% at service life temperatures, before and after aging. These last trends allow to predict the behavior of the asphalt mixtures towards permanent deformations. Thermal analysis on the different mixtures showed that the addition of fibers induced the increase in bitumen crystallinity. The existence of a semi-crystalline fiber network in the bitumen matrix improves the physico-mechanical characteristics of bitumen. The binder drainage tests performed on asphalt mixtures highlighted bitumen absorption by the fibers; this could be correlated to their microstructure and roughness. The results found in this study are encouraging for a potential use of date palm fibers at asphalt mixture scale.

Chemical and Rheological Evaluation of Aged Lignin-Modified Bitumen.

As bitumen oxidizes, material stiffening and embrittlement occur, and bitumen eventually cracks. The use of anti-oxidants, such as lignin, could be used to delay oxidative aging and to extend the lifetime of asphalt pavements. In this study, the chemical and rheological effect of lignin on bitumen was evaluated by using a single dosage organsolv lignin (10 wt.% dosage). A pressure aging vessel (PAV) was used to simulate the long-term aging process after performing the standard short-term aging procedure, and the lignin-modified bituminous binders were characterized by an environmental scanning electron microscope (ESEM), Fourier-transform infrared (FTIR) spectroscopy, and a dynamic shear rheometer (DSR). From the ESEM results, the uniform microstructure was observed, indicating that the addition of lignin did not affect the worm structure of bitumen. Based on the FTIR test results, lignin-modified bitumen showed that a lower number of carbonyl and sulfoxide compounds were generated after aging than for neat bitumen. Based on the linear amplitude sweep (LAS) results, the addition of lignin slightly reduced the fatigue life of bitumen. From the frequency sweep results, it showed that lignin in bitumen acts as a modifier since the physical interaction between lignin and bitumen predominantly affects the material rheology. Overall, lignin could be a promising anti-oxidant due to its economic and environmental benefits.

Determination of Construction Temperatures of Crumb Rubber Modified Bitumen Mixture Based on CRMB Mastic.

Crumb rubber modified bitumen (CRMB) has been widely used in pavement construction and provides an effective way to recycle waste tires and helps alleviate the “black pollution” problem. There are no current specifications regarding the appropriate mixing and compaction temperatures of the CRMB mixture. There is a direct relationship between the mixing and the compaction temperatures of the CRMB mixture and the viscosity of the CRMB mastic. In this study, we first prepared CRMB using crumb rubber powder and penetration grade 70 neat bitumen, then prepared the CRMB mastic using CRMB and fillers (limestone mineral powder and cement). Finally, we used the CRMB mastic and aggregate to make mixture specimens. The best air void of the specimens was subsequently used to demarcate the viscosity of the CRMB mastic, and the construction temperatures (including the mixing temperature and the compaction temperature) were calculated based on the viscosity of the CRMB mastic from the viscosity–temperature curves. Test results indicated that the best viscosity of the CRMB mastic was 2.7 ± 0.2 Pa·s and 3.9 ± 0.3 Pa·s that corresponded to the mixing and compaction temperatures, respectively.

Investigation of effect of bitumen chemical composition, elastomeric polymer and paraffin wax additives on the properties of bitumen by using response surface method

The effect of bitumen chemical composition, amounts of elastomeric polymer and a kind of warm mix additive on the Dynamic Shear Rheometer, Bending Beam Rheometer, Elastic Recovery and Viscosity responses of the bitumen binders was investigated by using Response Surface Methodology. The individual effects of parameters on response functıons were analyzed. Then the optimization was performed by the simultaneous analysis within the desired limits and optimum values of variables were determined as GI: 0.988, SBS: 3.2% and Wax: 3%. The performance grade of neat bitumen was increased from PG70-22 to PG82-16 by modification at optimum conditions.

Evaluation of Mixing and Compaction Temperatures (MCT) for modified asphalt binders using zero shear viscosity and Cross-Williamson model

The current study was conducted to examine the rheological properties and the performance characteristics of polymer-modified asphalt binders at various temperatures. Different types and concentrations of polymers were used; including Styrene Butadiene Styrene (SBS) with or without a cross linker, Honeywell (HW) and polyphosphoric acid (PPA) which were added based on the total weight of different Performance Grade bitumen contents. Two methodologies (traditional Superpave and zero shear rate viscosity (ZSV)) were used for comparing binder viscosity and mixing and compaction temperatures. Theory of ZSV measurement was used to assess the rheological characteristics of the asphalt binder while a rotational viscometer device was used to measure the relation of viscosity changes with shear rate for neat and modified Iraqi asphalt binders. The Cross Williamson model was used for the simulation of the viscosity–shear rate dependency for each of the studied temperatures. From the results, there were changes in the rheological properties of the bituminous binders after the modification process. The neat bitumen showed improved rheological properties after mixing with the modifiers. It was noticed that increases in the percentage of polymer had no effect on the calculated mixing and compaction temperatures by ZSV; however, an increase of about 8% was observed with the traditional system. Furthermore, the two methods were observed to provide slightly different values for the viscosity when applied over a considerable range of test temperature. For the modified binders, they showed different mixing and compaction temperatures when ranked according to their Superpave grading protocol or their ZSV. The ZSV for mixing temperature was lower by about 42–54 °C compared to the Superpave method.

Transitions of component, physical, rheological and self-healing properties of petroleum bitumen from the loose bituminous mixture after UV irradiation

In the bituminous mixture, the petroleum bituminous film wrapped in the surface of aggregate is very thin, which is obviously different from the neat bitumen. In this research, the most commonly used dense bituminous mixture (AC-13) was designated for the ultraviolet (UV) irradiation simulation test. The loose bituminous mixture was exposed under the UV irradiation for 7, 14 and 28 days respectively, and the UV irradiation intensity was 21.0 w/m2. After aging, the bitumen was recovered with the centrifuge separation method, the SARA components of the recovered bitumen (RB) was studied by the Thin-layer chromatography with flame ionization detection (TLC-FID). Meanwhile, the physical and rheological performance of the RB was investigated by the three major conventional indices and dynamic shearing parameters. In addition, the self-healing performance of bitumen was characterized by complex viscosity frequency-sweep test, capillary test and surface energy test before and after UV irradiation. The results show that with the extension of UV irradiation time, the chemical components of RB change obviously, which results in the deterioration of its colloid stability. Meanwhile, the physical and rheological performance of RB transitioned significantly (the decreases of penetration, ductility and phase angle of RB, and the increase of the softening point and complex modulus), indicates the RB becomes more embrittlement and hardening. Also, the worse flow behavior, the worse capillary fluidity and the lower surface free energy of RB result in the degradation of the self-healing performance of bituminous concrete.

Analysis of Influence of the Dolomite Inactive Mineral Filler Quantity on Properties of Deep Cold Recycled Mixtures with Foamed Bitumen

The subject of research presented in article was an assessment of the impact of inactive mineral filler content, i.e. dolomite dust, on the recycled cold mix properties with foamed bitumen. The analysis of the impact of dolomite mineral dust was made on the basis of the experiment design type 33. It consisted of three levels of foamed bitumen factor in the range from 1.2% to 3.6% with a 1.2% step and the amount of mineral dust factor in range from 5% to 20% with a 7.5% step. Dolomite dust is a waste material derived from aggregate mining. Foamed bitumen was obtained from foaming process of the neat bitumen 50/70 at water temperature of 25ºC and its amount of 2.7%. In order to increase the cohesion of the recycled cold mix with foamed bitumen, Portland cement CEM I 32.5 R in amount of 2.0% was used. The assessment of the impact of quantitative variables was carried out in accordance with the adopted plan of the experiment that assumed the determination of physical and mechanical properties such as: resistance to climatic factors, dynamic modulus (E*) and phase angle. Analysis of the test results shown that factors quantity affects the variability of analysed features. In the entire scope of experiment plan, the obtained free space values met the requirements in required guidelines. The highest sealing of the recycled mixture was observed for the entire dolomite dust dosage but at maximum amount of foamed bitumen amounted to 3.6%. It was also observed that the maximum water resistance (TSR) was obtained for mixtures with a minimum amount of mineral dust (5%) as well as the maximum amount of dust in the recycled cold mix (20%). However, it was depended of the amount of foamed asphalt in a recycled mixture composition. The study also was considered the influence of the amount of dolomite mineral dust on the change in stiffness modulus tested by means of IT-CY and DTC-CY procedure. It was shown that either stiffness modulus measured by IT-CY or DTC-CY are foam bitumen and dust amount dependent. To assess the rheological properties, the direct compression-compression test (DTC-CY) was used. All samples were subjected to a cyclic sinusoidal constant strain with an amplitude of εo <25με. The tests were carried out in the temperature range (-7ºC, 5ºC, 13ºC, 25ºC, 40ºC) and loading time (0.1 Hz, 0.3 Hz, 1 Hz, 3 Hz, 10 Hz, 20 Hz). It was found a significant variability of recycled base stiffness depending on loading time and temperature.

Performance of a sustainable asphalt mix incorporating high RAP content and novel bio-derived binder

The recent drive to find ways to increase sustainability and decrease costs in asphalt paving has led researchers to find innovative ways to incorporate more recycled materials and bio-derived binders into mixes with varying success. A new novel bio-derived binder made from refined pine chemistry stabilised with a polymer can increase the sustainability of asphalt mixes while maintaining pavement performance. Laboratory performance testing was conducted on asphalt mixes containing 50% Reclaimed Asphalt Pavement (RAP) by mix weight and the novel bio-derived binder. Results show that the bio-derived binder outperforms the conventional 50/70 pen grade binder mixes with respect to resistance to thermal cracking and adequately passes all requirements for pavements with 20-year design loadings of less than 30 million ESALs. This research shows that asphalt mixes containing 50% RAP and a bio-derived binder can be designed to pass performance criteria at low, intermediate, and high temperatures without the need of neat bitumen.

Low-Temperature Requirements for Bitumen in Central East European Road Construction

The paper presents the proposition of special assessment of low temperature requirements for bitumens in the region of Central and Eastern Europe where there is a moderate transitional area from sea to the continental type of climate. The results of the research program conducted on the road neat bitumens, Styrene-Butadiene-Styrene polymer and polymer-rubber modified bitumen, and multigrade bitumen types were presented and discussed. Based on the Superior Performing Asphalt Pavements Performance Grade procedure for low temperatures, climatic zones in Poland were developed and compared to analogous zones for other countries from the Central and Eastern Europe region as Estonia and Belarus. The results of functional Performance Grade tests and European standard test of bituminous binders were analysed. It was concluded that some of the bitumens were not meet the performance requirements in the range of low temperatures by Superior Performing Asphalt Pavements Superpave specification and the low-temperature properties of those bitumens should be improved.

Effect of SBS molecular structure on the rheological properties of ternary nanomodified bituminous binders

The work presented in this paper focused on the rheological properties of ternary composites for paving applications constituted by bitumen, nano-sized additives and polymer modifiers. Non-functionalized multiwall carbon nanotubes and two types of styrene-butadienestyrene polymers, linear and radial, were used to modify a reference neat bitumen with the specific goal of highlighting the effects of polymer structure on the final properties of composites. Binary blends containing a single additive were also investigated for comparative purposes. Materials were characterized by means of dynamic mechanical analysis and their internal structure was assessed with fluorescence microscopy observations. Experimental outcomes indicated that polymer architecture played a crucial role in promoting effective interactions between modifiers and carbon nanotubes. Specifically, in the presence of linear styrene-butadienestyrene, carbon nanotubes acted as compatibility activators, leading to the formation of stable and continuous ternary systems. On the contrary, in the case of radial styrene-butadienestyrene, beneficial effects provided by nano-modification were jeopardized by the increased thermodynamic instability which resulted from the combined use of these two components.

Relationship between processing parameters and aging with the rheological behaviour of SBS modified bitumen

The influence of shear rate and mixing time and, simulated long-term aging as a function of frequency and temperature on the rheological behaviour of SBS modified bitumen was evaluated from oscillatory rheology measurements. Complex shear modulus (G*) and phase angle (δ) values were measured and Master curves, Black diagrams and Cole-Cole plots constructed in an attempt to assess the effects of mixing conditions (i.e. short term aging) and long term aging on the rheological characteristics of SBS modified bitumen. Rutting (G*/sin(δ)) parameters were calculated to obtain the performance grade (PG) temperatures of each modified bitumen. It was observed that higher shear rates and longer mixing times promote oxidative aging of the SBS modified samples relative to neat bitumen and have higher activation energies for flow and temperature susceptibility. Additionally, for the same shear rate and mixing time a similar level of compatibility between SBS and bitumen is obtained.

On the Applicability of ATR-FTIR Microscopy to Evaluate the Blending between Neat Bitumen and Bituminous Coating of Reclaimed Asphalt

The utilization of Reclaimed Asphalt (RA) in the road construction sector induces considerable economic and ecological benefits. The blending of the recycled material with new components is believed to be of great importance for the mixture’s properties. An extensive knowledge of the blending of the materials is crucial in optimizing the use of RA, especially at higher recycling rates. In this paper, the applicability of Fourier transform infrared (FTIR) microscopy in attenuated total reflectance (ATR) mode to study the bituminous coating of RA granulates is investigated. This method is a promising alternative to trace heterogeneous areas within the coating compared to methods that require extraction and recovery of bitumen. A method for sample preparation and FTIR spectra analysis is proposed. Four different samples were analyzed: a reference RA granulate, two types of RA granulates mixed with neat bitumen, and a RA granulate with rejuvenator. The results show that the use of ATR-FTIR microscope allows the tracing of different components, indications of blending, as well as proof of rejuvenation of the aged bituminous area.

Evaluating the effect of asphalt binder modification on the low-temperature cracking resistance of hot mix asphalt

This study focused primarily on the effects of various polymer modifications on the low-temperature cracking performance of asphalt binders and resultant mixtures. Two air-blown bitumens were blended with four polymers with or without the addition of polyphosphoric acid (PPA). The low-temperature properties of the neat bitumens and the modified binders were characterized using bending beam rheometer (BBR). The prismatic samples of dense graded asphalt mixtures with the same content of different binders of 4.7% by weight were tested on direct tension at constant strain rate. The low-temperature cracking of the mixtures was also evaluated by tensile stress restrained specimen test (TSRST). The results indicated that the low-temperature parameters were dependent on base bitumen and on polymer modification. For all tested binders, the Superpave criterion E<300MPa appeared to be more restrictive than criterion m>0.30. Polymer modification showed significant benefits as compared to the corresponding base bitumen for direct tensile strength of asphalt mix at low temperatures. Addition of PPA reduced the strength at −30°C while raised at −20°C and −10°C. The BBR limiting binder stiffness temperature was close to the TSRST critical asphalt mix cracking temperature.