SBS Modifier Research Articles

Laboratory evaluation of the composition of nano-clay, nano-lime and SBS modifiers on rutting resistance of asphalt binder

The physical and rheological properties of asphalt mixtures affect pavement performance at high and low ambient temperatures, and thus can affect the final performance of the mixture. Adding modifiers such as polymers and nano additives to improve asphalt mixture performance has become popular in recent years. The purpose of this study is to modify the bitumen with nano-clay, nano-lime and Styrene-Butadiene-Styrene (SBS). PG 64-22 bitumen was modified using 2, 4 and 6 wt% of nano-clay and the results showed that increasing the nano-clay to the base bitumen improved the rheological properties and rutting resistance of asphalt binder. Also, it was examined the effect of adding 3% SBS to the bitumen sample, and the results indicated a positive effect of this additive, especially at lower temperatures. In the next step, bitumen was modified using 4 and 6 wt% of nano-lime and 3% SBS with 4 and 6 wt% of nano-clay in combination with the base bitumen and tested to evaluate the combined effect of these three materials. The effect of this modifier on reducing rutting failure was evaluated compared to the control sample. To this end, we evaluated the effect of these materials on the rheological properties of bitumen by performing multiple stress creep recovery (MSCR) test by Dynamic Shear Rheometer (DSR). Results showed that increasing the nano-clay to the base bitumen improved the rheological properties and rutting resistance of asphalt binder and best improvement is achieved with 6%. The effect of 3% SBS although did not produce results similar to nano-clay, but the results showed significant improvement in bitumen properties. Finally, the best combination in this study was a combination of 3% SBS, 4% nano-clay, and 6% nano-lime, which yielded good results.

Enhancement of permanent deformation resistance of modified asphalt concrete mixtures with nano-high density polyethylene

The present research was carried out to inspect the influence of Nano-High Density Polyethylene (Nano-HDPE) particles and Styrene-Butadiene-Styrene (SBS) on the rheological characteristics of modified asphalt binders and performance of modified asphalt concrete mixtures. In this study, the base asphalt binder of the PG (64-16) grade was modified with Nano-HDPE and SBS polymers at a concentration of 3% and 5% by weight of total asphalt binder content. The Superpave dynamic shear rheometer (DSR), rolling thin film oven (RTFO), rotational viscosity (RV), pressure aging vessel (PAV) and bending beam rheometer (BBR) were conducted to evaluate performance grade of base and modified asphalt binders, also gyratory compactor was used to find optimum asphalt content. Roller compactor and wheel track tests were utilized to assess the rutting performance of modified asphalt mixture with Nano and SBS polymers, and the Indirect Tension Test (IDT) was used to assess the strength of mixtures before and after water conditioning. The results of the study show that Nano-HDPE particles have a considerable influence on improving Performance Grade (PG) of the binder, but at an equal concentration of polymer, it is not as effective as the SBS. However, the HDPE shows a significant advantage in keeping the viscosity of the modified binder at significantly lower levels and thus allowing much lower mixing and compaction temperatures as determined by the equ-viscous standard procedure. Although the PG grades of the binders showed the SBS to be more effective in improving the high-temperature grade than the HDPE, the mixture rutting performance shows that the HDPE modified binders provide better rutting resistance at 3% and 5% than the SBS modified binders. This finding shows that binder testing of G*/sin δ only could give a misleading indication of the true contribution of modified binders to rutting resistance as polymers could improve mixtures in different mechanisms than what is measure with binder PG testing. The IDT testing also shows that the strength of the mixtures produced with the modified binders at 25 °C is superior to the control mixture, with the HDPE providing slightly higher strength values before and after water conditioning. The overall results of the study show that HDPE can be used as a viable modifier requiring lower mixing and compaction temperature and equal or significantly better rutting and strength performance than conventional SBS Modifier. The study also highlights the need to check mixture performance when using specialty modifiers and not depend on only DSR testing as specified in the Superpave PG grading.

Improving the Aging Effect of Bitumen and SBS Modified Bitumen by Using Newly Prepared Antioxidants

Thermal oxidative aging of bitumen has a bad effect on the durability of bitumen binder. We aim in this research to reduce the thermal oxidative aging of bitumen by preparing two compounds namely (R-OCH3=AO1) and (R-NO2=AO2) and examined as antioxidants. These compounds characterized via the conventional spectral tools of analysis (FTIR and 1H-NMR). They mixed with local bitumen (60/70) at different concentrations ratios (0.25, 0.5 and 1%) then aged via TFOT at 170°C for 5 hours. The effect of them evaluated based on the changes in FTIR, total acid number (TAN) and the physical properties of bitumen before and after the thermal oxidation. The results showed that 0.5, 1% of AO1 antioxidant gave the best results of modification of bitumen. After the samples modified with these two concentration ratios of antioxidant AO1, they mixed with 3% Styrene Butadiene Styrene (SBS) polymer then aged via TFOT at 170˚C for 5 hours. The effect of the antioxidant in reducing the aging of the SBS modified bitumen (SBSMB) was evaluated through the changes in FTIR, TAN and the physical properties of bitumen before and after the thermal oxidation. The results illustrated that the best modification of SBSMB was at 1% (AO1).

Probing the modification mechanism of and customized processing design for SBS-modified asphalts mediated by potentiometric titration

Styrene-butadiene-styrene (SBS)-modified asphalt plays an integral role in asphalt pavements. To facilitate the understanding of the correlations between the physical and chemical properties of asphalt cement and SBS, a method for the direct quantitative determination of the SBS modification mechanism via potentiometric titration is proposed. This method will theoretically guide the processing design of SBS-modified asphalts. Potentiometric titration is applied to investigate the unsaturation of SBS-mixed, SBS-modified, and SBS/sulfur-modified asphalts with different SBS dosages ranging from 0% to 10%. The unsaturation of SBS-mixed asphalt exhibits a good linear increase with an increase in SBS dosage. A noticeable loss of SBS unsaturation occurs in SBS- and SBS/sulfur-modified asphalts after undergoing complete modification. In addition, unsaturation presents an evident inflection point at approximately 5 wt% SBS with an increase in SBS dosage. This finding indicates SBS changing from a dispersed phase to a continuous phase in the modified asphalts. Remarkably, the addition of sulfur can accelerate the emergence of an inflection point. Results corroborate that various types of virgin asphalt exhibit different inflection points. SBS/sulfur-modified asphalt demonstrates stronger chemical cross-linking than SBS-modified asphalt. These findings are further confirmed via fluorescence imaging, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. Potentiometric titration potentially provides a direct quantitative method for probing the modification mechanism of and designing customized processing for SBS-modified asphalts.

Effect of ultraviolet absorber (UV-531) on the properties of SBS-modified asphalt with different block ratios

SBS modified asphalt with different block ratios (40/60, 30/70, 20/80) was prepared using a high-speed shearing apparatus to study the effect of the ultraviolet absorber (UV-531) on its properties. A melt blending method was used to prepare the modified asphalt with three doses of UV-531. The ultraviolet aging of asphalt was simulated in an indoor chamber. Dynamic shear rheological test, bending beam rheological test and force ductility test were used to assess the effects of different doses of UV-531 on high and low temperature performance of asphalt material modified with SBS of different block ratios. The results showed that UV-531 has little effect on the complex shear modulus of SBS-modified asphalt, and has a great influence on the phase angle of SBS-modified asphalt. The structural characteristics of SBS modifier is an important factor affecting the rheological properties at high temperature. UV-531 affects the distribution state of SBS modified medium hard segment (S) and soft segment (B) in asphalt, and has great influence on the low temperature performance of SBS-modified asphalt with different block ratios. The degree of aging and chemical changes in the UV-SBS modified asphalt were studied according to its softening point increment (SPI), complex shear modulus aging index (G*AI), infrared spectrum and scanning electron microscope. These results suggest that the degradation reaction of SBS modifier under UV leads to a significant reduction of polybutadiene segment (B) and cracking of SBS-modified asphalt. UV-531 can effectively reduce the aging of SBS-modified asphalt and prevent the decomposition reaction of SBS modifier in asphalt.

Rapid determination of styrene-butadiene-styrene (SBS) content in modified asphalt based on Fourier transform infrared (FTIR) spectrometer and linear regression analysis

A rapid method predicting SBS content in SBS modified asphalt was proposed. Portable Fourier transform infrared (FTIR) spectrometer was used to obtain infrared spectra of original asphalt, SBS modifier, and SBS modified asphalt. Two test methods and two software programs were applied for processing data in infrared spectra. Absorption peak at the wavenumber of 966 cm−1 was selected as the characteristic peak of the SBS modified asphalt, and absorption peaks at 1377 cm−1 and 813 cm−1 were used as characteristic peaks of original asphalt. Linear regression was conducted to establish the relationship between SBS content and characteristic peaks parameters. Finally, a prediction method was developed and its accuracy, repeatability, and applicability were verified. Results show that potassium bromide pellet method is better for FTIR testing. Characteristic peak height (or area) ratio of SBS and original asphalt linearly changed with SBS content. Peak area ratio has better correlation with SBS content.

Viscoelastic Properties of Asphalt Mixtures with Different Modifiers at Different Temperatures Based on Static Creep Tests

To obtain the viscoelastic parameters of asphalt mixtures and analyze the effect of temperatures and modifiers on viscoelastic properties of asphalt mixtures, the creep compliances of the neat asphalt mixture (AM), compound diatomite and basalt fibers reinforced asphalt mixture (DBFAM), and styrene-butadiene-styrene modified asphalt mixture (SBSAM) were tested and calculated by the static creep tests. And the creep compliances of the three asphalt mixtures at −20 °C, −10 °C, and 0 °C are deducted by the time–temperature equivalence principle (TTEP) and Arrhenius equation. Further, the relaxation modulus of the three asphalt mixtures from −20 °C to 50 °C at 10 °C increments are calculated by the convolution integral and Simpson method. Subsequently, the Burgers model, the generalized Kelvin model, and the generalized Maxwell model are applied to analyze the viscoelastic properties of the three asphalt mixtures at different temperatures. The results show that the generalized Kelvin model and the generalized Maxwell model are superior to the Burgers model in describing the variation of viscoelastic properties of asphalt mixtures with loading time. At low temperatures, asphalt mixtures have excellent properties in resisting permanent deformation and releasing internal stress. Besides, the addition of SBS modifier and compound diatomite and basalt fibers modifier can significantly raise the viscosity η1 and the elastic modulus E1 of the asphalt mixture, respectively.

Study on SBS/rubber composite modified asphalt ultra-thin wear layer

In this paper, the mix ratio of SBS/waste rubber powder composite modified asphalt was designed. The dosage of rubber powder (60 mesh) was determined to be 15%, and SBS modifier (linear) was 2%. Based on the optimum mix ratio of asphalt mixture, the road performance of composite modified asphalt was tested and the composite modified ultra-thin wear layer was designed. The noise reduction characteristics of the overlay structure were studied by using the impedance tube instrument, it is found that the composite modified rubber asphalt ultra-thin overlay structure has advantages in reducing the intermediate-frequency and high-frequency noise.

Fabrication and properties of wide temperature domain pavement seaweed modified bio-bitumen

In this paper, seaweed incorporated modified bio-bitumen was prepared using seaweed oil as a modifier. Preliminary studies demonstrated that 20 wt% seaweed bio-bitumen of the total mass of bitumen accounted as the best ratio. Styrene butadiene styrene (SBS)/seaweed bio-bitumen modified petroleum bitumen was prepared by adding 4 wt% SBS modifier to seaweed bio-bitumen modified petroleum bitumen. Furthermore, via in-situ polymerization, reaction of polystyrene (PS) with graphene oxide (GO) resulted in PS-GO with a spring-like structure as confirmed by atomic force microscopy. A wide temperature domain modified bitumen was prepared by adding 0.02 wt% PS-GO of the total mass of bitumen to SBS/seaweed bio-bitumen modified petroleum bitumen. Macroscopic tests showed that adding bio-bitumen and PS-GO effectively improved the performance of pristine SBS modified bitumen mainly attributed to their similar chemistry as confirmed by infrared spectroscopy. Fluorescence microscopy revealed swelling of SBS upon the addition of seaweed bio-bitumen and formed a network like structure in the petroleum bitumen, thereby improving its high temperature rutting resistance and low temperature embrittlement resistance. PS-GO entered the SBS network structure, thereby increasing the toughness and awarding modified bitumen a wide temperature domain. The wide temperature domain modified bitumen can solve the problems of high temperature rutting and low temperature cracking on roads in harsh environments, and can provide good pavement materials for road construction.

Study on Bending Resistance and Self-healing Property of SBS Modified Asphalt Mortar under Thermal Aging

At present, there are many studies on asphalt mixtures in China, but the research on asphalt mortar is not enough. In this paper, through trabecular bending tests of base asphalt mortar and SBS modified asphalt mortar under different aging degrees,and the change rules of mechanical properties of two kinds of asphalt mortar under different aging degrees were studied. By designing self-healing experiments of asphalt mortar specimens. The test results show that SBS modified asphalt mortar has better deformation resistance and load-bearing capacity than base asphalt mortar, SBS modified asphalt has better pavement performance, and the deformation resistance and stress relaxation performance of SBS modified asphalt mortar are greatly affected by short-term aging, which is the main factor affecting the healing degree. Therefore, controlling the short-term thermal aging of SBS modified asphalt mixture during paving and transportation is of great significance to the improvement of pavement service life.

Evaluation of the fatigue failure and recovery of SMA mixtures with cellulose fiber and with SBS modifier

Several studies have investigated the recovery of asphalt mixtures during fatigue life; however, there is still an inadequacy of determining fatigue failure and recovery of Stone Matrix Asphalt (SMA) mixtures under repeated loading. This paper presents the results of a laboratory study which was aimed to compare the effect of cellulose fiber with SBS modifier on the fatigue failure and recovery of SMA. Three different mixtures (containing cellulose fiber, 3% SBS, and 5% SBS) were fabricated by two types of aging conditions. In addition to fatigue failure and recovery of the SMA, resilient modulus, indirect tensile strength and long-term oxidative aging of this mixture were investigated. The results indicated that using the SBS modifier enhanced indirect tensile strength, resilient modulus, resistance to fatigue failure, and recovery of the mixture. Considering aged mixtures, although the long-term aged mixtures had higher failure life, resilient modulus and indirect tensile strength, they had lower recovery potential. Also, while using SBS modifier had a positive effect on reducing the impact of aging on the indirect tensile strength and the resilient modulus, it could not reduce the detrimental impact of aging on the recovery potential of the mixtures.

A chemo-rheological approach to the healing characteristics of asphalt binders under short- and long-term oxidative aging

Asphalt is known to have self-healing characteristics. This study was aimed to investigate the healing behavior of asphalt binders under short- and long-term oxidative aging conditions, and to evaluate the relationship between healing potential and chemical properties. Two asphalt binder types were evaluated which included one neat (unmodified) asphalt and one styrene-butadienestyrene (SBS) modified binder. Healing characterization was based on the recently developed linear amplitude sweep based healing (LASH) test. Chemical characterization consisted of the saturates, aromatics, resins, and asphaltenes (SARA) fractionation, and gel permeation chromatography (GPC) tests. Based on the obtained healing index from the LASH test, oxidative aging generally had negative effects on healing, and that the SBS modifier slightly reduced the healing potential within the crack initiation phase. Presence of more light fractions, small molecules, and molecules that are longer with less branches would promote the molecular self-diffusion across crack surfaces, thereby enhancing the healing process. The negative effect of oxidative aging on healing may be attributed to molecular agglomeration which results in a less dispersed structure with reduced capability of the asphalt to diffuse across crack interfaces. This study provided a preliminary validation of the LASH test and the healing index.

Microstructure of neat and SBS modified asphalt binder by small-angle neutron scattering

The microstructure of asphalt binders is believed to have a significant impact on the performance of binders used in roadway constructions. However, there are only limited studies of their nanoscale to microscale structures. Here, small angle neutron scattering (SANS) is used to study the nanoscale structure of neat asphalt binder, styrene-butadienestyrene (SBS) block copolymers and SBS modified asphalt binder. The SANS pattern for asphalt binder demonstrates that it exhibits a colloidal structure comprised of asphaltenes surrounded by resins dispersed in saturates and aromatics. Fractal-core-shell model fits to these patterns indicate that the asphaltene core size decreases with increasing temperature. Both SANS and rheology confirm that SBS modified asphalt has a thermo-reversible phase transition around 110 °C, where the SBS micelles swell and lose scattering contrast above this temperature. The thermo-reversibility of this phenomenon indicates that the mechanism of SBS modification is mostly a physical modification of the nanoscale structure as proposed in the colloidal model of asphalt. Modeling of the SANS patterns shows that neat SBS and SBS dispersed in asphalt binder have a lamellar structure surrounded by a shell. These results are useful for understanding the relationship between the nanoscale structure of asphalt binder and pavement performance, as well as potentially developing new types of modified asphalt binders.

Evaluation of Degradation of SBS Modified Asphalt Binder Because of RTFO, PAV, and UV Aging using a Novel Extensional Deformation Test

Styrene-butadiene-styrene (SBS) modified PG 64-22 and PG 76-22 binders are studied to investigate the degradation of polymer because of aging applied by: rolling thin film oven (RTFO), pressure aging vessel (PAV), and ultraviolet (UV). Upon observing the temperature increment of unmodified binder during high shear mixing, a polymer mixing procedure has been established. SBS (2%, 4%, and 6%), polyphosphoric acid (PPA) (0.5%, 2%, and 3.5%), and PPA (2%)-SBS (0.5%, 2%, and 3.5%) are mixed with PG 64-22 binder. Sentmanat extensional rheometer, based on dynamic shear rheometer, is used to investigate the extensional deformation characteristics in which SBS modified binders exhibit both first peak elongation force, F1, and second peak elongation force, F2, whereas, unmodified binders and PPA modified binders exhibit no F2. SBS is the most effective in increasing F2 with an increasing rate of 1.16N/% of SBS polymer. At 12°C and 16°C, F2 of RTFO aged SBS modified binder reduces, which indicates the polymer is degrading. In the case of PAV aged SBS modified binder, no F2 is found at 12°C and 16°C. With the increment of temperature, the PAV aged sample shows F2, but the value is less than the F2 of the original and RTFO aged binder of similar stiffness (F1). A normalized parameter, F2/F1, also shows that RTFO and PAV aging degrade SBS. Evaluation of UV aged SBS modified binder shows no F2 at any temperature while oven aged binder shows F2 value at similar aging temperature, duration, and thickness, indicating SBS completely degrades because of UV aging.

Effect and prediction of aromatic oil on swelling degree of direct-to-plant SBS modifier in bitumen

ABSTARCTThe effects of aromatic oil on the swelling degree of the modifier in bitumen were analyzed from macro and micro perspectives. The evaluation indicator of swelling degree was put forward and the prediction model of swelling degree was established. The result shows that the swelling degree of direct-to-plant SBS modifier in bitumen can be evaluated by the structure fineness of SBS after swelling. There is an optimal content of aromatic oil makes the direct-to-plant SBS has the best swelling degree. The swelling degree determines the performances of the direct-to-plant SBS modified bitumen to a certain extent.

Performance Test on Styrene-Butadiene-Styrene (SBS) Modified Asphalt Based on the Different Evaluation Methods

To uniform the evaluation indicators of Styrene-Butadiene-Styrene (SBS) modified asphalt, the SK70# and SK90# matrix asphalt were modified by different SBS modifier dosage in this study. The test methods in China and Superpave were used to test the performance of each SBS-modified asphalt respectively, from which the appropriate evaluation index of SBS-modified asphalt was determined. The results showed that the addition of SBS modifier improved the high temperature performance and lowered the temperature sensitivity of asphalt binder, while it increased the viscosity of asphalt binder in high temperatures. Due to the variability that appeared in the results of the penetration test by the swelling of SBS-modified asphalt, the penetration test was not recommended to evaluate the performances of SBS-modified asphalt. The softening point of SBS-modified asphalt with the modifier dosages of 4.5%, 5%, 5.5% and 6% increased 5.7%, 12.8%, 22.5% and 26.4% respectively compared to the matrix asphalt for SK70# matrix asphalt, and increased 21.2%, 26.3%, 33.6% and 46.6% respectively compared to the matrix asphalt for SK90# matrix asphalt. The effect of SBS-modifier on the softening point of SK90# matrix asphalt is significantly better than that of SK70# matrix asphalt. The improvement effect of SBS modifier on low temperature performance of matrix asphalt decreased with a decrease in test temperature. When studying the influence of the SBS modifier on the low temperature performance of asphalt binder, it was recommended to use the bending beam rheometer (BBR) test to evaluate the low temperature performance of SBS-modified asphalt.

The Effect of Direct-to-Plant Styrene-Butadiene-Styrene Block Copolymer Components on Bitumen Modification.

Five types of material, styrene-butadiene-styrene block copolymer (SBS), ethyl-vinyl-acetate (EVA), naphthenic oil, maleic anhydride grafted ethylene-vinyl acetate copolymer (EVA-g-MAH) and butylated hydroxytoluene (BHT) were used as the raw ingredients for manufacturing direct-to-plant SBS in this paper. Thirteen kinds of direct-to-plant SBS with different EVA/SBS and naphthenic oil/SBS were prepared as well as the processes diagrammatic sketch of dispersion and swelling of direct-to-plant SBS modifier in bitumen were discussed. Microscopic images of direct-to-plant SBS modified bitumen with different components were obtained using fluorescence microscopy. The micro-images were analysed and quantified with MATLAB software. The influence of key components on the micro-morphology of direct-to-plant SBS-modified bitumen is discussed, followed with the tests on melting points and the melting indexes of direct-to-plant SBS with different EVA/SBS and naphthenic oil/SBS. The performances test of bitumen and bituminous mixture modified by these direct-to-plant SBS were also conducted. Results show that, with the ratio improvement of EVA/SBS or naphthenic oil/SBS, the number of the pixel dot number of area (SBS) in microscopic images increased. Enlargement of the pixel dot number of centre line elongate and the structure fineness was observed, indicating that the dispersion and swelling effect of the SBS modifier in bitumen had been improved. Meanwhile, the macro index, such as the melting point and melting index of direct-to-plant SBS, was also improved corresponding to the increase of EVA/SBS ratio or naphthenic oil/SBS ratio. With the addition of EVA or naphthene oil content, penetration and ductility of direct-to-plant SBS modified bitumen received gradual enhancement, but the softening point and viscosity were found out to be decreased. The high-temperature and low-temperature performances of direct-to-plant SBS modified bituminous mixture can be effectively improved by adding EVA or naphthenic oil. By meeting the required performances of direct-to-plant SBS, modified bitumen and bituminous mixture, the component of direct-to-plant SBS is recommended as, SBS:EVA:naphthenic oil:EVA-g-MAH:BHT is 1:0.1–0.5:0.05–0.2:0.03:0.05. For the compatibleness of SBS with different bitumen are different, necessary tests verification is recommended to be carried out prior to usage.

Effect of material composition on nano-adhesive characteristics of styrene-butadiene-styrene copolymer-modified bitumen using atomic force microscope technology

To investigate the effect of the raw material composition on the nano-adhesive characteristics of styrene-butadiene-styrene (SBS) copolymer-modified bitumen, force-distance curves were obtained to examine the nano-adhesive forces of SBS-modified bitumen samples prepared using different virgin bitumen types, SBS modifiers, an extraction oil, and a stabilizer using atomic force microscopy (AFM). The influence of the composition of the raw materials, such as the virgin bitumen, SBS modifier, extracting oil, and stabilizing agent contents, on the cohesive characteristics were discussed for SBS-modified bitumen. The results show that force-distance curves obtained using AFM can be used to gain insight into nano-adhesive forces of SBS-modified bitumen samples. The force-spectrum technique using AFM can be used to obtain the nano-adhesive forces of the SBS-modified bitumen samples. Neat bitumen has good compatibility with a SBS modifier, which is suitable for forming SBS-modified bitumen with an increased nano-adhesive force. The nano-adhesive force of the branched-shaped SBS-modified bitumen was larger than that of linear-shaped SBS-modified bitumen. The nano-adhesive force of SBS-modified bitumen increased as the SBS modifier and stabilizer contents increased. The nano-adhesive force of the SBS-modified bitumen decreased when the extraction oil content increased.

Fatigue Properties of Rubber Modified SMA Asphalt Mixture

To evaluate fatigue propertiesof rubber modified SMA asphaltmixture, based on optimizing the preparation process of rubber asphalt, the splitting fatigue testsof three kinds of asphalt mixture is carried out including ordinary asphalt, modified asphalt with rubber powder and SBS modified asphalt. And the freezing and thawing conditions were considered in the tests. The results show that rubber powder can improve the fatigue properties of SMA asphalt mixture, but the modified effect of rubber powder is not as good as SBS modifier, the fatigue properties of asphalt mixture are deteriorated by freeze-thaw conditions, the deterioration degree of rubber modified asphalt mixture is less than SBS modified asphalt mixture, but rubber modified asphalt mixture has better freeze-thaw durability.

Low-temperature performance of SBS modified asphalt mixture in high altitude and cold regions

Due to the severe natural environment found in high-altitude and cold regions, where the altitude is around 4000 m, and the average annual temperature is below 0°C, the design method and quality indicators of asphalt mixture performance is different in comparison to inland cities. To optimize design parameters and low-temperature performance of SBS modified asphalt mixture in high-altitude and cold regions, the beam bending, splitting, aging, and freez-thaw cycle tests were conducted based on the test protocol, field experience and quantitative analysis. Standard mixing procedures and evaluation indexes for low temperature anti-cracking performance were used to reveal the low temperature decaying characteristics of SBS modified asphalt mixtures. The results show that the optimum binder-aggregate ratio of 5.3% and the optimum SBS modifier dosage of 4%∼5% are recommended for SBS modified asphalt mixture in the high altitude and cold regions of the Tibetan Plateau. The splitting test is suitable for assessing low-temperature performance of asphalt mixtures in high altitude and cold regions with a loading rate adjusted to 2 mm/min. When the loading rate is adjusted to 10 mm/min, the beam bending test is suitable for studying the low-temperature performance of asphalt mixtures after long-term aging in high altitude and cold regions. The freezing and thawing split test is suitable for assessing low-temperature performance of asphalt mixtures after freezing and thawing in high altitude and cold regions when the loading rate is adjusted to 2 mm/min. Under long-term aging conditions, as temperature increases (−15°C∼0°C), the decay rate of maximum flexural-tensile strain of traditional asphalt mixture is bigger than that of SBS modified asphalt mixture. Having endured freezing and thawing cycles, the splitting strength and the maximum flexural-tensile strain of asphalt mixtures decreases. After 40 cycles of freezing and thawing, the maximum flexural-tensile strain decreases by 15.2% in comparison to state.