SBS-modified Bitumen Research Articles

A novel method to improve the anti-ageing ability of bitumen by organic LDHs/SBS composite: Preparation, performance evaluation and mechanism analysis

γ-aminopropyltriethoxy silane organic layered double hydroxides (LDHs) and SBS were combined into LDHs/SBS composite to improve anti-ageing performance of SBS modified bitumen (SMB). XPS and SEM showed that organic LDHs (OLDHs) was successfully grafted onto SBS, and OLDHs could be more evenly distributed in SBS, which was conducive to improve the anti-degradation capability of SBS. Compared with SBS and LDHs/SBS composite, the interaction between OLDHs/SBS composite and bitumen was stronger, resulting in the better stabilization of SBS and LDHs in bitumen. Furthermore, OLDHs/SBS composite could enhance the high-temperature property of SMB. SMB became hard and brittle during ageing, the physical and rheological properties were remarkably deteriorated. LDHs/SBS and OLDHs/SBS composite could alleviate the damage of ageing on the high- and low-temperature performance of SMB and enhance the anti-ageing capacity, particularly OLDHs/SBS composite. Then, the improvement mechanism of OLDHs/SBS and LDHs/SBS composite on the anti-ageing capability of SMB was analyzed at microscopic scale. LDHs/SBS and OLDHs/SBS composite could hinder the infiltration of oxygen into bitumen and decrease the oxygen content, and simultaneously decelerate the oxygen diffusion rate in bitumen. The synergistic combination of these two functions conspicuously diminished the probability of oxygen colliding with bitumen or SBS, which relieved the ageing of bitumen and the degradation of SBS, and ultimately improved the anti-ageing capability of SMB. Furthermore, due to the better stability, the effectiveness of OLDHs/SBS composite was more notable than LDHs/SBS composite, OLDHs/SBS composite demonstrated superior improvement on the anti-ageing capability of SMB than LDHs/SBS composite.

Simulation and investigation of the mild-moderate aging properties of SBS modified bitumen: Physical, microscopic and rheological properties

Styrene-butadiene-styrene block copolymer (SBS) modified bitumen (SMB) is unable to meet usage requirements after being exposed to sun-light, heat and oxygen. The researches show that it is difficult to restore bitumen effectively when the penetration of the aged bitumen is below 20 dmm. Therefore, the penetration of 20 dmm is taken as the dividing line in this paper. Higher than 20 dmm is considered as mild-moderate aging, while lower than 20 dmm is considered as severe aging. The traditional rotating thin-film ovens (RTFO) and pressure aging vessels (PAV) methods are similar to simulate the aging behavior of the upper layer of bitumen pavement, but they are difficult to simulate the aging in the depth direction of bitumen pavement. In this paper, the aging of the modified bitumen is simulated by extending the aging time and deepening the depth of the aging mold, and then it is graded according to the penetration. We aimed to investigate the differences in physical, microscopic and rheological properties of SMB with including 0 wt%, 1.5 wt%, 2.5 wt%, 3.5 wt%, 4.5 wt% and 5.5 wt% SBS content before and after aging. Through the physical performance, such as penetration, softening point, ductility and elastic recovery, it was observed that a high SBS content leads to strong anti-aging ability. Fourier Transform Infrared (FTIR), fluorescence microscopy (FM), scanning electron microscopy (SEM) and atomic-force microscope (AFM) revealed that a good network structure can be formed through absorbing light components when the SBS exceeds 3.5 wt%. After that, it was found that there is a positive correlation between aromatic index and penetration, as well as a positive correlation between butadiene index and softening point. Additionally, rheological frequency scanning and temperature scanning indicated that the modulus was increased and the phase angle was decreased with increasing SBS content or aging. After aging, the rutting resistance of SMB was enhanced but the cracking resistance was weakened. This research can establish a theoretical support and foundation for the regeneration of the mild-moderate aged SMB.

Laboratory evaluation of synergistic blending with SBS-modified bitumen and rejuvenator to enhance the performance of recycled bitumen with a high content of RAP materials

Reclaimed asphalt pavement (RAP) stands as a pivotal construction material widely used in asphalt pavement rehabilitation. The prevailing focus and trajectory revolve around increasing the proportion and utility of RAP materials. However, the potential for temperature and fatigue cracking increases with the dosage of RAP materials. In this study, SBS modified bitumen (SBSMB) and four rejuvenators were combined synergistically with aged asphalt to enhance the performances of the recycled bitumen with high RAP content and consequently augment the value of the RAP material, all while ensuring compatibility between the SBSMB and aged base bitumen. Initially, the base bitumen was aged using a pressure aging vessel (PAV) test. Subsequently, a selection of virgin bitumen (VB), SBSMB, and four rejuvenators were utilized to revitalize the aged bitumen. A comprehensive battery of tests, encompassing conventional tests, temperature sweep, frequency sweep, multiple stress creep recovery (MSCR), bending beam rheometer (BBR), and linear amplitude sweep (LAS), were carried out to characterize the rheological properties. Finally, Fourier transform infrared spectroscopy (FTIR) was employed, along with the determination of polystyrene index (IPS) and polybutadiene index (IPB), to evaluate the compatibility between SBSMB and aged base bitumen. The results underscore that the incorporation of SBSMB and rejuvenator comprehensively enhances high-temperature performance and fatigue cracking resistance while effectively reinstating low-temperature cracking resistance. Furthermore, the values of IPS, IPB, and IPS/IPB exhibit an increase with the addition of a rejuvenator, indicating its potential to improve the compatibility between SBSMB and aged base bitumen. Thus, this research proposes a more cost-effective and environmentally sustainable approach to bolstering conventional asphalt pavement performance and grade.

Styrene-butadiene-styrene block copolymer modified bitumen with ultraviolet absorbent intercalated layered double hydroxide: Compatibility and anti-ageing properties

2-hydroxy-4-methoxybenzophenone-5-sulfonic acid (ultraviolet absorbent, BP) intercalated layered double hydroxide (LDH) was synthesized to enhance the anti-ageing properties of styrene–butadiene–styrene block copolymer (SBS) modified bitumen (SMB). X-ray diffraction and UV–vis spectroscopy indicated that BP has been successfully substituted into LDH interlamination, and BP intercalated LDH (BP-LDH) exhibited better UV absorptive capacity than LDH. Then, the physical and rheological properties, chemical structure of BP-LDH and LDH modified SMB before and after ageing were comprehensively studied. Compared with LDH, BP-LDH possessed the smaller difference in solubility parameters (δ) and the stronger interaction energy (Einter) with SMB, resulting in the better compatibility of BP-LDH modified SMB. The high-temperature stability of SMB was promoted with the addition of BP-LDH or LDH, especially BP-LDH. After ageing, the temperature susceptibility, low-temperature anti-cracking and anti-fatigue cracking of SMB were deteriorated, the oxygen-containing groups (C = O and S = O) in SMB noticeably increased and carbon–carbon double bond (C = C) concurrently decreased. LDH could mitigate the ruin of ageing on the performance and chemical structures of SMB, and strengthen the anti-ageing performance. Furthermore, BP intercalated modification could further significantly heighten the performance of LDH.

Performance Evaluation of Multiple Aging-Regeneration of SBS-Modified Bitumen Regenerated by a Composite Rejuvenator

In this study, compound regeneration of SBS-modified bitumen (SMB) was carried out by a composite rejuvenator composed of furfural extraction oil (FEO) and 1,6-hexanediol diglycidyl ether (HDDGE) in the presence of catalyst triethanolamine (TEOA). SMB was subjected to three aging-regeneration cycles, and the physical and rheological properties, toughness and tenacity, and chemical structures of the SMB after each aging-regeneration cycle were tested to investigate the regeneration effect of the composite rejuvenator on SMB at different numbers of cycles. The ductility decreases and low-temperature properties deteriorate as the number of cycles increased, but the high-temperature properties of the SMB are improved. The complex modulus aging index and phase angle aging index indicate that the viscous behavior of SMB weakens after the second and third aging. The degree of viscoelasticity and toughness recovery decreases with the increase in the number of cycles, and the tenacity of SMB after the third aging-regeneration cycle is basically lost. The results of the Fourier transform infrared (FTIR) spectra tests prove that with the increase in the aging–regeneration cycles of SMB, the intensity of FTIR peaks of oxygen-containing functional groups is greater, and the recovery of aged SMB is gradually weakened.

Investigation of the cohesive behavior of water-intervened rejuvenated SBS-modified bitumen

When water interacts with bitumen, the diffusion and cohesion characteristics between the components of bitumen are negatively impacted. Molecular dynamics simulations were employed to construct various bitumen models, including bitumen–bitumen (without water), water-containing single bitumen, water-containing bitumen–bitumen, and bitumen–water–bitumen models. The primary research objectives were as follows: comparing the changes in the densities of bitumen models with and without water, analyzing the interlayer cohesive energies of bitumen models interacting with water, evaluating the hydrogen bonds in water-containing bitumen models, and characterizing the diffusion behaviors of bitumen components. The results indicated that when water interacted with the bitumen, it filled internal voids, leading to an overall increase in volume and reduction in density. The interaction energies between the rejuvenated bitumen models and water molecules decreased as the numbers of polar sites exposed to SBS molecules decreased. The numbers of hydrogen bonds between water molecules and rejuvenated bitumen models were similar to those in aged bitumen models. As the number of fractured SBS molecular chains gradually increased, the interlayer cohesive energy in the Methylene-bis(4-cyclohexylisocyanate) (HMDI)-rejuvenated bitumen model gradually increased. Water molecules significantly influenced the interactions at the rejuvenated bitumen–rejuvenated bitumen interface, weakening the cohesion characteristics between bitumen molecules. Water interactions significantly reduced the interlayer cohesive energy of the bitumen–water–bitumen model. Conversely, the recovery process improved the interlayer cohesion characteristics of the bitumen. The diffusion characteristics of the components of bitumen SARA were significantly greater under wet conditions than under dry conditions.

Evolution of aging depth gradient distribution in SBS-modified bitumen during the aging of field

This study investigated the distribution of aging depth gradients in styrene-butadiene-styrene modified bitumen (SBSMB) during natural aging. SBSMB was sourced from bitumen recycling tests and was stratified into upper, middle, and lower layers according to depth. To examine the effects of various aging depths, SBSMB samples from different depths were prepared for subsequent bitumen recycling tests. Then, studying the rheological performance of the SBSMB involved conducting multiple stress creep recovery tests. Subsequently, investigating the bee structure and nanoscale indicators of SBSMB at various aging depths involved utilizing atomic force microscopy testing. Finally, the Verhulst model was applied to assess the aging of SBSMB at different depths. The results have shown that natural aging has gradually diffused from the surface to the interior of the bitumen. An increase in aging time leads to a more pronounced aging effect at the upper levels and an accelerated the downward diffusion rate. This ultimately results in a gradient behavior of the rheological properties of SBSMB at different depths. The quantity of bee structures and the distribution density of bee structures in SBSMB both progressively decrease with increased aging depth. As aging time increases, the aging properties of SBSMB exhibit significant gradient behavior at different depths. Simultaneously, the Verhulst model accurately explain the aging trend of bitumen at different nanoscale depths.

Preparation and properties of self-healing SBS modified bitumen with dynamic acylhydrazone bonds

Styrene-butadiene-styrene triblock copolymer (SBS) modified bitumen (SMB) with excellent self-healing performance not only saves resources, but is also important for the sustainable development of pavement and construction industry. In this paper, a self-healing agent (SHA) with acylhydrazone bond was synthesized, and the dynamic acylhydrazone bond was introduced into the SBS molecular chains to prepare the self-healing SMB (SHMB). The structure of SHA was characterized, and the physical properties, chemical structure, microstructure and self-healing performance of the SHMB were investigated. Fourier transform infrared (FTIR) spectra and nuclear magnetic resonance spectra demonstrated that SHA was successfully synthesized. The physical performances of SMB were significantly improved by SHA and its optimal dosage was 0.6 %. FTIR indicated that the dynamic acylhydrazone bond was introduced into the SBS molecular chains, and formed hydrogen bonds in SHMB. The fluorescence microscope showed that SHMB had a denser network structure than SMB. The crack healing observation indicated that the crack healing speed of SHMB was much higher than that of SMB. The break tensile performance recovery showed that the recovery rate of elongation at break (Rε) of SMB and SHMB were 14.38 % and 58.27 % after self-healing at 25℃ for 32 h, and the Rε of SMB and SHMB was elevated to 50.12 % and 92.58 % after self-healing at 40℃ for 4 h, which indicated that the introduction of dynamic acylhydrazone bonds greatly enhanced the self-healing ability of SHMB.

Evolution of Structure and Properties of SBS-Modified Asphalt during Aging Process

To explore the performance evolution mechanism of SBS-modified bitumen (SMB) during construction and service, the chemical structure, molecular weight and properties of styrene–butadiene–styrene triblock copolymer (SBS) and SMB under multiple aging levels were assessed via Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC) and a dynamic shear rheometer (DSR). The results indicate that the polybutadiene segments in SBS are susceptible to oxidative degradation, and the molecular weight of SBS decreases rapidly during the aging process. The complex modulus and temperature sensitivity of SMB show relatively small changes during the early aging stage, which is mainly attributed to the impact of SBS oxidative degradation. While its temperature sensitivity decreases sharply after double PAV aging, it means the influence of asphalt aging on its performance is dominant. And there is a significant difference in the effect of aging on the creep recovery behavior of SMB under high and low shear stresses. The percentage recovery (R) of SMB decreases and then increases under low shear stress as aging progresses. While the value R of SMB increases gradually under high shear stress with the extension of aging. Meanwhile, the viscoelastic properties of SMB have gradually transformed to those of aged matrix asphalt after serious aging, which is also confirmed by the gradual destruction and degradation of the SBS cross-linked network in the binder from a fluorescence micrograph. This research will help to understand the performance failure mechanism of SMB during service, providing a theoretical reference for the selection of maintenance and renovation opportunities during the service process of SBS-modified asphalt pavement, as well as the avenue to achieve high-performance recycling.

Enhancing aged SBS-modified bitumen performance with unaged bitumen additives

This study investigated the performance of SBS-modified bitumen (SBSMB) after aging and rejuvenation by utilizing macroscopic performance and microscopic characterization methodologies. The blending of aged SBS-modified bitumen (SBSPAV) with different proportions of SBSMB or 80–100 penetration grade base bitumen (90BB) was performed to produce SMB-rejuvenated bitumen (a blend of SBSMB and SBSPAV) and 90BB-rejuvenated bitumen (a blend of 90BB and SBSPAV). To evaluate high-temperature rutting behavior, multiple stress creep recovery (MSCR) tests were conducted on the binders, and the outcomes were analyzed using the Burgers model to elucidate their viscoelastic behaviors. Low-temperature performance was assessed using an asphalt binder cracking device (ABCD). Furthermore, the microscopic structure, roughness, and Young's modulus of the binders were investigated using an atomic force microscope (AFM). Thermal stability was assessed using a thermogravimetric analyzer (TGA). The findings indicated that SMB-rejuvenated bitumen exhibited favorable resistance to high temperatures and the ability to withstand heavy traffic loads. The stress sensitivity of 90BB-rejuvenated bitumen surpassed that of SMB-rejuvenated bitumen. The high-temperature performance rating of 90BB-rejuvenated bitumen displayed a continuous decline, indicating poor load-bearing capacity. Regardless of the unaged bitumen type, higher doses of unaged bitumen led to a gradual decrease in the rejuvenated bitumen's cracking temperature, indicating the enhancement of low-temperature performance of SBSPAV. However, both SMB-rejuvenated bitumen and 90BB-rejuvenated bitumen fell short of matching the performance level of pure SBSMB. AFM outcomes demonstrated that with increasing SMB dosage, the number of bee-like structures initially decreased before rising again, coupled with an increase in their volume. Conversely, an increase in 90BB dosage led to a gradual reduction in bee-like structures, accompanied by increased volume. The roughness of both SMB-rejuvenated bitumen and 90BB-rejuvenated bitumen exhibited improvements compared to SBSPAV, suggesting enhanced adhesion performance of the rejuvenated bitumen. TGA results unveiled lower thermal stability in 90BB-rejuvenated bitumen in comparison to SMB-rejuvenated bitumen. This study introduces a novel perspective on the design of SBS-rejuvenated bitumen.

Life cycle assessment of SBS modified bitumen waterproofing membrane

Building waterproofing membranes constitute essential components of construction materials. This study utilizes the life cycle assessment (LCA) methodology to develop a comprehensive life cycle inventory and conduct an environmental impact assessment of typical styrene-butadiene-styrene (SBS) modified bitumen waterproofing membrane products. The main research objective of this paper is to identify the key factors influencing the environmental impact of products and to provide data for the selection of green materials in the construction industry. The results reveal that the production of raw materials for SBS-modified bitumen waterproofing membranes contributes the most to all environmental impact categories, followed by the transportation and energy production stages, while the production stage of the membranes exhibits a relatively smaller contribution. Within the raw material production stage, the bitumen production process exhibits the highest contribution to fossil fuel depletion (FFP) environmental impact, surpassing 50%. The production process of polyester tire cloth demonstrates the greatest influence on human toxicity potential (HTPc), global warming potential (GWP), freshwater eutrophication (FEP), marine eutrophication potential (MEP), and mineral resource scarcity potential (SOP), accounting for 54.63%, 32.86%, 68.55%, 72.41%, and 61.69%, respectively. Additionally, the production process of base oil exhibits the most significant contribution to fine particulate matter formation (PMFP) and terrestrial acidification potential (AP) among the environmental impact indicators. Variations in the quantities of polyester tire cloth and base oil exhibit the most notable influence on the environmental indicators of the product. Specifically, the sensitivity analysis reveals that polyester tire cloth has the greatest impact on mineral resource scarcity potential (SOP); base oil exhibits the highest sensitivity to fossil fuel depletion (FFP).

Chemical modification of sustainable bagasse fiber and its absorption mechanism on SBS-modified emulsified bitumen

At present, there are few reports on the application of bagasse fibers (BFs) in the pavement field, and the interaction mechanism between BFs and bitumen is still blank. In this paper, novel chemical modified BFs were introduced as sustainable additives and absorption mechanism between chemical modified BFs and styrene–butadiene–styrene (SBS)-modified bitumen was also revealed through theoretical models and experimental methods. The results show that the concentration of sodium hydroxide solution as 1.5 %, reaction temperature of 40 °C and soaking time of 100 min are the optimal experimental parameters of chemical modification. Compared to virgin BFs, the chemical modified BFs increase the oil absorption rate from 6.46 times to 8.96 times, heat loss decreases from 7.76 % to 1.65 % and total pore volume, micro-pore area and volume increase by 241 %, 170 % and 276 %, respectively. The main component of modified BFs adsorbing SBS-modified bitumen is resin and per unit mass of adsorbed resin by modified BFs decreases gradually with the increased contents of modified BFs. The equilibrium adsorption capacity calculated by quasi-second-order model is closer to the experimental results than that calculated by the pseudo-first-order model. The resin is first adsorbed by adsorption sites on outer surface of fiber, and then diffuses into interior of fiber. With the decrease of resin concentration during absorption, the gradually saturation of adsorption sites leads to weakening adsorption, which finally reaches equilibrium.

Recycling of discarded face masks for modification and use in SBS-modified bitumen.

Since the outbreak of the COVID-19 pandemic, the discarded face masks have attracted widespread attention in society. In line with sustainable development, a physicochemical treatment method was used to recycle discarded face masks into styrene-butadiene-styrene (SBS) modified bitumen. Utilizing the highly adhesive polydopamine-polyethyleneimine (PDA-PEI) coating, it has improved the surface damage of the discarded face mask fibers (DFMF) caused by natural aging and mechanical fragmentation, simultaneously strengthening the connection between the fibers and bitumen. At 46°C, the 2% embellish-face mask fiber (E-FMF)/SBS modified bitumen, compared to the 2%DFMF/SBS modified bitumen, exhibited improvements in complex modulus (G*), elastic modulus (G'), and loss modulus (G″) by 12.27%, 16.39%, and 13.35%, respectively. Furthermore, at 0.1kPa and 3.2kPa, the creep recovery rate (R) increased by 23.3% and 32%, and the average creep compliance (Jnr) decreased by 54.7% and 64%. It was demonstrated that DFMF adhered with the coating, were more effective in improving the mechanical properties, deformation resistance, and shear resistance of the bitumen. This approach enriches the application scenarios of discarded single-use face masks and supports environmental protection and road construction.

Effects of solvent-free bentonite fluid on physical, rheological and aging properties of SBS modified bitumen

Layered silicate materials were often used for bitumen modification, but their improvement effect on bitumen performance was limited due to their poor compatibility with bitumen. Introducing long-chain organic compounds on the surface of inorganic materials can make them exhibit solvent-free fluid characteristics, which can significantly enhance the compatibility between inorganic and organic materials. In this study, 3-(trimethoxysilyl propyl) dimethyl octadecyl ammonium chloride (DC5700) and nonylphenol polyoxyethylene ether sodium sulfate (NPES) were used to organically treat bentonite (Ben) to prepare solvent-free bentonite fluid (Ben-fluid) so as to effectively improve the overall performance of styrene-butadiene-styrene copolymer (SBS) modified bitumen (SMB). Ben and DC5700 organically treated bentonite (DC5700-Ben) were used as comparative samples. The microstructure, ultraviolet reflectance and lipophilicity of Ben, DC5700-Ben and Ben-fluid as well as fluidization characteristics of Ben-fluid were tested and characterized. The results of X-ray diffraction spectrometer and Fourier transform infrared spectrometer (FTIR) demonstrated that DC5700 intercalated into the layers of the Ben and chemically grafted on the Ben surface, and the NPES was anchored on DC5700 molecules through ionic bonds. Compared with Ben and DC5700-Ben, Ben-fluid had the highest ultraviolet reflectance and the best lipophilicity. As the temperature exceeded 82.3 ℃, the fluidization characteristics of Ben-fluid began to appear. Meanwhile, the effects of Ben-fluid on physical, rheological and aging properties of SMB were investigated. Ben-fluid was more conducive to enhance the high-temperature stability of SMB than Ben and DC5700-Ben, and has less adverse effects on the low-temperature physical and rheological properties. The aging results of different SMBs revealed that the change in physical properties of SMB containing Ben-fluid after thermal and ultraviolet aging was significantly lower than that of SMB containing Ben and DC5700-Ben. In addition, FTIR showed that compared with Ben and DC5700-Ben, the Ben-fluid could inhibit the increase of carbonyl index and the decrease of butadiene index of SMB after aging. Comprehensive analysis suggested that Ben-fluid was more conducive to improve the physical, rheological and anti-aging properties of SMB.

Multi-scale evaluation of sodium dodecyl sulfate intercalated LDHs on the ageing resistance of SBS modified bitumen

Sodium dodecyl sulfate (SDS) intercalated layered double hydroxides (LDHs) were prepared to enhance the ageing resistance of SBS modified bitumen (SMB). X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) showed that SDS has been intercalated into the interlayers of LDHs. Compared to LDHs, the interaction between SDS intercalated LDHs (OLDHs) and SMB was obviously stronger, and OLDHs exhibited better dispersity and stability in SMB. After ageing, the viscoelastic properties of SMB were deteriorated. LDHs and OLDHs could obviously alleviate the deterioration of ageing on the properties of SMB, which could improve the ageing resistance of SMB, especially OLDHs. Additionally, the enhancement mechanisms of OLDHs and LDHs for the ageing resistance of SMB at the microscopic scale were investigated by molecular dynamics. The incorporation of LDHs could obstruct the invasion of oxygen into the interior of SMB and inhibit the diffusion rate of oxygen in SMB, which reduced the oxidation reaction probability of SMB during ageing, and eventually achieved the improvement on ageing resistance of SMB. The effectiveness of LDHs was further improved after SDS intercalated modification, that was, SDS intercalated modification was beneficial to enhance the ageing resistance of LDHs for SMB.

Evaluation of olive pomace and SBS modified bitumen to the performance characteristics

This study investigated the applicability of olive pomace (OP) waste, a biomass waste, in bitumen modification. The OP modification was compared with styrene butadiene styrene (SBS) modified bitumen, which is widely used in asphalt modification, in terms of performance and cost. The OP and SBS binders were tested with conventional and rheological experiments. For this, modified asphalt binders were obtained by adding OP (wt. 4, 8, 15, 19, 25, 30%) and SBS (wt. 4, 4.5%) to pure B 50/70 penetration bitumen. The conventional test results of OP and SBS modified bitumen are close to each other, both modified bitumen decreased the penetration and temperature sensitivity of pure bitumen and increased the softening point. According to rheological test results, it was seen that the critical OP ratio was obtained from the 19% OP addition, and the critical SBS ratio was obtained from the 4% SBS addition and they exhibited the same performance grade. Then, for the hot mix asphalt (HMA) design, the optimum bitumen content was determined according to the Marshall method by using aggregate and B 50/70 pure bitumen, 19% OP, and 4% SBS modified bitumen. The effects of OP and SBS-modified bitumen on the mechanical properties of HMA mixtures were evaluated using Marshall stability tests. It could be said that OP-modified bitumen behaves like a more elastic solid at high temperatures, due to its lower penetration and higher softening point than pure bitumen. It has been observed that 19% OP additive provides an improvement, especially in rutting resistance, fatigue, and thermal crack resistance and 19% OP modified binder can be considered as an alternative to 4% SBS modified binder in general in terms of performance and cost. As a result, it is evaluated that OP can be used as a remedial additive in asphalt modification and contribute to the increase of pavement performance, and also that the damage of this waste material to the environment can be eliminated.

Effect of MA-EPR-ESO Compound Rejuvenator on Rheological Properties of Aged SBS-Modified Bitumen

Abstract The rejuvenation of aged styrene-butadiene-styrene–modified bitumen (SBSMB) can be achieved by adding a compound rejuvenator, consisting of maleic anhydride (MA), epoxidized polybutadiene resin (EPR), and epoxidized soybean oil (ESO). However, the optimal combination of this compound rejuvenator dosage was determined according to traditionally physical property indicators, so the obtained optimal combination may be imprecise. In this research, the rejuvenation effects of the compound rejuvenator were demonstrated based on physical property indicators. Then, to accurately obtain the optimum combination of the compound rejuvenator, a three-factor versus three-level (MA dosage levels were 0.05 %, 0.1 %, and 0.2 %; EPR dosage levels were 1 %, 2 %, and 3 %; ESO dosage levels were 4 %, 6 %, and 8 %) orthogonal scheme was designed. The rejuvenation effects of aged SBSMB were evaluated by rheological properties of rejuvenated SBSMB, and the optimal combination of the compound rejuvenator was obtained based on the continuous performance grade (PG) of the rejuvenated SBSMB at different dosage combinations. Finally, the rejuvenation effects of the optimal combination were verified by physical properties and fluorescence microscope tests. The results suggest that the preselected dosage combination of the compound rejuvenator can recover the base bitumen from its aged state (brittle and hard) and may repair the broken SBS fragments. The influence magnitude of the three components on the rheological properties of aged SBSMB is ESO, EPR, and MA in order. When the addition dosages of MA, EPR, and ESO are 0.2 %, 2 %, and 4 %, respectively, the rejuvenated SBSMB has similar physical and rheological properties with the original SBSMB. In addition, the FM result shows that the homogeneous distribution SBS network structure of SBSMB, which is destructed during long-term aging, is effectively recovered by the addition of the optimal combination of the compound rejuvenator.

Recycling shredded waste cigarette butts as stabilising fibres in stone mastic asphalt concretes

ABSTRACT Considering the global burden of cigarette consumption, the disposal of cigarette butts has become an inevitable issue. Compared to traditional disposal methods, such as landfilling or incinerating, the recycling of these wastes is clearly an eco-friendlier solution. In this research, waste electronic cigarette butts (E-CBs) were collected and recycled in bituminous mixtures, aiming to increase the use of sustainable road construction materials. The objective of this research is to explore the possibility of using waste E-CBs as an alternative stabilising fibre in asphalt mixtures. To this end, shredded waste E-CBs were incorporated in Stone Mastic Asphalt (SMA) and compared with the conventional cellulose fibres. Furthermore, to investigate the effects of powders (below 0.063 mm) from the waste E-CBs on the rheological properties of bitumen, tests were conducted on base SBS-modified bitumen and its mastics. Results show that the waste powder was unfavourable to the thermal susceptibility of the resulting binder. SMA samples with shredded E-CBs were also characterised through physical and mechanical tests and compared to the reference mixture using cellulose fibres. It was concluded that using waste E-CBs in SMA can be considered a promising alternative for replacing cellulose fibres and avoiding the disposal of cigarette butts.

Laboratory Investigation of Storage Stability and Aging Resistance of Slightly SBS-Modified Bitumen Binders

Slightly SBS-modified bitumen binders have been applied for the asphalt concrete impermeable layer of pumped storage power stations (PSPSs) in China. However, the storage stability and aging resistance of slightly SBS-modified bitumen are big concerns. In this study, three different types of slightly SBS-modified bitumen binders were evaluated by using a commonly used virgin bitumen and a normal SBS polymer-modified bitumen as references. All of the bitumen binders were subjected to short-term and long-term aging that were simulated by using a 5 h and 24 h thin film oven test (TFOT), respectively. A Fourier transform infrared (FTIR) spectroscopy test, storage stability test, dynamic shear rheological test, stress relaxation test, and direct tensile (DT) test were carried out to obtain insight into the storage stability and aging resistance. FTIR analysis indicated that slightly SBS modified bitumen exhibited serious aging of base bitumen together with higher polymer degradation. The aging indexes obtained from the carbonyl index and the polybutadiene (PB) index can well rank the aging resistance. Slightly SBS-modified bitumen binders had excellent storage stability, and even after a long-term period of 7 days of storage, the complex modulus and phase angle remained fairly constant. The rheological master curves were constructed to investigate the effects of short-term and long-term aging. Slightly modified bitumen binders were well identified by the plateau of the phase angle master curves. The aging resistance was well distinguished by the deviation of the complex modulus master curve using unaged bitumen as a baseline. It was found that three types of slightly SBS-modified bitumen binders exhibited inconsistent aging resistance in terms of rheological aging index. The relative change of the initial instantaneous modulus and the modulus relaxation rate was able to explain the relaxation properties. With respect to the direct tensile test, the increase in stiffness modulus and the loss of ultimate tensile strain can be used to evaluate the susceptibility of bitumen aging. An attempt was made to establish the relationship of the aging index between FTIR analysis, rheological properties, and low-temperature performance. It was found that the relationship among these aging indexes was weak. In general, slightly SBS modified bitumen should be well designed to obtain good aging resistance and low-temperature performance. Highly modified bitumen is foreseen to be promising in the case of extremely low temperatures and long-term durability.

STUDY OF INTERFACIAL ADHESION OF PAVEMENT SEALANTS BASED ON MOLECULAR DYNAMICS

To study the performance of bitumen mixture pavement sealants from their micro-mechanisms, the physical properties of base bitumen, SBS-modified bitumen and epoxy resin sealant as well as the adhesive properties of sealant-aggregate interfaces were studied using a molecular dynamics simulation. The adhesion of a sealant-pavement crack wall was studied using a contact angle test based on the surface energy theory. The results show that the epoxy resin sealant has excellent adhesion properties. Its physical properties and interfacial adhesion work are more significant than those of base bitumen and SBS-modified bitumen. An increase in the SBS can improve base bitumen’s mechanical properties and interfacial interaction. The interaction between three kinds of crack sealants and aggregate is identified as mainly the physical adsorption behavior. The van der Waals force plays a significant role in the adhesion behavior of bitumen crack sealant-aggregate interface. In contrast, the electrostatic force and van der Waals forces significantly affect the epoxy resin binder-aggregate interface. The adhesion work of 90# base bitumen, SBS-modified bitumen and epoxy resin binder for the asphalt pavement crack wall is (37.76, 44.86 and 77.63) mJ/m2, respectively.