Modified Asphalt Research Articles

Uncovering the energy-carbon-water footprint of waste rubber recycling: Integrated environmental and economic perspectives

The commitment to waste management has gained increasing momentum as global waste generation continues to skyrocket and threaten the environment. However, detailed assessments and clear insights remain absent to address the global waste utilization conundrum. This study evaluated the impact-oriented energy, carbon, and water (ECW) footprints of three typical scenarios for a waste recycling activity (i.e., waste rubber recycling) from environmental and economic dimensions, and explored key factors, nexus characteristics, and optimization measures. Results indicated that the rubber powder as an asphalt modifier scenario had a 93% greater environmental impact and 87% higher economic cost compared with the pyrolysis and reclaimed rubber production scenarios. Key processes, such as direct processes, electricity generation, and transportation, were identified as the major contributors to the ECW footprints, with the internal costs of raw materials, equipment, and taxes coupled with the external costs of human health dominating the economic impact. The nexus analysis results highlighted the urgent need to optimize the energy system for waste rubber recycling. Greening the production process revealed the benefits, with natural additives mitigating 85% of the environmental burden and 97% of the external costs compared with conventional additives. Industrial green microgrids, clean energy generation, proximity waste management, and electrified transportation were explored to foster sustainable optimization of waste rubber recycling systems. Moreover, a joint tax-subsidy mechanism for rubber production-recycling systems can stimulate recycling-oriented product design and increase the motivation to recycle waste rubber.

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.

Study of the Effect of Modification of Asphalt on the Rheological Properties Employing Microwave Radiation—An Aging Study

This study focuses on producing asphalt with improved rheological properties that differ from the original asphalt and are less affected by aging conditions. The rheological properties of Qayara asphalt were enhanced by modifying the asphalt using spent rubber tire (SRT) with different percentages of anhydrous aluminum chloride. Percentages ranging from 1.0% by weight of the spent tire rubber were added after proceeding with the thermal crushing process. The percentages of anhydrous aluminum chloride catalyst were 0.4 and 0.8%, respectively. This mixture was microwaved at 270 watt of power for 4, 8, and 12 min, respectively. The measurements performed are plasticity, penetration, softening point, and penetration index. The previously mentioned measurements were also made on the modified asphalt one year after the modification process to understand the effect of aging conditions. The microstructure and thermodynamics have been characterized by FE-SEM and EDX measurements. This study provides good rheological properties of the modified bitumen binder that is aging-resistant.

Enhancement of rheological performance and compatibility of tire rubber-modified asphalt binder with the addition of graphene

Rubber segregation and workability are issues associated with tire rubber powder (TRP) modified asphalt binder, restricting its widespread application. Meanwhile, graphene nanoparticles have gained considerable interest in asphalt modification due to their outstanding properties. This work has explored the influence of graphene incorporation on the compatibility and rheological behavior of TRP-modified asphalt binder. Firstly, TRP-modified asphalt and two kinds of TRP/graphene composite-modified asphalt were prepared. Then, the rheological characteristics of the asphalts were investigated using the frequency sweep, temperature sweep, multiple stress creep and recovery (MSCR), linear amplitude sweep (LAS), and bending beam rheometer (BBR) tests. The compatibility and microstructure of the different modified asphalt binders were evaluated using the cigar tube test and scanning electron microscopy. Results showed that adding graphene to the TRP-modified asphalt resulted in a notable improvement in rutting performance, as evidenced by the increase in rutting parameter (G*/sinδ) and % recovery (R) and a decrease in non-recoverable creep compliance (Jnr). The graphene addition also enhanced the anti-aging performance of TRP-modified asphalt. The results obtained from the LAS test, including the damage-characteristic curves and the number of cycles to fatigue failure, suggested that the fatigue performance of the TRP/graphene composite-modified asphalt was higher compared to the TRP-modified asphalt. Similarly, the BBR test results with 12% TRP and 0.5% graphene demonstrated that the composite-modified asphalt was more resistant to low-temperature cracking. Finally, the incorporation of graphene can potentially reduce the degree of phase separation in TRP-modified asphalt binder and improve its compatibility.

Utilization of high contents desulfurized crumb rubber in developing an asphalt rubber pellets modified asphalt

In this paper, two kinds of asphalt rubber modifier pellets (ARP) and asphalt desulfurized rubber modifier pellets (ADRP) that can be directly injected were prepared by a screw extruder. Scanning electron microscopy (SEM) was employed to examine the internal microstructure of the two types of modifier pellets, and the storability were further evaluated. The rotational viscosity, high and low temperature rheological behaviors and fatigue properties of asphalt with two modifier pellets were investigated by rotational viscometer, dynamic shear rheometer (DSR), and bending beam rheometer (BBR), respectively. Infrared spectroscopy was used to explore the modification mechanism. The findings reveal that the content of desulfurized crumb rubber in the ADRP can be elevated to 80%, compared with 50% of crumb rubber in ARP. The surface of crumb rubber (CR) is smooth with prominent edges and corners, while desulfurized crumb rubber (DCR) reflects the rough surface with unclear edges and corners. Micro morphology verifies that asphalt and rubber manifest a good fusion phenomenon in ADRP. Incorporating anti-sticking agent lifts the collapse height of ARP and ADRP to nearly 9 cm and prevents their complete agglomeration, endowing their excellent storability. 20% DCR-MA reveals a Nf(5%) of 106,839 and superior fatigue resistance than 20% CR-MA, while it presents lower viscosity, rutting resistance, crack resistance and anti-aging performance. ADRP-MA demonstrates higher viscosity, rutting resistance, fatigue resistance and almost equivalent low-temperature performance than that of ARP-MA under the same dosage. Action mechanism of modified asphalt with both types of modifier pellets is regarded as a physical process. The modifier pellets prepared in this study reveal the merits of easy transportation, convenient direct injection, and wide application field.

Characterization of the micromorphology of asphalt surfaces using atomic force microscopy

The surface micromorphology (SMM) of asphalt considerably affects its macroperformance. Herein, the SMM of seven types of asphalt was observed using atomic force microscopy. Moreover, the roughness theory was employed to quantitatively analyze and evaluate the surface roughness of the asphalt. The influences of the oil source, grade, styrene–butadiene–styrene (SBS) modification, aging, and water immersion of asphalt on the SMM of five types of matrix asphalt and two types of modified asphalt were elucidated. Results show that the surface roughness of KL-90 asphalt is considerably higher than those of KL-70 and KL-110 asphalts for the same oil sources. The surface roughness of SMM varies with variations in the asphalt oil source, and the surface roughness of ZH-90 asphalt is greater than that of SK-90 asphalt. After SBS modification, the SMM of the asphalt becomes smooth. The surface roughness of the asphalt first gradually increases and then rapidly decreases with aging. After the water immersion of the asphalt, its SMM roughens under the action of “water–asphalt” interfacial tension.

Micro-characterization of the adhesion properties and mechanisms at the asphalt-silica aggregate interface under combined thermal-oxygen aging and chloride salt erosion

In this investigation, various Atomic Force Microscopy (AFM) probes were used to characterize changes in the adhesion properties of aged asphalt under different concentrations of chloride salt. The characterization included analyzing the surface morphology, roughness parameters, height-height correlation function (HHCF), and force-distance curves of the asphalt. Additionally, Molecular Dynamics (MD) simulation was employed to reveal the underlying mechanisms that govern changes in adhesion properties between aged asphalt and aggregate when subjected to chloride salt erosion. Interfacial erosion and internal erosion models were constructed to facilitate a comprehensive analysis from multiple perspectives. The results demonstrate that chloride salts interact with the interface between asphalt and silica aggregates, engaging in competitive adsorption with the asphalt. The strength of this competitive adsorption is influenced by the constituents of the asphalt and the concentration gradient of chloride salts both within and outside the asphalt matrix. Under this concentration gradient, polar components are attracted to the asphalt surface by chloride ions, forming triangular adsorption structures with water molecules and aggregates such as asphaltene. Components with lower polarity exhibit distinct distributions and diffusion states due to variations in molecular weight and spatial configuration. As the concentration of chloride salts increases, the concentration gradient intensifies, resulting in enhanced transformations, migrations, and dissolutions of asphalt components. Consequently, the micro-morphology of the asphalt tends to smoothen, the HHCF undergoes significant modifications, roughness decreases, and the adhesion performance between asphalt and aggregate weakens. Moreover, at higher concentrations, the formation of precipitated chloride salt crystals disrupts the continuity of the asphalt, further compromising interfacial adhesion performance. This study is expected to provide theoretical guidance for the modification of asphalt and the improvement of asphalt pavement lifespan in complex service environments.

Development and Mechanism Analysis of High Temperature Resistant Nanocomposite Modified Asphalt

With the intensification of global warming, continuous extreme high temperature weather occurs frequently, and asphalt materials are prone to softening under continuous high temperature conditions, which can easily cause traffic accidents. Therefore, it is necessary to develop a high-temperature resistant modified asphalt. This study focuses on the research and development of high-temperature resistant nanocomposite modified asphalt under sustained extreme high temperature weather conditions, selects nanocomposite modification schemes, conducts aging, dynamic shear creep, bending small beam, and segregation tests on nanocomposite modified asphalt, comprehensively analyzes the aging resistance, segregation resistance, and high and low temperature performance of nanocomposite modified asphalt, and analyzes the mechanism of nanocomposite modified asphalt from the perspective of molecular dynamics. The research results indicate that the nano/polymer composite modification scheme for sustained extreme high temperature areas is: 3% ZnO+0.5% TiO2+3.5% SBS; The aging resistance and high temperature resistance of nanocomposite modified asphalt are obviously better than that of base asphalt; At a temperature of 413K (160℃), a more stable structure can be formed between asphalt and SBS. At a temperature of around 140℃, each interaction can reach its maximum value, and the modification effect is good.

Comparison on the performance of solid coumarone-indene resin and liquid coumarone-indene resin modified asphalt

Coumarone-indene resin (CIR) has great potential for use as an asphalt modifier because of the cost-effective, high viscosity, and excellent mechanical properties. CIR is classified into two types based on polymerization degree: solid coumarone-indene resin (S-CIR) and liquid coumarone-indene resin (L-CIR). In this study, solid coumarone-indene resin modified asphalt (S-CMA) and liquid coumarone-indene resin modified asphalt (L-CMA) were prepared, and the comparison of the high-temperature performance, compatibility, aging performance, low-temperature performance, microstructure and modification mechanism of S-CMA and L-CMA was researched following the SuperPave standard. The results reveal that S-CIR is a solid resin with a high molecular weight that improves the high-temperature performance, permanent deformation resistance, and viscosity of asphalt, but impact on low-temperature performance negatively. In contrast, L-CIR is a liquid resin with low molecular weight that enhances the low-temperature properties and plasticity of asphalt, but decreases high-temperature properties. Additionally, solid resins with large molecular weight are prone to agglomeration in asphalt, while liquid resins with small molecular weight have better dispersibility, especially in high-content situations. Meanwhile, CIR exhibits good compatibility with asphalt. Based on the FTIR test results, chemical compositions and structures of S-CIR and L-CIR are similar, and physical miscibility was demonstrated between CIR and asphalt. In summary, modifier with different molecular polymerization degrees have a greater impact on modified asphalt, S-CMA has better high-temperature performance and viscosity than L-CMA, L-CMA has better low-temperature performance and plasticity than S-CMA, and S-CMA and L-CMA can be used for pavement construction in hot and cold areas respectively.

Research on the effects of asphalt performance on rutting resistance and its correlation with rutting performance indicators

The rutting development of asphalt pavement is generally divided into two stages including the initial densification and the shear slow. The rutting resistance of asphalt mixture is greatly affected by the performance of asphalt. However, the effects of asphalt performance on the different rutting development stages are not fully clear. This paper is aimed to evaluate the applicability of rutting performance indicators to asphalt performance and further identify the correlation of changes in asphalt performance with rutting development stages. The rutting tests were carried out to study the effect of asphalt performance on the rutting resistance, in which the asphalt grade, modifier type and content, and asphalt type were involved. The dynamic stability (DS), complex stability index (CSI), Tseng-Lytton (A/C), and Gladkikh (1/E) models were selected as the rutting performance indicators. Results of the rutting test show that the application of low-grade asphalt and modifier has a larger reduction in the rutting depth. The polyethylene (PE) modifier has the largest contribution to the rutting resistance and a better composite modified effect with the styrene–butadiene–styrene (SBS) modified and 30# asphalt. The asphalt mixtures with low-grade and crumb rubber (CR) modified asphalt have the lowest temperature sensitivity. Furthermore, the asphalt performance has great effects on the initial densification stage, as well as the shear slow stage. The A/C and CSI that are related to both the initial and secondary rutting stages are the most reliable indicators to characterize the effect of asphalt performance on the rutting resistance of asphalt mixture. The correlations of DS and 1/E with the rutting depth are lower than the former two indicators, indicating that these only related to the secondary rutting stage are not recommended.

Reološka svojstva sintetiziranih aditiva u vrućoj asfaltnoj mješavini: stanje područja

In civil engineering, pavement, which is a mixture of aggregate and bitumen, is the layer most affected by traffic loads. Thus, problems, such as cracking, rutting, fatigue, aging, and moisture damage occur in the asphalt pavement layer throughout its service life. Such problems are generally caused by the increase in the number of heavily loaded vehicles, design and construction errors, and climate and environmental conditions. Scientists and engineers are continuously working on improving the performance of asphalt pavements. Particularly, recent studies have focused on improving multiple properties of asphalt simultaneously by chemically synthesising a novel material in the laboratory. This study aims to present a review of the effects of chemically synthesised additives on the performance of asphalt binders and mixtures. The findings of this study show that these new additives had a significant effect on the rheological properties of asphalt, such as rutting, elasticity, and fatigue life, when used in appropriate proportions. This study is expected to serve as a reference and guide for future studies on the production of new synthesised additives as asphalt modifiers.

RUTTING PERFORMANCE OF TREATED LOW-DENSITY POLYETHYLENE AS ADDITIVE ON THE SUSTAINABLE MIXTURE

Rutting is a major distress issue in conventional flexible pavements causing the service life of road pavement reduced. A lot of efforts had been carried out to modify the hot mix asphalt mixture to overcome the problems. However, asphalt modification mainly increased the initial cost of road construction, which had forced many road agencies and researchers to use waste materials as modifiers. In this study, the potential use of low-density polyethylene powder made by waste plastic bag (treated) as an additive on the performance of rutting resistance was investigated by Marshall, resilient modulus, dynamic creep and double wheel tracker tests. The results showed that 0.75% of treated plastic (TP) by weight of total aggregate attained higher performance in rutting resistance than the conventional mixture. It can be concluded that the waste material additive not only increases the mixture performance but more towards mixture sustainability.

Effect of different waste plastic modifiers on conventional asphalt performance: optimal preparation parameters determination and mechanism analysis.

The typical treatment of waste plastics has become a global environmental problem. In light of recent developments, waste plastics used as asphalt modifiers offer an efficient approach to solve this problem. This paper studied the effects of three kinds of waste plastic-modified asphalts (WPMA), with polypropylene (PP), polyethylene (PE) and ethylene-vinyl acetate copolymer (EVA) as their respective modifiers, on the conventional asphalt performance. Furthermore, an orthogonal experimental design (OED) was used to determine the preparation parameters of WPMA. Thereafter, thermogravimetric-differential scanning calorimetry (TG-DSC) and Fourier transform infrared spectroscopy (FTIR) were employed to expound the mechanism of WPMA. It was then subsequently ascertained that the optimum preparation parameters of PP-modified asphalt (PPMA) and PE-modified asphalt (PEMA) were 170 °C, 3000 rpm, and 30 min, while the optimum preparation parameters of EVA-modified asphalt (EVAMA) were 180 °C, 3000 rpm, and 30 min. In addition, WPMA displayed better high-temperature performance and are inherently more suitable for pavement in high-temperature regions. Ultimately, this study will effectively solve the disposal of waste plastic and promote the research and application of WPMA in the future.

Research on Improving the Performance of Emulsified Asphalt Modifiers

Research on Improving the Performance of Emulsified Asphalt Modifiers

Laboratory testing and field application of devulcanized rubber/SBS composite modified asphalt

Styrene-butadiene-styrene copolymer (SBS) and recycled tire rubber are the typical polymers for asphalt modification. The dispersion of crumb tire rubber (CTR) dominates the composite effect of rubberized asphalt. And the multiscale of CTR in mixtures always challenges the design and construction of asphalt mixtures. The multiscale dispersion of CTR can be controlled by pre-devulcanization. In this study, lightly devulcanized rubber (LDR) with various dispersive scales in asphalt from microns to dozens of microns, and deeply devulcanized rubber (DDR) with micro-nano scales were prepared and analyzed, respectively. The devulcanized rubber (DR) was further compounded with SBS to prepare composite modified asphalt. The influences of rubber content on the structure and properties of modified asphalt and mixtures were investigated, and the dispersive structure model of asphalt mixture was also established. Furthermore, a high viscoelastic rubberized asphalt was prepared with 4% SBS and 20% DDR in the field plant and paved in a field project, a new first-grade national highway. The results showed that the devulcanization of CTR can help the dispersion of CTR in asphalt by improving the compatibility among CTR, SBS, and asphalt. And the dispersive scale and the content of DR can affect the binder content, high and low temperature performance of asphalt mixtures. The field project showed that the high viscoelastic rubberized asphalt exhibited similar mix design and construction process but better high and low temperature performance compared to SBS modified asphalt.

Study on the high-temperature and aging properties of agricultural waste-modified asphalt based on rheology.

The modifier of road materials from agricultural waste (AW) as raw material has been widely noticed. Considering the environmental impact of AW treatment and the National policy on the promotion of resource reuse, the feasibility of four AW (namely, bamboo powder, rape straw, corn cob, and wheat straw) for styrene butadiene styrene (SBS) asphalt modification is studied from the properties and mechanism perspectives. Through properties evaluation tests (such as the dynamic shear rheometer, multiple stress creep recovery, and rotating thin film oven test), the influence of four AW and different mixing amounts on the properties of SBS modified asphalt pavement is analyzed from the aspects of high-temperature deformation resistance and anti-aging properties. The results reveal that the four AW can improve the SBS asphalt's high-temperature deformation resistance and anti-aging properties, among which rape straw has the most significant improvement effect. In addition, through the fourier transform infrared spectroscopy test, the microscopic mechanism of the AW/SBS composite modified asphalt binder is revealed from the functional groups. The analysis shows that the AW is physically mixed with the SBS asphalt binder, which inhibits the growth of sulfoxide groups and the cracking of the SBS modifier during aging.

Experimental Study on the Physicochemical Properties of Asphalt Modified by Different Anti-Stripping Agents and Their Moisture Susceptibility with Aggregates.

Erosion and the stripping effect of moisture on asphalt mixtures is one of the main reasons for the shortened service life of asphalt pavements. The common mean of preventing asphalt pavements from being damaged by moisture is adding anti-stripping agents (ASAs) to asphalt mixtures. However, the effect regularity and mechanism of anti-stripping agents on the physicochemical properties of asphalt is not exactly defined. This study compared the physical properties of ASA-modified asphalt (AMAs) to determine the optimal dosage and investigated the rheological and adhesion properties. Based on the roller bottle method and water immersion method, the moisture susceptibility of AMAs with three particle sizes was investigated. The results showed that the modification of asphalt using anti-stripping agents was a physical modification. At the optimum dosage of anti-stripping agents (0.3%), the basic physical properties of AMA1 were the most desirable. ASA2 increased the resistance of asphalt for deformation at high temperature by 46%, and AMA3 had the best low-temperature performance. ASAs enhanced the dispersed and polar components in the asphalt binder, improving the adhesion energy of asphalt. AMA3 had the strongest adhesion to the aggregate, with an increase in adhesion work by 2.8 times and a 45% of increase in ER value. This was attributed to ASA3 containing with a large number of metal cations and polar functional groups. It was shown that ASAs provided the most improvement in the anti-stripping performance of asphalt mixtures with 9.5-13.2 mm particles. The amide ASA, phosphate ASA and aliphatic amine ASA improved the water damage resistance of asphalt by 65%, 45% and 78%, respectively. This study can help engineers realize the effects of different types of ASAs on the physicochemical properties of asphalt and select the most suitable type of ASAs according to the service requirements.

Engineering properties, microplastics and emissions assessment of recycled plastic modified asphalt mixtures

The use of recycled plastic in asphalt is raising interest since contributing to increase the sustainability of roads pavements. The engineering performance of such roads are commonly assessed but scarcely correlated to the environmental impacts of incorporating recycled plastic in asphalt. This research encompasses an evaluation of the mechanical behaviour and environmental impact of introducing low melting point recycled plastics, low density polyethylene and commingled polyethylene/polypropylene, to conventional hot mix asphalt. While this investigation reveals a reduction in moisture resistance between 5 and 22 % contingent on the plastic content, the benefits include a significant 150 % enhancement in fatigue resistance and 85 % improvement in rutting resistance when compared with conventional hot mix asphalt (HMA). From an environmental perspective, high-temperature asphalt production with higher plastic content resulted in decreased gaseous emissions for both types of recycled plastics up to 21 %. Further comparison studies indicate that microplastic generation from recycled plastic-modified asphalt is comparable to that from commercial polymer-modified asphalt products, long employed by the industry. Overall, the use of low melting point recycled plastics as an asphalt modifier is promising since offering both engineering and environmental benefits when compared to conventional asphalt.

Performance Evaluation of Waste High Density Polyethylene as a Binder Modifier for Hot Mix Asphalt

Performance Evaluation of Waste High Density Polyethylene as a Binder Modifier for Hot Mix Asphalt

Optimisation of composite asphalt mixture involving glass fibre and nano clay based on central composite design

ABSTRACT Different types of additives are used in asphalt modification to enhance several properties within the asphalt pavement. In various cases, modification is needed by using multiple additives, which is called composite modification. In this study, glass fibre and nano clay were used to modify the asphalt pavement. The amount of these two additives, together with the optimum bitumen content, was determined by the response surface methodology (RSM). Central composite method (CCD) was used for determining the optimum amount of independent variables (nano clay, glass fibre, bitumen content), by evaluating the dependent variables. Marshall mixture design criteria and minimum bitumen content, were the optimal conditions. As a result, the mixture containing 0.2% glass fibre, 3.693% nano clay and 4.096% bitumen content, was predicted to give the most desirable characteristics. Additionally, verification tests were conducted to evaluate the adequacy of the predicted model. The results were within the 95% confidence intervals for all response variables, which demonstrates the validity of the model obtained in the study. Consequently, CCD can be used to obtain design optimisation of asphalt modification with less mixture production for experimental stages. This is a substantial advantage, which supports human safety and environment- friendly practices.