Search Results (56)

As the global demand for electronic equipment continues to grow, many devices are being replaced more frequently, resulting in a rapid rise in electronic waste (e-waste), now the fastest growing waste stream worldwide. Motivated by this, the objective of this study is to present an environmentally friendly method to recycle acrylonitrile–butadiene–styrene (ABS), one of the most common e-waste plastics, by using it for asphalt production. In contrast to earlier methods of plastic-modified asphalt production involving complex pretreatments or complimentary additives unsuitable for plant-scale use, this study aims to demonstrate a practical, low-cost solution through the use of carbon black. This approach included physically pretreating ABS plastics for size reduction and incorporating waste tire-derived carbon black to promote effective dispersion in asphalt during wet modification. The rheological properties of the e-waste-modified asphalt were subsequently assessed. The test results indicated that recycling ABS plastics with a blending content of 5% alongside 5% carbon black can enhance cold-weather cracking resistance and high-temperature anti-rutting performance of asphalt. The enhancement can be attributed to the proper preparation procedures of ABS plastics and the addition of carbon black, which can further improve the performance by promoting the proper dispersion of plastic particles in asphalt. The outcome of this study indicates that recycling e-waste plastics through asphalt production can lead to more green and sustainable asphalt construction, reduce total construction costs, and most importantly enhance performance. Full article

In recent years, the employment of rejuvenators and warm mix asphalt (WMA) additives for reclaimed asphalt pavement (RAP) has been recognized as a popular approach to increase the recycling rate of waste materials and promote the sustainable development of pavement engineering. However, the composition of warm mix recycled asphalt binder is complicated, and the microstructural changes brought about by the rejuvenators and WMA additives are critical in determining its macroscopic mechanical properties. This research focuses on the atomic modeling of the rejuvenators and WMA additives diffusion behavior of the warm mix recycled asphalt binder. The objective is to reveal the thermodynamic performance and diffusion mechanism of the WMA binder under the dual presence of rejuvenators and WMA additives. Three types of mutual diffusion systems (Aged and oil + virgin + wax, Aged + virgin + wax, and Aged and oil + virgin) were established, respectively, for a comparative investigation of the glass transition temperature, viscosity, thermodynamics, free volume, and diffusion behavior. The results indicate a 44.27% and 31.33% decrease in the glass transition temperature and apparent viscosity, respectively, after the incorporation of 5% oil rejuvenators in the Aged + virgin + wax asphalt binder, demonstrating the improved cracking resistance and construction workability. The presence of the RAP binder and organic WMA additives raised the cohesion of the asphalt binder and decreased self-healing ability and free volume, and these detrimental influences can be offset by the introduction of rejuvenators. The combined use of rejuvenators and organic WMA additives remarkably enhanced the de-agglomeration to asphaltenes, stimulated the activity of aged RAP macromolecular components, and ultimately improved the blending efficiency of virgin binders with the overall structure of RAP binders. Full article

The large-scale production of waste plastics has brought serious environmental pollution problems and its recycling and high value-added utilization technology remains a global challenge. Therefore, this study uses waste polyethylene (PE) to prepare high-performance polyethylene composite modified asphalt (HPEA), solving the problem of poor stability and low temperature performance of traditional plastic modified asphalt, while achieving high value-added utilization of waste plastics. A high-performance polyethylene composite modifier (HPE) was prepared through mechanochemical and thermochemical interactions. Then HPEA with different HPE content and styrene-butadiene-styrene (SBS) modified asphalt (SBSMA) with different SBS content were prepared. Compare and analyze the conventional performance, storage stability, anti-aging performance and microscopic properties of HPEA and SBSMA. The results are as follows: (1) the conventional performance of HPEA is comparable to, or superior to, that of SBSMA. The addition of HPE resulted in a significant decrease in asphalt penetration. The modification effect achieved by adding 3–5% SBS to Kunlun 70# asphalt is equivalent to that achieved by incorporating 4–6% HPE. (2) HEPA exhibits good storage stability and no obvious segregation phenomenon. When the HPE content changes from 4% to 8%, the maximum difference in 48 h softening point of HPEA is 1.1 °C, which is significantly smaller than the 48 h softening point difference of SBSMA when the SBS content changes from 3% to 5%. (3) When HPE attains a specific concentration, HPEA can exhibit an anti-aging performance that is comparable to, or superior to, that of SBSMA. (4) The infrared spectrum of HPEA closely resembles that of SK70# matrix asphalt. The modification of HPEA primarily involves physical blending, with HPE undergoing development and re-crosslinking within the system, leading to interactions between smaller particles and asphalt, resulting in the formation of a relatively stable three-dimensional spatial structure. Full article

Currently, there is limited research on the utilization of spent coffee grounds (SCG) in asphalt pavement. This study explores using SCG as a novel rejuvenator together with waste cooking oil (WCO) to enhance the performance of aged asphalt (AA). The high-temperature performance of recycled asphalt was preserved using SCG containing oily components. However, the low-temperature performance of long-term aged asphalt could not be completely restored to the level of virgin asphalt. Therefore, various dosages of SCG and WCO were utilized to optimize the recovery of low-temperature properties while maintaining high-temperature performance. The recycled asphalt (RA) was analyzed through conventional indexes, microscopic characteristics, and rheological properties using penetration and softening point tests, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and a dynamic shear rheometer (DSR). The results showed that the G* of W₇S₁₂ increased by 90% relative to virgin asphalt. Additionally, at strain levels of 2.5% and 5%, the fatigue life of W₈S₁₈ was approximately 3.39 times and 2.34 times greater, respectively, than that of the virgin asphalt. The addition of a rejuvenator can enhance the low-temperature cracking resistance of aged asphalt. Moreover, the FTIR results indicated that the regeneration mechanism of recycled asphalt consisted of physical blending. In summary, W₇S₁₂ exhibited the highest high-temperature performance, while W₈S₁₈ demonstrated superior fatigue life. This study may promote the sustainable development of asphalt pavements by utilizing organic waste as a rejuvenator through resource recovery. Full article

This research focuses on a mineral–cement mixture containing bitumen emulsion, designed for cold recycling procedures, the formulation of which includes 80% (m/m) of waste material. Deep cold recycling technology from the MCE mixture guarantees the implementation of a sustainable development policy in the field of road construction. The utilised waste materials include 50% (m/m) reclaimed asphalt pavement (RAP) from damaged asphalt layers and 30% (m/m) recycled aggregate (RA) sourced from the substructure. In order to assess the possibility of using a significant amount of waste materials in the composition of the mineral–cement–emulsion (MCE) mixture, it is necessary to optimise the MCE mix. Optimisation was carried out with respect to the quantity and type of binding agents, such as Portland cement (CEM), bitumen emulsion (EMU), and redispersible polymer powder (RPP). The examination of the impact of the binding agents on the physico-mechanical characteristics of the MCE blend was performed using a Box–Behnken trivalent fractional design. This method has not been used before to optimise MCE mixture composition. This is a novelty in predicting MCE mixture properties. Examinations of the physical properties, mechanical properties, resistance to the effects of climatic factors, and stiffness modulus were conducted on Marshall samples prepared in laboratory settings. Mathematical models determining the variability of the attributes under analysis in correlation with the quantity of the binding agents were determined for the properties under investigation. The MCE mixture composition was optimised through the acquired mathematical models describing the physico-mechanical characteristics, resistance to climatic factors, and rigidity modulus. The optimisation was carried out through the generalised utility function U^III. The optimisation resulted in indicating the proportional percentages of the binders, enabling the assurance of the required properties of the cold recycled mix while utilising the maximum quantity of waste materials. Full article

An enormous surge in the pavement sector requires the evaluation of interface bonding in asphalt composite, since the assessment of bonding brings considerable cost savings. Microscopic and mechanical analyses were performed to study the status of the interface transition zone of four groups of asphalt mixtures, using thin-slice preparation to obtain asphalt mixture slices with a flat surface for microscopic analysis. The interface transition zones were characterized using good knowledge of blending or diffusion phenomena by conducting tests both at the micro and macro levels to determine mixture quality. Asphalt mixture components were observed using fluorescence microscopy imaging and evaluated by the gray value change law. Asphalt mixture groups, (virgin, recycled of 30% aged and 70% unaged, 6%, and 4% rejuvenator dosage mixtures) under the same process parameters, which are a mixing time of 270 s and a mixing temperature of 150 °C, been considered optimum for component fusion in a hot asphalt mixture were used. This study relied on the influence of morphology law, assessed through rutting tests for high temperature performance, semi-circular bending tests for low temperature performance, and pull-off tests for interface bonding strength. The relationship between interface transition zones and macro performance was studied. The self-developed pull-off method was a research innovation which can be used as an alternative to study interface transition zones in asphalt mixtures, and provides the necessary data needed with 3D surface failure mode calculations. The device measured the bonding strength of a single aggregate in distinct positions using the bitumen penetration test method. The main goals were to determine a correction factor, identify the appropriate alteration, and compute the actual fracture surface area. Using scanning electron microscopy for interface characterization and micro-morphologies of mortar transition zone, our analysis provides adequate knowledge about interface position and the components present. The applied approaches to characterize asphalt mixture interfaces proved workable and reliable, as all methods have similar trends with useful information to determine asphalt pavement quality. Full article

In this study, a critical evaluation and the benefits of using a waste and a virgin polymer in an asphalt mixture are presented. The present paper is the result of a three-year research effort to find a suitable recyclate compatible with asphalt binder and setting reaction conditions in the preparation of asphalt mixtures with the mentioned recyclate. This suitable candidate was recycled low-density polyethylene (LDPE), which was produced by recycling old, worn-out bags and films. An amount of 6% of LDPE by the weight of the binder content was suggested as the best amount of the modifier. Physical tests, including penetration, softening point, and kinematic viscosity have been carried out to prove the effectiveness of the modification on the binder properties. The effectiveness of the blending process and the appropriate concentration of additives led to a homogeneous polymer-modified bitumen without any imperfections in the structure. After successful preparation under laboratory conditions, this paper describes the preparation of asphalt mixtures directly in an asphalt-mixing plant and the subsequent implementation of a verification section. The overall composition of prepared polymer-modified asphalt mixtures has been studied. An important result of this study is the preparation of the asphalt mixture with waste LDPE that meets all the technical requirements. Moreover, it has been proven that this type of waste PE is fully applicable in asphalt-mixing plants in Slovakia, with zero or minimal financial burden on construction companies to complete the construction of their production facilities. Using such a technology, we can reduce the amount of waste plastics that otherwise end up in landfill. Full article

The continuous increase in solid waste materials, such as waste tires, underscores the critical importance of recycling them to mitigate environmental impact and promote sustainable resource management. This research study evaluated the effectiveness of utilizing waste tire pyrolysis oils (WTPOs) as recycling agents for asphalt materials. The chemical composition and thermal behavior of WTPO were analyzed using Fourier transform infrared (FT-IR) spectroscopy and thermogravimetric analysis (TGA). Mechanically, the prepared WTPO binders were assessed by measuring dynamic viscosity and changes in high- and intermediate-temperature performance grades. Additionally, the cracking susceptibility of the binders was evaluated using the Glover-Rowe (G-R) parameter. The findings indicated that WTPOs might contain water and light aromatics in varying percentages, depending on the pyrolysis process. Incorporating WTPOs enhanced the workability of asphalt mixtures and ensured a high degree of blending between recycled/aged asphalt and raw binder. A 12% WTPO dosage was identified as the most effective for enhancing fatigue and low-temperature cracking resistance, facilitating improved interactions between the virgin binder and recycled asphalt materials. Finally, utilizing WTPOs as rejuvenating agents in pavement construction supports sustainable practices by recycling waste materials and significantly improving the performance and durability of asphalt mixtures. Full article

The blending degree between virgin asphalt and aged asphalt has a significant effect on road performance of reclaimed asphalt mixture. This study presented an innovative examination of blending behavior between virgin asphalt and aged asphalt incorporating a new bio-based warm-mix rejuvenator (BWR) by utilizing Atomic Force Microscopy (AFM). Through analyzing the variation of several micro-morphology parameters between virgin asphalt and aged asphalt (or recycled asphalt) after blending, an index of regenerative blending degree (RBD) was proposed to quantitatively evaluate their blending behavior, and the effect of various blending temperatures and durations on regenerative blending degree was investigated. The results show that the regenerative blending degree between virgin asphalt and aged asphalt was higher than that between virgin asphalt and recycled asphalt under the same blending condition. A clear linear correlation was observed between the regenerative blending degree calculated by 3D micro-morphology parameters and the dosage of bio-based warm-mix rejuvenator in recycled asphalt, with a correlation coefficient of 0.98. With the increase in blending duration, the regenerative blending degree between virgin asphalt and recycled asphalt increased first and then decreased, but continued to improve with the increase in blending temperature, which indicates that a higher blending temperature and prolonging the blending duration properly have a positive effect on the blending processing between virgin asphalt and recycled asphalt. Compared with the regenerative blending degree calculated by 2D micro-morphology parameters, the regenerative blending degree calculated by 3D micro-morphology parameters is more reasonable to quantify the blending behavior between virgin asphalt and recycled asphalt. Full article

A drawback of recycled mixtures containing reclaimed asphalt is their increased stiffness, further worsened by the accelerated aging of binders in extreme weather conditions. Previous studies have shown that while rejuvenating agents can mitigate some of these issues by improving flexibility and reducing brittleness, they often present challenges, such as performance variability and the potential for rutting. This study aims to develop an optimal blend of reclaimed bitumen, a rejuvenating agent, and pure bitumen to achieve rheological properties similar to a control 35/50 pen-grade bitumen for road paving. Hence, the rejuvenated binders comprised 30:70 blends of reclaimed asphalt bitumen and 50/70 pen-grade bitumen, adding 0.2% to 0.6% of a rejuvenating agent by mass of the reclaimed asphalt. Sample testing included conventional penetration grade, softening point, and viscosity tests, followed by dynamic shear rheometer tests under unaged, short-term, and long-term aging conditions. The results show that the binder blend with 0.4% rejuvenator closely resembles the rheological properties of 35/50 pen-grade bitumen. This blend exhibits a 20% to 55% stiffness reduction for recycled mixtures with 30% reclaimed asphalt. Notably, the rejuvenated binders exhibited a similar level of aging resistance to the control bitumen, with a marginal difference of less than 5% in aging ratios. Meanwhile, large strain amplitude tests showed the importance of defining maximum rejuvenating incorporation rates in recycled mixtures to avoid rutting problems, where binders with 0.4% rejuvenator doubled the rutting potential (J_nr values). This innovative study highlights the potential for enhancing recycled mixtures’ performance by evaluating rejuvenated reclaimed binders’ rheology subjected to different aging conditions, thus contributing to sustainability in pavement construction. Full article

Cold-mix asphalt is a greener alternative to pavement construction, processed at 10–40 °C, which is typically lower than other techniques like warm-mix asphalt and hot-mix asphalt. Huge amounts of construction and demolition waste, such as broken bricks, recycled concrete aggregates, reclaimed asphalt pavement, ceramic waste, etc., are generated every year due to the acceleration in infrastructure development. The production of such massive amounts causes landfilling issues, and their disposal is a serious issue nowadays. This study examines the effect of binary blended fillers on the performance of cold asphalt mixes using emulsified binders and 50% reclaimed asphalt pavement materials. Moreover, three types of binary blended fillers (BBFs), cement, fly ash, and Stabil Road, were used at different dosages. Overall, 500 samples were prepared for the mix design, and the optimum emulsion content was determined as 11% and 9% for the CM and 50R mixes, respectively, based on the Marshall stability peak value and volumetric properties such as voids in the mineral aggregates, total voids, and dry density. The moisture susceptibility of the recycled cold-mix asphalt (RCMA) mixture was evaluated using the tensile strength ratio. Cantabro abrasion loss was used to assess the cohesion resistance of the mixtures. The dynamic response of the mixes to the applied load was evaluated using the resilient modulus. The results of the present study reveal that using BBFs in the RCMA improved the inter-particle bonding and strength. Furthermore, BBF incorporation enhanced the performance of the recycled cold-mix asphalt. Full article

Exploring the interface of environmental sustainability and civil infrastructure development, this study introduces waste butter (WB), a byproduct of animal fat processing, as a novel bio-modifier in asphalt production. This approach not only recycles animal waste but also charts a course for sustainable infrastructural development, contributing to a reduced environmental impact and promoting circular economy practices. The experiments incorporated varying WB concentrations (e.g., 3%, 6%, and 9% by weight of binder) into standard AP-5 asphalt, employing advanced analytical tools for comprehensive characterization. These included thin-layer chromatography–flame ionization detection (TLC-FID), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and Differential Scanning Calorimetry (DSC). The critical properties of the asphalt blends, such as penetration, softening point, viscosity, ductility, rutting factor (Dynamic Shear Rheometer), and thermal susceptibility (Penetration Index, Penetration–Viscosity Number), were assessed. FT-IR analysis indicated negligible chemical alteration with WB addition, suggesting predominantly physical interactions. TLC-FID showed a decrease in aromatic and asphaltene components but an increase in resin content, highlighting the influence of WB’s fatty acids on the asphalt’s chemical balance. The colloidal instability index (I_C) confirmed enhanced stability due to WB’s high resin concentration. Meanwhile, SEM analysis revealed microstructural improvements with WB, enhancing binder compatibility. TGA demonstrated that even a minimal 3 wt. % WB addition significantly improved thermal stability, while the DSC results pointed to improved low-temperature performance, reducing brittleness in cold conditions. Rheologically, WB incorporation resulted in increased penetration and ductility, balanced by decreased viscosity and softening point, thereby demonstrating its multi-faceted utility. Thermal susceptibility tests emphasized WB’s effectiveness in cold environments, with further evaluation needed at higher temperatures. The DSR findings necessitate careful WB calibration to meet Superpave rutting standards. In conclusion, this research positions waste butter as a superior, environmentally aligned bio-additive for asphalt blends, contributing significantly to eco-friendly civil engineering practices by repurposing animal-derived waste. Full article

Refined separation not only controls the variability of reclaimed asphalt pavement (RAP), but also improves the mixing ratio of RAP and the quality of recycled asphalt mixtures. This study examines RAP treated with various refined separation frequency parameters, analyzes the variation rules and the variability of RAP aggregate gradation, asphalt content, asphalt properties, and aggregate properties, and calculates the maximum mixing percentage of coarse RAP material by using the gradation variability control method and the asphalt content variability control method. The results show that the variability of gradation and asphalt content of coarsely separated RAP is considerable, and a refined separation process significantly reduces the variability of gradation and asphalt content of RAP; the agglomeration of RAP decreases with an increase in the refined separation frequency; and the RAP agglomeration of three kinds of RAPs (E1, E2, and E3) under a refined separation frequency of 55 Hz reduces by 6.40%, 4.30%, and 4.30%, respectively, as compared with that of coarsely separated RAPs. The asphalt content of the refined separation RAP gradually decreases with an increase in frequency, and the asphalt content of E1 and E2 (55 Hz) was only 0.95% and 1.10%, respectively. The maximum percentage of RAP in recycled asphalt mixtures was calculated using the gradation variability control method and the asphalt content variability control method, respectively. The maximum proportions of RAP were 45% and 33% for A1 (0 Hz), respectively, and the maximum proportions of RAP for E1 (55 Hz) were all 100%. The results of the two methods show that the process of refined separation can increase the maximum proportion of blended RAP materials. They also demonstrate that the refined separation process can increase the maximum blending ratio of coarse RAP materials, thereby improving the quality of the RAP, increasing the proportion of RAP blending, and ensuring the quality of the recycled asphalt mixture. In conclusion, the refined separation process holds promise for maximizing the potential value of RAP and optimizing its recycling, environmental, and economic benefits. Full article

The extraction and utilization of non-renewable mineral resources impose significant transportation and economic challenges in infrastructure construction. At the same time, recycling fly ash derived from the bottom ash in municipal solid waste incineration residues (MSWIRs) presents a waste management hurdle. This study investigates the viscoelastic characteristics and mechanical performances at different scales of asphalt mastic and mixture with fly ash from MSWIRs. Firstly, Fourier transform infrared spectrometry (FTIR) was adopted to distinguish the physically blended states of asphalt and fillers. Then, a frequency test using a dynamic shear rheometer (DSR) was conducted to construct viscoelastic master curves, focusing on asphalt mastic. A dynamic modulus test characterized the viscoelastic behavior at the asphalt mixture scale. Furthermore, the mechanical performances of asphalt mixtures were evaluated, including the resilient modulus through indirect tension tests, moisture susceptibility via the immersed Marshall stability test, and anti-cracking properties with a low-temperature bending test. The FA incorporation in the mixture decreased the immersion residual stability by 7.40%, and increased the flexural tensile strength by 5.03% and the stiffness modulus by 78.67%. The mechanical evaluation of the mixture with FA could meet the application requirements of the asphalt layer. Finally, statistical analyses were conducted to present strong correlations (coefficient R² over 0.70) among the mechanical results. Fly ash in asphalt mixtures revealed potential as a sustainable approach for waste reuse in road construction. Additionally, substituting mineral fillers at the mastic scale significantly influences the viscoelastic characteristics and mechanical performances of asphalt materials at the mixture scale. Full article

Reclaimed asphalt pavement (RAP) has been utilized as a potential partial substitute for virgin asphalt binder in asphalt mixtures. However, a primary concern with increasing RAP content in asphalt mixtures is the cracking potential, attributed to the aged RAP asphalt binder (RAP-binder). To address this, the use of petroleum-based and bio-derived recycling agents (RAs) in enhancing the cracking resistance of high-RAP asphalt mixtures has been explored. The objective of this study is to ascertain the effectiveness of six RAs in mitigating cracking in high-RAP asphalt mixtures. The RAs considered include petroleum-crude-oil-derived aromatic oil, soy oil, and four types of tall-oil-derived phytosterol (industrial by-product, intermediate, purified, and fatty acid-based). The RAs’ dosages were optimized, based on RAP-binder and unmodified asphalt binder properties, to produce target PG 70-22 asphalt binder when incorporated in asphalt mixtures containing 30% RAP. To assess the engineering performance of these 30%-RAP asphalt mixtures for each RA, a conventional asphalt mixture incorporating styrene-butadiene-styrene (SBS)-modified PG 70-22 asphalt binder without RAP or RAs was benchmarked for comparison. Mechanical tests performed included Hamburg wheel-track testing (HWTT), intermediate-temperature fracture tests (semi-circular bend, Illinois flexibility index, and IDEAL cracking tolerance), and thermal stress-restrained specimen tensile strength test to evaluate permanent deformation, intermediate-temperature cracking resistance, and low-temperature cracking resistance, respectively. Results showed that petroleum-crude-oil-derived aromatic oil and tall-oil-derived fatty-acid-based oil RAs were able to rejuvenate RAP-binder as measured by the cracking tests performed. Further, the use of these RAs did not adversely impact the asphalt mixtures’ permanent deformation performance. Full article