Search Results (76)

With rising global temperatures and increasing sustainability demands, the need for advanced pavement solutions has never been greater. This study breaks new ground by integrating phase change materials (PCMs), including paraffin-based wax (Rubitherm RT55), hydrated salt (Climator Salt S10), and fatty acid (lauric acid), as binder modifiers within warm mix asphalt (WMA) mixtures. Moving beyond the traditional focus on binder-only modifications, this research utilizes recycled cigarette filters (CFs) as a dual-purpose fiber additive, directly reinforcing the asphalt mixture while simultaneously transforming a major urban waste stream into valuable infrastructure. The performance of the developed WMA mixture has been evaluated in terms of stiffness behavior using an Indirect Tensile Strength Modulus (ITSM) test, permanent deformation using a static creep strain test, and rutting resistance using the Hamburg wheel-track test. Laboratory tests demonstrated that the incorporation of PCMs and recycled CFs into WMA mixtures led to remarkable improvements in stiffness, deformation resistance, and rutting performance. Modified mixes consistently outperformed the control, achieving up to 15% higher stiffness after 7 days of curing, 36% lower creep strain after 4000 s, and 64% reduction in rut depth at 20,000 passes. Cost–benefit analysis and service life prediction show that, despite costing USD 0.71 more per square meter with 5 cm thickness, the modified WMA mixture delivers much greater durability and rutting resistance, extending service life to 19–29 years compared to 10–15 years for the control. This highlights the value of these modifications for durable, sustainable pavements. Full article

In response to the escalating climate crisis, reducing greenhouse gas emissions (GHG) has become a top priority for both the public and private sectors. The pavement industry plays a key role in this transition, offering innovative technologies that minimize environmental impacts without compromising performance. Among these, the incorporation of recycled tire rubber and warm-mix asphalt (WMA) additives represents a promising strategy to reduce energy consumption and resource depletion in road construction. This study conducts a comparative life cycle assessment (LCA) to evaluate the environmental performance of an asphalt pavement incorporating recycled rubber and a WMA additive—referred to as R-W asphalt—against a conventional hot-mix asphalt (HMA) pavement. The analysis follows the ISO 14040/44 standards, covering material production, transport, construction, and maintenance. Two service-life scenarios are considered: one assuming equivalent durability and another with a five-year extension for the R-W pavement. The results demonstrate environmental impact reductions of up to 57%, with average savings ranging from 32% to 52% across key impact categories such as climate change, land use, and resource use. These benefits are primarily attributed to lower production temperatures and extended maintenance intervals. The findings underscore the potential of R-W asphalt as a cleaner engineering solution aligned with circular economy principles and climate mitigation goals. Full article

Warm-mix recycled asphalt (WMA-R) technology for reclaimed asphalt pavement (RAP) significantly reduces energy consumption and environmental pollution while maintaining the performance of asphalt mixtures. Significant progress has been made at home and abroad in evaluating the impact of regenerated asphalt mixtures on the performance of regenerated asphalt. However, the performance improvement of WMA-R depends on the effective diffusion of regenerated agents and their interaction mechanism with aged asphalt, which has not been fully studied. This paper systematically studies the diffusion characteristics of biomimetic-based warm-mix regenerant in aged asphalt and its impact on the high- and low-temperature performance of asphalt mixtures through MD and experimental verification. The results show that biomimetic-based warm-mix regenerant can significantly improve the diffusion performance of aged asphalt. Through the rutting test and low-temperature bending test, the significant improvement of the biomimetic-based warm-mix regenerant in the rutting resistance and crack resistance of asphalt mixtures was verified. Full article

This investigation aimed to assess the influence of warm-mix additives on the performance characteristics of recycled asphalt mixtures. Pressure-aging vessels were employed to simulate the aging of asphalt binders. Warm-mix recycled asphalt (WMRA) and mixtures were prepared by incorporating self-developed plant-oil-based rejuvenators and surfactant-based warm-mix additives. The rheological properties of asphalt were tested by a dynamic shear rheometer (DSR). Furthermore, the pavement performance of the asphalt mixture was evaluated by a rutting test, beam bending test, Marshall stability test, and freeze–thaw splitting test. The experimental results demonstrated that the addition of warm-mix additives reduces the penetration and softening point of recycled asphalt while enhancing its ductility. Performance improvement was quantitatively evaluated using a recovery index. The complex modulus and rutting factor of the WMRA were found to be lower than those of recycled asphalt, indicating a decrease in the asphalt’s resistance to deformation owing to the surfactant. Both the hot-mix and warm-mix recycled asphalt mixtures met the specified requirements for various performance indicators. The warm-mix rejuvenator outperformed the regular rejuvenator in evaluating water stability using the soaked Marshall residual stability method, whereas the evaluation based on the freeze–thaw splitting strength ratio demonstrated the opposite trend. Full article

Plastic waste management remains a significant global challenge, with limited recycling opportunities contributing to its status as one of the highest waste producers. In Australia, the recovery rate for plastic waste is 12.5%, resulting in a high percentage of plastics being landfilled. Common disposal methods, such as incineration and landfilling, are environmentally damaging, with incineration emitting harmful gases and landfilling causing contamination. Recycling, while preferable, faces difficulties due to contamination and infrastructure challenges. However, alternative solutions, such as integrating waste plastic into concrete, present an opportunity to both reduce plastic waste and enhance the economic value of recycled materials. This study evaluates the potential of waste plastic milk bottles (PMBs) in residential concrete by assessing their mechanical strength, environmental impact, and variability in greenhouse gas (GHG) emissions. This study demonstrated that replacing up to 10% of cement with silica fume-modified plastic milk bottle (SFPMB) waste granules maintained comparable compressive strength to traditional concrete. The addition of metakaolin to the SFPMB mix design (SFMKPMB) further improved the material’s strength by 28%. Life cycle assessment (LCA) results revealed reductions in global warming potential (GWP), human toxicity potential (HTP), and fossil depletion potential (FDP), with SFMKPMB showing the greatest environmental savings. A Monte Carlo simulation evaluated variability factors, revealing that additional transportation and energy requirements increased GHG emissions, though the SFMKPMB mix ultimately resulted in the lowest overall material GHG emissions. This study demonstrates the complexity of assessing “green” materials and highlights how material variability and energy use can influence the sustainability of waste-derived composites. Despite challenges, incorporating waste plastics into concrete offers a promising strategy for mitigating landfill waste and reducing environmental impacts, especially as renewable energy adoption increases. Full article

Concrete, having evolved over the last 2000 years, is integral to modern infrastructure, with continuous innovations aiming to address sustainability challenges. From Roman concrete mixes to the invention of Portland cement (PC), concrete has evolved to meet growing infrastructure demands. As urbanization and energy consumption increase, the construction industry is focusing on high-performance materials, recycling, and minimizing harmful substances. Research on sustainable concrete alternatives shows promising reductions in global warming potential and other environmental impacts compared to traditional PC. However, challenges such as higher material costs and performance limitations remain. Alternatives such as alkali-activated concrete (AAC), self-healing concrete, and bacterial concrete (BC) have emerged in response to environmental concerns, along with fiber-reinforced AAC, waste-based concrete composites, and the reuse of construction and demolition waste (CDW), further enhancing sustainability. Foamed concrete, with its lightweight and insulating properties, offers additional potential for reducing environmental impact due to its ability to incorporate recycled materials and reduce raw material consumption. Technologies like three-dimensional concrete printing (3DCP) are improving resource efficiency and reducing carbon footprints while also lowering labor and material waste. However, concerns regarding cost-effectiveness and social sustainability persist. Overall, continued innovation is the key to balancing performance, cost, and sustainability in the development of concrete and to meet the growing demands of global infrastructure. 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

Expanding the road network is inevitable due to the accelerated economic growth of countries. However, the development of road infrastructure has generated considerable concern among society, governments, and environmental organizations. This concern mainly stems from the significant environmental effects and the omission of the sustainability of materials associated with road construction. Current literature suggests Life Cycle Assessment (LCA) as a solution to address greenhouse gas emissions and other environmental impacts of road infrastructure. This research uses the PRISMA-SCR methodology to identify strategies to mitigate environmental impact during the life cycle stages of asphalt pavements and emission-generating activities. This study identifies the critical life cycle stages responsible for the largest amount of emissions, highlighting “material extraction and production” and “transportation” as key areas of intervention. The results demonstrate how the incorporation of recycled materials (RAPs) and warm mix asphalts (WMAs) can reduce between 15% and 45% of total emissions. It is concluded that it is possible to develop asphalt pavement construction projects with a sustainability perspective, allowing not only to identify opportunities to optimize construction processes but also to establish a reference framework for transportation agencies to integrate more sustainable practices, including the reduction of emissions, the responsible use of non-renewable resources and proper waste management. Full article

This paper presents a comparative life cycle assessment (LCA) of the traditional and modern materials used in heritage building restoration, focusing on mud, limestone, decorative plaster, blended hydraulic cement, and ready-mix concrete. The analysis examines key environmental impact categories, including global warming potential (GWP), ozone depletion potential (ODP), acidification potential (AP), eutrophication potential (EP), and water use across multiple life cycle stages. The results reveal that mud and limestone, while having lower initial environmental impacts in production, contribute significantly to ODP and GWP during transportation due to their heavy weight. Modern materials like blended hydraulic cement and ready-mix concrete exhibit the highest overall environmental impacts, particularly in GWP, AP, and water use, due to their energy-intensive production processes. Decorative plaster, while lower in initial impacts, gains higher environmental burdens over time due to its frequent replacement. This study highlights the need to optimize transportation and improve recycling practices for traditional materials, while also encouraging the exploration of alternative materials for reducing the environmental footprint of heritage restoration. Full article

Reclaimed Asphalt Pavement (RAP) materials are used as substitutes for new materials in asphalt pavement construction, leveraging the engineering and commercial benefits of the aged binders and aggregate matrixes in RAP. These asphalt mixtures impart significant variations in volumetric properties and asphalt mixture characteristics. The current study investigates the Marshall properties, moisture susceptibility, and rutting behavior of 24 recycled asphalt mixtures developed with nanosilica and nanoclay. RAP material percent, nanomaterial content, binder grade, and extra binder were considered the factors influencing asphalt mixture performance. The above factors were analyzed using the Response Surface Methodology (RSM) to predict the Marshall and volumetric properties. Also, this investigation covers the moisture susceptibility and rut characteristics of recycled nanomaterial-modified Hot Mix Asphalt (HMA) and Warm Mix Asphalt (WMA) mixes developed with Viscosity Grade 30 (VG-30) and Polymer-Modified Bitumen-40 (PMB-40). The chemical additive Zycotherm was used to develop WMA mixes. The test results indicate that adding RAP material at higher percentages and modifying the binder with nanomaterials affected moisture susceptibility with reduced moisture damage. Recycled nanosilica-modified HMA mixes developed with PMB-40 at higher RAP percentages reported higher tensile strength ratio (TSR) values in contrast with VG-30 mixes, indicating their greater susceptibility toward moisture-induced damage. The rutting potential of all of the recycled asphalt mixture combinations was enhanced by densely packed aggregate structures optimized with nanomaterials, total binder content, and RAP materials developed using the Marshall method. Overall, the nanosilica-modified recycled asphalt mixes developed with PMB40 at higher RAP percentages showed better performance in terms of strength and durability. Full article

To solve the problems on resource utilization and environmental pollution of waste concrete and waste polypropylene (PP) plastics, the recycling of them into asphalt pavement is a feasible approach. Considering the high melting temperature of waste PP, this study adopted a thermal-and-mechanochemical method to convert waste PP into high-performance warm-mix asphalt modifiers (PPMs) through the hybrid use of dicumyl peroxide (DCP), maleic anhydride (MAH), and epoxidized soybean oil (ESO) for preparing an asphalt mixture (RCAAM) containing recycled concrete aggregate (RCA). For the prepared RCAAM containing PPMs, the mixing temperature was about 30 °C lower than that of the hot-mix RCAAM containing untreated PP. Further, the high-temperature property, low-temperature crack resistance, moisture-induced damage resistance, and fatigue resistance of the RCAAM were characterized. The results indicated that the maximum flexural strain of the RCAAM increased by 7.8~21.4% after using PPMs, while the sectional fractures of the asphalt binder were reduced after damaging at low temperature. The use of ESO in PPMs can promote the cohesion enhancement of the asphalt binder and also improve the high-temperature deformation resistance and fatigue performance of the RCAAM. Notably, the warm-mix epoxidized PPMA mixture worked better close to the hot-mix untreated PPMA mixture, even after the mixing temperature was reduced by 30 °C. Full article

This study investigates the transformative effects of incorporating Trinidad Lake asphalt (TLA), crumb rubber modifier (CRM), and the warm mix additive leadcap (LC) into petroleum-based asphalt binder PG 64-22. Our results show that LC significantly reduces binder viscosity, leading to easier application and lower energy consumption, especially when combined with TLA and CRM. The addition of TLA and CRM enhances rutting resistance, with notable improvements in both pre- and post-aging conditions, particularly in formulations combining PG 64-22, 20% TLA, and 10% CRM. These formulations exhibit superior performance metrics, such as increased percentage recovery (% rec) and reduced non-recoverable creep compliance (J_nr), indicating improved flexibility and deformation resistance. Furthermore, LC balances increased rigidity and susceptibility to fatigue cracking from higher TLA and CRM levels, respectively. These modifications also promote environmental sustainability by reducing energy usage and emissions during production and paving. This study highlights LC’s critical role in advancing high-performance, eco-friendly warm mix asphalt binders, offering valuable insights for sustainable pavement engineering and setting a new benchmark for advanced asphalt technologies. Full article

A significant waste material threatening sustainability efforts are post-consumer food packaging goods. These ubiquitous multi-materials comprise chemically disparate components and are thus challenging targets for recycling. Herein, we undertake a proof-of-principle study in which we use a single-stage method to convert post-consumer multi-material food packaging (post-consumer peanut butter jars) to a high compressive strength composite (PBJS₉₀). This is accomplished by thiocracking the ground jar pulp (10 wt. %) with elemental sulfur (90 wt. %) at 320 °C for 2 h. This is the first application of thiocracking to such mixed-material post-consumer goods. Composite synthesis proceeded with 100% atom economy, a low E factor of 0.02, and negative global warming potential of −0.099 kg CO₂e/kg. Furthermore, the compressive strength of PBJS₉₀ (37.7 MPa) is over twice that required for Portland cement building foundations. The simplicity of composite synthesis using a lower temperature/shorter heating time than needed for mineral cements, and exclusive use of waste materials as precursors are ecologically beneficial and represent an important proof-of-principle approach to using thiocracking as a strategy for upcycling multi-materials to useful composites. 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

To determine the formula for biomimetic warm-mix regeneration and fulfill the requirements of a “high waste asphalt mixture content, high quality, and high level” for its usage in reclaimed asphalt pavement (RAP), this paper first determined the suitable preparation process and formula for biomimetic warm-mix regeneration based on orthogonal experiments and a gray correlation analysis. Then, the optimum dosage of the warm-mix regenerant was determined by a uniaxial penetration test, low-temperature splitting test, and freeze–thaw penetration test. The rutting test was conducted to characterize the high-temperature performance of the asphalt mixture. The Immersion Marshall Test and the freeze–thaw splitting test were used to characterize the water stability of the recycled asphalt mixture. The low-temperature small beam test was employed to study the low-temperature performance of the recycled asphalt mixture. The asphalt’s short-term and long-term aging processes were simulated using the rotary thin-film oven test (RTFOT) and the pressure aging test (PAV). The action mechanism of biomimetic warm-mix regeneration was revealed by Fourier-transform infrared spectroscopy (FTIR). Finally, a comprehensive thermal performance test was conducted on the aged asphalt after biomimetic warm-mix regeneration. The results showed that the self-made biomimetic warm-mix regeneration agent exhibited an excellent regenerative effect on RAP and significantly reduced the mixing temperature of the styrene–butadiene–styrene (SBS)-modified asphalt mixture. In addition, the self-made biomimetic warm-mix regeneration agent effectively improved the high- and low-temperature performance of the recycled asphalt mixture, but had no noticeable effect on the water stability. The suggested dosage of the biomimetic warm-mix regeneration agent was 6%, and the mixing temperature was 130 °C. The microscopic chemical analysis revealed that biomimetic warm-mix regeneration restored the performance of aged asphalt by supplementing the light component. The change rules of the chemical functional groups and the comprehensive thermal properties of the recycled mixture showed a good correlation with the change rules of its high- and low-temperature performance. Full article