Search Results (298)

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

Due to the increasing environmental concerns and the growing generation of electronic waste and plastic, sustainable waste management solutions are essential for the construction industry. This study explores the potential of using electronic waste toner powder (WTP) and recycled low-density polyethylene (LDPE), either individually or in combination as modifiers for asphalt binder to enhance pavement performance and reduce environmental impact. The analysis focused on three key components: (1) binder development and testing; (2) performance evaluation through Marshall stability, indirect tensile strength, and Dynamic Shear Rheometer (DSR) testing for rutting resistance; and (3) sustainability assessment in terms of carbon footprint reduction. The results revealed that the formulation of 25% WTP and 8% LDPE processed at 160 °C achieved the best mechanical performance and lowest carbon index, enhancing Marshall stability by 32% and rutting resistance by 41%. Additionally, this formulation reduced the carbon footprint by 27% compared to conventional asphalt. The study demonstrated that the combination of WTP and LDPE significantly improves the sustainability and performance of asphalt pavements, offering mechanical, environmental, and economic benefits. By providing a quantitative assessment of waste-modified asphalt, this study uniquely demonstrates the combined use of WTP and LDPE in asphalt, offering a novel dual-waste valorization approach that enhances pavement performance while promoting circular economy practices. Full article

Chronic infected wounds remain a major medical challenge, particularly in the context of increasing antibiotic resistance. The objective of this study was to develop and evaluate chitosan-based (CS) sponges enhanced with graphene oxide (GO) as potential antimicrobial wound dressings. The composite sponges were fabricated using microcrystalline CS (MKCh) and 5% (w/w) GO, followed by freeze-drying and γ-sterilization (25 kGy). Physico-mechanical characterization showed that GO incorporation did not significantly alter tensile strength, while absorption and sorption capacities were improved, especially after sterilization. Structural and spectroscopic analyses confirmed increased porosity and molecular interaction between CS and GO. Cytocompatibility was verified in vitro using L-929 fibroblasts, with no cytotoxic effects observed in indirect contact. Antimicrobial activity tests demonstrated that GO-modified dressings exhibited enhanced activity against E. coli and S. aureus, though results were strain-dependent and not uniformly superior to CS alone. Notably, antifungal efficacy against C. albicans was reduced with GO addition. Overall, the developed GO-enriched CS sponges present favorable biocompatibility, mechanical resilience, and selective antimicrobial activity, supporting their potential application in chronic wound management. Further optimization of GO concentration and formulation is warranted to maximize antimicrobial efficacy across a broader spectrum of pathogens. Full article

This study investigated the fracture behavior of asphalt mixtures under indirect tensile loading by comparing the performance of homogenized and micromechanical finite element (FEMs) models based on the cohesive zone model (CZM). Five asphalt mixture types were tested experimentally, and both models were calibrated and validated using load–displacement curves from indirect tensile tests (IDTs). The micromechanical model, incorporating random aggregate generation and three-phase material definition, exhibited significantly higher predictive accuracy (R² = 0.86–0.98) than the homogenized model (R² = 0.66–0.77). The validated micromechanical model was further applied to quantify the impact of construction-related deficiencies—namely, increased air voids, non-continuous gradation, and aggregate segregation. The simulation results showed that higher void content (from 4% to 10%) reduced peak load by up to 35% and increased localized stress concentrations by up to 40%. Discontinuous gradation and uneven aggregate distribution also led to premature crack initiation and more complex fracture paths. These findings demonstrated the value of micromechanical modeling for evaluating sensitivity to mix design and compaction quality, providing a foundation for performance-based asphalt mixture optimization and durability improvement. Full article

Maintenance dredging produces large volumes of fine sediments that are commonly discarded, despite increasing pressure for beneficial reuse. Lime–cement stabilization offers one pathway, yet field performance is highly variable. This study juxtaposes two French marine dredged sediments—DS-F (low plasticity, organic matter (OM) ≈ 2 wt.%) and DS-M (high plasticity, OM ≈ 18 wt.%)—treated with practical hydraulic road binder (HRB) dosages. This is the first French study that directly contrasts two different DS types under identical HRB treatment and proposes practical boundary thresholds. Physical indexes (particle size, methylene-blue value, Atterberg limits, OM) were measured; mixtures were compacted (Modified Proctor) and tested for immediate bearing index (IBI). IBI, unconfined compressive strength, indirect tensile strength, and elastic modulus were determined. DS-F reached IBI ≈ 90–125%, UCS ≈ 4.7–5.9 MPa, and ITS ≈ 0.40–0.47 MPa with only 6–8 wt.% HRB, satisfying LCPC-SETRA class S2–S3 requirements for road subgrades. DS-M never exceeded IBI ≈ 8%, despite 3 wt.% lime + 6 wt.% cement. A decision matrix distilled from these cases and recent literature shows that successful stabilization requires MBV < 3 g/100 g, plastic index < 25%, OM < 7 wt.%, and fine particles < 35%. These thresholds permit rapid screening of dredged lots before costly treatment. Highlighting both positive and negative evidence clarifies the realistic performance envelope of soil–cement reuse and supports circular-economy management of DS. Full article

Although asphalt mixtures can be applied to railway tracks due to their viscoelastic properties, caution is required, as their ductility and brittleness are highly sensitive to temperature variations. In recent years, interest in the application of asphalt in railway infrastructure has increased, driven by the development of modified mixtures and the broader availability of performance-enhancing additives. Additionally, evaluation methods for railway tracks should be adapted to account for the distinct loading mechanisms involved, which differ from those of conventional roadways. In this study, the comprehensive properties of asphalt binders, mixtures, and testing methods—including physical and engineering characteristics—were assessed to improve the performance of asphalt concrete layers for potential applications in railroad infrastructure. The results of this study indicate that (1) the higher the performance grade (PG), the higher the indirect tensile strength (ITS) value achieved by the 13 mm mixture using PG76-22, which is higher than that of the PG64-22 mixture. This indicates that higher PG grades and modification contribute to improved tensile strength, beneficial for upper layers subjected to dynamic railroad loads. (2) The tensile strength ratio (TSR) increased from the unmodified mixture to over 92% in mixtures containing crumb rubber modifier (CRM) and styrenic thermoplastic elastomer (STE), demonstrating enhanced durability under freeze–thaw conditions. (3) Wheel tracking test results showed that modified mixtures exhibited more than twice the rutting resistance compared to PG64-22. The 13 mm aggregate mixtures also generally performed better than the 19 mm mixtures, indicating reduced permanent deformation under repeated loading. (4) It was concluded that asphalt is a suitable material for railroads, as its overall characteristics comply with standard specifications. Full article

Due to the growing consumption of plastic and rubber products, effective waste management solutions are crucial. This study evaluates the use of crumb rubber (CR), low-density polyethylene (LDPE), and their combination (CR+LDPE), as asphalt binder modifiers for improving pavement performance and sustainability. The analyses covered two critical pavement layers: the wearing surface (WS) and the treated base (TB). The methodology included (1) Binder Development and Testing; (2) Superpave Mix Design; (3) mechanical testing, including Indirect Tensile Strength Testing and Semi-Circular Bending Testing; (4) life cycle cost analysis; and (5) carbon footprint analysis. The results revealed that CR+LDPE significantly enhanced the fatigue resistance of the TB mixes, with a fracture energy increase of 47%, and increased the flexibility index by 53% in the WS. CR increased the flexibility index by about 146% in the TB layer, while LDPE increased the fracture energy by 21% in the WS layer. The life cycle cost analysis demonstrated that using LDPE, CR, and CR+LDPE reduced the life cycle costs by about 16% in the WS layer. Meanwhile, the life cycle carbon footprint analysis showed that using LDPE and CR+LDPE reduced the carbon footprint by about 87% and 81% for the TB and WS layers, respectively. The study findings highlight the mechanical, economic, and environmental benefits of incorporating wastes into asphalt pavements. Full article

With increasing traffic loads and the continuous deterioration of asphalt pavements, it has become necessary to explore alternative materials that enhance both performance and sustainability. This study aims to investigate the effect of using cement kiln dust (CKD) as a filler substitute in hot mix asphalt composites, focusing on the mechanical and durability properties of pavements. The results indicate that replacing conventional filler with CKD in different proportions (1.5%, 3%, 4.5%, and 6%) positively affects the properties of asphalt mixtures. Marshall stability values increased by 58.4% when using 100% CKD, indicating a significant improvement in the mixture’s ability to withstand traffic loads. Flow tests revealed that replacing CKD by up to 50% enhances the flexibility of the mixture, but exceeding this percentage makes the mixture stiffer, which may lead to premature cracking. In terms of moisture sensitivity, incorporating CKD by 25% improves the mixture’s resistance to water damage, while increasing it to 100% reduces this resistance, highlighting the need to improve the adhesion properties of asphalt. Indirect tensile strength tests have confirmed that CKD enhances the cohesion of the mixture, reducing the likelihood of cracking under pressure and contributing to longer pavement life. Based on these results, it is recommended that CKD be used for up to 50% to achieve a balanced combination of strength, flexibility, and moisture resistance, with further studies being needed to evaluate the long-term performance and potential improvements through additional material modifications. Full article

Semi-flexible pavement (SFP) materials have garnered extensive application and research attention owing to their exceptional deformation resistance. The crack resistance of SFP materials constitutes a critical aspect of their road performance. This study conducts a comprehensive analysis of the crack resistance of SFP materials through material characterization and structural mechanical response evaluation. To assess the cracking behavior of SFP materials across the entire temperature spectrum, three experimental methodologies were employed: low-temperature flexural tensile testing, indirect tensile testing, and semi-circular bending tensile testing. Experimental findings reveal that SFP materials exhibit superior crack resistance compared to SMA-13 under ambient and elevated temperature conditions, while demonstrating inferior performance relative to SMA-13 in low-temperature environments. Through a comparative analysis of structural mechanical responses between SMA-13 and SFP pavements, it was determined that the implementation of a single-layer SFP material can reduce pavement tensile strain by 30–50%. This investigation provides comprehensive insights into the crack resistance characteristics of SFP materials and offers valuable guidance for material selection in pavement structural design. Full article

Stone mastic asphalt (SMA) is the most widely adopted asphalt mixture on highway pavement in China. However, the cost of SMA is rising continually due to the increasing shortage of high-quality basalt aggregate. On the other hand, China’s steel slag and reclaimed asphalt pavement (RAP) stock is abundant, and steel slag has excellent strength and wear-resistant performance, which can fully or partially replace part of the basalt aggregate. The content of asphalt may be increased due to the porosity of the steel slag. If fine RAP rich in asphalt is also used for SMA, it can partially fill the voids of steel slag and reduce the amount of new asphalt and fine aggregate. For this objective, SMA 13 was designed with two particle sizes of coarse steel slag aggregate (5–10 mm, 10–15 mm) and one fine RAP (0–5 mm), named SR-SMA. The fundamental pavement performance of SR-SMA was evaluated through a wheel-tracking test, low-temperature beam bending test, freeze–thaw indirect tensile test, and four-point bending fatigue test. For comparison, the mix design and performance tests of two SMAs involving coarse steel slag and fine basalt aggregate (named SB-SMA), and coarse and fine basalt aggregates (named B-SMA), respectively, were conducted. The results indicated that SR-SMA (dynamic stability of 4865 passes/mm) shows the best rutting resistance, followed by SB-SMA (dynamic stability of 4312 passes/mm), and B-SMA (dynamic stability of 4135 passes/mm) comes in last. Additionally, the dynamic stability values of three SMAs have significant differences. SR-SMA has better low-temperature cracking resistance with a failure strain of 3150 με, between SB-SMA and B-SMA (failure strain values are 4436, 2608 με). Compared to B-SMA and SB-SMA, the moisture stability of SR-SMA is relatively poor but meets Chinese specification. While the fatigue resistance of SR-SMA is the worst among three SMAs, their differences are insignificant. Furthermore, SR-SMA reduces material cost by approximately 35% per ton compared to conventional B-SMA. Overall, SR-SMA is cost-effective and can be used as an alternative material to traditional B-SMA. Full article

This study develops a meso-structural modeling approach for asphalt mixtures by integrating computed tomography (CT) technology and the discrete element method (DEM), which accounts for the morphological characteristics of aggregates, asphalt mortar, and voids. The indirect tensile (IDT) tests of SMA-13 asphalt mixtures, a commonly used skeleton-type asphalt mixture for the surface course of asphalt pavements, were numerically simulated using CT-DEM. Through a comparative analysis of the load–displacement curve, the peak load, and the displacements corresponding to the maximum loads from the IDT tests, the accuracy of the simulation results was validated against the experimental results. Based on the simulation results of the IDT tests, the internal force transfer paths were obtained through post-processing, and the force chain system was identified. The crack propagation paths and failure mechanisms during the IDT tests were analyzed. The research results indicate that under the external load of the IDT test, there are primary force chains in both vertical and horizontal directions within the specimen. The interaction between these vertically and horizontally oriented force chains governs the fracture progression of the specimen. During IDT testing, the internal forces within the aggregate skeleton consistently exceed those within the mortar, while interfacial forces at aggregate–mortar contacts maintain intermediate values. Both the aggregate’s and mortar’s internal forces exhibit strong linear correlations with temperature, with the mortar’s internal forces showing a stronger linear relationship with external loading compared to those within the aggregate skeleton. The evolution of internal meso-cracks progresses through three distinct phases. The stable meso-crack growth phase initiates at 10% of the peak load, followed by the accelerated meso-crack growth phase commencing at the peak load. The fracture-affected zone during IDT testing extends symmetrically 20 mm laterally from the specimen centerline. Initial meso-cracks predominantly develop along aggregate–mortar interfaces and void boundaries, while subsequent propagation primarily occurs through interfacial zones near the main fracture path. The microcrack initiation threshold demonstrates dependence on the material’s strength and deformation capacity. Furthermore, the aggregate–mortar interfacial transition zone is a critical factor dominating crack resistance. Full article

The aim of this study is to develop a simple and reliable laboratory testing procedure for evaluating the bond strength of cement–formation sheaths that considers cement slurry composition and contamination as well as formation strength and formation surface conditions (roughness and contamination). Additionally, a simple and practical empirical correlation is developed for predicting cement–rock bond strength based on the routine mechanical properties of hard-set cement and formation rock. Cement slurries composed of Yamama cement type 1 and 25% local Saudi sand, in addition to 40% fresh water, are used for all investigations in this study. Oil well cementing is a crucial and essential operation in the drilling and completion of oil and gas wells. Cement is used to protect casing strings, isolate zones for production purposes, and address various hole problems. To effectively perform the cementing process, the cement slurry must be carefully engineered to meet the specific requirements of the reservoir conditions. In oil well cementing, the cement sheath is a crucial component of the wellbore system, responsible for maintaining structural integrity and preventing leakage. Shear bond strength refers to the force required to initiate the movement of cement from the rock formation or movement of the steel casing pipe from the cement sheath. Cement–formation sheath bond strength is a critical issue in the field of petroleum engineering and well cementing. Cement plays a crucial role in sealing the annulus (the space between the casing and the formation) and ensuring the structural integrity of the well. The bond strength between the cement and the surrounding geological formation is key to preventing issues such as fluid migration, gas leaks, and wellbore instability. To achieve the study objectives, sandstone and sandstone–cement composite samples are tested using conventional standard mechanical tests, and the results are used to predict cement–formation sheath bond strength. The utilized tests include uniaxial compression, direct tensile, and indirect tensile (Brazilian) tests. The predicted cement–rock sheath bond strength is compared to the conventional laboratory direct cement–formation sheath strength test outcomes. The results obtained from this study show that the modified uniaxial compression test, when used to evaluate cement–formation shear bond strength using cement–rock composite samples, provides reliable predictions for cement–formation sheath bond strength with an average error of less than 5%. Therefore, modified uniaxial compression testing using cement–rock composite samples can be standardized as a practical laboratory method for evaluating cement–formation sheath bond strength. Alternatively, for a simpler and more reliable prediction of cement–formation sheath bond strength (with an average error of less than 5%), the empirical correlation developed in this study using the standard compressive strength value of hard-set cement and the standard compressive strength value of the formation rock can be employed separately. For the standardization of this methodology, more generalized research should be conducted using other types of oil well cement and formation rocks. Full article

Subsurface characterisation is a fundamental aspect of the planning and design of hydroelectric projects, as it enables the assessment of the technical and geotechnical feasibility of the proposed infrastructure, ensuring its stability and functionality. This study focuses on the characterisation of rock masses from boreholes in the “Santa Rosa” and “El Rosario” areas, located in Morona Santiago, Ecuador, to determine key parameters for the design of hydroelectric projects. Field and laboratory tests were conducted, including uniaxial compression tests, indirect tensile–Brazilian tests, point load tests, tilt tests, and geomechanical classifications using the RMR and Q systems. The results show that igneous rocks, such as basalt and andesite, exhibit mechanical properties ranging from moderate to high, with uniaxial compressive strengths exceeding 120 MPa in the case of basalt, classifying it as a strong rock. In contrast, metamorphic rocks, such as chert, exhibit lower strength, with values ranging between 69.69 MPa and 90.63 MPa, classifying them as moderately strong. The RMR and Q index values indicate a variable rock mass quality, ranging from excellent in diorite and granite sectors to low in areas with significant discontinuities and alterations. Additionally, variations in basic friction angles were identified, ranging from 18° to 38°, which directly influence the stability of the proposed structures. In conclusion, this study highlights the importance of geomechanical characterisation in ensuring the technical feasibility of hydroelectric projects, providing key information for the design and development of safe and sustainable infrastructure in the region. Full article

Gap-graded asphalt mixtures like stone mastic asphalt (SMA), porous asphalt (PA), and asphalt mixtures for very thin layers (fr. Béton Bitumineuse Très Mince—BBTM) are usually made with the use of SBS (styrene-butadiene-styrene) polymer-modified bitumen. This is a binder that allows one to achieve the required parameters, but at the same time, its use increases the costs of making pavement layers. An alternative to polymer-modified bitumen (SBS) is rubber-modified bitumen. The research presented in this publication includes an assessment of the resistance to permanent deformation and susceptibility to aging of SMA and porous asphalt (PA) mixtures containing both SBS polymer-modified bitumen and rubber-modified bitumen, where the modification process was carried out directly in the refinery. The laboratory tests of resistance to deformation were assessed based on the rutting test and on the assessment of the dynamic modulus (SPT). The changes in the tested asphalt mixtures after aging in laboratory conditions were assessed based on the changes in the stiffness modulus (IT-CY) and the changes in the indirect tensile strength (ITS) after the short-term and long-term aging processes. The presented research results clearly show that the use of rubber-modified bitumen produced in industrial conditions (i.e., in a refinery) allows one to obtain gap-graded mixtures that are as resistant to permanent deformation as mixtures containing SBS polymer-modified bitumen. Similar conclusions resulted from the study of susceptibility to aging. Changes after aging for both types of asphalt mixtures were at a similar level. The presented results clearly indicate that, in the case of gap-graded mixtures such as SMA- and PA-type mixtures, they meet the rutting and aging expectations when either expensive modified bitumen or a cheaper, more environmentally friendly alternative (rubber-modified bitumen) is used. Full article

Predicting the performance of hot mix asphalt (HMA) is crucial for ensuring pavement durability, especially as the use of rejuvenated reclaimed asphalt pavement (RAP) increases in sustainable construction. Indirect tensile strength (ITS) is a critical parameter that indicates a pavement’s resistance to cracking and distress under traffic loads. This study developed statistical and machine learning models—linear regression, support vector machine (SVM), and artificial neural network (ANN)—to predict ITS and ITS loss in RAP-incorporated HMA rejuvenated with waste cooking oil (WCO) and waste engine oil (WEO). The models used key input variables, including rejuvenator type and the composition of asphalt, rejuvenator, and RAP. Results showed that WCO increased initial ITS, while WEO enhanced durability by reducing ITS loss. Additionally, lower RAP and asphalt content contributed to improved pavement durability. Among the predictive models, ANN demonstrated the highest accuracy, exhibiting lower error metrics and less variation in scatterplots compared to regression and SVM models. The only exception was ITS loss percentage prediction, where the mean absolute error was nearly identical across all models. These predictive models provide valuable insights for designing and testing modified asphalt mixtures, particularly those containing RAP. By optimizing mix design and enabling proactive maintenance strategies, they contribute to the development of more durable and sustainable pavement infrastructure with the provision of accurate and workable models for prediction of ITS and loss prediction which can be used for design. Full article