Search Results (429)

Fillers (<0.075 mm) in hot mix asphalt (HMA) play a pivotal role in optimizing bitumen content, filling voids, and improving mechanical performance. In many agricultural countries, large quantities of rice and wheat husk waste are produced, while the road construction industry faces material shortages of conventional filler materials and related performance challenges. This study evaluates the feasibility of using rice husk (RH) and wheat husk (WH) fillers on HMA performance. Unlike previous studies that primarily focused on ash-derived agricultural residues, this work investigates the direct utilization of raw husk materials, eliminating the need for energy-intensive processing. Few studies directly examine the aggregate gradation and binder concentration with respect to rice and wheat husk ash. As a result, the relative effectiveness of these two agricultural waste fillers in improving the volumetric and Marshall properties of asphalt mixtures is yet unknown. Fifteen mixtures with varying bitumen contents (3.0–5.0%) were tested to determine the optimum bitumen content (OBC). Subsequently, modified mixtures were prepared at the OBC using RH and WH fillers at five replacement levels (5.0–15.0%). The Marshall Mix design method was employed to assess stability, flow, density, and air voids content. The control mixture showed a Marshall stability of 14.86 kN, flow of 3.52 mm, density of 2.342 g/cm³, and air voids of 2.9%. At their optimum filler contents (i.e., 10.33% for RH and 10.43% for WH), the modified mixtures achieved higher Marshall stability (14.96 kN and 15.06 kN, respectively), with flow values of 3.51 mm and 2.83 mm, and densities of 2.335 g/cm³ and 2.330 g/cm³. Statistical analysis using ANOVA at the OBC confirmed that RH and WH fillers can be used as alternative fillers in HMA without adversely affecting Marshall performance, while contributing to agricultural waste valorization and resource conservation. Full article

Stone mastic asphalt (SMA) derives its performance from the coupled action of a load-bearing coarse aggregate skeleton and a binder-rich mastic phase. This study evaluates polymer-modified SMA using an integrated drainage–skeleton–mastic framework that combines drainage-based cellulose fiber selection, controlled gradation variation, aggregate-type comparison, binder-content sensitivity analysis, pre-compaction laboratory conditioning, and FTIR–SEM–EDX characterization. A 50/70 penetration-grade bitumen modified with 4.5% SBS was used with basalt and limestone aggregates, limestone filler, and Viatop cellulose fiber. The fiber dosage was selected using the Schellenberg binder-drainage test, while a separate preliminary load–deformation series was used to examine the response sensitivity to higher fiber contents. Increasing fiber content from 0.30% to 0.35% reduced mean binder drainage from 0.27% to 0.18% and decreased the standard deviation from 0.020% to 0.006%, supporting 0.35% as a drainage-based design dosage rather than a mechanical optimum. Higher fiber contents increased the maximum recorded load within the fixed test window; however, these results were interpreted only as preliminary load–deformation sensitivity rather than as conventional Marshall stability or MQ responses. The binder-content series showed that lower- and upper-limit gradations followed different volumetric and Marshall response patterns; therefore, these results were interpreted as binder-content sensitivity rather than complete optimum binder content determination. Aggregate-type comparisons showed the mechanical advantage of basalt, while the non-replicated post-extraction gradation results were directionally consistent with greater skeleton preservation in basalt mixtures. FTIR, SEM, and EDX observations indicated that cellulose fiber acted mainly through physical mastic stabilization rather than chemical binder modification. Overall, the results demonstrate that SMA response is governed by the combined contribution of drainage-controlled fiber dosage, SBS-modified binder, aggregate skeleton configuration, and limestone-filler mastic integrity. Full article

This study presents, for the first time, an assessment of the dual role of waste enamels from heating device production in asphalt mixtures, as additives to modify euro bitumen (50/70) and as fillers, with a detailed analysis of their influence on properties of asphalt mixtures. Three types of enamels were investigated—premix (WEP), classic (WETM), and acid-resistant (WEART). Different characterization methods confirmed that these materials possess a borosilicate matrix enriched with various elements, including heavy metals (Cd, Cr, Cu, Ni, Pb, and Zn). Although classified as hazardous by-products, enamels replaced 100% of conventional stone dust filler, with confirmed leaching test. Their role in bitumen modification was interpreted through a structure–property approach: bitumen (4–6 wt.%) acts as a viscoelastic polymer-like matrix, while enamel particles serve as micro-scale reinforcements that govern binder–filler interactions. The results demonstrate that, despite their hazardous nature, waste enamels are compatible with asphalt technology containing 5 wt.% bitumen, achieving satisfactory stability, acceptable deformation response, and favorable volumetric characteristics. By valorizing industrial waste in this novel way, this study opens a sustainable pathway for transforming hazardous materials into functional components for the asphalt industry. Full article

To enhance the comprehensive performance of crumb rubber (CR)/SBS-composite-modified bitumen, an orthogonal experimental design was first adopted to analyze the effects of process parameters—including the addition sequence, shearing duration, shearing temperature and shearing speed—on the conventional properties of bitumen. Furthermore, based on the Box–Behnken response surface methodology, quadratic regression predictive models for the dosages of SBS, waste crumb rubber and aromatic oil were constructed, and the entropy-weighted TOPSIS method was introduced to comprehensively evaluate and multi-objectively optimize the proportioning schemes. The results indicate that a reasonable preparation process can significantly promote the uniform dispersion of modifiers, distinct non-linear interactions exist among the dosages of each modifier, and the optimal proportion balancing both high- and low-temperature performance was obtained through optimization. The constructed models exhibit good predictive accuracy, and the optimized CR/SBS-composite-modified bitumen showed excellent conventional properties and storage stability, which can provide a theoretical reference for the recycling of waste tires and the engineering application of composite-modified bitumen. Full article

Polymer-modified bitumen (PMB) is widely used in motorway pavements due to its proven mechanical performance; however, economic and sustainability considerations have stimulated interest in alternative modification strategies. This study evaluates the mechanical performance of asphalt mixtures incorporating wet-process crumb-rubber-modified bitumen (CRMB) and a dry-process crumb rubber–bitumen concentrate (CRBC) system in comparison with conventional PMB mixtures in a motorway trial section. Particular emphasis was placed on comparing wet- and dry-process rubber modification approaches under the same production and service conditions. Surface and binder-course mixtures were assessed through volumetric characterization, indirect tensile strength ratio (ITSR), indirect tensile stiffness modulus (IT-CY) at 0 °C, 15 °C, and 27 °C, wheel tracking at 50 °C and 60 °C, and semicircular bending (SCB) fracture testing, including laboratory ageing. All mixtures met the relevant specification limits for volumetric properties, water sensitivity (ITSR ≥ 80%), and resistance to permanent deformation. Rubber-modified mixtures exhibited improved resistance to permanent deformation and reduced temperature susceptibility compared with PMB references. Stiffness results indicated improved high-temperature stability for CRBC mixtures, while fracture resistance showed temperature-dependent trends influenced by mixture type and binder modification. Overall, the findings demonstrate that both CRMB and CRBC mixtures achieved mechanical performance comparable to PMB under the evaluated conditions, supporting their use as technically viable alternatives for high-performance motorway pavements while promoting the beneficial reuse of end-of-life tyre rubber. Full article

Asphalt concrete pavements in many regions suffer from premature deterioration caused by low-temperature cracking and rutting resistance under heavy traffic loads and high summer temperatures. While polymer-modified bitumen is widely used to improve pavement performance, the high cost of commercial polymers restricts its extensive application. This study evaluates the potential of polymer waste as an alternative modifier for asphalt binders to enhance mechanical performance while reducing economic and environmental costs. Experimental results demonstrate that an optimal plastic waste content of 1.0–1.5% significantly improves rutting resistance and increases binder rigidity. The incorporation of 1.5% low-density polyethylene (LDPE) and high-density polyethylene (HDPE) enhances deformation resistance, elastic modulus, and temperature stability. LDPE exhibits better compatibility with bitumen and dissolves more readily, contributing to improved binder homogeneity, whereas HDPE provides higher stiffness and thermal stability. The combined use of polymer waste with styrene–butadiene–styrene (SBS) produces a pronounced synergistic effect, leading to improvements in physical and mechanical properties exceeding 25% compared to Kazakhstan regulatory standards. Increasing polymer waste content further enhances the rigidity of both the binder and asphalt concrete, thereby improving rutting resistance and plastic deformation at elevated temperatures. The proposed approach offers a cost-effective and sustainable solution for road construction, promoting plastic waste recycling, reducing reliance on virgin polymers, and improving pavement durability, particularly under the climatic and traffic conditions of Kazakhstan. Full article

The integration of biochar into asphalt binders represents a significant advancement toward global sustainability in pavement engineering. Produced through biomass pyrolysis, biochar enables the valorization of agricultural and industrial waste while reducing dependence on petroleum-derived binder constituents. This review critically synthesizes current research regarding the impact of biochar on the physical, rheological, and aging performance of bitumen. The evidence consistently shows that biochar improves binder stiffness, raises softening points, and strengthens rutting resistance at elevated temperatures, largely due to its porous microstructure and high carbon content. Biochar-modified binders also exhibit enhanced aging resistance through the adsorption of volatile light fractions. These improvements are primarily ascribed to the carbonaceous composition and high porosity of the biochar particles. However, systemic challenges, including phase stability at high concentrations, long-term oxidative aging, and a lack of standardized characterization protocols, hinder widespread implementation. By identifying consistent findings, contradictions, and critical research gaps across the literature, this review provides a consolidated foundation to guide the transition of biochar-modified bitumen from laboratory investigation to large-scale pavement infrastructure applications. Full article

The increasing generation of waste toner from printers and photocopiers presents significant environmental and disposal challenges. This study investigates the feasibility of utilizing waste toner as a modifier in asphalt binder to enhance performance and sustainability. Bitumen with a penetration grade of 60/70 was modified with waste toner at varying contents (0–30%). The modified binders were evaluated using penetration, ductility, and softening-point tests to assess their physical behavior. Results indicate that increasing toner content reduces penetration and ductility while improving the softening point, indicating enhanced temperature resistance. Furthermore, asphalt mixtures were evaluated using both destructive (Marshall stability) and non-destructive testing (ultrasonic pulse velocity) methods to provide a comprehensive performance assessment. In addition, an artificial neural network (ANN) model was developed to predict and evaluate the performance of toner-modified mixtures. The findings demonstrate that waste toner can be effectively used as a sustainable modifier in asphalt mixtures, thereby improving material performance and reducing environmental impact. Full article

This study aims to solve the problems of the high carbon emissions, poor compatibility, and insufficient storage stability of conventional polymer–modified bitumen (PMB). A novel High–Modulus Polyurethane Prepolymer (HM–PU) bitumen modifier was independently prepared to explore its modification effect and optimal application parameters. Experimental results show that the optimal isocyanate group (NCO) content and dosage of the HM–PU modifier are both 5%. The thermal stability and high– and low–temperature performance of modified bitumen are significantly enhanced, and HM–PU exhibits excellent compatibility with base bitumen (BA). This work innovatively synthesizes the HM–PU modifier and clarifies its physicochemical modification mechanism via macroscopic performance tests, thermal analysis, and microscopic characterization, providing a new strategy for the development and application of eco–friendly bitumen modifiers. Full article

To investigate the rheological properties and compositional changes in SBS-modified bitumen under different aging conditions in the unique environmental conditions of the Xinjiang region, this study selected a local 70# base bitumen from Xinjiang and prepared modified bitumen by adding 4.0%, 4.5%, and 5.0% SBS modifier, respectively. RTFOT and PAV were used to simulate the short-term thermal-oxidative aging and long-term oxidative pressure aging processes of the bitumen samples, respectively. The three key indicators and dynamic rheological properties of the bitumen were tested for the original sample, as well as before and after short-term thermal-oxidative aging and long-term oxidative pressure aging. Thin-layer chromatography/flame ionization detection (TLC/FID) was used to analyze the migration patterns of the samples’ chemical components, and a random forest model was employed to establish a quantitative mapping between the four components of the modified bitumen and the rutting factor over a wide temperature range. The results indicate that aging weakens the improvement effect of SBS on the high-temperature performance of bitumen. However, 4.5% SBS-modified bitumen subjected to long-term oxidative pressure aging still maintains the best high- and low-temperature performance, elastic recovery capacity, and fatigue resistance compared to other dosage levels. It also has the highest bitumen content, which verifies the high-temperature performance of this dosage at the component level. Therefore, the optimal SBS dosage is recommended to be 4.5%. Notably, as the SBS content increases, it significantly regulates the increase in heavy fraction content during the aging process, while the decrease in light fraction content is not significantly affected by the content. Based on the random forest algorithm, a mapping relationship between fractions and properties under fully aged conditions was established. This study provides a theoretical basis for research on the modification and aging mechanisms of Xinjiang bitumen. Full article

Low-temperature conditioning is a key procedure in the flexibility evaluation of waterproofing membranes and directly affects the reliability of subsequent performance assessments. However, the internal unsteady-state heat transfer kinetics and the thermal gradient evolution mechanisms in multi-layer composite membranes under transient cold shocks require further investigation. Focusing on commonly utilized 3 mm and 4 mm thick SBS (Styrene–Butadiene–Styrene)-modified bitumen waterproofing membranes as subjects, this study investigated the internal dynamic temperature fields and microstructural response of bituminous waterproofing membranes under standard low-temperature flexibility testing conditions. By accurately pre-embedding micro-temperature sensors in situ at the interface between the surface layer and the reinforcement matrix, the transient thermal response profiles of specimens with varying specifications in a −25 °C liquid environment were quantified. Simultaneously, a three-dimensional transient heat conduction finite element model was established to elucidate the dynamic evolution of internal spatial temperature gradients. The congruence between experimental and numerical results demonstrates that upon exposure to extreme cold, composite membranes of different thicknesses exhibit a pronounced “surface-to-core” heat transfer lag effect. The cooling rate maximized within the initial 10 min of exposure. Conversely, the internal interface layer—acting as a high-thermal-resistance zone and the most unfavorable point for heat conduction—necessitated 10~20 min of nonlinear thermal dissipation to stabilize at the target ambient temperature. This study clarifies the transient thermal response and temperature-field evolution laws of bituminous waterproofing membranes, providing a robust theoretical framework for elucidating low-temperature embrittlement mechanisms and informing the material design and application of waterproofing projects in cold regions. Full article

Increased and excessive axle loads (exceeding design specifications) at high temperatures stimulate premature distresses in flexible pavements. This study utilizes the novelty of engineered bituminous composite—crumb rubber-modified (CRM) stone mastic asphalt (SMA) for pavement longevity and sustainable performance. Dynamic modulus testing was employed at four temperatures and six frequency sweeps. The experimental design included the preparation of SMA 19 specimens with six different percentages of crumb rubber (CR) mixed in bitumen. CR addition to the mix translated into an improved stiffness of the mix, as a 64% increase in dynamic modulus (on average) was reported at 10% CR as compared to a neat mixture. Master curves were produced using |E*| test results, which revealed that 10% modified SMA was relatively stiffer and more rut-resistant than the other mixtures. Performance prediction models were developed for |E*| using artificial neural networks (ANNs) and non-linear regression, wherein the former proved to be more robust. Sensitivity analysis revealed that a temperature rise (21.1 to 37.8 °C) translated into a 65% drop in |E*| (on average) and a rise in frequency (0.1 to 25 Hz) divulged a 72% upsurge in |E*| (on average). This research demonstrates the promise of deploying CR SMA mixtures, particularly for high-traffic and heavy-load scenarios. Full article

Deep-to-ultra-deep marine carbonate reservoirs represent an important frontier for hydrocarbon exploration in the Tarim Basin, yet fluid sources and accumulation processes in the Ediacaran (Sinian) succession remain poorly constrained due to extreme burial depth and complex tectono-thermal evolution. Here, we investigate fracture–vug reservoirs of the Sinian Qigebulake Formation in Well LT3 (Tabei Uplift) using an integrated dataset including petrography and cathodoluminescence, fluid-inclusion microthermometry, fluorescence and Raman spectroscopy, in situ major/trace element analysis and C–O–Sr isotope geochemistry, and LA-ICP-MS carbonate U–Pb dating of authigenic minerals. The paragenetic sequence comprises early dolomite (Dol-I), later dolomite (Dol-II), co-precipitated calcite (Cal-I) and quartz (Qtz-I), and late solid bitumen (Bit). Dolomite veins show PAAS-normalized REE patterns and 87Sr/86Sr ratios (0.70918–0.70984; average 0.70942) comparable to the surrounding Sinian marine wall rocks, indicating precipitation from diagenetic fluids dominated by closed-system water–rock interaction. In contrast, Cal-I displays LREE enrichment, pronounced positive Eu anomalies (δEu = 4.91–7.21), radiogenic ⁸⁷Sr/⁸⁶Sr ratios (0.71161–0.71417; average 0.71256), and negative δ¹⁸O_VPDB values (down to −9.439‰), suggesting a large-scale influx of deep-seated, high-temperature, Sr-rich hydrothermal fluids likely linked to fault-assisted fluid circulation. Fluid inclusions record four hydrocarbon charging episodes, evolving from lower- to higher-maturity oils and ultimately to dry gas. Dol-II hosts pale-yellow to pale-blue oil inclusions, whereas Cal-I and Qtz-I predominantly contain deep-blue oil inclusions and methane-rich gas inclusions (Raman peak near 2917 cm⁻¹). Carbonate U–Pb ages constrain dolomite precipitation to the Middle Ordovician (~468–463 Ma) and hydrothermal-related carbonate filling to the Early Triassic (~247–244 Ma). Collectively, these results support a time-resolved evolution in which early diagenetic fluid circulation in a marine carbonate system was overprinted by a later hydrothermal pulse that modified pore structures and thermal conditions, followed by late-stage deep burial leading to cracking of retained liquids, widespread bitumen formation, and methane charging. This framework provides new information on the constraints for fluid–rock interaction and hydrocarbon evolution in deep marine carbonate successions. Full article

In Europe, bitumen classification has traditionally relied on empirical tests, namely penetration and the Ring and Ball softening point, originally developed for unmodified binders and considered insufficient for modern modified binders. As an alternative, a rheology-based method, the Bitumen Typisierungs Schnell Verfahren (BTSV) rapid bitumen categorization method, has been developed in Germany to characterize high service temperature performance, with performance requirements introduced in 2025 in the German specifications. In this study, the performance of five bitumen types commonly used in Hungarian road construction was investigated using the BTSV method. During testing, the softening temperature corresponding to a rheological threshold value of G* = 15.0 kPa (T_BTSV) and the phase angle (δ_BTSV) were determined. T_BTSV is defined as the temperature corresponding to G* = 15 kPa, representing the softening state, while δ_BTSV reflects the viscoelastic balance between elastic and viscous behaviour. The objective of this study is to evaluate the high-temperature performance of commonly used Hungarian bituminous binders using the BTSV method and to compare the results with traditional empirical parameters and German classification systems. A total of 137 binder samples from production control were tested and analysed, including paving-grade, SBS-modified, and chemically stabilized rubber-modified binders. Statistical evaluation included mean values and 95% confidence intervals. For rubber-modified bitumens, the recoverable, insoluble rubber content was determined using the Soxhlet extraction method. Based on the results, it can be concluded that with increasing rubber content, the T_BTSV value shows an increasing trend, while the δ_BTSV value decreases. As discussed in the paper, a strong linear relationship was observed between the investigated parameters in the T_BTSV–δ_BTSV diagram, with a coefficient of determination of R² = 0.99. Full article

The disposal of waste tyres presents a significant environmental challenge, necessitating sustainable, high-value recycling solutions. This study explores the incorporation of waste tyre metal fibre (WTMF) into hot mix asphalt (HMA) to enhance mechanical performance while reducing its electrical resistivity as well as the landfill burden. The primary goal of this research is to apply response surface methodology (RSM) to experimental data for modelling and optimizing WTMF-modified HMA mixes by capturing the coupled effects of fibre reinforcement and binder content on mechanical and functional performance. The microstructural characteristics of WTMF were examined using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). WTMF-modified mixes containing five WTMF dosages (from 0% to 1.50%) and bitumen contents from 4% to 6% were prepared and tested in the laboratory. The resulting dataset was used for RSM modelling, with WTMF and bitumen contents as input factors and Marshall stability, flow, porosity, and electrical resistivity as response variables. The central composite design (CCD) technique was employed to quantify interaction effects and to identify statistically significant trends. The developed models were validated using statistical indicators, and optimal mixture compositions were determined and experimentally verified. Microstructural analysis revealed WTMF’s irregular, rough surface with microcracks and pits, aiding crack-bridging and stress transfer. RSM results indicated 0.71% WTMF and 5.1% bitumen as an optimal combination of factors. Furthermore, high R² (>0.80) and adequate precision (>4.0) values from analysis of variance (ANOVA) underscore the significance of the proposed models, revealing a robust correlation between experimental and predicted data. This study demonstrated WTMF’s potential to be used in conventional HMA mixes, offering a sustainable recycling pathway for waste tyres. Full article