Search Results (29)

The application of nanomaterials as modifiers in the field of asphalt is increasingly widespread, and this paper aims to systematically review research on the impact of nanomaterials on asphalt viscosity. The results find that nanomaterials tend to increase asphalt’s viscosity, enhancing its resistance to high-temperature rutting and low-temperature cracking. Zero-dimension nanomaterials firmly adhere to the asphalt surface, augmenting non-bonding interactions through van der Waals forces and engaging in chemical reactions to form a spatial network structure. One-dimensional nanomaterials interact with non-polar asphalt molecules, forming bonds between tube walls, thereby enhancing adhesion, stability, and resistance to cyclic loading. Meanwhile, these bundled materials act as reinforcement to transmit stress, preventing or delaying crack propagation. Two-dimensional nanomaterials, such as graphene and graphene oxide, participate in chemical interactions, forming hydrogen bonds and aromatic deposits with asphalt molecules, affecting asphalt’s surface roughness and aggregate movement, which exhibit strong adsorption capacity and increase the viscosity of asphalt. Polymers reduce thermal movement and compact asphalt structures, absorbing light components and promoting the formation of a cross-linked network, thus enhancing high-temperature deformation resistance. However, challenges such as poor compatibility and dispersion, high production costs, and environmental and health concerns currently hinder the widespread application of nanomaterial-modified asphalt. Consequently, addressing these issues through comprehensive economic and ecological evaluations is crucial before large-scale practical implementation. Full article

High-viscosity modified asphalt binder (HVMA) is used widely as a polymer-modified binder in porous asphalt pavement because it can improve the cohesiveness of the asphalt mixture. However, because of the high voidage in the mixture, HVMA is vulnerable to aging induced by temperature, oxygen, water, sunlight, and other climatic conditions, which degrades the performance of pavement. The properties of asphalt binder are affected adversely by the effects of hygrothermal environments in megathermal and rainy areas. Therefore, it is essential to study the aging characteristics of HVMA under the influence of hygrothermal environments to promote its application as a high-viscosity modifier. A hygrothermal cycle aging test (HCAT) was designed to simulate the aging of HVMA when rainwater was kept inside of the pavement after rainfall in megathermal areas. One kind of base bitumen and three kinds of HVMA (referred to as SBS, A, and B, respectively) were selected in this study. Short-term aging tests, hygrothermal cycling aging tests, and long-term aging tests were performed on the base bitumen and three kinds of modified asphalt binder. Fourier-transform infrared spectroscopy (FTIR), thermo-gravimetric analysis (TGA), and dynamic shear rheological (DSR) tests were used to evaluate the properties of the binders on the micro and macro scales. By comparing the index variations of the four binders before and after aging, the effects of the hygrothermal environment on the properties of HVMA were studied. It was found that the effects of the hygrothermal environment expedited the decomposition of the polymer and the formation of carbonyl groups compared with the TFOT and PAV test, which TGA confirmed further. Moreover, the thermal stability of the samples was improved after HCAT. In addition, the master curves of the complex modulus showed that hygrothermal cycles made the high-temperature rutting resistance of asphalt binder increase significantly. All of the results above verified that the effect of hygrothermal cycling could accelerate the aging of HVMA and shorten its service life. Full article

The main tasks of this research are an extended analysis of the technological rut formation process’s geometric, force, and energy characteristics as a result of repeated passage of a forest machine on the soil surface. Existing experimental studies of the rutting process are associated with significant material costs and disruption of the forest ecosystem. The purpose of this study is to obtain similar experimental data in laboratory conditions, as well as establishing the correspondence of these experimental results to the results of field studies. The experiments were carried out on the specialized “soil channel” stand of Technical University in Zvolen (Slovakia), as well as in natural conditions in Brody Forestry of the Lviv Region (Ukraine). Geometric track characteristics were determined by length gauges. Power and energy characteristics of the track development process were determined using dynamometers, ammeters, and voltmeters. The physical and mechanical characteristics of the soil with which the mover interacted were determined by a dynamic hardness tester, a penetrometer, and a moisture meter. The characteristics of rut development processes in natural and laboratory conditions are similar to each other. This makes it possible to carry out a wide range of studies of a wheel with soil on a specialized stand and save considerable money during the implementation of full-scale experiments. So, the process of track development can be analyzed with the help of the geometric, force, and energy characteristics of the “wheel-soil” system obtained on laboratory equipment. Full article

For achieving the better modifying effect of polyurethane on asphalt pavement materials, the PUA powder modifier was prepared with fine grinding at the glass transition temperature, and polyurethane-modified asphalt (PUA-MA) with different dosages of modifier was prepared. The impact of the PUA on the physical properties of asphalt binder was studied. The modifying mechanism of PUA on asphalt was explored by investigating the thermal performance and chemical composition of asphalt (thermogravimetric analysis, differential scanning calorimetry test, and Fourier transform infrared spectroscopy). The micrograph of the interactive interface was characterized by scanning an electron microscope. Furthermore, the rheological properties of PUA-MA were also investigated and analyzed. The results indicated that the PUA had a dense structure with few pores on the surface. After mixing with asphalt, it altered the asphalt’s internal structure via physical fusion and chemical reaction (carbamate formation). PUA improved the thermal stability of asphalt, enhanced the asphalt’s thermal decomposition temperature, and further reduced the thermal mass loss while decreasing the glass transition temperature. The addition and dosage increase in the PUA modifier significantly improved the softening point, viscosity, complex shear modulus, and rutting factor of asphalt. Also, the PUA could improve the elastic recovery ability of asphalt and enhance the rutting resistance of asphalt at high temperatures. However, the crack resistance at low temperatures was not effectively improved (ductility and penetration decreased). When the dosage was 6–9%, PUA-MA had the best high-temperature performance, but asphalt showed poor low-temperature performance at this dosage. This study provides a theoretical reference for popularizing and applying polyurethane as an asphalt modifier in road engineering. Full article

This study investigates the microscopic mechanism of the force on particles of different particle sizes in the asphalt mixture during rutting formation. The gradation was optimized by analyzing the particle force results. The enhanced discrete element method (EDEM) was used to simulate the rutting test, study the correlation state between different particle sizes in the rutting process, and analyze the rutting of asphalt pavement from the aggregate level. From a microscopic perspective, the specific forces acting on particles at different times were determined to investigate the particle size range of stressed particles in two types of asphalt mixtures. Furthermore, the role of particles with different sizes in the rutting process was analyzed. The force limit values of particles with different particle sizes are fitted, and the force of particles in two types of asphalt mixtures is compared and analyzed. After that, the gradation of the asphalt mixture is optimized, and the feasibility of the gradation optimization method is verified by laboratory experiments. The results show that the change rule of the rutting simulation test is gradually transformed from compacted rutting to unstable rutting. The force of the asphalt concrete-13 (AC-13) asphalt mixture is borne by the particles with a radius greater than 1.8 mm. The force of the stone matrix asphalt-13 (SMA-13) asphalt mixture is borne by the particles with a radius greater than 3.6 mm, and the small particle size particles play a filling role. When the particle radius is less than 5.1 mm, the force value of AC-13 asphalt mixture particles is greater than that of SMA-13. When the particle radius exceeds 5.1 mm, the force value of SMA-13 asphalt mixture particles is greater than that of AC-13. The force of particles with a radius of 5.7 mm and 7.3 mm in the SMA-13 asphalt mixture is 30% higher than that in AC-13, and the force limit of particles is proportional to the particle size. The dynamic stability, flexural tensile strength, water immersion residual stability, and freeze-thaw splitting strength ratios of the optimized asphalt mixture are improved compared with those before optimization. The AC-13 asphalt mixture is increased by 8.5%, 9.2%, 1.6%, and 1.9%, respectively, and the SMA-13 asphalt mixture is increased by 10.6%, 7.3%, 0.7%, and 2.1%, respectively. It shows that the grading optimization method is feasible. Full article

In order to raise the utilization rate of industrial waste and mitigate issues involving land resource occupation and environmental damage, in this study, industrial-waste-based artificial aggregates (IWAAs) were fabricated using steel slag powders, fly ash, and cement. They were processed under accelerated carbonation and were utilized in a bitumen mixture. During the experiment, the micromorphology, internal structure, and phase composition of IWAAs before and after accelerated carbonation were characterized using X-ray phase analysis, thermal analysis, and scanning electron microscopy (SEM); concurrently, the possibility of IWAAs being used as a partial substitute for natural aggregate to prepare bituminous mixture was qualitatively and quantitatively analyzed based on Marshall’s design procedure in combination with road performance tests and microcosmic analyses. The results indicated that the presence of carbonate crystals brought about by accelerated carbonation was the main phase composition inside the IWAAs, enhancing the microstructure densification and diminishing the immersion expansion and crushing values; this is due to the depletion of the interior Ca-based (e.g., f-CaO and Portlandite) and Mg-based (e.g., periclase and brucite) compounds together with the formation of cement hydration products. Additionally, the 12 h carbonation time obtained the optimum CO₂-sequestration efficiency on the premise of satisfying the performance standard. The expansion rate and crushing value of the IWAAs decreased by 82.21% and 41.58%, respectively, whilst the anti-rutting properties, the moisture damage resistance, and the skid resistance rose by 31.92%, 5.59%, and 10.00%, respectively, in the IWAAs–bituminous mixture. This study lays a foundation for research on the CO₂ sequestration and resource utilization of industrial wastes in bitumen mixtures. Full article

Styrene-butadiene rubber (SBR) is commonly used as a modifier to enhance the low-temperature performance of asphalt. However, it is worth noting that while SBR modified asphalt exhibits good low-temperature performance, its high-temperature performance is comparatively inferior. This limitation significantly restricts the widespread use of SBR modified asphalt. As a new type of nanomaterial, graphene (GR) can change the microstructure of asphalt binder and provide asphalt with better mechanical, thermal, and adhesion properties. The main purpose of this study is to explore the influence of GR and SBR composite incorporation on the performance indexes of modified asphalt, and to study its compatibility and modification mechanism from the microscopic point of view of asphalt. The weight factor optimization system of modified asphalt was established by an analytic hierarchy process, and the optimum content of GR was determined to be 0.1% in a quantifiable way. The test results demonstrate that the inclusion of graphene substantially enhances the high-temperature rutting resistance of asphalt, reduces the temperature sensitivity of modified asphalt, and improves its storage stability. However, its effect on the low-temperature performance of asphalt is relatively minimal. Microscopic experimental results reveal the formation of a stable structure at the interface between GR and SBR in the composite modified asphalt. Furthermore, the dispersed phase exhibits improved uniformity, which positively impacts the stability of the asphalt binder. Full article

This study focuses on unknown crystal precipitates from an asphalt mixture used in bridge deck pavement layers. X-ray fluorescence spectroscopy was used to analyze the composition and source of crystals in the asphalt mixture used in bridge deck pavement, and infiltration tests, porosity tests, splitting tests and multi-wheel rutting tests were carried out to determine the precipitation area and non-precipitation area to explain the influence of crystals on the road performance of an asphalt pavement. A nuclear-free densitometer and 3D ground-penetrating radar (3D GPR) were used to detect the porosity and thickness uniformity of the whole section to study the formation mechanism of crystals. The results showed that the main components of crystals were water molecules, while the rest mainly came from machine-made sand, and there was no significant difference in pavement performance in the areas where crystals precipitated. The crystals were mainly caused by rainwater penetrating into the pavement through coarse segregation areas and collecting in the depression of the lower bearing layer. Under high temperature, the solution precipitated out of the pavement and formed crystals. Full article

This paper investigates the use of steel slag in the place of basalt coarse aggregate in Stone Mastic Asphalt-13 (SMA-13) gradings in the early forming of an experimental pavement and evaluates the test performance of the mixes, combined with 3D scanning techniques to analyse the initial textural structure of the pavement. Laboratory tests were carried out to design the gradation of the two asphalt mixtures and to assess the strength, chipping and cracking resistance of the asphalt mixtures using water immersion Marshall tests, freeze–thaw splitting tests, rutting tests and for comparison with laboratory tests, while surface texture collection and analysis of the height parameters (i.e., Sp, Sv, Sz, Sq, Ssk) and morphological parameters (i.e., Spc) of the pavement were performed to assess the skid resistance of the two asphalt mixtures. Firstly, the results show that a substitution of steel slag for basalt in pavements is a good alternative for efficient resource utilization. Secondly, when steel slag was used in place of basalt coarse aggregate, the water immersion Marshall residual stability improved by approximately 28.8% and the dynamic stability by approximately 15.8%; the friction values decayed at a significantly lower rate, and the MTD did not change significantly. Thirdly, in the early stages of pavement formation, Sp, Sv, Sz, Sq and Spc showed a good linear relationship with BPN values, and these texture parameters can be used as parameters to describe steel slag asphalt pavements. Finally, this study also found that the standard deviation of peak height was higher for steel slag–asphalt mixes than for basalt–asphalt mixes, with little difference in texture depth, while the former formed more peak tips than the latter. Full article

Oxygenase activity of the flavin-dependent enzyme RutA is commonly associated with the formation of flavin-oxygen adducts in the enzyme active site. We report the results of quantum mechanics/molecular mechanics (QM/MM) modeling of possible reaction pathways initiated by various triplet state complexes of the molecular oxygen with the reduced flavin mononucleotide (FMN) formed in the protein cavities. According to the calculation results, these triplet-state flavin-oxygen complexes can be located at both re-side and si-side of the isoalloxazine ring of flavin. In both cases, the dioxygen moiety is activated by electron transfer from FMN, stimulating the attack of the arising reactive oxygen species at the C4a, N5, C6, and C8 positions in the isoalloxazine ring after the switch to the singlet state potential energy surface. The reaction pathways lead to the C(4a)-peroxide, N(5)-oxide, or C(6)-hydroperoxide covalent adducts or directly to the oxidized flavin, depending on the initial position of the oxygen molecule in the protein cavities. Full article

A runway pavement during its useful life is subject to a series of deteriorations because of repeated load cycles and environmental conditions. One of the most common deteriorations is the formation of rutting (surface depression in the wheel path) on the runway surface. Rutting negatively affects aircraft performance during landings and will behave even worse during precipitation or with the existence of fluid contaminations on the surface. This paper aims to develop a model for calculating aircraft braking distance during landing on wet-pavement runways affected by rutting based on dynamic skid resistances generated by tire–fluid–pavement interactions. Intense precipitation, variable rutting depths for a 100 m length step, water film depths (e.g., 1 to 26 mm), and aircraft wheel loads (e.g., 10 to 140 kN) are considered as the boundary conditions of the developed model. The output is a model that can estimate aircraft braking distance as a function of rutting depth and can perform further assessment of the probability of the occurrence of landing overrun. After validating the model with existing methodologies and calibrating it according to the actual landing distance required for each type of aircraft, an Italian airport is simulated using a model with real data regarding the level of service of its pavement surface characteristics. Full article

Clays encountered during road construction are mostly weak and result in major pavement failures due to their low California bearing ratio (CBR) and high swelling potential. In this study, sustainable and eco-friendly waste materials including brick dust waste (BDW), ground granulated blastfurnance slag (GGBS), recycled plastic (RP) and recycled glass (RG) at varying proportions of 11.75% and 23.5% were used as partial replacement for cement and lime in clay treatment. After determining the water content by conducting Atterberg limit and compaction test, A CBR and swell characteristics of treated and untreated clay were also conducted. A road pavement design was conducted using the Design Manual for Road and Bridges (DMRB) as a guide to determine the performance of treated clay with varying CBR values. A road pavement failure analysis was also conducted to understand the defect formation within pavement structures supported by eco-friendly treated clay. The embodied carbon of treated clay was calculated and a life cycle cost analysis (LCCA) of flexible pavement with treated clay and road with imported materials was conducted. The results show a liquid limit of 131.26 and plastic limit of 28.74 for high plasticity index (clay 1) and liquid limit of 274.07 and a plastic limit of 45.38 for extremely high plasticity index (clay 2). An increase in CBR values from 8% and 9% to 57% and 97% with a reduction in swell values from 4.11% and 5.03% to 0.38% and 0.56% were recorded. This resulted in a reduction in pavement thickness and stresses within the road pavement leading to reduced susceptibility of the pavement to fatigue, rutting and permanent deformation. Very low embodied carbon was recorded for eco-friendly treated clay and a high life cycle cost (LCC) with clay removed and replaced with imported materials compared with clay treated using eco-friendly waste materials. The study concluded that carbon and overall construction costs can be reduced using waste materials in road construction. Owners and operators can save money when clay is treated and used in road construction instead of removing clay and replacing it with imported materials. Full article

For the first time, by atomic force microscopy (AFM) methods, micro- and nanofragments of micronized powder elastomeric modifier (PEM) formed at the short-term (3 min at 160 °C) interaction of PEM with hot bitumen have been demonstrated. It is the technology of high-temperature shear-induced grinding of a worn-out tire’s crumb rubber or its co-grinding with styrene–butadiene–styrene (SBS) block copolymer which provides the creation of the PEM structure inclined to rapid degradation in hot bitumen. The formation just after the preparation process of a new structure of a modified binder, more resistant to external effects, is supported by the data of rheological tests. Performance tests for a modified binder using Superpave standard adopted by the road industry for bituminous binders showed an extended temperature range, resistance to rutting, and low-temperature and fatigue cracking. The better resistance to low-temperature and fatigue cracking is certainly related to energy absorption and crack growth stopping in the presence of micron and submicron resilient PEM fragments in accordance with the mechanism of increasing impact toughness in plastics. Full article

The fuzzy logic technique is one of the effective approaches for evaluating flexible and rigid pavement distress. The process of classifying pavement distress is usually performed by visual inspection of the pavement surface or using data collected by automated distress measurement equipment. Fuzzy mathematics provides a convenient tool for incorporating subjective analysis, uncertainty in pavement condition index, and maintenance-needs assessment, and can greatly improve consistency and reduce subjectivity in this process. This paper aims to develop a fuzzy logic-based system of pavement condition index and maintenance-needs evaluation for a pavement road network by utilizing pavement distress data from the U.S. and Canada. Considering rutting, fatigue cracking, block cracking, longitudinal cracking, transverse cracking, potholes, patching, bleeding, and raveling as input variables, the variables were fuzzified into fuzzy subsets. The fuzzy subsets of the variables were considered to have triangular membership functions. The relationships between nine pavement distress parameters and PCI were represented by a set of fuzzy rules. The fuzzy rules relating input variables to the output variable of sediment discharge were laid out in the IF–THEN format. The commonly used weighted average method was employed for the defuzzification procedure. The coefficient of determination ($R^2$), root mean squared error (RMSE), and mean absolute error (MAE) were used as the performance indicator metrics to evaluate the performance of analytical models. Full article

Using hydrological models with a high temporal resolution to predict risk for rutting may be a possible method to improve planning of forwarder trails or to schedule logging operations in sites with low bearing capacity to periods when soil moisture content is at a minimum. We have studied whether descriptions of rut variations, collected in 27 logging sites, can be improved by using hydrological data, modeled by Swedish HYdrological Prediction for Environment (S-HYPE). Other explanatory variables, such as field-surveyed data and spatial data, were also used to describe rut variations within and across logging sites. The results indicated that inclusion of S-HYPE data led to only marginal improvement in explaining the observed variations of the ruts in terms of both “rut depths” within the logging sites and “proportion of forwarder trails with ruts” across the logging sites. However, application of S-HYPE data for adapting depth-to-water (DTW) maps to temporal changes of soil moisture content may be a way to develop more dynamic soil moisture maps for forestry applications. Full article