Search Results (120)

To investigate temporal deformation mechanisms of hydraulic asphalt concrete slope flow under evolving temperatures, this study developed a novel temperature-controlled slope flow intelligent test apparatus. Using this apparatus, slope flow tests were conducted at four temperature levels: 20 °C, 35 °C, 50 °C, and 70 °C. By applying nonlinear dynamics theory, the temporal evolution of slope flow deformation and its nonlinear mechanical characteristics under varying temperatures were thoroughly analyzed. Results indicate that the thermal stability of hydraulic asphalt concrete is synergistically governed by the phase-transition behavior between asphalt binder and aggregates. Temporal evolution of slope flow exhibits a distinct three-stage pattern as follows: rapid growth (0~12 h), where sharp temperature rise disrupts the primary skeleton of coarse aggregates; decelerated growth (12~24 h), where an embryonic secondary skeleton forms and progressively resists deformation; stabilization (>24 h), where reorganization of coarse aggregates is completed, establishing structural equilibrium. The thermal stability temperature influence factor (δ) shows a nonlinear concave growth trend with increasing test temperature. Dynamically, this process transitions sequentially through critical stability, nonlinear stability, period-doubling oscillatory stability, and unsteady states. Full article

The inherent limitations of ordinary cement mortar—characterized by its high brittleness and low flexibility—result in a diminished load-bearing capacity, predisposing concrete pavements to cracking. A novel approach has been proposed to enhance material performance by incorporating emulsified asphalt and latex into ordinary cement mortar, aiming to improve the flexibility and durability of concrete pavements effectively. To further validate the feasibility of this proposed approach, a series of comprehensive experimental investigations were conducted, with corresponding conclusions detailed herein. As outlined below, the flexibility properties of the modified cement mortar were systematically evaluated at curing durations of 3, 7, and 28 days. The ratio of flexural to compressive strength can be increased by up to 38.9% at 8% emulsified asphalt content at the age of 28 days, and by up to 50% at 8% latex content. The mechanism of emulsified asphalt and latex-modified cement mortar was systematically investigated using a suite of analytical techniques: X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TG-DTG), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Through comprehensive analyses of microscopic morphology, hydration products, and elemental distribution, the enhancement in cement mortar toughness can be attributed to two primary mechanisms. First, Ca²⁺ ions combine with the carbonyl groups of emulsified asphalt to form a flexible film structure during cement hydration, thereby reducing the formation of brittle hydrates. Second, active functional groups in latex form a three-dimensional network, regulating internal expansion-contraction tension in the modified mortar and extending its service life. Full article

Cracking in semi-rigid cement-stabilized macadam bases constitutes a prevalent distress in asphalt pavements. While extensive research exists on grouting materials for crack rehabilitation, quantitative assessment methodologies for treatment efficacy remain underdeveloped. This study proposes a novel evaluation framework integrating fiber Bragg grating (FBG) technology to monitor pavement mechanical responses under traffic loads. Conducted on the South China Expressway project, the methodology encompassed (1) a method for back-calculating the modulus of the asphalt layer based on Hooke’s Law; (2) a sensor layout plan with FBG sensors buried at the top of the pavement base in seven sections; (3) statistical analysis of the asphalt modulus based on the mechanical response when a large number of vehicles passed; and (4) comparative analysis of modulus variations to establish quantitative performance metrics. The results demonstrate that high-strength geopolymer materials significantly enhanced the elastic modulus of the asphalt concrete layer, achieving 34% improvement without a waterproofing agent versus 19% with a waterproofing agent. Polymer-treated sections exhibited a mean elastic modulus of 676.15 MPa, substantially exceeding untreated pavement performance. Low-strength geopolymers showed marginal improvements. The modulus hierarchy was as follows: high-strength geopolymer (without waterproofing agent) > polymer > high-strength geopolymer (with waterproofing agent) > low-strength geopolymer (without waterproofing agent) > low-strength geopolymer (with waterproofing agent) > intact pavement > untreated pavement. These findings demonstrate that a high-strength geopolymer without a waterproofing agent and high-polymer materials constitute optimal grouting materials for this project. The developed methodology provides critical insights for grout material selection, construction process optimization, and post-treatment maintenance strategies, advancing quality control protocols in pavement rehabilitation engineering. Full article

Urban microclimates, which include phenomena such as urban heat islands (UHIs) as well as cooler environments created by shaded areas and green spaces, significantly affect social behavior and contribute to varying levels of social isolation in cities. UHIs, driven by heat-absorbing materials like concrete and asphalt, can increase urban temperatures by up to 12 °C, discouraging outdoor activities, especially among vulnerable populations like the elderly and those with chronic health conditions. In contrast, shaded areas and green spaces, where temperatures can be 2–5 °C cooler, encourage outdoor engagement and foster social interaction. This narrative review aims to synthesize current literature on the relationship between urban microclimates and social isolation, focusing on how UHIs and shaded areas influence social engagement. A comprehensive literature review was conducted, selecting sources based on their relevance to the effects of localized climate variations on social behavior, access to green spaces, and the impact of urban design interventions. A total of 142 articles were initially identified, with 103 included in the final review after applying inclusion/exclusion criteria. Key studies from diverse geographical and cultural contexts were analyzed to understand the interplay between environmental conditions and social cohesion. The review found that UHIs exacerbate social isolation by reducing outdoor activities, particularly for vulnerable groups such as the elderly and individuals with chronic health issues. In contrast, shaded areas and green spaces significantly mitigate isolation, with evidence showing that in specific study locations such as urban parks in Copenhagen and Melbourne, such areas increase outdoor social interactions by up to 25%, reduce stress, and enhance community cohesion. Urban planners and policymakers should prioritize integrating shaded areas and green spaces in city designs to mitigate the negative effects of UHIs. These interventions are critical for promoting social resilience, reducing isolation, and fostering connected, climate-adaptive communities. Future research should focus on longitudinal studies and the application of smart technologies such as IoT sensors and urban monitoring systems to track the social benefits of microclimate interventions. Full article

In this study, the feasibility of using three-dimensional (3D) printing technology to investigate the impact of macrotexture and microtexture on the skid resistance of asphalt pavement was verified. The macrotexture characteristics of the five types of real asphalt mixtures were captured, reconstructed, and printed. The comparison analysis of the skid resistance between the pavement and printed specimens was conducted, and the correlations and contribution proportions of the macrotexture and microtexture on skid resistance were also calculated. Results show that five printed asphalt mixtures present good consistency in the microtexture with a roughness of about 100 nm. The impact of thin water film on the skid resistance is insignificant for real asphalt mixtures, while it is significant for printed mixtures. The printed specimens under dry conditions show a similar British pendulum number (BPN) with the real pavement specimens under wet conditions, while the BPN under wet conditions for printed specimens are much smaller than the real ones but follows a similar variation trend. Mean profile depth (MPD) values of four printed asphalt concrete (AC) mixtures are well linearly correlated with their BPN under dry and wet conditions, especially for wet conditions with the R² of 0.91. The contribution proportion of macrotexture to the skid resistance is nearly 90% for the dry condition and about 50% for the wet condition. Full article

Salts can have detrimental effects on asphalt pavements, leading to permanent damage that compromises their durability and sustainability. This study investigates the damage mechanisms of asphalt pavements under coupled salt–thermal–mechanical effects using multi-scale modeling. Pull-off and semicircular bending (SCB) tests were conducted to determine material parameters and validate numerical models. Experimental data demonstrated that after 48 h of salt treatment at −10 °C, specimens exhibited reductions in cohesive strength ranging from 23.5% to 26% and adhesive strength decreasing by 25% to 44% compared to untreated controls. More severe degradation was observed at 0 °C, with cohesive strength diminishing by up to 63.8% and adhesive strength declining by up to 71.6%. A multi-scale finite element (FE) pavement model incorporating cohesive zone modeling (CZM) was developed to simulate damage behavior within asphalt concrete. Salt diffusion analysis revealed limited penetration depth within short exposure periods, and results showed that salt penetration reached only about 10 mm into the pavement layers after 48 h. Results indicated significant reductions in adhesive and cohesive strengths due to salt exposure, with damage susceptibility increasing under combined thermal fluctuations and mechanical loading. Additionally, the effects of moving load magnitude and speed on pavement damage were examined, showing higher damage accumulation at lower speeds and heavier loads. This research provides insights into pavement deterioration mechanisms, contributing to improved durability and maintenance strategies for asphalt pavements in salt environments. Full article

In this paper, the mechanism of interlayer bonding under a low-temperature environment is systematically revealed in terms of the temperature control difficulties in the continuous multilayer construction of an asphalt concrete core wall in winter. A field simulation paving test was conducted using a temperature-controllable simulated paving system, and the key laws of the temperature transfer and mechanical property evolution were discovered by precisely regulating the surface temperature of the bonded surface (the test range covered from −5 °C to 70 °C). This study shows that a bonding surface temperature of 40 °C is a critical point of engineering importance, at which the material exhibited a unique performance compensation effect. Under this temperature condition, although the mechanical index was reduced compared with the parent material, the flexural strength was reduced by 11.39%, the maximum bending strain was reduced by 9.65%, the tensile strength was reduced by 7.89%, the critical tensile strain was reduced by 16.11%, and the crack curvature coefficient was reduced by 10.06%. However, thanks to the unique structural reorganization characteristics of asphalt materials, these performance losses were effectively compensated, thus ensuring the stability of engineering applications. In particular, a fast rise–stable–slow decline evolution law of the interlayer temperature transfer was found, proving the existence of a temperature-adaptive interval of the bond surface. The research results not only enrich the theory of asphalt concrete interlayer bonding but also provide innovative technical solutions for the construction of water conservancy projects in cold regions. In particular, the fast rise–stable–slow drop evolution law of the interlayer temperature transfer was found, which proves the existence of a temperature-adaptive interval of the bond surface. The research results not only enrich the theory of asphalt concrete interlayer bonding but also provide innovative technical solutions for the construction of water conservancy projects in cold regions. Full article

The fundamental material parameter used in the thermal analysis of road pavement structures is the thermal conductivity. This parameter can be determined using various methods. The main objective of this paper is to compare and evaluate the thermal conductivity test results obtained using two different measurement methods. Thermal conductivity was determined using the steady-state and transient methods. The transient method is more cost-effective and faster but tends to produce a higher dispersion of results. In contrast, the steady-state method is more challenging to apply, particularly when testing large and heavy specimens of heterogeneous materials such as road pavement materials. For this reason, it is essential to assess the differences in results obtained by these two methods when applied to road materials. Two types of materials were tested in this study: an asphalt mixture and a cement concrete. The obtained results show statistically significant differences (α = 0.05), taking into account the two methods considered. The average difference can be estimated at 10% and 11% for asphalt mixtures and cement concretes, respectively. The obtained results are important for quantifying material parameters used in thermal and coupled thermal/structural analysis of pavement structures. This is particularly relevant in areas affected by urban heat islands and in road sections used as solar collectors. Full article

Aggregates are the main material forming the skeleton structure of asphalt mixtures and are of great importance to resist external load for asphalt pavement. This study analyzed the packing characteristics and mechanical performance of aggregate blend to provide a reference for improving the bearing capacity of asphalt mixtures. The single-size, two-size, and multi-size aggregate blends were chosen to conduct the laboratory packing and California bearing ratio (CBR) tests. Six particle sizes were selected to design the single-size aggregate blends. Six size combinations were included and various mass ratios were considered for each size combination in the two-size aggregate blends. The multi-size aggregate blends were designed through the gradually filling method according to stone matrix asphalt with a nominal maximum particle size (NMPS) of 16 mm (SMA16) and dense asphalt concrete with an NMPS of 26.5 mm (AC25). The packing characteristics of the blends were quantified by the air voids and the percentage of contribution to the packing volume (PCPV). The mechanical performance of the blends was analyzed by the CBR value. The relationship between packing characteristics and mechanical performance was explored by data fitting. The results showed that the particle size and the size ratio have an effect on the packing characteristics and mechanical performance of aggregate blend. The smaller the particle size, the larger the air void of the blend. The blends composed of larger particles have better load bearing capacity than those composed of smaller particles. The larger the particle size ratio, the greater the air void of the blend and the weaker the load bearing capacity. The particles smaller than 1.18 mm and those smaller than 0.3 mm in AC25 mainly play a role in filling the voids and have little contribution to the load bearing. There is a certain correlation between the packing characteristics and mechanical performance of aggregate blend. Full article

The current design methods employed for composite pavement structures predominantly rely on cement concrete slabs, which unfortunately lack established design standards and associated control indicators for determining the appropriate thickness of the asphalt layer. Therefore, the emergence of reflective cracks at the bottom of the asphalt layer has become a prevalent issue in composite pavement. This article aims to enhance the existing design methodology for composite pavement structures by proposing the inclusion of “cracking at the bottom of the asphalt layer” as a design indicator. An extensive analysis was conducted to assess the influence of various factors, including the elastic modulus and thickness of the asphalt layer, the elastic modulus, and thicknesses of the cement concrete slab, as well as the dimensions of the cement concrete slab (length and width), foundation reaction modulus, and joint width, on the comprehensive stress at the bottom of the asphalt layer. Additionally, formulas were derived to calculate the temperature warping stress and load stress, and a formula was also provided for determining the equivalent modulus of the structure, taking into account the stress-absorbing layer. Subsequently, the proposed methodology was applied to the Weixu Expressway. The results suggest adopting a surface structure design scheme consisting of a 6 cm asphalt concrete + 2 cm stress absorption layer. This study found that, when the thickness of the stress-absorbing layer is less than 2 cm, the load stress is highly sensitive to changes in the thickness of this layer. Specifically, a 1 cm thick stress-absorbing layer reduces the maximum tensile stress at the bottom of the asphalt layer by approximately 69.7%, decreases the equivalent stress by about 34.1%, and lowers the maximum shear stress by around 30.9%. However, once the thickness exceeds 2 cm, the load stress remains relatively constant. Thus, it was advisable to utilize an optimal stress-absorbing layer thickness of 2 cm. Full article

This study articulates findings from research pertaining to the utilisation of recycled geogrid in asphalt concrete. The issue of contamination of reclaimed waste with geosynthetic materials persists as a significant concern that warrants attention. In Poland, the allowable quantity of geogrid contaminants within the mineral–asphalt composition is 0.1% w/w. The preliminary evaluation of the validity of the research topic was conducted based on an analysis of correspondence and survey outcomes. The fundamental material research was executed employing elements of experimental design theory. The experimental domain considered two qualitative factors: the type of bituminous mixture for the binding layer (AC16W and AC22W) and the type of geogrid material (glass, carbon), in addition to two quantitative factors: the length of the recycled geogrid fibres ranging from 1 cm to 5 cm, and the quantity of recycled geogrid fibres varying from 0.2% to 1%. A generalised linear model was employed for the analysis, enabling the consideration of dependent qualitative factors in forecasting characteristics. The qualitative evaluation of the resultant solution was conducted using multi-criteria optimisation via the Harrington function. Consequently, recycled carbon mesh fibres demonstrated a notably positive impact, enhancing the material’s quality by 22%. Regarding glass mesh, the fibre content should not exceed 0.2% in the AC22W mixture, whereas it can be increased to 1% in the AC16W mixture. Comparing all evaluated mixtures, it was ascertained that surpassing the allowable contamination limit of 0.1% in geogrid form does not result in a significant reduction in the quality of asphalt concrete compared to the reference mix. Full article

The quality of bicycle path surfaces significantly influences the comfort of cyclists. This study evaluates the effectiveness of smartphone sensor data and smart bicycle lights data in assessing the roughness of bicycle paths. The research was conducted in Hasselt, Belgium, where various bicycle path pavement types, such as asphalt, cobblestone, concrete, and paving tiles, were analyzed across selected streets. A smartphone application (Physics Toolbox Sensor Suite) and SEE.SENSE smart bicycle lights were used to collect GPS and vertical acceleration data on the bicycle paths. The Dynamic Comfort Index (DCI) and Root Mean Square (RMS) values from the data collected through the Physics Toolbox Sensor Suite were calculated to quantify the vibrational comfort experienced by cyclists. In addition, the data collected from the SEE.SENSE smart bicycle light, DCI, and RMS computed results were categorized for a statistical comparison. The findings of the statistical tests revealed no significant difference in the comfort assessment among DCI, RMS, and SEE.SENSE. The study highlights the potential of integrating smartphone sensors and smart bicycle lights for efficient, large-scale assessments of bicycle infrastructure, contributing to more informed urban planning and improved cycling conditions. It also provides a low-cost solution for the city authorities to continuously assess and monitor the quality of their cycling paths. Full article

Pavement skid resistance is significant for driving safety. British Pendulum Number (BPN) is commonly used as a low-speed skid resistance indicator, whereas sometimes it is impractical for data collection on roads in service. Since skid resistance is greatly affected by pavement surface texture, this research aims to evaluate pavement surface texture comprehensively and estimate the low-speed friction BPN from road surface texture on macro- and micro- scale. Asphalt Concrete (AC) and Stone Mastic Asphalt (SMA) were included. Road surface texture was evaluated from four aspects, texture depth, amplitude-related Root Means Square (RMS), elevation variances corresponding to different wavebands and texture spectral analysis. Texture depth indicators include Mean Texture Depth (MTD) and Mean Profile Depth (MPD). Elevation variances with three wavebands, from 5 mm to 50 mm, from 0.5 mm to 5 mm and from 0.024 mm to 0.5 mm respectively, were obtained. The results show that MPD is well correlated with MTD. Elevation variances with different wavebands demonstrates that the elevation variance of macro-texture with long wavelengths from 5 mm to 50 mm dominates the total variance. Spectral analysis shows that texture level is larger when the wavelength is beyond 4 mm, which is consistent with elevation variances. A linear regression between BPN and single texture index, as well as multiple linear regression analysis were conducted. The former regression result indicates that it is not feasible to estimate BPN using single index due to low correlation coefficient R². The latter shows that the BPN can be estimated from texture levels corresponding to 64 mm and 2 mm, and the micro-texture. The R² can be up to 0.684. This research will contribute to fast acquisition of BPN from pavement surface texture, thus improving skid resistance. Full article

With the increasing number of electric vehicles taking to the roads, the impact of tailpipe emissions on air quality will decrease, while resuspended road dust and brake/tire wear will become more significant. This study quantified PM₁₀ emissions from tire wear under a range of real highway conditions with measurements across different seasons and roadway surface types in Phoenix, Arizona. Tire wear was quantified in the sampled PM₁₀ using benzothiazoles (vulcanization accelerators) as tire markers. The measured emission factors had a range of 0.005–0.22 mg km⁻¹ veh⁻¹ and are consistent with an earlier experimental study conducted in Phoenix. However, these results are lower than values typically found in the literature and values calculated from emissions models, such as MOVES (MOtor Vehicle Emission Simulator). We found no significant difference in tire wear PM₁₀ emission factors for different surface types (asphalt vs. diamond grind concrete) but saw a significant decrease in the winter compared to the summer. Full article

This study conducted dynamic triaxial tests on a typical poured asphalt concrete material of core walls in Xinjiang, exploring the dynamic characteristics of poured asphalt concrete under various confining pressures, principal stress ratios, and vibration frequencies. On this basis, the dynamic constitutive relationship of poured asphalt concrete was investigated using the Hardin–Drnevich model. The results indicate that under different confining pressures, principal stress ratios, and vibration frequencies, the variation patterns of the backbone lines of dynamic stress-strain of poured asphalt concrete are basically identical, consistent with a hyperbolic curve. The confining pressure and principal stress ratio significantly affect the backbone line of dynamic stress-strain. By comparison, frequency has a minimal effect. The changing trends of dynamic elasticity modulus and damping ratio of poured asphalt concrete under various factors are almost the same. When the material has high dynamic stress and strain, the hysteresis loop is large. When the curve of the damping ratio becomes flat, the asymptotic constant can be used as the maximum damping ratio. The relationship between the reciprocal of the dynamic elasticity modulus and the dynamic strain of poured asphalt concrete exhibits a linear distribution. Under different ratios of confining pressure to principal stress, there are large discrepancies between the calculated values from the formula and the experimental fitting values of the maximum dynamic elasticity modulus, and the maximum relative errors reach 16.65% and 18.15%, respectively. Therefore, the expression for the maximum dynamic elasticity modulus was modified, and the calculated values using the modified formula were compared with the experimental fitting values. The relative errors are significantly reduced, and the maximum relative errors are 3.02% and 2.04%, respectively, in good agreement with the fitting values of the experimental data. The findings of this article render a theoretical basis and reference for the promotion and application of poured asphalt concrete. Full article