Journal of Road Engineering最新文献

In the induction heating of airport pavement to remove snow and ice, soft magnetic geopolymer composite (SMGC) can be used to gather the dissipated electromagnetic energy, thus enhancing the energy utilization efficiency. The aim of this work is to analyze the influence mechanism of iron powder content on the electromagnetic and mechanical performance of SMGC, so as to provide theoretical guidance for the design of soft magnetic layer within airport pavement structure. The results show that the increase of iron powder content reduces the resistance and magnetoresistance of SMGC by decreasing the content of non-magnetic phases between iron powder. However, the reduction of iron powder spacing also provides a shorter transmission path for the inter-particle eddy currents in the SMGC specimen, which enhances the exchange coupling between iron powder, thus increasing the electromagnetic loss. Therefore, the compatibility between magnetic permeability and electromagnetic loss should be considered comprehensively in the mix design of SMGC. In addition, although iron powder can enhance the mechanical properties of SMGC by improving the density of geopolymer matrix, the excessive amount of iron powder can lead to a weak interfacial transition zone between geopolymer matrix and iron powder. According to the induction heating results, optimized SMGC can improve the energy transfer efficiency of induction heating by 24.03%.

Cohesive failure is one of the primary reasons for low-temperature cracking in asphalt pavements. Understanding the micro-level mechanism is crucial for comprehending cohesive failure behavior. However, previous literature has not fully reported on this aspect. Moreover, there has been insufficient attention given to the correlation between macroscopic and microscopic failures. To address these issues, this study employed molecular dynamics simulation to investigate the low-temperature tensile behavior of asphalt binder. By applying virtual strain, the separation work during asphalt binder tensile failure was calculated. Additionally, a correlation between macroscopic and microscopic tensile behaviors was established. Specifically, a quadrilateral asphalt binder model was generated based on SARA fractions. By applying various combinations of virtual strain loading, the separation work at tensile failure was determined. Furthermore, the impact of strain loading combinations on separation work was analyzed. Normalization was employed to establish the correlation between macroscopic and microscopic tensile behaviors. The results indicated that thermodynamic and classical mechanical indicators validated the reliability of the tetragonal asphalt binder model. The strain loading combination consists of strain rate and loading number. All strain loading combinations exhibited the similar tensile failure characteristic. The critical separation strain was hardly influenced by strain loading combination. However, increasing strain rate significantly enhanced both the maximum traction stress and separation work of the asphalt binder. An increment in the loading number led to a decrease in separation work. The virtual strain combination of 0.5%-80 provided a more accurate representation of the actual asphalt's tensile behavior trend.

Pavement management systems (PMS) are used by transportation government agencies to promote sustainable development and to keep road pavement conditions above the minimum performance levels at a reasonable cost. To accomplish this objective, the pavement condition is monitored to predict deterioration and determine the need for maintenance or rehabilitation at the appropriate time. The pavement condition index (PCI) is a commonly used metric to evaluate the pavement's performance. This research aims to create and evaluate prediction models for PCI values using multiple linear regression (MLR), artificial neural networks (ANN), and fuzzy logic inference (FIS) models for flexible pavement sections. The authors collected field data spans for 2018 and 2021. Eight pavement distress factors were considered inputs for predicting PCI values, such as rutting, fatigue cracking, block cracking, longitudinal cracking, transverse cracking, patching, potholes, and delamination. This study evaluates the performance of the three techniques based on the coefficient of determination, root mean squared error (RMSE), and mean absolute error (MAE). The results show that the $R^2$ values of the ANN models increased by 51.32%, 2.02%, 36.55%, and 3.02% compared to MLR and FIS (2018 and 2021). The error in the PCI values predicted by the ANN model was significantly lower than the errors in the prediction by the FIS and MLR models.

The anti-skid performance of snowy and icy pavements is a popular research topic among road workers. Snow and ice are pollutants on a road surface. They significantly reduce the skid resistance of pavements, and thus, cause traffic accidents. Pertinent research progress on the skid resistance of snowy and icy pavements was reviewed and summarized in this work. The formation and classification of snowy and icy pavements were described on the basis of the state of snow and ice. The friction mechanisms between tires and snowy and icy pavements were revealed. Measurement methods and their applicability to the skid resistance of snowy and icy pavements were summarized. Factors that affect the skid resistance of pavements were discussed from the perspectives of pavement, environment, and vehicle. In addition, models of snowy and icy pavement resistance were classified into experience, mechanical, and numerical models. The advantages and disadvantages of these models were then compared and analyzed. Some suggestions regarding snowy and icy pavements were presented in accordance with the aforementioned information, including the development of efficient testing tools, the quantification of skid resistance under the coupling effects of multiple factors, the establishment of unified evaluation standards, and the development of more effective skid resistance models.

Concrete pavement is accompanied by two major functional properties, namely noise emission and friction, which are closely related to pavement surface texture. While several technologies have been developed to mitigate tire-pavement noise and improve driving friction by surface texturization, limited information is available to compare the advantages and disadvantages of different surface textures. In this study, a state-of-the-art and state-of-the-practice review is conducted to investigate the noise reduction and friction improvement technologies for concrete pavement surfaces. The commonly used tests for characterizing the surface texture, skid resistance, and noise emission of concrete pavement were first summarized. Then, the texturing methods for both fresh and hardened concrete pavement surfaces were discussed, and the friction, noise emission and durability performances of various surface textures were compared. It is found that the next generation concrete surface (NGCS) texture generally provides the best noise emission performance and excellent friction properties. The exposed aggregate concrete (EAC) and optimized diamond grinding textures are also promising alternatives. Lastly, the technical parameters for the application of both diamond grinding and diamond grinding & grooving textures were recommended based on the authors' research and practical experience in Germany and the US. This study offers a convenient reference to the pavement researchers and engineers who seek to quickly understand relevant knowledge and choose the most appropriate surface textures for concrete pavements.

The motivation for cost-effective management of highway pavements is evidenced not only by the massive expenditures associated with these activities at a national level but also by the consequences of poor pavement condition on road users. This paper presents a state-of-the-art review of multi-objective optimization (MOO) problems that have been formulated and solution techniques that have been used in selecting and scheduling highway pavement rehabilitation and maintenance activities. First, the paper presents a taxonomy and hierarchy for these activities, the role of funding sources, and levels of jurisdiction. The paper then describes how three different decision mechanisms have been used in past research and practice for project selection and scheduling (historical practices, expert opinion, and explicit mathematical optimization) and identifies the pros and cons of each mechanism. The paper then focuses on the optimization mechanism and presents the types of optimization problems, formulations, and objectives that have been used in the literature. Next, the paper examines various solution algorithms and discusses issues related to their implementation. Finally, the paper identifies some barriers to implementing multi-objective optimization in selecting and scheduling highway pavement rehabilitation and maintenance activities, and makes recommendations to overcome some of these barriers.

Semi-flexible composite mixture (SFCM) is a kind of pavement material formed by pouring cement-based grout material into a porous asphalt mixture with air voids from 20% to 30%. SFCM is widely used for its outstanding anti-rutting performance. Its mechanical performance is complicated due to its heterogeneity and interlocking structure. According to the present study, asphalt deforms at different temperatures, whereas cement-based grout has no similar characteristics. Rare research focuses on the temperature-based performance of SFCM. Therefore, the study was on the thermal performance of SFCM by seven open-graded asphalt mixture skeletons with different porosities and two types of grouts with early strength (ES) and high strength (HS). The test temperatures ranged from −10 ​°C to 60 ​°C. The mechanical investigation was performed using the semi-circular-bending (SCB) and beam bending tests. The strain sensor was used for analyzing the thermal performance of SFCM. The results show that the temperature significantly affected the SFCM's performance. The porosity was selected for three sections based on the trend of fracture energy (G_f) curves at 25 ​°C. The turning points were the porosity values of 20% and 26%. The initiation slope during elastic deformation increases with the porosity increase. This trend was more evident at intermediate temperature. The shrink strain of SFCM was lower than that of the usual asphalt mixture (AC). The thermal stress of the SFCM filled with HS (HS-SFCM) was higher than that of the SFCM filled with ES (ES-SFCM) at −10 ​°C. Moreover, the thermal failure characteristics of SFCM were influenced by porosity.

Microbial-induced calcium carbonate precipitation is a promising technology for self-healing concrete due to its capability to seal microcracks. The main goal of this study was to evaluate the effects of adding hydrogel-encapsulated bacteria on the compressive strength and the self-healing efficiency of concrete. To achieve this objective, 12 sets of mortar samples were prepared, including three different mineral precursors (magnesium acetate, calcium lactate, and sodium lactate), at two concentrations (67.76 and 75.00 ​mM/L), and under two different biological conditions (with and without bacteria). In addition, a set of plain mortar samples was prepared to serve as a control. For each sample set, three mortar cubes and three beams were prepared and subjected to compression and flexural strength tests. From the compression tests, it was found that the sample containing calcium lactate along with yeast extract and bacteria displayed the best results. As for the flexural tests, once cracked, the beams were subjected to 28 ​d of wet/dry cycles (16 ​h of water immersion and 8 ​h of drying), where the bottom crack width was monitored (at 0, 3, 7, 14, 28 ​d of wet/dry cycles). Once the sample with the highest healing efficiency was identified (the one containing calcium lactate and hydrogel-encapsulated bacteria), the study was scaled up to concrete specimens. Two sets of concrete cylinders (consisting of three control samples and three samples with bacteria along with calcium lactate) were tested under compression in order to evaluate the effect of the bacteria-precursor combination on the concrete mechanical properties. The samples that yielded the greatest compressive strength were the ones containing calcium lactate and bacteria, displaying an improvement of 17% as compared to the control specimen. Furthermore, a flexural strength recovery analysis was performed on the concrete specimens revealing that the control showed better flexural strength recovery than the bacteria-containing variant (41.5% vs. 26.1%) after 28 ​d of wet/dry cycles. A healing efficiency analysis was also performed on the cracked samples, revealing that the control displayed the best results. These results are due to the fact that the control specimen showed a narrower crack width in comparison to the bacteria-containing samples.

Domestic waste incineration slag (WIS) includes fly ash and slag. Fly ash is classified as hazardous waste because it contains heavy metals. Most of slag are directly stacked or landfilled due to problems such as large output and low utilization rate. Harmless treatment is imminent. If WIS is used effectively in the road engineering, which can realize the high-quality and high-efficiency recycling of WIS, and it is of great significance to save resources and protect the environment. This study applies a geopolymer prepared from WIS fly ash as a stabilizing agent in WIS blending macadam for use as a pavement base mixture, and reports the mechanical properties (unconfined compressive strength, splitting strength, and resilience modulus) of the geopolymer-stabilized WIS blending macadam (GeoWIS). The leaching concentrations of harmful heavy metals of GeoWIS soaked in water were also investigated. Finally, the strength formation and heavy metal stability mechanisms were explored. The unconfined compressive strength, splitting strength, and compressive resilient modulus of GeoWIS all increased with increasing geopolymer content and decreasing WIS content. The strength of GeoWIS was derived from its geopolymerization and hydration products (C-S-H gel, N-A-S-H gel, and AFt). When the geopolymer content reached 12%–14%, the GeoWIS without natural macadam met the strength criterion of the asphalt pavement base. Through physical adsorption and chemical bonding, the geopolymer significantly reduced the leaching of harmful heavy metals. In GeoWIS with 50% WIS and stabilized with 10% geopolymer, the Cr, Ni, Cd, and Pb concentrations met the grade Ⅲ groundwater standard. Concentrations of heavy metals leached from GeoWIS are low and exert little impact on environment.

The modification of asphalt binder with natural rubber latex (NR) significantly improves the rutting and fatigue resistance of asphalt mixtures. However, NR-modified binder is prone to low workability and wettability due to its high viscosity. Therefore, this research focuses on examining the influences of silane and wax-based additives on the wettability of natural rubber-modified binders and the binder-aggregates adhesion performances. In this study, experimental and analytical approaches were used. The contact angles of asphalt binder were measured using a goniometer through the sessile drop method with three solvents: deionised water, formamide, and glycerol. The C++ algorithm was adopted to compute the surface free energy (SFE) elements of the asphalt binder. Analytical methods were employed to analyse the results based on the Young-Dupre equation, followed by linear regression to establish a correlation between the compatibility ratio (CR) and the SFE components. The results inferred that modified asphalt binders with additives possessed improved moisture resistance, wherein dry work adhesion values were less than 210 ​mJ/m² under granite interfaces, whereas the limestone interface exhibited higher dry adhesion values of 340 ​mJ/m² and below. Similar performance results were observed under wet adhesion conditions; with granite wet adhesive values observed below 120 ​mJ/m², while limestone wet adhesion values were ascertained below 180 ​mJ/m² for all tested samples and conditions. According to the spread–ability coefficient results, the limestone interface has greater spread-ability than granite interfaces. Meanwhile, compatibility ratio values indicated better compatibility of 1.9 or higher for tested samples under granite interfaces, whereas compatibility values of 1.7 and below were observed under limestone interfaces. Among the SFE components studied for correlation with CR, the acidic SFE component demonstrated excellent correlations (with R² values greater than 0.91) under all ageing conditions. An inclusion of micro-level additive enhanced binder adhesion properties, resulting in a more resilient asphalt pavement.