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As a vital and integral component of transportation infrastructure, pavement has a direct and tangible impact on socio-economic sustainability. In recent years, an influx of groundbreaking and state-of-the-art materials, structures, equipment, and detection technologies related to road engineering have continually and progressively emerged, reshaping the landscape of pavement systems. There is a pressing and growing need for a timely summarization of the current research status and a clear identification of future research directions in these advanced and evolving technologies. Therefore, Journal of Road Engineering has undertaken the significant initiative of introducing a comprehensive review paper with the overarching theme of “advanced road materials, structures, equipment, and detection technologies”. This extensive and insightful review meticulously gathers and synthesizes research findings from 39 distinguished scholars, all of whom are affiliated with 19 renowned universities or research institutions specializing in the diverse and multidimensional field of highway engineering. It covers the current state and anticipates future development directions in the four major and interconnected domains of road engineering: advanced road materials, advanced road structures and performance evaluation, advanced road construction equipment and technology, and advanced road detection and assessment technologies.

Limestone calcined clay cement (LC3), enhanced through reactions with volcanic ash and the interaction between limestone and clay, significantly improves the performance of cementitious materials. It has the potential to cut CO2 emissions by up to 30% and energy consumption in cement manufacture by 15% to 20%, providing a promising prospect for the large-scale production of low-carbon cement with a lower environmental effect. To effectively manufacture LC3 concrete, this study utilized limestone (15%), calcined clay (30%), and gypsum (5%) as supplementary cementitious materials (SCMs), replacing 50% of ordinary Portland cement (OPC). However, in regions abundant in sulfate, sulfate attack can cause interior cracking of concrete, reducing the longevity of the building. To address this issue, microcapsules containing microcrystalline wax, ceresine wax, and nano-CaCO3 encapsulated in epoxy resin were prepared and successfully incorporated into LC3 concrete. Sulfate resistance tests were conducted through sulfate dry–wet cycles, comparing samples with and without microcapsules. The findings revealed that the initial mechanical and permeability properties of LC3 concrete did not significantly differ from OPC concrete. LC3 concrete with added microcapsules (SP4) exhibited enhanced resistance to sulfate attack, reducing mass loss and compressive strength degradation. SEM images displayed a mesh-like structure of repair products in SP4. After 14 days of self-repair, SP4 exhibited a 44.2% harmful pore ratio, 98.1% compressive strength retention, 88.7% chloride ion diffusion coefficient retention, 91.12 mV maximum amplitude, and 9.14 mV maximum frequency amplitude. The experimental results indicate that the presence of microcapsules enhances the sulfate attack self-healing performance of LC3 concrete.

Summary: The inherent self-healing ability of asphalt is insufficient and fails to timely repair the cracks due to the combined effect of temperature variation, air oxidation, ultraviolet exposure and traffic loading. Rejuvenator encapsulation based on self-healing asphalt is a green sustainable preventive maintenance technology for asphalt pavement. During the last decade, rejuvenator encapsulation for asphalt self-healing has been a research hotspot and calcium alginate hydrogels encapsulating rejuvenator is a promising self-healing technology. Hence, this review sheds light on the recent advances of calcium alginate hydrogels encapsulating asphalt rejuvenator including self-healing capsules and fibers. The synthesis methods of calcium alginate capsules and fibers containing rejuvenator were elaborately introduced, and their surface morphology, interior structure, mechanical strength, thermal stability, rejuvenator content, distribution and survival in asphalt materials were systematically analyzed. Besides, the effect of capsules and fiber on the mechanical property and pavement performance of asphalt concrete were explored. Additionally, a comprehensive review about the effect of calcium alginate capsules and fibers on self-healing ability of asphalt materials were presented, and the rejuvenator release mechanism and release ratio of them in asphalt mixtures were expounded. In a nutshell, this review aims at highlighting the current research achievements on alginate capsules and fibers containing rejuvenator in asphalt materials, and inspiring enhanced self-healing methods for smart and sustainable maintenance of asphalt pavement.

Under the action of repeated load of vehicles, asphalt pavement tends to suffer rutting and other failures at high temperatures, which shortens the service life of the pavement. Meanwhile, asphalt pavement aggravates the urban heat island (UHI) effect, reducing the livability of the city. Research shows that lower road temperatures can mitigate the UHI effect. For this reason, researchers have launched lots of studies to cool asphalt pavement under high temperatures, such as reflective pavement and phase change pavement, etc. Although these technologies are effective at reducing the temperature of asphalt pavement, there are still some limitations. This paper mainly discusses the latest development of asphalt pavement temperature reduction strategies, classifies them according to different action mechanisms, and discusses the advantages and limitations of each strategy in detail. Suggestions for future research are given to address the limitations of each strategy, such as passive radiation technology can provide new ideas for reflective pavement, planting trees should consider plant physiological parameters and spatial distribution of planting, and phase change materials can be encapsulated by high thermal conductivity materials, etc. This study can provide a guidance for further development of asphalt pavement cooling technologies.

Summary: Asphalt binder is inevitably aged by ultraviolet (UV) light during its service period. UV ageing can significantly decrease the technical properties of asphalt binder. The sensitivity of asphalt to UV ageing and thermal-oxidative ageing differs, such that the UV ageing performance cannot be determined based on the thermal-oxidative ageing performance. Previous researches mainly focused on the chemical composite and technical performance changes of asphalt binder during UV ageing, and the UV light parameters effect on the ageing rate of asphalt binder. However, the theory for characterizing and explaining the development of UV ageing depth does not get too much attentions, and the UV ageing mechanism of asphalt binder is not very clear. Therefore, it cannot guide to develop or select the good methods or anti-UV ageing additives for asphalt binders. This paper focuses on the latest researches of the mechanisms and anti-ageing methods of asphalt binders. With the increase of UV ageing time, the UV ageing of asphalt binder develops gradually from the surface to inner part. There are various methods, such as low-penetration grade asphalt, less air void ratio, UV stabilizers and UV light absorbers, that can improve the UV ageing resistance of asphalt binders. A new theory of sensitive wavelengths of asphalt UV ageing is proposed, which can enrich the basic theory of asphalt UV ageing. Depending on this theory, different wavelengths of UV light have different ageing effects on asphalt binder. The composite anti-UV ageing additives with barrier and specific absorption effects on UV light is proposed, and may have better improvement effect on the anti-UV ageing performance of asphalt binder.

This research aims to prepare different antioxidant intercalated layered double hydroxides (LDHs) and compare the thermal oxidation and ultraviolet (UV) aging resistances of different modified asphalts. The ion exchange technique was used to intercalate three different antioxidants: 3-(3,5-di-tert-butyl-4-carboxyphenyl) propionic acid, antioxidant 1222, and sodium dibutyl dithiocarbamate (rubber accelerator TP) into the interlayer of LDHs. The morphology, structures, UV blocking, and free radical scavenging properties of different antioxidant intercalated LDHs were characterized, respectively. The effects of the anti-aging agents on the physical properties (penetration, softening point, ductility, and viscosity); rheological behaviors (complex modulus and phase angle); and functional groups (C=O and S=O) of asphalt both before and after thermal oxidation aging and UV aging were systematically investigated. The results of the crystal structure and functional group analysis show that the three different antioxidants can be successfully inserted into the interlayer of LDHs without destroying their layered structures. Antioxidant intercalated LDHs exhibit a remarkable capacity for absorbing UV rays, coupled with a moderate ability to reflect UV light. Moreover, the inclusion of antioxidants into the interlayers of LDHs confers upon them the ability to scavenge free radicals. After 2 h of reaction, the free radical scavenging rates of LDHs-3, LDHs-1222, and LDHs-TP were 57.7%, 35.6%, and 17.1%, respectively. With an increase in the content of the antioxidant intercalated LDHs, the performance of the modified asphalt varies, and 4% is the optimal content of the anti-aging agents. Asphalts with the three antioxidant intercalated LDHs all had favorable storage stability, and their physical and rheological properties were improved after aging compared to LDHs-modified asphalt. The LDHs-3-modified asphalt showed the best anti-ultraviolet aging effect, while LDHs-1222-modified asphalt showed the best anti-thermal oxidation aging effect. This research lays the foundation for developing aging-resistant asphalt and improving the durability of asphalt pavement.

The UV aging of bitumen has a significant influence on the pavement service life, therefore, the research on UV aging has attracted increasing attention recently. It is known that the aging of bituminous pavements does not occur instantly through the full depth, instead, the aging depth of the bitumen increases gradually with the increasing aging time. The limitation of the research is that the development mechanism of the aging depth of bitumen is not clearly known. Various thicknesses of bituminous membranes were prepared and the UV light transmission and absorption properties of bituminous membranes were investigated by UV–visible spectrophotometric, aiming to determine the penetration depth of UV light in bitumen after UV aging. It is concluded that, for the same bituminous membrane, the transmittance of UV light increases with the increase of the light wavelength; while the transmittance of UV light decreases significantly with the increase of bituminous membrane thickness. The penetration depth of UV light in bitumen increases gradually with increasing UV aging time. The relationship between UV light penetration depth in bitumen and aging depth of bitumen was analyzed, and UV aging models of three parts of bitumen were established to reveal the development mechanism of the UV aging depth of bitumen during UV aging. The increasing aging depth of bitumen is due to the increase of UV light penetration depth in bitumen, and the diffusion action of aging products from surface bitumen to deeper bitumen. During the UV aging, the bitumen actually comprises three parts, namely, the surface direct aging part (UV light can reach), the deeper diffusion aging part (aged by the diffusion action) and the internal unaged part (UV light and diffusion action can not affect).

It is consensual that the self-healing property of asphalt concrete can repair the damage inside it during high temperature and rest period. In order to not affect the traffic, the rest period of asphalt pavement is very short and uncontrollable; so, it is necessary to obtain enough high temperature in a limited time to achieve higher healing efficiency of asphalt concrete. The purpose of this paper is to study the induction heating efficiency and healing behaviors of asphalt concretes doped with different conductive additives. Steel fiber, steel grit, and steel slag were added to asphalt mixtures as conductive additives to prepare induction healing asphalt concretes. The steel grit and steel slag were added to replace the aggregates of corresponding particle size by equal volume to ensure the consistency of asphalt concrete volume, which can avoid degrading the performance of asphalt concrete due to the change of porosity. The induction heating efficiency and healing rate of asphalt concrete were quantified by infrared camera and three-point bending-healing experiment, respectively. The results showed that the thermal properties of asphalt concrete changed with the addition of different conductive additives. The asphalt concrete with steel fiber had the best induction heating property. While steel slag had extremely weak induction heating speed, the better thermal insulation property of the asphalt concrete with steel slag resulted in a higher induction healing rate. It was suggested to add steel slag to induction healing asphalt concrete to improve the healing rate.

Ultraviolet (UV) radiation causes serious ageing problems on pavement surface. In recent years, different UV blocking materials have been used as modifiers to prevent asphalt ageing during the service life of the pavement. In this study, three different materials have been used as modifiers in base asphalt to test their UV blocking effects: layered double hydroxides (LDHs), organomontmorillonite (OMMT), and carbon black (CB). UV ageing was applied to simulate the ageing process and softening point, penetration, ductility, DSR (Dynamic Shear Rheometer) test, and Fourier Transform Infrared Spectroscopy (FTIR) test were conducted to evaluate the anti-UV ageing effects of the three UV blocking modifiers. Physical property tests show that base asphalt was influenced more seriously by UV radiation compared to the modified asphalt. DSR test results indicate that the complex modulus of asphalt before UV ageing is increased because of modifiers, while the complex modulus of base asphalt after UV ageing is higher than that of the modified asphalt, which shows that the UV blocking modifiers promote the antiageing effects of asphalt. FTIR test reveals that the increment of carbonyl groups and sulfoxide groups of modified asphalt is less than that in base asphalt. Tests indicate the best UV blocking effect results for samples with LDHs and the worst UV blocking effect results for samples with CB.

In this paper, steel slag/steel fiber composite asphalt mixture were prepared. The effects of the addition of steel slag and/or steel fibers on the mechanical, thermal, induction heating and healing properties of asphalt mixture were investigated. The results showed that adding steel slag and/or steel fibers improves the water stability, particle loss resistance and fracture energy of asphalt mixtures. The addition of steel fibers increased the thermal conductivity and thermal diffusion of the asphalt mixture, and steel slag showed a reverse effect. Steel slag asphalt mixture cooled more slowly than steel fiber asphalt mixture, which is beneficial to crack healing of asphalt mixture. The composite of steel fibers and steel slag can enhance the induction heating speed, heating homogeneity and thus enhance the induction healing ratio of asphalt mixture. It is concluded that steel slag/steel fibers composite asphalt mixture achieves good mechanical and induction healing properties.

As a vital and integral component of transportation infrastructure, pavement has a direct and tangible impact on socio-economic sustainability. In recent years, an influx of groundbreaking and state-of-the-art materials, structures, equipment, and detection technologies related to road engineering have continually and progressively emerged, reshaping the landscape of pavement systems. There is a pressing and growing need for a timely summarization of the current research status and a clear identification of future research directions in these advanced and evolving technologies. Therefore, Journal of Road Engineering has undertaken the significant initiative of introducing a comprehensive review paper with the overarching theme of "advanced road materials, structures, equipment, and detection technologies". This extensive and insightful review meticulously gathers and synthesizes research findings from 39 distinguished scholars, all of whom are affiliated with 19 renowned universities or research institutions specializing in the diverse and multidimensional field of highway engineering. It covers the current state and anticipates future development directions in the four major and interconnected domains of road engineering: advanced road materials, advanced road structures and performance evaluation, advanced road construction equipment and technology, and advanced road detection and assessment technologies. [ABSTRACT FROM AUTHOR]

In recent years, nanoparticles with special structures have been widely used in the traditional building material bitumen. For that, mesoporous hollow silica (MHS) particles were synthesized in this work. Scanning electron microscope, transmission electron microscope, and Brunauer-Emmett-Teller tests were conducted to characterize the specific structure. Then, MHS was used to improve the properties of the traditional construction binder material bitumen. Penetration, softening point, and dynamic shear rheometer tests were performed to study the physical and rheological properties of MHS-modified bitumen. A pyrolysis gas chromatography mass spectrometry test was used to evaluate the inhibition effect of MHS on the emission of the bitumen volatile organic compounds (VOCs). The results showed that MHS with continuous distributed pore diameters were simply synthesized in one step by hydrothermal method. MHS as a kind of additive could improve the high temperature rutting resistance of bitumen. In addition, because of the higher specific surface area and massive micropores, MHS had a significant inhibition effect on the emission of bitumen VOCs. [ABSTRACT FROM AUTHOR]

Asphalt binder is a self-healing material and it has a potential to heal faster with increased temperatures. This paper investigates the thermally activated healing of fatigue damage in three asphalt binders, trying to answer the question: At what temperatures do asphalt binders heal? After fatiguing the sample, a heating treatment was applied and the sample was fatigued for the second time. The recovered fatigue life and the recovered accumulated dissipated energy are used to quantify the thermally activated healing rates of asphalt binders. It is found that these two healing indexes coincide well with each other in different healing conditions. Base asphalt binders can heal the fatigue damage completely after heating for 20 min at the softening-point temperatures. Styrene-butadiene-styrene (SBS)-modified asphalt binder can achieve full healing at a temperature 20°C below its softening point, where the elastic recovery of the SBS chain segment may play an important role in healing. It is also found that healing of fatigue damage in asphalt binder is highly strain dependent: the healing ratio is higher at high strain amplitude. It proved that thermally activated healing can be repeated when damage returns in asphalt binder. It is concluded that thermally activated healing of fatigue damage is definitely useful to increase the fatigue life of asphalt binders and different asphalt binders should be heated to certain temperatures related to their specific softening points. [ABSTRACT FROM AUTHOR]