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Rejuvenating the reclaimed asphalt pavement by crumb rubber modified binder for recycling in new pavements arouses a great interest as a sustainable paving technology that uses waste to recycle waste and hinders resource depletion. By investigating rheological and adhesion/cohesion characteristics of the asphalt binder, this study aims to divine optimal dosages of reclaimed asphalt and crumb rubber that enhance the overall performance of the binder without undermining any feature. Thirty binders produced from two types of virgin binder, two sources of reclaimed asphalt, three dosages of reclaimed asphalt, and two dosages of crumb rubber were prepared and tested. Bonding, rheological, and physiochemical characteristics of binders were investigated using pull-off test, dynamic shear rheometer, and Fourier transformed infrared spectroscopy. The results show that mixing reclaimed asphalt with rubberized asphalt greatly enhances the cohesion strength, rutting resistance, creep resistance, and colloid homogeneity. However, certain reclaimed asphalt and crumb rubber dosages undermine the fatigue cracking resistance. The physiochemical investigation revealed that the crumb rubber chains intensively swell and disintegrate simultaneously during mixing with virgin binder and further mixing with reclaimed asphalt. Through correlation analysis, it was emphasized that the improvement of cohesion strength and rheological characteristics is ascribed to the physiochemical changes caused by crumb rubber interaction and reclaimed asphalt addition. [Display omitted] [ABSTRACT FROM AUTHOR]

Semi-rigid base asphalt pavement has been widely utilized and various interlayer distresses occur during its service life due to temperature, vehicle loads and water, which weaken the interlayer performance between the base and surface layers. This review primarily investigates the mechanisms of interlayer distress in semi-rigid base asphalt pavement, as well as the evaluation methods for interlayer performance and the methods for treating interlayer distress. Interlayer distress is caused by the weakening of interlayer performance, manifested specifically in inadequate interlayer bonding strength and cracking resistance. Accordingly, researchers have proposed various methods for evaluating interlayer performance, including shear tests, tensile tests, torsional tests, fatigue tests, and non-destructive testing methods. Measures for treating interlayer distress can be categorized into pavement materials and structural design, application of tack coats, and installation of interlayers. Among them, asphalt emulsion is the most commonly used tack coat material to enhance interlayer bonding performance significantly. Meanwhile, during the application of tack coats, mechanical parameters should be controlled strictly and ensure high construction quality. Interlayers installation was proven to delay and prevent crack propagation effectively, reducing crack-related distress significantly. The lower life cycle cost (LCC) of permanent semi-rigid base asphalt pavement makes it present high application potential. It is recommended to consider interlayer installation in semi-rigid base asphalt pavement design and take appropriate measures to enhance interlayer performance effectively. [Display omitted] • Inadequate interlayer performance can easily lead to deformation, cracks and other distresses. • Shear test is the easiest way to evaluate bonding properties but non-destructive test becomes popular. • It was found that application of tack coats can effectively minimize interlayer distresses. • Semi-rigid base asphalt pavements are a viable alternative to permanent pavements. [ABSTRACT FROM AUTHOR]

[Display omitted] • Optical fiber sensors have better corrosion, electromagnetic interference resistance and signal-to-noise ratio. • Optical fiber sensors can measure the strain, temperature and pressure information of pavement in real time. • The applications of optical fiber sensors in pavement are more and more extensive. Optical fiber sensor (OFS) is a commonly used tool to monitor the serviceability and integrity of pavements. The earliest application of optical fiber sensors in the road can be traced back to the early 21st century, and development of this technique has been extensively studied after that. In view of the increasing demand for pavement nondestructive testing and the rapid development of optical fiber sensor technology, this work summarizes the optical fiber sensors commonly used in road engineering and the classification methodologies. After that, the basic principle of fiber Bragg grating (FBG) sensor and the application of this sensor in the pavement were discussed. Finally, the principle and application of distributed optical fiber sensors (DOFS) in the pavement were included as well. Overall, this review found that FBG sensors can accurately measure and monitor road strain, temperature, pressure and WIM measurement by employing analytical-based methods. Distributed optical fiber sensors can measure pavement crack width, identify the void under the concrete slab, and obtain vehicle load (load size, load moving speed, axle type) and other data. Currently, it has been proved that the installation of the installation of fiber optic sensors on the road surface is an effective method to monitor the integrity of the road structure under traffic, but further tests in real traffic environment to further improve the survival rate of fiber optic sensors and evaluate the accuracy of the measured results are still needed. [ABSTRACT FROM AUTHOR]

Considering the enormous amounts of virgin materials consumed in road construction and rehabilitation, recycling reclaimed asphalt pavement has aroused great interest recently. Among different modifiers, crumb rubber is a waste material that significantly enhances different characteristics of the asphalt binder. This study investigates the bonding strength of asphalt mastic of reclaimed asphalt binder modified by crumb rubber-modified binder. The study also attempts to model the mastic bonding strength and understand its mechanism. Thirty binders with different percentages of crumb rubber and reclaimed asphalt were mixed with two filler types to produce the asphalt mastics. Moreover, the two phases of the binder colloid, gel and liquid phases, created by crumb rubber modification, were separated to evaluate the crumb rubber interaction and its impact on mastic bonding. The pull-off test was used to evaluate the bonding strength of asphalt mastics and binders, while dynamic shear rheometer and Fourier-transformed infrared spectroscopy were used to evaluate the physiochemical and rheological characteristics of the asphalt binders. The results show that crumb rubber and reclaimed asphalt modifications greatly strengthen the mastic bonding. The accretion of carbonyl groups due to the reclaimed asphalt addition and withdrawal of light components due to the crumb rubber interaction improves the stiffness of the liquid phase binder, which is strongly correlated to the mastic bonding strength. Furthermore, despite its role in strengthening the binder stiffness, the crumb rubber particles as fillers no longer affect the mastic bonding, where this role is undermined by the mineral fillers. [Display omitted] • Crumb rubber and reclaimed asphalt pavement binder modifications enhance the mastic bonding strength. • Mastic bond is highly correlated to the binder bond strength. • Crumb rubber interaction with asphalt binder strengthens mastic bond. • Mastic bond increases by increasing the carbonyl intensity. • The incorporation of mineral filler undermines the crumb rubber impact as filler. [ABSTRACT FROM AUTHOR]

With the development of urban underground space and increased infrastructure functions, both the scale of engineering construction and engineering difficulties have increased globally. In the construction of structures in soft strata, especially in coastal areas, the limited bearing capacity of the foundations poses a significant challenge. The composite pile technologies employing an organic combination of the rigid pile andthe flexible column can enable efficient soft ground treatment. In light of prominent global environmental issues, low-carbon energy-saving curing technologies have been rapidly developed for application in geotechnical engineering. This paper discusses progress in research on the mechanical properties of the efficient and low-carbon pile technologies, including the stiffened deep mixing (SDM) column, squeezed branch pile, pre-bored grouting plated nodular (PGPN) pile, precast cement pile reinforced by cemented soil with a variable section (PCCV), and carbonized composite pile (CCP). In addition, it reviews the technical characteristics and recent progress of feasible low-carbon energy-efficient curing technologies. The paper also proposes future directions for theoretical research and technological development of low-carbon pile technologies. The key contribution of this review is to provide insights into efficient and low-carbon pile technologies. In addition, the findings from the study of the pile technologies used in extra-thick soft strata also provide industry practitioners with a comprehensive guide regarding the specific applications and mechanical performance of the pile technologies, which can serve as a stepping stone to facilitate the technological development of the underground space industry. [ABSTRACT FROM AUTHOR]

Incorporating reclaimed asphalt pavement (RAP) increases concern about long-term fatigue and cracking resistance of the resultant mixture due to the presence of an aged binder. Using a rejuvenator is one of the most promising methods to prolong the aging time for initial cracking and allow the inclusion of higher RAP content. Many discrepancies exist in the literature about rejuvenators' effectiveness in improving the fatigue performance of RAP binder and mixture. These ambiguous and contradictory findings are attributed to using different rejuvenator types and dosages, RAP sources and percentages, binders and mixture fatigue testing approaches. This paper comprehensively reviews and investigates the existing literature to fully understand the rejuvenation mechanism and its impact on the fatigue and cracking resistance of RAP binder and mixture using the most available tests and indicators. In addition, a rigorous laboratory study is carried out to determine the sensitivity of indicators to mix composition and variability. It is concluded that the inclusion of rejuvenators into RAP binders and mixtures may not improve their fatigue and cracking performance to the same level as virgin materials. But by utilizing polymer modification, the bonding between materials increases significantly, which results in better fatigue performance of rejuvenated RAP materials. Despite the positive impact of rejuvenators on RAP mixture fatigue performance, a comparison of different tests results does not offer a consistent indicator for determining fatigue resistance. Hence, it is recommended that the future research should be carried out with reasonable test methods, more complicated analytical techniques, service life characterization models, and climate identical test conditions, to clarify the durability index. Also, a complete evaluation of field performance utilizing RAP and rejuvenator is valuable. [ABSTRACT FROM AUTHOR]