New Trends in Long-Life Road Infrastructures: Materials and Structures

1. Introduction

The development of long-life road infrastructure has become a pressing global priority, fueled by escalating demands stemming from rapid urbanization, escalating environmental concerns, and the critical necessity for sustainable, environmentally friendly transportation alternatives [1]. With global and ongoing rapid urbanization, current road networks are encountering increasing difficulty in adapting to rising traffic volumes and changing mobility needs. Concurrently, the urgent need to tackle climate change and lower the environmental impact of transportation infrastructure has underscored the importance of constructing environmentally sustainable and resilient road networks [2].

Conventional road designs and methods often fall short of meeting these evolving demands, as they tend to focus on immediate concerns and do not sufficiently prioritize enduring performance and resilience. For instance, the typical design lifespan of road pavements is often restricted to 15–20 years in China, significantly below the benchmarks established by its economic development [3]. This disparity between the existing capacities and emerging demands has instigated a coordinated endeavor to transform the materials, structures, and technologies utilized in the creation and upkeep of road infrastructure.

The quest for long-life road infrastructures has driven researchers and practitioners worldwide to explore innovative approaches that can enhance the performance, serviceability, and sustainability of road systems. The key areas include the development of advanced eco-friendly materials with superior durability [4], the design of resilient structural systems capable of withstanding escalating demands [5], and the integration of cutting-edge numerical and intelligent technologies to optimize the performance and life-cycle management of road networks [6].

In the materials domain, significant advancements have been made in the development of novel cementitious, asphalt, and composite materials that can offer improved strength, flexibility, and resistance to the environmental degradation of road infrastructures [7]. The incorporation of supplementary cementitious materials, such as fly ash and slag, has demonstrated the potential to enhance the sustainability and long-term durability of concrete-based road infrastructures [8]. Similarly, the utilization of modified asphalt binders and renewable aggregates has shown promise in improving the performance and service life of flexible pavement systems [9,10].

Alongside materials innovation, researchers have also dedicated effort to the enhancement of structural design and analysis capabilities. The integration of advanced numerical modeling techniques, including finite element analysis and discrete element modeling, has enabled a deeper understanding of the complex behavior of road structures under various loading and environmental conditions. This, in turn, has facilitated the development of optimized structural designs that can withstand the demands of increased traffic, climate change, and natural hazards better.

In summary, the convergence of these technological innovations, combined with a holistic emphasis on sustainability and life-cycle performance, has set the stage for a new era in road infrastructure development. This book, titled New Trends in Long-Life Road Infrastructures: Materials and Structures, aims to showcase the latest research and advancements in this critical field, providing a platform for the dissemination of cutting-edge knowledge and the exploration of transformative solutions. By advancing our understanding of material behavior, structural performance, and life-cycle management strategies, these research findings can inform the design, construction, and maintenance of more durable, eco-friendly, and adaptable road infrastructures.

2. An Overview of Published Articles

From the Special Issue on “New Trends in Long-Life Road Infrastructures: Materials and Structures”, this book features a diverse collection of 20 state-of-the-art research contributions and 1 comprehensive review article. The articles collected in this book span a wide range of topics, including material characterization, structural behavior, performance assessment, and maintenance planning, all aimed at advancing the state of the art in long-life road infrastructure design and construction.

Contribution 1 investigated the field compaction properties of ultra-thin, porous friction course (UPFC) mixtures designed using the Marshall compaction method. Through laboratory simulation and virtual compaction tests, the researchers revealed significant differences between the laboratory and field compaction characteristics of UPFC, highlighting the need for more appropriate design methods to ensure adequate field performance.

Contribution 2 investigated the effects of modification with glass fiber recycled from wind turbine blades on SBS-modified asphalt and their mechanisms. This study evaluated the performance of the GF-WTB/SBS composite-modified asphalt and explored the underlying modification mechanisms.

Contribution 3 investigated the use of a silane coupling agent to enhance the adhesion properties between recycled concrete aggregates (RCAs) and asphalt. The researchers examined the macroscopic properties, interfacial microstructure, and nanoscale interactions to elucidate the mechanism by which the silane coupling agent improved the RCA/asphalt interface, contributing to the development of sustainable asphalt mixtures.

Contribution 4 explored the use of a composite modifier of rock asphalt and montmorillonite to improve the rutting resistance and anti-aging performance of bio-asphalt. This study determined the optimum content of the components and evaluated the rheological properties and anti-aging performance of the modified bio-asphalt.

Contribution 5 investigated the effect of thermo-oxidative aging and the test temperature on the cracking resistance of asphalt mixtures. The researchers analyzed the stress–strain curves and evaluation indexes of asphalt mixtures with different aging degrees and at test temperatures.

Contribution 6 explored the anisotropic swelling characteristics of expansive soils. The researchers developed a nonlinear elastic constitutive model that incorporated the directionally dependent swelling behavior, providing practical tools for assessing the pressures exerted by expansive soils more comprehensively and guiding their utilization and design.

Contribution 7 presents an extensive examination of the dynamic elastic modulus and damping ratio of coarse-grained soils under varying relative densities. The researchers conducted dynamic triaxial tests to reveal the complex relationships between these critical dynamic parameters and the relative density of the soil, providing valuable insights for geotechnical engineering applications.

Contribution 8 explored the effect of mixing homogeneity on the compaction of soil–rock mixtures using the discrete element method. Analysis of the particle motion and energy dissipation mechanisms revealed the critical role of rolling slip energy dissipation in promoting compaction, offering insights for improving the compaction of heterogeneous granular materials.

Contribution 9 investigated the permanent deformation of coal gangue subgrade filler under cyclic loading. This study examined the effects of the confining pressure, grading, and compaction degree on permanent deformation and proposed a unified calculation model for the permanent deformation of coal gangue subgrade filler.

Contribution 10 examined the influence of lime content on the road performance of low liquid limit clay. This study used a limit water content test, a compaction test, and the California bearing ratio test to evaluate the improvements in the basic properties of the subgrade soil after adding lime.

Contribution 11 investigated the use of high volumes of fly ash in the development of high-performance, low-carbon concrete. Through compressive strength, flexural strength, and microscopic tests, the researchers demonstrated the beneficial effects of fly ash on the mechanical properties and microstructure of the concrete, contributing to the promotion of green and sustainable construction materials.

Contribution 12 aimed to clarify the negative pressure distribution in drainage structures of soft foundations reinforced by vacuum preloading. This study established numerical models to analyze the consolidation process of the soft foundation and the distribution of negative pressure in the drainage structure.

Contribution 13 focused on enhancing the seismic resilience of tunnels crossing active fault zones. The researchers conducted large-scale shake table tests and numerical simulations to analyze the seismic responses of a twin-tube tunnel and evaluate the effectiveness of various mitigation measures, such as rock grouting and shock absorption layers, in reducing the amplified seismic demands caused by fault zones.

Contribution 14 explored the effect of combining fiber reinforcement and microbial curing technologies to enhance the deformation resistance and toughness of the soil. This study analyzed the effects of basalt fibers on the strength and toughness of microbial consolidated soil and the stability of the reinforced slope.

Contribution 15 used critical state soil mechanics to study the mechanical properties of Aeolian sand, a special road-building material in desert areas. This study conducted a series of triaxial compression tests to obtain the three-dimensional state boundary surface of the Aeolian sand and provided a basis for constitutive modeling and a reference for road construction in desert areas.

Contribution 16 developed a novel normal cloud framework for a holistic evaluation of the performance of existing asphalt pavements. The researchers integrated a comprehensive weighted indicator system and a cloud model approach to address the fuzziness and randomness inherent in pavement condition data, offering a more sensitive and accurate assessment tool for highway reconstruction and expansion projects.

Contribution 17 introduced a novel approach that employed blind number theory to evaluate the reliability of pavement performance test data. The proposed method aimed to enhance the representativeness of the Pavement Quality Index (PQI) and was demonstrated using detection data on highway asphalt pavements.

Contribution 18 explored the influence of the properties of paint and glass beads on the retroreflectivity performance of pavement markings. By analyzing field data from three test sites, the researchers developed a statistical model that identified the key characteristics with the greatest impact on the retroreflectivity of pavement markings, offering valuable insights for their improved durability and safety.

Contribution 19 investigated the causes of accelerated damage to urban cement concrete pavements. Through field evaluations, including visual inspections, ground-penetrating radar surveys, and permeability tests, the researchers identified the critical roles of an inadequate subgrade bearing capacity and poor drainage conditions in the premature deterioration of urban concrete roads, offering insights for improved pavement foundation design and maintenance.

Contribution 20 focused on the challenges in maintaining and managing rural road networks in China under limited budgets. The researchers proposed an evaluation framework, performance prediction models, and an optimization method for developing cost-effective long-term maintenance strategies for rural roads, providing a theoretical basis for the scientific management of these critical transportation assets.

In Contribution 21, this review discussed the microscopic mechanisms of microbial-induced calcite precipitation (MICP) and its effects on the mechanical properties of unsaturated soils, highlighting the influence of MICP on the moisture-dependent properties of unsaturated soils.

3. Conclusions

The collection of articles presented in this book showcases the latest advancements in the research on long-life road infrastructures, covering a wide range of topics, from materials and structures to performance evaluation and modeling.

The research on evaluating the performance of pavements using blind number theory and confidence models demonstrates an innovative approach to quantifying the reliability of pavement data, which can aid in more accurate and representative assessments of overall pavement quality. Studies on the cracking resistance and aging behavior of asphalt mixtures provide important insights into the durability of road surfaces under various environmental conditions.

Investigations into the use of alternative materials, such as low liquid limit clay stabilized with lime and glass fiber recycled from wind turbine blades, highlight the potential for sustainable and cost-effective solutions in road infrastructure construction. Techniques like fiber–microbial curing and the utilization of coal gangue as subgrade filler also show promise in enhancing the mechanical properties and long-term performance of road structures.

Fundamental research on the mechanical behaviors of specialized geotechnical materials, including Aeolian sand in desert environments and the moisture-dependent properties of unsaturated soils, contributes to a better understanding of the unique challenges faced in different geographical and geological settings. The models proposed and the experimental findings obtained in these studies can inform the design and construction of long-life road infrastructures.

Overall, the articles in this Special Issue demonstrate the multidisciplinary nature of the research in the field of long-life road infrastructures, encompassing advances in materials science, geotechnical engineering, and innovative evaluation and modeling techniques. The knowledge and insights gained from these studies will undoubtedly contribute to the development of more sustainable, durable, and efficient road systems that can withstand the demands of modern transportation networks.