A road/airport pavement is a multi-layered structure generally composed of several layers of bituminous materials, cement-bound materials on unbound granular materials. In the design phase, the different bituminous layers are considered perfectly bonded and therefore expected to work as a unique structure throughout the service life of the pavement. However, due to environmental, traffic and/or material-related conditions, the quality of the bond varies in time. The layers in the structure tend to work more and more independently with degrading bonding capacity, which induces a reduction of the pavement life. Therefore, the mechanical behavior of the interface between bituminous layers has been recently studied with original approaches. There were tests developed to focus on the interface study, for example Ancona shear testing research and analysis device at the Marche Polytechnic University, the shear-torque fatigue testing device at the University of Limoges and other tests. Most of the studies on this topic present several limits. One or few loading configurations can be applied to the sample (for example, pure shear of the interface) and studies focus only on the interface strength. Moreover, stress and strain fields within the sample are not homogenous, therefore not allowing investigating the intrinsic mechanical behaviour of the interface. In this study, the 2T3C (“Torsion, Traction/Compression sur Cylindre Creux” in French, Torsion, Traction/Compression on Hollow Cylinder) apparatus developed at ENTPE is used to investigate the behaviour of a bituminous interface under shear loading and small strain cycles.

The device consists of different basic parts: (1) a servo-hydraulic press capable of imposing axial and shear loading (cyclic or monotonic) on a hollow cylindrical specimen, equipped with a thermal chamber controlling the temperature; (2) four cameras gathered by pairs used to perform digital image correlation (DIC) analysis, in order to determine the three-dimensional strain field in upper and lower layers and calculate the relative displacements at the interface between different layers; (3) several displacement sensors around the specimen to control its global deformation: one pair of noncontact sensors to control displacements in the vertical direction, and another pair to control torsional displacement. The sample has a total height of 125 mm, an outer radius of 86 mm and an inner radius of 61 mm. The small thickness of the cylindrical wall of the sample allows considering quasi-homogeneous strain and stress fields.

Cyber-Physical Systems (CPS) are connected embedded devices with computing power, networking ability, control, and decision capability. The network connecting these devices is different from the Internet as they can sense their environment, share information, make decisions, and act based on local and global information. These capabilities enable the CPS to improve transportation, agriculture, healthcare, mining industry, and surveillance. The remarkable achievement in the development of cost-effective, reliable, smaller, networked, and more powerful systems allows us to build new control and communication mechanisms, as well as cooperative and coordinated motion planning algorithms to enable these devices to assist humans to cope with real-time problems. In this paper, we proposed a learning-based distributed framework for intelligent decision-making in networks of heterogeneous systems, to optimally plan their activities in a highly dynamic environment. We leverage the multi-Agent deep Reinforcement Learning (MADRL) technique to develop control and coordination strategies for teams of UAVs and group ground moving robots. The developed framework enables the team of Unmanned Aerial Vehicles (UAVs) to observe the defined region above the ground correctly and efficiently, and to share information with ground robots, to perform robust actions. Our main objective is to maximize the utilization of the strong abilities of each CPS device. UAVs can observe the environment from the top and gather fast and reliable information to share with the rescue robots working on the ground, but they cannot perform rescue tasks on the ground; on the opposite, rescue robots cannot gather reliable information due to a lack of visual limitation. In this framework, we train several DQN-agents to learn the optimal control policy for the team of cooperative heterogeneous robots in a centralized fashion, performing then the actions in a decentralized way. These learned policies are further transferred in real-time to the robots and evaluated against the real-time deployment of robots to perform tasks in the environment.

While the planet is experiencing the roughest ecological disruption in our history, it is of utmost importance to try to mitigate the impact of intensifying natural disasters. Bridges are the priority for enabling climate resilience in transport infrastructure. They are inarguably the most valuable assets of transportation networks. Capital investment in bridge construction and maintenance in Europe is enormous, representing 30% of the total cost of transport networks. Nonetheless, bridges are too vulnerable. They are disproportionately exposed to natural hazards, especially floods, while getting increasingly deficient because of ageing and urbanization trends.

Emerging Technologies are enablers of bridge resilience. Advocating for the use of UAVs in disaster response, the study provides solid and well-documented case studies discussing lessons learnt from the systematic analysis of field evidence after a recent (September 2020) Mediterranean Hurricane that struck central Greece. The use of UAVs proved essential for the rapid site reconnaissance and mapping of complex and severely damaged structures, including sinking piers, and collapsed abutments, with increased safety. UAVs effectively bypassed access blockages, resulting from failures in the road network, while, most importantly, allowing execution of works with the minimum of human exposure to health risks, during the peak of the COVID-19 pandemic.

The produced 3D models are powerful visualization tools that were found to fully compensate for the inability to physically visit the site, inspect and make decisions for severely damaged bridges. The value of this capability is also acknowledged by the researchers and engineers who performed the virtual inspections and who could not be present because of COVID-induced travel restrictions.

These models significantly facilitated the identification and analysis of the various bridge failure mechanisms, providing a uniquely comprehensive database of bridge response patterns under extreme flow velocities [1]. Furthermore, they proved useful as benchmarks for comparisons and informed decisions concerning the progress of restoration activities [2]. As such, they enabled accurate monitoring of bridge recovery and, incidentally, rapid assessment of the impact of an earthquake sequence that shook the region shortly after the flood, while mitigation works were underway. Thanks to this coincidence, we were given the opportunity to document a unique case study of the long-term performance of bridges in a multi-hazard environment, which should be of interest to all engineers and researchers in the field of civil infrastructure.

The incorporation of Reclaimed asphalt (RA) in hot mix asphalt mixtures is widely considered a sustainable solution for road infrastructure development. Under the scope of circular economy (CE), the multiple recycling capability of RA has to be assessed in order to ensure its performance at each recycling cycle and also its viability with different additives. The performance of asphalt mixture with RA strongly depends on the type of rejuvenator, binder, and their degree of blending in the mix. For this reason, it is essential to know the properties of aged binder extracted from RA to better understand its rheological properties and optimal dosage of rejuvenation to design a satisfactory blend design for the recycled mixture. To analyse the multi-recycling potential of such recycled mixture with high RA content, it is imperative to study its characteristics at every recycling cycle. Therefore, in this study, a preliminary binder-scale study is carried out to better understand the ageing, rejuvenating effects and morphological changes occurring on bituminous binders at every recycling cycle. The study has been conducted on a RA binder, extracted from RA from a rural road, in Italy and the simulation of multiple recycling is conducted through a laboratory ageing protocol on both binder and asphalt mixture scale. The long-term binder level ageing is performed by Pressure Ageing Vessel (PAV) after the short-term ageing by Rolling Thin Film Oven Test (RTFO). The asphalt mixture ageing is performed through protocols recommended by the Strategic Highway Research Program (SHRP) and the aged binder is extracted from the mixture for further investigations. Multiple recycling is simulated by repeating the ageing procedure after rejuvenating both the aged binder and aged mixture up to the number of recycling needed for the study. The rheological properties of the aged binder obtained from both binder-scale and mixture-scale ageing methods are evaluated using a Dynamic Shear Rheometer (DSR) and Bending Beam Rheometer (BBR). Moreover, the morphological changes that occurred are analysed using SARA (Saturates, Aromatics, Resins, Asphaltenes) fractionation and Atomic Force Microscopy (AFM). The results of the study can help towards answering the uncertainties regarding the performance of high RA% in asphalt mixtures and establishing its viability in multi-recycling towards a full-scale implementation of this sustainable approach.

The application of BIM methods and tools play a key role in transportation infrastructure asset management. Road pavements represents one of the main components of the asset which greatly influences safety and quality of service for users. The work presented herein exploited the potentialities of BIM processes and methods for management of road pavement structures. The specific goal was to define best practice for development of a methodological framework for Pavement Information Modelling (PIM). The starting point of the process was the identification of the specific BIM use, as intended by Kreider and Messner [1]. In this case, the BIM use identified concerned the 3rd (3D), 4th (4D) and 5th (5D) dimensions of BIM. The adopted approach had the aim to define the steps to build PIM based on geometrical and structural parameters, to be used as database for different kinds of maintenance strategies. Within this context, the main objectives of the study can be summarized as follows: 1)Define the steps to develop a PIM including all the relevant information to be stored for management purpose, from data collection to data restitution, 2)Define a best practice for the integration among BIM tools and road pavement management methods in order to obtain a digital repository for predictive maintenance strategies, 3)Define a planning and cost database for the different technologies and materials involved in the different maintenance strategies. From a practical point of view, the methodological framework has been divided under three main categories of dealing with data: (i) data collection and input definition, which includes the analysis of available data and the BIM tools to be used to develop specific workflows; (ii) data processing, by dividing the workflows and related tasks in sub-sections for the fulfilment of the previously enounced objectives; (iii) data output, by defining the final result of each workflow.

In recent years, the recycling of waste materials has attracted considerable attention due to the scarcity of natural resources on earth. For instance, researchers have been working on various techniques to utilize construction and demolition wastes as substitutes for natural materials in the construction industry, which is one of the major consumers of natural resources. From this point of view, concrete roads, as one of the frequently used infrastructural facilities [1] of the construction industry, have significant environmental impacts during their construction period and service life in different aspects. Therefore, great importance should be given to the construction of concrete roads to minimize their environmental impacts considering their dependence on the high volume of concrete production. Using recycled materials to produce the concrete roads is one of the methods implemented in this respect, as their usage provides benefits through natural resources and landfill conservation [2].

The use of recycled aggregates to reduce the environmental impact of concrete is one of the well-known methods, and their impacts on performance have been studied in various respects up to now. However, the number of studies on structural requirements of concrete pavements produced with recycled aggregates is very limited. This study aimed to investigate the structural performance of concrete pavements produced with recycled coarse aggregates as total (100%) and partial (50%) replacement of natural coarse aggregates.

To this end, three different concrete pavement mixtures (Control, RAC-50, and RAC-100) were designed and tested for compressive strength, modulus of elasticity, flexural strength, and density. Then, material parameters obtained from the applied tests were used to determine the required thickness values for a sample pavement (based on IRC 58 [3]), and the results were compared.

According to the test results, percent reduction compared to control mixture in average compressive strength, modulus of elasticity, flexural strength, and density values were 12.7, 7.7, 16.5, and 2.5 for RAC-50, and 18.9, 14.0, 24.9, and 4.5 for RAC-100, respectively. Test results indicate that the reduction in all the measured parameters increased with an increase in the replacement ratio of natural coarse aggregates with recycled coarse aggregates. The required concrete pavement thickness values for Control, RAC-50, and RAC-100 mixtures were determined to be 18, 20, and 23 cm, respectively (for the sample road and traffic data considered). The required thickness increased with an increase in the amount of recycled aggregate utilized (11% and 25% increase for RCA-50 and RCA-100, respectively). Besides, concrete pavement thickness values were well-correlated with the flexural strength values obtained for the corresponding concrete mixtures.

To summarize, this study numerically presented the change in the mechanical performance of concrete due to the replacement of natural coarse aggregate with recycled aggregate and the effect of obtained performance on the thickness requirement of a sample pavement. It should be noted that the test results are dependent on the properties of recycled aggregate used in this study, and various aggregate sources may yield different results.

Funding: This research received no external funding.

Conflicts of Interest: The authors declare no conflict of interest.

References:

1. Abut, Y.; Yildirim, S.T.; Ozturk, O.; Ozyurt, N. A comparative study on the performance of RCC for pavements casted in laboratory and field. J. Pavement Eng. 2020.
2. Ozturk, O.; Yildirim, H.; Ozyurt, N.; Ozturan, T. Evaluation of mechanical properties and structural behaviour of concrete pavements produced with virgin and recycled aggregates: an experimental and numerical study. J. Pavement Eng. 2022.
3. Indian Roads Congress. Guidelines for the design of plain jointed rigid pavements for highways (IRC 58). New Delhi, India, June 2015, Fourth revision.

The utilization of waste materials in pavement systems such as recycled concrete aggregates (RCA) and tire derived aggregates (TDA) has become a common practice in the design of surface wearing course layers. Though research is emerging on the use of RCA and TDA in the subbase layers, very limited studies are available that quantify their effect on the overall behavior of the pavement systems. Therefore, the major objective of this study was to develop a framework that could assist in quantifying pavement performance responses by using finite element method under standard wheel load of 80 kN. The information pertinent to the material characteristics of pavement systems comprising three distinct subbase layers were collected, and the designs were performed in accordance with global pavement design guidelines. The control pavement system comprised granular subbase layer, while the other two pavement designs consisted of subbase layers, which utilized RCA, and blends of RCA and TDA (RCA-TDA) as alternatives to natural aggregates. Further, axisymmetric finite element models of the three pavement systems resting over the subgrade were generated, and the stresses and strains developed in the different layers of the pavement were quantified. Test results indicated that the magnitude of vertical compressive strains for the combined RCA-TDA subbase were the highest followed by subbase layers with RCA and natural aggregates designed separately. However, it is important to mention that the cost of 1 km long and 3.5 m wide pavement subbase with coarse granular aggregates was about 45.34% higher than the RCA subbase course and 18.74% higher than the combined RCA-TDA subbase layer. Though recycling of waste materials such as RCA and RCA-TDA resulted in slightly higher stresses and strains compared to pavement systems with virgin granular materials, the cost of construction reduced significantly along with the decreased need for extraction of virgin materials, which is certainly an approach towards low-impact development sustainable infrastructure. The framework proposed in this research may be extended further by incorporating variable traffic and different layer thicknesses or materials to ascertain the performance of a diversified set of pavements. It is envisioned that this research will not only assist in understanding the structural response of various pavement systems from a holistic design point of view but also promoting recycling of waste materials as applications in pavement technology from sustainability perspective, i.e., focused on waste-to-wealth and circular economy concepts.

Digital twins (DTs) are an emerging technology that enables interaction between physical assets and their virtual replicas. These virtual replicas enclose the geometry coming from complex modelling procedures and the dynamism coming from artificial intelligence. Nowadays, DTs' applications are found almost in every engineering area; DTs serve different purposes, e.g., testing how new devices would behave under diverse conditions or while being controlled, or monitoring existing processes and helping improve them.

The Building Information Modelling (BIM) methodology, for its part, has revolutionized and changed the construction engineering and architecture sector in recent times. BIM refers to a collaborative work methodology for the conception and management of building and civil works projects that include a digital model that centralizes all the information (e.g., geometric, costs, maintenance, etc.). BIM models are the theoretical ones resulting from the design phase where this methodology is applied. Instead, the As-Built models refer to the representation of the actual work progress at each moment and reflect the reality and evolution of the construction site through time.

With the improvement of artificial intelligence in software capabilities for 3D modelling and simulation in construction environments (BIM models) related to Computer Aided Design and Engineering (CAD/CAE) and Geographical Information System (GIS) technologies, DTs began to have a place in urban projects, land management and public infrastructure. However, until now, the use of DTs in this area has been limited, as in most cases, it is used only as a high-quality 3D digital representation without connecting to other systems, dynamic analysis, or simulation.

This work proposes the creation of a DT for monitoring the construction of a wind farm. It permits to compare the BIM model (which contains the construction specifications) and the As-Built models that represent the actual construction at different times. It allows control of deviations, regarding civil works, that may occur during construction. All the data obtained (position of the wind turbines, the platform of the footing, the trace of the road, the width of the roadway, the slope of the road, etc.) must be stored to be displayed in the most didactic way possible so that the user can clearly understand it. Then, the DT includes a connection to a database to obtain the necessary information for the 3D representation. The models' comparison must be displayed according to what the user considers relevant in each case, e.g., delivering the BIM model and the As-Built model of a specific construction area.

The authors propose using Unreal Engine to create the interface for user interaction that includes CAD/CAE models obtained from the BIM and As-Built models corresponding to different steps during the construction. Also, using non-relational databases (MongoDB) is proposed since the data to be stored is semi-structured (not all areas of a model will have the same parameters), and the project needs are unpredictable since they can change as it progresses. The flexibility of non-relational databases will allow these variations to be captured efficiently without making significant changes to the database structure.

As a consequence of ever-increasing urban population and continuous development of industrialization and economies of countries around the world, construction and demolition industry gained eye-catching popularity, although it is also considered one of the largest producers of solid wastes globally. In an effort to counteract the negative effects of the growing construction and demolition waste (CDW) issue, the current study focused on the utilization of mixed CDW-based materials such as hollow brick (HB), red clay brick (RCB), roof tile (RT), glass (G) and concrete (C) in the production of geopolymer binders. These materials were acquired from the demolished residential buildings in an urban transformation area and then subjected to identical two-step crushing-milling procedure to reach sufficient fineness for geopolymerization. In the first stage of the study, these materials were used singly in the production of geopolymer binders to analyse the effects of material characteristics (e.g., fineness, chemical composition and crystalline nature) on the geopolymerization performance. Thereafter, these materials were used altogether in a quinary mixture to produce geopolymer binders with the purpose of better simulating the real life conditions where CDWs are obtained altogether and time-/energy-consuming to separate. In order to characterize the performance of different CDW-based materials, several mixture designs were made by the use of sodium hydroxide (NaOH) as the alkali activator. After applying thermal curing to the geopolymer pastes, compressive strength tests were performed in addition to the microstructural analyses. Results showed that, compressive strength values of up to 55 MPa can successfully be achieved depending on the mixture proportioning. While RT was found to be the most effective material in terms of mechanical performance of CDW-based geopolymer binders, G and C exhibited poor performances due to relatively coarse particle size distribution and inadequate chemical composition of SiO2 and Al2O3 which is a necessity for an effective geopolymerization. In-depth microstructural analyses supported that the geopolymer pastes with higher compressive strength have a denser and more homogeneous microstructure. The main reaction products of geopolymer binders were mostly sodium aluminosilicate hydrate (N-A-S-H) gels with zeolite-like structures and partially calcium aluminosilicate hydrate (C-A-S-H) gels arisen from the use of C with high CaO content. Our results proved that CDW-based materials can successfully be used in the production of geopolymers can be regarded as promising alternatives to traditional systems based on Portland cement.

Cold recycling materials (CRM) with bitumen emulsion are getting increasingly important aiming at highly efficient road infrastructure and tackling energy consumption. Normally, cement is added to get improved strength, but its usage leads to risk again mixture performance such as brittleness behavior and drying shrinkage [1], [2]. The objective of the present study is to analyze how eco-friendly by-product fillers affect the moisture resistance as well as the stiffness of CRM. The aggregate blend of the mortars was obtained by removing the coarse aggregate (larger than 2 mm) CRM granulate. The emulsion and filler content was fixed to 5% emulsion content and filler content of 3 %. Cationic slow-setting bitumen emulsion was used. Various fillers were selected to provide an extensive overview of the effect of fillers on the mechanical properties and water sensitivity of CRM materials: Cement (CE), ladle slag (LD), silica fume (SF), Ettringite binder (ET:70%LD+30%gypsum), geopolymer (GO:55% LD 35%Fly ash+10% SF). Two different methods were used to assess the water sensitivity which are Rolling Bottle Test (RBT) and Shaking Abrasion Test (SAT). In general, Figure 1 shows that the curing time has a clear influence on the coating ability, abrasion resistance, and dynamic modulus especially at the initial stage of curing (within 28 days). Figures 1 a and b show that the used fillers improved the bitumen coverage for both basalt and limestone aggregate compared with CE as a control filler, except SF which exhibited poor bitumen covering ability. It is worth noting that bitumen affinity to basalt aggregate is higher, especially at an early age, this finding is lined up with. When compared with CE, ET filler improved the bitumen coating ability after water erosion due to the early formed crystallin that increases the interlocking force between bitumen and aggregate surface, which improves adhesion between the mastic and the aggregate surface. In contrast, the bitumen coating ability of the CE specimen was considerably low. In the CE blended aggregate, the rigid hydration products improve the stiffness properties of the bitumen which in turn increases the stiffness of the mortar as shown in Figure 1 c, which improves the cohesion considerably but the adhesion slightly, and since the stripping resistance mostly depends on adhesion. Generally, all used fillers showed comparable abrasion resistance in 90 days of observation except SF. However, CE has slightly higher abrasion resistance on the first days of curing. Considering the effect of fillers on E, mortars with CE and ET exhibited the highest long-term and short-term performances, respectively.

Adding the active fillers provided a higher bitumen coverage and abrasion resistance than the SF, resulting in better affinity and moisture resistance, especially ET. The effect of filler on moisture sensitivity was found to be higher than the effect of aggregates. Adding ET filler provided higher E values at an early age, while the CE led to higher stiffening behavior in long term. LD and GO allowed for general lower stiffness and higher bitumen coverage and comparable abrasion resistance compared with CE. The result of the E test is generally correlated with abrasion resistance.