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Bituminous binders are thermal-dependent visco-elastic materials commonly used in pavement engineering. However, synthetic binders represent quite a new family of products that can be used in the substitution of conventional binders with various purposes. Among them, clear synthetic resins recently experienced a quick diffusion since they can be employed in the production of sustainable road pavements (which address aesthetic concerns, thermal aspects, etc.). Since specific studies addressing the rheological modeling of clear synthetic binders cannot be found in the literature, the purpose of this research is setting up an advanced rheological protocol to characterize such materials, bridging the existing knowledge gap. An extensive laboratory investigation with the dynamic shear rheometer was carried out in oscillatory mode (amplitude and frequency sweeps) to analyze the stress–strain state of such binders. An innovative test at a constant strain rate was used to construct non-linear master curves, overcoming various criticisms about the stress state of the binder when subjected to time-dependent deformations. Results indicated that, using non-linear data, horizontal and vertical shift factors (functions of temperature and strain rate) can be modeled through power law equations to obtain the master curves. This method was considered suitable for depicting the rheological response of the binders displaying such complex behaviors.

This article investigated the effect of waste polyethylene (PE) on the modified asphalt binders' rheological behavior from a statistical point of view. The interlaboratory testing results from the RILEM Technical Committee 279 Valorization of Waste and Secondary Materials for Roads Task Group 1 were used for this purpose. First, an unaged 70/100 penetration graded neat binder was selected as the reference material. Next, a single 5 % content of waste PE additives (PE-pellets and PE-shreds) was mixed with a 95 % neat binder to prepare two PE modified binders. Then, dynamic shear rheometer-based temperature-frequency sweep tests were performed over a wide range of temperatures and frequencies to evaluate the rheological properties of these three binders. Different rheological behaviors were observed in the isochronal plots at high temperatures. Based on a reproducibility precision requirement proposed for phase angle, 28 degrees C was set as the transition temperature across the rheological behaviors. Next, according to the three rheological behaviors defined in a previous study by the authors, statistical analysis was introduced to identify sensitive rheological parameters and determine the thresholds. Results indicate that the phase angle measured above 28 degrees C and 1.59 Hz can be used as a sensitive parameter to discriminate the three rheological behaviors of PE modified binders. The thresholds among different behaviors were also calculated as an example for phase angle measured at the highest common testing temperature of 70 degrees C. Additional experimental evaluations on more types of PE modified binders, especially at intermediate and high temperatures, are recommended to better understand their influence on the rheological behavior of PE modified binders.

Part of this research was funded by the project RTI2018-096224-J-I00 that has been cofounded by the Spanish Ministry of Science and Innovation, inside the National Program for Fostering Excellence in Scientific and Technical Research, National Subprogram of Knowledge Generation, 2018 call, in the framework of the Spanish National Plan for Scientific and Technical Research and Innovation 2017-2020, and by the European Union, through the European Regional Development Fund, with the main objective of Promoting technological development, innovation and quality research. Part of this work was financially supported by the Italian Ministry of University and Research with the research Grant PRIN 2017 USR342 Urban Safety, Sustainability and Resilience., This paper describes the development of novel/state-of-art computational framework to accurately predict the degree of binder activity of a reclaimed asphalt pavement sample as a percentage of the indirect tensile strength (ITS) using a reduced number of input variables that are relatively easy to obtain, namely compaction temperature, air voids and ITS. Different machine learning (ML) techniques were applied to obtain the most accurate data representation model. Specifically, three ML techniques were applied: 6th-degree multivariate polynomial regression with regularization, artificial neural network and random forest regression. The three techniques produced models with very similar precision, reporting a mean absolute error ranging from 12.2 to 12.8% of maximum ITS on the test data set. The work presented in this paper is an evolution in terms of data analysis of the results obtained within the interlaboratory tests conducted by Task Group 5 of the RILEM Technical Committee 264 on Reclaimed Asphalt Pavement. Hence, despite it has strong bonds with this framework, this work was developed independently and can be considered as a natural follow-up, Spanish Government RTI2018-096224-J-I00, European Commission, Ministry of Education, Universities and Research (MIUR) PRIN 2017 USR342

To predict the mixed damage modes of unidirectional fiber-reinforced polymer (FRP) laminates under dynamic loading, an FEM-based peridynamic model is introduced in this paper. Based on its geometric structure and material composition, a long fiber lamina is considered a transversely isotropic medium as a result of homogenization at the meso-scale. The laminated structure is modeled by stacking surface mesh layers with arbitrary fiber angles along the thickness direction. The peridynamic bonds between Gauss points connect the separated elements. These bonds are classified as inner-layer bonds and inter-layer bonds. To represent the anisotropy of a laminate, the micro-elastic modulus of the inner-layer and inter-layer bonds is calculated from the anisotropic engineering material constants separately. To capture complex failure behaviors of laminate structures, an empirical damage model is proposed for the tension/ compression breakage of peridynamic bonds. This damage model can control the in-plane and delamination failure process. Benchmark tests are conducted to validate the elastic response of laminates under dynamic loading. In terms of damage analysis, the proposed model can capture the complex damage modes and resistive force of laminate structures.

Nowadays, budget restrictions for road construction, management, and maintenance require innovative solutions to guarantee the user acceptable service levels respecting environmental requirements. Such goals can be achieved by the re-use of various waste materials at the end of their service life in the pavement structure, therefore avoiding their disposal in landfill. At the same time, significant savings are achieved on natural aggregate by replacing it with such waste materials, improving the economic and environmental sustainability of road constructions. The purpose of this study is to discuss a laboratory investigation about foamed bitumen-stabilized mixtures for road foundation layers, in which the aggregate structure was entirely made up of industrial by-products and civil wastes, namely metallurgical slags such as electric arc furnace (EAF) and ladle furnace (LF) slags, coal fly (CF) ash, bottom ash from municipal solid waste incineration (MSWI), glass waste (GW) and reclaimed asphalt pavement (RAP). Combining these recycled aggregates in different proportions, six foamed bitumen mixtures were produced and investigated in terms of indirect tensile strength, stiffness modulus, and fatigue resistance. The leaching test carried out on the waste materials considered did not show any toxicological issue and the best foamed bitumen mixture's composition was characterized by 20% of EAF slags, 10% of LF slags, 20% of MSWI ash, 10% of CF ash, 20% of GW, and 20% of RAP. Its mechanical characterization presented a dry indirect tensile strength at 25 degrees C of 0.62 MPa (well above the Italian technical acceptance limits), a stiffness modulus at 25 degrees C equal to 6171 MPa, and a number of cycles to failure at 20 degrees C equal to 6989 for a stress level of 300 kPa.

Funding Information: The authors would like to acknowledge the contributions of the active members of the RILEM technical committee TC 264-RAP in terms of experimental results, data analysis and proofreading. The authors would also like to thank Nynas AB, Kraton Chemical BV and Technical University of Braunschweig for supporting the interlaboratory activity by providing bituminous materials, ARA and RA binder. Publisher Copyright: © 2022, The Author(s). This recommendation is based on the results of an inter-laboratory study organised by the RILEM technical committee TC 264-RAP "Asphalt Pavement Recycling"—Task Group 3 (TG3) focusing on Asphalt Binder for Recycled Asphalt Mixture. The TG3 aimed to evaluate the effect of a specific family of materials known as asphalt recycling agent (ARA) on the aged binder under different configurations. Even though ageing is an irreversible phenomenon, effective ARA must have the capability to improve the flexibility of the bituminous materials and their resistance against cracking susceptibility with no adverse effect on the rutting resistance of pavements containing reclaimed asphalt. A total of 17 participating laboratories analysed the properties of binder blends composed of aged binder from reclaimed asphalt in three different contents (60, 80, 100%), ARA and virgin binder. The physical properties of the blends were thoroughly evaluated through traditional and rheological binder testing. This recommendation proposes to restore the original material properties at low and intermediate temperatures (i.e. cracking resistance) while balancing the high-temperature characteristics (i.e. rutting susceptibility) with durable impact throughout the progression of ageing phenomena. Therefore, useing of the Dynamic Shear Rheometer is foreseen as a more suitable and sustainable means to evaluate binder blends containing an asphalt recycling agent. Compared with conventional testing, the proposed approach requires fewer materials while resulting in a faster experimental procedure with one single test.

Steel slag is a by-product obtained through the separation of molten steel from impurities in steel-making furnaces. It can be produced by different types of furnaces (blast, basic oxygen, electric arc, ladle furnaces). The reuse of metallurgical slags in road pavements can pursue aims of recycling and environmental sustainability. Based on the extensive literature, the paper presents a state-of-the-art review concerning the use of slags in asphalt pavements, discussing the main controversial literature findings. Slag manufacturing processes, chemical, morphological, and physical characteristics, affect its contribution to the asphalt mixture, when it partially or fully substitutes natural aggregates. Legislative state-of-the-art environmental issues, weathering, and leaching aspects are also discussed. The main mechanical and durability properties of pavements containing different types of slags are analyzed based on laboratory and field studies. Generally, the higher mechanical properties of steel slag suggest that its inclusion in asphalt mixtures can provide high-performance pavement layers (excellent strength and stiffness, superior rutting and fatigue resistance, low moisture susceptibility). However, several research gaps still exist (e.g., mix design and seasoning procedure, bitumen–aggregate affinity, low-temperature behavior, brittleness); they are discussed to direct possible future study efforts to clarify specific technical aspects, such as, for example, the effect of slag morphology and physical properties on the final mix properties and the development of specific mix design guidelines.

The circular use of resources (i.e., reuse and recycling of materials) aiming for zero waste is also gaining increasing attention in pavement engineering. In this regard, the possible use of waste plastics in asphalt materials is of strategic importance since a considerable amount of plastic waste from construction and demolition waste and municipal solid waste is generated every year. Given this background, this experimental study aimed to investigate the feasibility of recycling waste polyethylene (PE) into asphalt mixtures. For this purpose, the dry addition of plastic shreds was evaluated to overcome the drawbacks observed in a previous interlaboratory research on PE-modified bituminous binder (i.e., instability/inhomogeneity of blend as well as the need for PE grinding). A comparative laboratory study was carried out on dense graded asphalt mixtures containing different amounts of waste plastics (i.e., 0%, 0.25%, and 1.5% by weight of the mixture). The selected asphalt mixes were investigated in terms of workability, linear visco-elastic characteristics, stiffness, strength, resistance to permanent deformation, and moisture sensitivity. Overall, the experimental findings show that the mixes prepared with the dry addition of plastic wastes were able to guarantee almost the same workability and moisture resistance as the reference material while leading to enhanced performance in terms of stiffness and permanent deformation resistance, with better responses for the higher investigated PE dosage.

inter-laboratory experiments were designed to evaluate the impact of plas- tic waste blended directly in bitumen and to assess the properties, using conventional and advanced bituminous binder testing. The blends tar- geted 5% of plastic waste in 95% bitumen, using two types of polyethy- lene (PE) primary (pellets) and secondary (shreds) waste. The experiments showed that the addition of PE waste to bitumen does not alter the chem- istry of the bitumen, the blending is physical. The DSR results indicate a strong dependency on the testing temperature as at low temperatures the composite material bitumen and PE behave both elastically whereas, at higher temperatures, the bitumen becomes viscoelastic. The MSCR tests indicated that the neat binder is more sensitive to permanent deformation compared to the blends with PE. The fatigue performance using the Linear Amplitude Sweep test showed a better performance in terms of stress and fatigue life for the PE blends.

Solar harvesting systems applied to asphalt roads consist of pipes or coils installed a few centimeters below the asphalt pavement surface. They work thanks to a circulating fluid able to collect the heat coming from solar irradiation of the pavement surface and convert it into thermal gradients that can be used for electric energy supply. Specific attention must be paid to the design of the asphalt mixtures comprising the system. In this sense, the high in-service temperature rutting potential is one of the main issues to be assessed in such applications since the thermal optimization of asphalt mixes could lead to excessively deformable materials. The present study is a part of a wider research area aimed at developing an efficient asphalt solar collector. Here, a laboratory mixture-scale investigation is proposed to verify the anti-rutting potential of specific asphalt layers that were initially designed based on thermal properties only. Repeated load axial and wheel tracking tests are carried out on limestone- and steel slag-based bituminous mixtures. Overall, the tested layers were not fully able to satisfy the permanent deformation acceptance criteria; in this regard, possible improvements in terms of mix constituents and properties are ultimately addressed.

Acknowledgments The Swiss company Innoplastics is acknowledged for providing the waste plastics. Empais participation is supported by Swiss National Science Foundation grant SNF 205121_178991/1 for the project titled “Urban Mining for Low Noise Urban Roads and Optimized Design of Street Canyons”. The participation of University of Belgrade, Faculty of Civil Engineering, is supported by the Ministry of Education, Science, and Technological Development of the Republic of Serbia under research project No. 2000092., This research aims to determine if the observed improvements using polyethylene (PE) waste in asphalt binder translate into better performance at the asphalt mixture scale in the laboratory environment while overcoming the stability and homogeneity issues experienced at the binder level. This is accomplished through a round-robin multinational experimental program covering four continents, with the active participation of eleven laboratories within the RILEM TC 279-WMR. PE modified AC16 mixtures were prepared employing the dry process using local materials with the PE waste provided by one source. Various mechanical tests were performed to investigate the compactability, strength, moisture sensitivity, stiffness and permanent deformation. Compared to the control mixtures, the following observations were made for PE modified mixtures: easier to compact, lower time dependence of stiffness, higher elastic behavior, lower creep rate, and higher creep modulus. Furthermore, cyclic compression test results showed that the resistance to permanent deformation is improved when using PE in asphalt mixtures, whereas the wheel tracking tests showed relatively similar or better results when 1.5% PE was added to the control mixture. The wheel tracking test results in water showed an increase in deformation with increasing PE content. The interlaboratory investigation showed that the use of PE as a performance-enhancing additive in asphalt pavements is a viable, environmentally friendly option for recycling waste plastic and could potentially reduce the use of polymer additives in asphalt., Swiss National Science Foundation grant SNF 205121_178991/1, Ministry of Education, Science, and Technological Development of the Republic of Serbia under research project No. 2000092

This work develops, discretizes, and validates a continuum model of a molybdenum disulfide (MoS$_2$) monolayer interacting with a periodic holey silicon nitride substrate via van der Waals (vdW) forces. The MoS$_2$ layer is modeled as a geometrically nonlinear Kirchhoff-Love shell, and vdW forces are modeled by a Lennard-Jones potential, simplified using approximations for a smooth substrate topography. The material parameters of the shell model are calibrated by comparing small-strain tensile and bending tests with atomistic simulations. This model is efficiently discretized using isogeometric analysis (IGA) for the shell structure and a pseudo-time continuation method for energy minimization. The IGA shell model is validated against fully-atomistic calculations for several benchmark problems with different substrate geometries. The continuum simulations reproduce deflections, strains and curvatures predicted by atomistic simulations, which are known to strongly affect the electronic properties of MoS$_2$, with deviations well below the modeling errors suggested by differences between the widely-used reactive empirical bond order and Stillinger-Weber interatomic potentials. Agreement with atomistic results depends on geometric nonlinearity in some cases, but a simple isotropic St. Venant-Kirchhoff model is found to be sufficient to represent material behavior. We find that the IGA discretization of the continuum model has a much lower computational cost than atomistic simulations, and expect that it will enable efficient design space exploration in strain engineering applications. This is demonstrated by studying the dependence of strain and curvature in MoS$_2$ over a holey substrate as a function of the hole spacing on scales inaccessible to atomistic calculations. The results show an unexpected qualitative change in the deformation pattern below a critical hole separation.

In view of increasing social and environmental consciousness, a circular approach in waste materials management in order to convert them into new secondary resources is becoming more necessary. Given this context, an interlaboratory testing program (ILTP) focusing on maximizing the use of waste aggregates replacing conventional virgin ones has been launched in the framework of the RILEM Technical Committee on “Valorisation of Waste and Secondary Materials for Roads”. Construction and demolition wastes, recycled concrete aggregates and steel slags were selected as waste aggregates to be investigated. A reference mixture prepared with natural virgin aggregates was al-so considered for comparison purposes. This paper describes the results achieved during the first steps of the ILTP concerning: i) the basic characterization of the selected marginal aggregates; ii) the Marshall mix design of different asphalt mixtures prepared with one or more waste aggregates. Overall, the experimental results collected during these preliminary steps seem to confirm that the selected marginal aggregates can be considered as valid alternatives for the traditional road materials, while not jeopardizing their performance

The use of rejuvenators has seen a consistent increase over the years in the asphalt pavement industry. This is due to the need for maximizing the demand for incorporating a higher amount of Reclaimed Asphalt (RA) in the pavement asphalt mixtures. In order to tackle this challenge, the Task Group 3, focusing on asphalt binders and additives, of the RILEM TC RAP conducted an interlaboratory activity to evaluate the effect of aging on blends of virgin and rejuvenated RA binders. A set of conventional tests including penetration value at 25 °C, softening point temperature and rheological measurements by means of Dynamic Shear Rheometer (DSR) were selected to involve a large number of participants. A binder, recovered from field RA, was treated with a bio-based rejuvenator and blended with a virgin binder to simulate recycling at three different percentages 60, 80, and 100%. These blends, as well as the pure virgin binder, were next short and long term aged and tested to evaluate the changes in the corresponding properties. Relatively consistent results were obtained for the entire set of blends. The aging of combined rejuvenated RA and virgin binders was comparable to that experienced for the pure virgin binder. DSR data provided a more precise evolution of the impact of aging on the materials.

State-based peridynamics is a non-local reformulation of solid mechanics that replaces the force density of the divergence of stress with an integral of the action of force states on bonds local to a given position, which precludes differentiation with the aim to model strong discontinuities effortlessly. A popular implementation is a meshfree formulation where the integral is discretized by quadrature points, which results in a series of unknowns at the points under the strong-form collocation framework. In this work, the meshfree discretization of state-based peridynamics under the correspondence principle is examined and compared to traditional meshfree methods based on the classical local formulation of solid mechanics. It is first shown that the way in which the peridynamic formulation approximates differentiation can be unified with the implicit gradient approximation, and this is termed the reproducing kernel peridynamic approximation. This allows the construction of non-local deformation gradients with arbitrary-order accuracy, as well as non-local approximations of higher-order derivatives. A high-order accurate non-local divergence of stress is then proposed to replace the force density in the original state-based peridynamics, in order to obtain global arbitrary-order accuracy in the numerical solution. These two operators used in conjunction with one another is termed the reproducing kernel peridynamic method. The strong-form collocation version of the method is tested against benchmark solutions to examine and verify the high-order accuracy and convergence properties of the method. The method is shown to exhibit superconvergent behavior in the nodal collocation setting.

Funding Information: The RILEM Technical Committee on Valorisation of Waste and Secondary Materials for Roads (TC 279-WMR) and the members of Task Group 1 are gratefully acknowledged. The authors would also like to thank Nynas AB and Swiss company Innorecycling for supporting the interlaboratory activity by providing reference neat binder and PE-pellets, PE-shreds additives. The contribution of the Swiss National Science Foundation ( 205121_178991 ) to the Swiss partners is also acknowledged. Funding Information: The RILEM Technical Committee on Valorisation of Waste and Secondary Materials for Roads (TC 279-WMR) and the members of Task Group 1 are gratefully acknowledged. The authors would also like to thank Nynas AB and Swiss company Innorecycling for supporting the interlaboratory activity by providing reference neat binder and PE-pellets, PE-shreds additives. The contribution of the Swiss National Science Foundation (205121_178991) to the Swiss partners is also acknowledged. Publisher Copyright: © 2022 Significant volumes of waste materials such as plastics is generated every year worldwide with a potentially harmful impact on the environment. At the same time, the demand for asphalt modifiers has seen an increase over the year with consequent higher costs for these types of additives. Therefore, combining large amounts of available waste plastics with asphalt binder as an extender or modifier would potentially improve the paving material properties while limiting the disposed waste. While several rheological studies have been performed in the past, they were restricted to single research efforts hindering a consistent comparison among the valuable results of these investigations. For this reason, the Task Group 1 of the RILEM Technical Committee 279-WMR established a research activity with 11 international institutions to conduct interlaboratory research to evaluate the possibility of using waste polyethylene (PE) as an additive in asphalt binder. The study addressed the combined impact of PE materials andexperimental conditions on the rheological properties of asphalt binder. For this purpose, conventional tests (penetration value, softening point temperature, and Fraass breaking point temperature) and the linear viscoelastic characterization using the Dynamic Shear Rheometer (DSR) were adopted. An unaged pen grade 70/100 neat binder was selected as the reference binder; PE-pellets and PE-shreds, produced from the recycled waste polyethylene materials, were used as the polymer additives. A single content (5%) of PE-pellets and PE-shreds was used to blend the PE material with the reference binder (95%) and prepare the two PE modified binders. Results indicate that the use of plastic modifiers leads to an overall higher complex shear modulus and softening point temperature while decreasing the penetration value. Higher dispersion in the results, especially in phase angles, was observed for blended binders at high temperatures. The PE modified binders exhibited poor reproducibility among laboratories and a low level of repeatability. Such a scatter in the data could result from an uneven dispersion of plastic material at high temperatures. In contrast, plastic shapes and batches appeared to have a limited impact. Three different rheological behaviors, neat binder, modified binder, and complex modified binder, were visually identified among the interlaboratory results and based on a simple statistical analysis of variance. Further analysis of the data suggested that the Glover Rowe (G-R) parameter can be used as a sensitive tool to classify the rheological behaviors of PE modified binders. Further experimental evaluation on specific testing conditions, such as measurement gaps of DSR at high temperatures, is recommended to advance the understanding of their influence on the rheological behavior of PE modified binders.

The recycling of Construction and Demolition Waste (CDW) is an actual challenge regarding the construction industry because of the increasing volumes worldwide produced and the related environmental impacts. In this regard, a suitable application can be developed in the road construction field, in particular for the production of hydraulically bound mixtures for road subbase and foundation layers. In this sense, the reuse of CDW can strongly enhance the environmental sustainability of road construction thanks to the achievable savings of natural resources such as the mineral aggregates obtained from quarry operations. Indeed, the utilization of a CDW as aggregate must ensure the production of mixtures with adequate mechanical and environmental characteristics. Therefore, the herein paper presents the results of an experimental characterization aimed at assessing the suitability of CDW for the production of hydraulically bound mixtures for road pavements. In particular, the main mechanical properties of some mixtures including different percentages and gradations of CDW were analysed and compared with the main technical prescriptions and classification criteria indicated by the reference European standards. Basic properties and production processes of the CDW materials were also studied to determine their effects on the optimum binder and water contents of the mixtures. The research clearly demonstrated that the use of a preliminary-washed CDW coarse aggregate was able to enhance the overall structural properties and the water resistance of mixtures.

Muscle motor-evoked potentials are commonly monitored during brain tumour surgery in motor areas, as these are assumed to reflect the integrity of descending motor pathways, including the corticospinal tract. However, while the loss of muscle motor-evoked potentials at the end of surgery is associated with long-term motor deficits (muscle motor-evoked potential-related deficits), there is increasing evidence that motor deficit can occur despite no change in muscle motor-evoked potentials (muscle motor-evoked potential-unrelated deficits), particularly after surgery of non-primary regions involved in motor control. In this study, we aimed to investigate the incidence of muscle motor-evoked potential-unrelated deficits and to identify the associated brain regions. We retrospectively reviewed 125 consecutive patients who underwent surgery for peri-Rolandic lesions using intra-operative neurophysiological monitoring. Intraoperative changes in muscle motor-evoked potentials were correlated with motor outcome, assessed by the Medical Research Council scale. We performed voxel–lesion–symptom mapping to identify which resected regions were associated with short- and long-term muscle motor-evoked potential-associated motor deficits. Muscle motor-evoked potentials reductions significantly predicted long-term motor deficits. However, in more than half of the patients who experienced long-term deficits (12/22 patients), no muscle motor-evoked potential reduction was reported during surgery. Lesion analysis showed that muscle motor-evoked potential-related long-term motor deficits were associated with direct or ischaemic damage to the corticospinal tract, whereas muscle motor-evoked potential-unrelated deficits occurred when supplementary motor areas were resected in conjunction with dorsal premotor regions and the anterior cingulate. Our results indicate that long-term motor deficits unrelated to the corticospinal tract can occur more often than currently reported. As these deficits cannot be predicted by muscle motor-evoked potentials, a combination of awake and/or novel asleep techniques other than muscle motor-evoked potentials monitoring should be implemented., Graphical Abstract Graphical Abstract

Dimensional stability of manufactured aggregates represents a matter of interest for many applications in civil engineering. Past results evidenced how steel slag might be affected by potential swelling, due to several concurring causes linked to the presence of free lime and periclase in their chemical composition. In this work, a detailed analysis about physical and chemical properties of Electric Arc Furnace slag (EAFS) is developed, using thermogravimetry, scanning electron microscopy, X-ray diffraction and porosity analysis. The efficiency of a commonly used method for slag treatment on reducing its swelling-potential is also experimentally assessed and confirmed, through expansion tests carried out in an experimental apparatus developed specifically for this scope, based on steam diffusion within the test sample. Lastly, a maximum allowable limit for slag swelling is proposed for some applications of interest.

In the conventional Newmark family for time integration of hyperbolic problems, both explicit and implicit methods are inherently sequential in the time domain and not well suited for parallel implementations due to unavoidable processor communication at every time step. In this work we propose a Waveform Relaxation Newmark (WRN $$_\beta $$ ) algorithm for the solution of linear second-order hyperbolic systems of ODEs in time, which retains the unconditional stability of the implicit Newmark scheme with the advantage of the lower computational cost of explicit time integration schemes. This method is unstructured in the time domain and is well suited for parallel implementation. We consider a Jacobi and Gauss–Seidel type splitting and study their convergence and stability. The performance of the WRN $$_\beta $$ algorithm is compared to a standard implicit Newmark method and the obtained results confirm the effectiveness of the Waveform Relaxation Newmark algorithm as a new class of more efficient time integrators, which is applicable, as shown in the numerical examples, to both the finite element method and meshfree methods (e.g. the reproducing kernel particle method).

The most common discretization method for peridynamic models used in engineering problems is the node-based meshfree approach. This method discretizes peridynamic domains by a set of nodes, each associated with a nodal cell with a characteristic volume, leading to a particle-based description of continuum systems. The behavior of each particle is then considered representative of its cell. This limits the convergence rate to the first order. In this paper, we introduce a reproducing kernel (RK) approximation to the field variables in the peridynamic equations to increase the order of convergence of peridynamic numerical solutions. The numerical results demonstrate improved convergence rates in static peridynamic problems using the proposed method.

The paper describes the main results from a study of cement bound mixtures for road foundations with the aggregate matrix consisting of industrial wastes, i.e. foundry sands (FS), electric arc furnace (EAF) steel slags and bottom ash from municipal solid waste incineration (MSWI), combined in five different proportions. The laboratory investigation involved a preliminary analysis of the chemical, leaching, physical and mechanical properties of the industrial wastes, followed by a mechanical characterization of the cement bound mixtures. The mix design was conducted in terms of Proctor, compression and indirect tensile tests. Lastly the dynamic elastic modulus of the mixtures was investigated through ultrasonic tests, at different seasoning times. The results were entirely satisfactory for all the mixtures, especially for the one composed of 50% foundry sand, 10% bottom ash and 40% steel slag, with a compression strength of up to 5.28 MPa at 7 days and a corresponding indirect tensile strength of 0.498 MPa. The results met the main national Specifications, thus demonstrating the feasibility of recycling industrial by-products as substitutes for conventional natural aggregates in the production of hydraulically bound mixtures for road foundations.

The valorisation and reuse of waste materials can enhance the environmental sustainability of road constructions, especially by means of cold recycling techniques, which, moreover, allow to reduce polluting emissions in atmosphere. Among the various technological approaches, the use of bitumen emulsion to stabilize waste materials is very common, especially in case of reclaimed asphalt pavement (RAP) aggregates. However, even other types of waste materials could be considered using a Cold Central Plant Recycling (CCPR) approach. The paper discusses the main results of a laboratory investigation aimed to evaluate the mechanical performance of bitumen emulsion stabilized mixtures for road pavements base courses, prepared with RAP, steel slag, coal ash and glass wastes, used with various percentages. In a first step of the laboratory study, both physical and toxicological properties of each waste material have been investigated, in order to assess their environmental compatibility. Subsequently, an extensive mechanical analysis of the bitumen emulsion stabilized mixtures has been carried out in the laboratory, in terms of indirect tensile strength, indirect tensile stiffness modulus at three temperatures (10°C, 25°C, 40°C) and repeated load axial tests at 30°C. The moisture resistance of the mixes has been also investigated by means of indirect tensile strength tests carried out on soaked specimens. Very good results have been observed, depending on the mix composition: indirect tensile strength at 25 °C on dry specimens up to 0.52 MPa and stiffness modulus up to 4,056 MPa (at 25 °C, for a rise time equal to 124 ms). Therefore, it has been verified that the waste materials considered in the study can be successfully reused to completely substitute conventional aggregates in bitumen emulsion stabilized mixtures for road pavements base courses.

A circular approach to managing resources that will promote their reuse and recycling is nowadays of crucial importance for a sustainable society. In this regard, the substitution of natural aggregates by steel slag in construction materials represents a promising option. In this paper, the use of Ladle Furnace Slag (LFS) as sustainable filler and fine aggregate for asphalt mixtures is studied. In particular, the evaluation of the LFS contribution in mastic and mortar mixes at mid-range and high-service temperatures is investigated, employing a dynamic shear rheometer to assess the main viscoelastic properties as well as the fatigue and the permanent deformation resistance of the blends. The experimental findings showed that the addition of LFS led to a clear stiffening effect, altering the chemo-physical interaction with the bitumen and producing an appreciable difference in complex stiffness moduli and phase angles. Regardless of the aging condition, the use of LFS lowered the linear viscoelastic limits and increased the elasticity of blends in the case of both mastics and mortars. It caused also a slightly higher thermal dependence of the linear viscoelastic properties even if the enhanced stiffness and elasticity produced appreciable improvements in the permanent deformation resistance. In contrast, a slight reduction of fatigue resistance was observed under the test conditions and was reasonably ascribed to the higher stiffness of LFS blends. Further research is needed to strengthen these promising results and to address the issues at a multiscale level, in particular to evaluate possible lower workability and reduced ductility due to the encountered higher stiffness of slag-based materials.

The Infrastructure Building Information Modeling (I-BIM) is a digital information management system utilized in the transport infrastructures construction, becoming increasingly important. BIM modeling aims at bringing improvements to all design stages. The use of BIM modeling will also provide cost reduction and control, increase awareness to data, design information availability and usability in each phase of infrastructure life cycle. Although the advanced modeling of the building components and systems leads to advantages well highlighted by practice and literature, in case of transportation infrastructures a critical analysis could show if this design methodology carries out the same benefits. The limited availability of infrastructure components libraries and the difficulty in assigning parameters to the geometries of the objects (many of them with unique characteristics) have been frequently quoted as main obstacles to the BIM use for the transport infrastructures. With this background, the problem is to understand which BIM-for-building features must be preserved in the production and management practices of each infrastructure model (classes, information exchanges and relationship between the classes and the spatial decomposition). This work is focused on the study of the I-BIM methodologies for the transport infrastructures (in particular railway infrastructures), analyzing a case study related to the port of Venice. The upward trend of goods quantity daily passing through the port infrastructures, led to the need to expand the container loading/unloading ship areas and, at the same time, to find a new and faster goods exit from the port areas, compared to the existing railway infrastructures. The authors developed a pre-feasibility study to identify the railway connection between the new port station and the existing line Padova – Mestre and to evaluate the difficulties and the ripeness of available means for an integrated design with the BIM tools

The use of reclaimed asphalt (RA) in road pavements is continuously gaining interest thanks to the technical, economic and environmental advantages guaranteed by such sustainable practice. Cold recycling techniques compared to traditional asphalt mixes allow a significant reduction of energy, fume emissions, use of natural resources, etc. In this perspective, the Task Group 1 on “Cold Recycling” of the RILEM Technical Committee on “Asphalt Pavement Recycling” (TC 264-RAP) launched an interlaboratory test program (ITP) aimed at ensuring a better understanding for cold recycled mixtures. The paper presents the results collected by a restricted group of the participating laboratories testing cement-bitumen treated materials that included a single RA source and prepared with foamed bitumen. Gyratory compacted specimens were used to evaluate the influence of curing (free, partial or restricted-surface drying for 14 days at 40 °C at a relative humidity of 55 ± 5%). Stiffness was evaluated as a function of the curing stage and the corresponding water loss; strength was tested after 14 days of curing testing specimens in both dry and wet conditions to also determine the water sensitivity. As expected, the different curing conditions clearly influenced the rate of water loss of tested samples with clear effects on mechanical properties and durability.

This chapter deals with pavements for roads, cycle tracks, and footways. More specifically, attention is focused on particular applications aimed at mitigating heat-related concerns using high-albedo materials. First, the albedo significance, relevance, and usefulness for effectively producing thermally optimized pavements are analyzed. After a short contextualization, the physics of albedo is discussed, in order to understand its theoretical meaning and its function in determining the radiative properties of materials that affect the general energetic balance of pavement surfaces. Some research contributions from the literature are then presented in which the in-field albedo variability, monitored on real pavements during short and long periods (daily as well as seasonal), has been studied. Next, possible high-albedo paving solutions (mainly flexible bituminous pavements and rigid concrete-based surfaces) are described, with details on constituent materials, chromatic characteristics, and surface properties. The dependence of albedo on pavement’s functional characteristics is then analyzed, in order to evaluate its plausible modifications due to aging and the related deterioration of pavements in service. Finally, some general issues regarding the overall benefits and drawbacks involved with the utilization of high-albedo pavement materials are debated. Concluding remarks concern the present specification and regulatory framework and technical perspectives, with the purpose of delineating potential future trends regarding the use and the standardization of high-albedo materials for pavements.

Current needs require the use of low environmental impact technologies in construction works. At the same time, the natural deterioration of roads makes maintenance and rehabilitation operations inevitable, with the consequent production and storage (or disposal) of huge quantities of Reclaimed Asphalt Pavement (RAP). Extensive research has thus been conducted and is still ongoing to maximize RAP recycling, trying to minimize the issues related to production and in-service properties, in particular in cold climates. This paper evaluates the feasibility of using large amounts of RAP in asphalt mixtures subjected to cold temperatures. With this aim, mixes were analyzed with different RAP contents (50% and 70%) and prepared with or without the addition of rejuvenator (two types of rejuvenators were selected). A traditional control mixture was also produced for comparison purposes. Dry and wet indirect tensile strength as well as stiffness and resistance to repeated loading properties at low and mid-service temperatures were assessed. Overall, the results showed a similar efficacy of the two rejuvenators in guaranteeing satisfactory mixture performance at low temperatures.

Ti6Al4V components, for biomedical and aerospace sectors, are receiving a great interest especially after the advent of additive manufacturing technologies. The most used techniques are Selective Laser Sintering (SLS), Selective Laser Melting (SLM) and Electron Beam Melting (EBM). In the current research, we developed 3D-printed Ti6Al4V scaffolds by Direct Ink Writing (DIW) technology. Appropriate ink formulations, based on water-titanium powder suspensions, were achieved by controlling the rheological properties of the developed inks. After printing process, and drying, the printed components were sintered at 1400 °C under high vacuum for 3 h. Highly porous titanium scaffolds (with porosity up to 65 vol%) were produced and different geometries were printed. The influence of the porosity on the morphology, compression strength and biocompatibility of the scaffolds was investigated.

In the reproducing kernel particle method (RKPM), the approximation is achieved through construction of shape functions in the physical domain and the interaction of neighbouring nodes. When modelling large deformation problems, Lagrangian and semi-Lagrangian formulations have been proposed, where the RK functions are evaluated in the reference initial coordinates and in the current configuration, respectively. The Lagrangian RKPM breaks down when the mapping between current and reference configuration is not one-to-one and the deformation gradient is not invertible, such as in modelling high velocity impact and penetration processes. On the other hand, the semi-Lagrangian RKPM formulation with RK functions evaluated in the current configuration eliminates the requirement on the deformation mapping but results in a high computational cost. In order to retain the advantages of both formulations, a blending-based spatial coupling scheme is proposed to allow transition from the Lagrangian to the semi-Lagrangian RKPM meshfree formulation. Spatial consistency and temporal stability of the proposed coupling approach are analysed. The analysis results show that the critical time step of the coupled formulation is larger than the worst case between the pure Lagrangian and pure semi-Lagrangian RK cases. Moreover, an algorithm to update three-dimensional semi-Lagrangian kernel supports and smoothing cells is introduced to enhance the solution accuracy of the semi-Lagrangian portion of the proposed coupling scheme. The proposed update algorithm avoids the numerical issues of either insufficient support coverage or loss of locality associated with the conventional pure semi-Lagrangian formulation under large deformations. The performance of the proposed Lagrangian/semi-Lagrangian coupling approach is verified through a suite of benchmark problems, including extreme deformation problems.

This paper discusses a visco-elastoplastic constitutive model to analyze the creep deformability of asphalt concretes at high service temperatures, finalized to improve the interpretation of permanent deformation phenomenon and performance design of road pavements. A three dimensional constitutive visco-elastoplastic model is introduced, in tensor as well as in numerical form. The associated uniaxial model is used to arrange a plastic element in series with the viscoelastic component. The latter is defined by an elastic spring placed in parallel with three Maxwell elements. Three different hardening laws, namely isotropic, kinematic and mixed hardening, are included in the constitutive model to compare the creep deformability. The proposed constitutive model has been calibrated and validated on the basis of uniaxial creep-recovery test results at 40 °C. This is performed with a high performance hot mix asphalt concrete (HP-HMA) at different stresses and loading times. Depending on the hardening law considered, permanent deformation data predicted by the proposed model results are reasonably consistent with the experimental creep-recovery data. A rational constitutive model that is physically congruent with the creep phenomenon of asphalt concretes was developed and calibrated to achieve a deeper understanding of the stress-strain response of such materials. The fundamental relevance of an appropriate plastic response modeling, in the study of the creep behavior of asphalt concretes for highway and road pavements.