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Increasing environmental awareness has led to a great research effort towards the formulation of increasingly sustainable pavements, mainly by developing bituminous mixtures incorporating waste materials. Furthermore, some waste materials have been proved to be useful for enhancing the performance of road bitumen and bituminous products, so their use is a potential solution for ensuring environmental, economic, and also technical benefits. Amongst the different wastes to be used for bitumen modification, a possible one is that obtained via the pyrolysis of biomass, named biochar. In the research reported here, a selected biochar was added to bitumen to verify the possibility of improving bitumen performance in terms of photo-oxidation resistance, which is a major problem in urban areas where black flexible pavements contribute to the urban heat island effect. Different biochar amounts were selected, and two different aging methods were performed: short-term aging and UVB aging resistance; they were monitored using rheological and spectroscopic analysis. The structural changes in bitumen in terms of carbonyl and hydroxyl accumulation were observed at various UV irradiation times. All the experimental data indicate that the use of biochar can have a positive effect on the UV resistance of bitumen, lowering its photo-oxidation tendency. This may lead to reductions in use of natural, non-renewable materials, since intervention maintenance may be scheduled at longer terms.

For the purpose of the Airport Pavement Management System (APMS), in order to optimize the maintenance strategies, it is fundamental monitoring the pavement conditions’ deterioration with time. In this way, the most damaged areas can be detected and intervention can be prioritized. The conventional approach consists in performing non-destructive tests by means of a Heavy Weight Deflectometer (HWD). This equipment allows the measurement of the pavement deflections induced by a defined impact load. This is a quite expensive and time-consuming procedure, therefore, the points to be investigated are usually limited to the center points of a very large mesh grid. Starting from the measured deflections at the impact points, the layers’ stiffness moduli can be backcalculated. This paper outlines a methodology for predicting such stiffness moduli, even at unsampled locations, based on Machine Learning approach, specifically on a feedforward backpropagation Shallow Neural Network (SNN). Such goal is achieved by processing HWD investigation and backcalculation results along with other variables related to the location of the investigation points and the underlying stratigraphy. Bayesian regularization algorithm and k-fold cross-validation procedure were both implemented to train the neural model. To enhance the training, a data analysis technique commonly referred to as data augmentation was used in order to increase the dataset by generating additional data from the existing ones. The results obtained during the model testing phase are characterized by a very satisfactory correlation coefficient, thus suggesting that the proposed Machine Learning approach is highly reliable. Notably, the proposed methodology can be implemented to evaluate the performance of every paved area.

To obtain road bitumen with improved temperature and fatigue resistance, polymers and/or rubbers could be added to it. A particularly suitable polymer for bitumen modification is styrene-butadiene-styrene (SBS) copolymer but limited information is available about the ageing behaviour of modified binders. In this work, two neat bitumens, with different penetration grades, and two SBS-modified bitumens, containing different SBS amounts, were selected, and their short-term and UVB ageing behaviour were investigated considering dynamic shear rheometry and Attenuated Total Reflectance-Fourier Transformation InfraRed spectroscopy (ATR-FTIR). Short-time ageing behaviour was investigated performing the rolling thin film oven test (RTFOT), while artificial UV ageing was examined/investigated using UVB lamps. The structural changes in bitumen were monitored at different UV exposure times. All the results suggest that the bitumen having higher penetration grade is more stable than the one with a lower penetration grade in the RTFOT ageing condition, and SBS addition exerts a beneficial effect on thermal stability during processing. Further, SBS addition also has a beneficial effect on the UV ageing resistance of bitumen, reducing its oxidation tendency.

The international commitment to achieve carbon neutrality in the next few decades has oriented human activities towards the preservation of natural and non-renewable resources. In this context, a great research effort has been devoted to the search for sustainable solutions for the infrastructure construction sector, based on a thorough assessment of the environmental impact (EI). In this regards, Life Cycle Assessment (LCA) is considered one of the main components of Environmental Impact Assessment (EIA) and, for a comprehensive analysis, all the costs incurred by stakeholders during the useful life of the infrastructure should also be taken into account, applying the Life Cycle Cost (LCC) methodology. So far, there is a lack of combined LCA and LCC analyses of railway projects to support a proper sustainable decision-making process at a project level. Therefore, this study aimed to contributed to this topic by determining the environmental effect and related costs of different planning and construction choices in terms of material and maintenance strategies. For this purpose, first, an LCA of typical railway infrastructures with a ballasted track was developed. The case study considered two different functional units of a double-track railway line: 1 km of embankment section and 1 km of a cut section, in straight alignment. After defining five alternative railway infrastructure scenarios with different materials (virgin or recycled material) and construction methods (e.g., lime stabilization), two different railway track maintenance approaches were analysed. SimaPro was used to analyse the case study, and the results were compared with those obtained using the PaLATE software, suitably adapted for use in the railway sector. Finally, a cost analysis was carried out using Life Cycle Cost (LCC) methodology for all the scenarios analysed. The results obtained in terms of EI and related costs of each scenario provide useful information, allowing a sustainable planning approach: as a general result, the initial construction phase always involves the larger part of the total environmental impact while the material production is the most polluting phase, reaching percentages always higher than 50% of the total.

Floods are becoming more frequent, especially in urban environments where most of the surface is waterproofed. Permeable pavement (PP) can be applied as low impact development (LID) systems for runoff mitigation in urban areas. Their effectiveness can be assessed, case by case, by numerical simulations. In this study, the effectiveness of mitigating runoff of different permeable pavements has been evaluated. In particular, porous asphalt (PA), pervious concrete (PC), permeable interlocking concrete pavement (PICP) and grid pavement (GP) have been investigated using EPA Storm Water Management Model (SWMM) software. To this aim, a car parking area located in the University Campus of Palermo (Italy) has been taken as a case study, considering several scenarios, each having a different percentage and planimetric layout of a PP type combined with an impermeable pavement. All the scenarios were tested assuming four synthetic rainfall events, referring to return periods of 5, 10, 50 and 100 years, and a real high return period event that occurred in Palermo in 2020. The results showed that amongst the different PPs considered, only the PA, bounded at the bottom by an impermeable layer, was practically ineffective. The other three PPs, proved to be effective in a noticeable way and furthermore for each scenario studied, they proved to bear almost the same mitigated runoff. The results proved appreciable differences in runoff as a function of the location of the PP over the study area.

The aggregate gradation of bituminous mixtures (hot mix asphalts, HMA) is one of the major factors affecting their surface texture. In turn, this latter is a crucial factor and influences drivers and bystanders’ safety, comfort, and health. Despite this, the design of texture levels still lacks sound bases and dedicated algorithms and this negatively affects the acoustic design of bituminous mixtures. Consequently, the objectives of this study were confined into the derivation of relationships to be used in mix design to predict texture levels. Experimental data were analyzed, in the pursuit of setting up appropriate models and algorithms. Analyses involved the consideration of Bailey-related indicators. Algorithms were then calibrated and tested, in order to allow the validation of the algorithms set up. Results demonstrate that the texture level is well correlated to the asphalt mixture composition. Researchers can benefit from the results obtained for improving understanding of noise-related and rolling resistance-related implications. Furthermore, the same results can be useful for practitioners facing the need to design mixtures complying with ISO or project-specific requirements.

In recent years, a growing attention on environmental issues affecting all fields and procedures of the productive sectors has raised, aiming to reduce energy and raw-material consumptions and pollution effects on environment. Due to the involved volumes and to the nature of the related materials and productive processes, the civil and road sectors have been strongly invested by this change of perspective. Therefore, a proper estimation of the environmental impacts for the entire life cycle of the asphalt mixtures for road construction and maintenance activities is extremely important. For performing similar investigations, Life Cycle Assessment (LCA) has become one of the most reliable and effective methodologies, assuring the possibility to include in a comprehensive analysis all the relevant processes and products, such as raw material extraction, production, use and final recycling. In this paper, a specific LCA analysis, based on the international standards of the ISO 14040 series, of an asphalt mixture is performed, based on primary data, i.e. through data collected or measured directly at a production plant in Sicily. The results, presented in terms of aggregated environmental indicators, are useful for better understanding the overall impact of the productive process, as well as the contribution of its single phases. The results of this research can provide a more reliable and exhaustive analysis on the environmental impacts of an asphalt mixture, assuring a useful numerical reference to producers, contractors and designers that can assume more conscious, informed and sound decisions.

Finding an appropriate technical solution for reusing waste plastics is crucial for creating a circular plastic economy. Although mechanical recycling is the best option for recycling post-consumer plastics, some heterogeneous mixed plastics cannot be recycled to produce secondary material due to their very low properties. In this case, alternative routes should be considered in order to limit their disposal as much as possible. Therefore, in order to solve the environmental problems in the landfills of plastic waste recycling, and to improve the mechanical performance of bitumen for road pavement, the reuse of these post-consumer plastic wastes are preliminarily evaluated for the modification of bitumen for road use. The field of polymers used so far and widely studied concerns virgin materials, or highly homogeneous materials, in case of recycled plastics. In this work, a highly heterogeneous mixed plastic—Plasmix—from the separate collection in Italy, is used as a bitumen modifier for road construction. The research focused on the dry (into the mixture) and wet (into the binder) addition of different content of the Plasmix compound, with the aim of assessing the feasibility of the modification itself. Results of the mechanical tests carried out prove an increase in performance and that there is a potential of the addition of the Plasmix compound both for binder and mixture modifications.

Establishing the structural integrity of an airport pavement is crucial to assess its remaining life and implement strategies or priorities for action. In this context, the elastic modulus represents an effective indicator of the condition of the pavement which can be calculated through back-calculation procedures starting from surface deflections, obtained from a non-destructive test (such as the Heavy Weight Deflectometer). Nevertheless, the conventional inverse engineering analysis involves the use of an axial-symmetric pavement finite-element program able to evaluate stiffness values exclusively at the deflection measuring points. This study presents an alternative methodology for spatial modelling of the load- bearing capacity of the runway surface pavement layer from deflection data measured at specific points, using Shallow Artificial Neural Networks. The search of the optimal neural model hyperparameters has been addressed through a Bayesian Optimization procedure and a 5-fold cross-validation has been implemented for a fair performance evaluation, given the limited number of deflection measures available. Once the optimal model has been defined, the measured surface deflection data were linearly interpolated and resampled gridding data were used as a new input matrix of the neural model to predict the expected value of elastic moduli at non-sampled points on the runway. The optimal BO model has returned very satisfactory results with a value of Pearson Coefficient R averaged over 5-fold equal to 0.96597 and of Mean Squared Error averaged over 5-fold equal to 0.01849. In such a way, a contour map of the runway stiffness has been drawn, to provide a support tool for the planning of intervention priorities.

The paper presents the results of a characterization of kinetic characteristics of pozzolanic reaction with the aim to investigate the time-dependent modification of clay properties as a consequence of mixing with lime. Results of chemical analyses are in agreement with the increase of mechanical properties and with the observed microstructure modifications up to one year of curing time. The rate of development of pozzolanic reactions seems to be almost constant while the time required for their completion is dependent on the lime content. Pozzolanic products are responsible for the time reduction of swelling strain upon saturation as well as for the increases of yielding stress, stiffness and hydraulic conductivity. However, the data analysis proves that a significant component of settlement measured during loading may be induced by the secondary compression process (creep). These results are significant for the prediction of the long-term behaviour of the stabilized soil.

An integrated approach based on machine learning and data augmentation techniques has been developed in order to predict the stiffness modulus of the asphalt concrete layer of an airport runway, from data acquired with a heavy weight deflectometer (HWD). The predictive model relies on a shallow neural network (SNN) trained with the results of a backcalculation, by means of a data augmentation method and can produce estimations of the stiffness modulus even at runway points not yet sampled. The Bayesian regularization algorithm was used for training of the feedforward backpropagation SNN, and a k-fold cross-validation procedure was implemented for a fair performance evaluation. The testing phase result concerning the stiffness modulus prediction was characterized by a coefficient of correlation equal to 0.9864 demonstrating that the proposed neural approach is fully reliable for performance evaluation of airfield pavements or any other paved area. Such a performance prediction model can play a crucial role in airport pavement management systems (APMS), allowing the maintenance budget to be optimized.

The results of a comprehensive experimental programme are presented for assessing the long-term microstructural modifications and evaluating the effects of microstructural rearrangement on the stress–strain behaviour of a lime-treated high-plasticity clay for road embankments. The stress–strain behaviour at different lime content and curing time was investigated by means of direct shear tests; microstructural analyses were carried out combining Scanning Electron Microscope observations and Mercury Intrusion Porosimetry tests. The results show that the stress–strain behaviour of treated clay is strongly dilatant with a high peak of strength, which increases with time and lime content. Furthermore, a hyperbolic function may be used for predicting the increase in strength at the end of the stabilisation process. Microstructural analysis shows that the treatment induces a redistribution of the porosity between macro- and micropores and an increase in matric suction, associated to a low reduction of water content and to aggregates shrinkage. This behaviour is affected by lime content and curing time since it results from the formation of the pozzolanic compounds on the surface of clay aggregates that induces both a bonding between hardened clay aggregates and an increase of their interlocking degree, with a consequent increase in the shear strength.

Polymer-modified bitumen (PMB) is bitumen that has been specifically engineered with polymer for providing enhanced performance in service. The aging of bitumen is a main aspect that is able to affect its final performance: during the production phase in a hot mix plant, all the binders experience short-term aging due to the high processing temperature. The same is true during the production of the modified binder, when the polymer is dispersed at high temperature in the bitumen mass. This paper aims at studying the effect of short-term aging when using different types of modifiers such as recycled polymers obtained from waste materials. A 50/70 penetration-grade bitumen has been modified, and bitumen characterization has been carried out before and after short-term aging, conventional tests, viscosity measurements, and dynamical mechanical analysis have been used to investigate the properties. Different aging indices have been determined for predicting the effect of short-term aging based on the type of modifier. Furthermore, the morphology of the modified bitumen has been investigated via fluorescent microscopy, before and after aging, in order to highlight morphological changes due to aging. The results confirm that aging affects all the modified binders, due to the thermal stress imposed during PMBs production. Nevertheless, polymer modification is proved to reduce the aging effect in terms of an increase in the elastic modulus as experienced by the original binder.

The paper presents some experimental results obtained on samples extracted from a full-scale embankment obtained by compacting a lime-treated clayey soil. A comprehensive test programme was carried out in order to highlight the improvement of mechanical behaviour induced by lime treatment as well as to assess the durability of the improved material, which may be affected by severe seasonal wetting and drying cycles. Direct shear tests, triaxial compression tests, swelling potential measurement and oedometric tests were performed on samples cured in controlled environmental conditions for at least 18 months. Wetting and drying cycles were applied in a very wide range of suction values with different experimental techniques. Test results show that the cyclic variations in total suction in the range 2-110 MPa give rise to significant irreversible deformations of shrinkage, since the material, during the wetting stages, proves to be unable to recover most of the deformations developed in the previous drying stages. However, this volumetric behaviour shows an almost reversible pattern after a few suction cycles. In contrast, saturation after drying implies a strong variation in the mechanical response due to the irreversible pattern of the observed volumetric behaviour. Accumulation of swelling deformation, reduction of the yielding stress, increase of compressibility and loss of shear strength due to softening of bonding, induced by the pozzolanic reaction products, were measured with the increase of the number of wetting and drying cycles. Mercury intrusion porosimetry (MIP) tests, carried out before and after the wetting and drying cycles, highlighted that cyclic suction paths result in a collapse of the structure since the pore size distribution of microstructure changes, its peculiar double-porosity network becoming almost unimodal in type.

The paper presents the results of the rheological characterisation of polymer-modified bitumen for paving applications. In order to find a simple interpretation of the influence of polymer type on the blends produced, in this study high density and low density polyethylene (PE) with different chemical properties were used, as well as ethylene-vinyl acetate. The chemical characteristics of the base bitumen and the polymers used were determined by means of SARA analysis and Fourier Transform Infrared Spectroscopy, FTIR, respectively. The morphology of the produced blends was investigated by means of fluorescent light optic microscopy, while the mechanical properties were investigated with both conventional tests and rheological measurements (dynamic mechanical analysis through frequency sweep test and viscosity measurements). The analysis of the modified bitumens was carried out based on the chemical structure and crystallinity properties of the polymer used. The flow curves (viscosity vs shear rate), in particular, proved to be an initial indicator of the type of modification attained. This shows that simple tests can be helpful in predicting the internal structure of the polymer modified binders (PMBs) and thus in selecting promising polymer/bitumen blends of the PE family to be submitted to full characterization for production purposes.

In this paper, considering the sever impact of road infrastructures on both the surrounding environment as well as on the consumption of locally available natural resources, different road construction techniques have been studied and compared, in order to be able to rank the best solution in terms of environmental sustainability. For the aims of this study, a Life Cycle Analysis has been carried out on a road infrastructure with the most representative geometrical characteristics among those widely used in Italy, in suburban areas, with the help of an appropriate software, the PaLATE. The environmental effects due to both the use of recycled materials, such as the Reclaimed Asphalt Pavement (RAP) from dismissing of damaged pavement layers, and the reuse of fine soil from excavation, traditionally sent to landfill, has been studied. The latter is possible thanks to lime stabilization of clayey soils, that allows to reduce the need of transport to the dump as well as the need for non-renewable natural resources for road subgrades and embankments. The results here obtained show how the use of RAP, can lead to a significant reduction in pollutant emissions and energy consumption compared to that due to pavements constructed with virgin material only. A similar observation can be made for fine soils stabilized (in situ) with lime: it is demonstrated that this technique is able not only to significantly improve the mechanical properties of useless soils that, otherwise, would be considered as a waste to be dumped but also to provide considerable environmental benefits. Finally, in order to identify a criterion for achieving lower generalized costs in the whole life cycle of a road, the different construction options have been estimated in terms of total direct costs, assessed as the sum of construction and maintenance costs. It has been verified that the use of sustainable construction techniques (RAP and lime stabilization of clayey soils) can lead to the reduction of total cost and thus allows allocating greater financial resources to perform an “ideal” maintenance plan.

The recent developments of road pavement survey technologies guarantee acquisition of detailed data regarding the main functional and structural indicators, at a very high frequency and levels of accuracy and precision unconceivable few years ago. The relevant information, regarding surface distresses too, is thus available in economical, high-speed and high-resolution forms, with limited disturbance on traffic and road agencies issues. However, the availability of such a mass of data poses interesting questions concerning the most efficient processing and analysis methods, for optimizing maintenance operation planning. Unfortunately, the PMS adoption is not very common and widespread, as they are significantly complicated and sophisticated, with critical consequences in their actual and intense practical use. Then, there is a need of simplifying the pavement maintenance process, by defining smart tools actually supporting the operators in the analysis and decisional phases. BIM (Building Information Modeling) procedures can absolutely represent a strategical solution. Indeed, BIM models, already widely adopted in the structural fields, have been recently introduced in the infrastructural design phases, simplifying the entire life-cycle of the construction, with representation clarity, mistake reduction, and money savings. However, although the BIM advantages have been significantly exploited in the design phases, pavement maintenance has not been directly involved in the BIM processes. Then, this paper focuses on a methodological analysis of the problem, aiming to propose a novel BIM-based approach for managing pavement maintenance. The goal is to define proper “smart objects”, based on specific relational databases, that may represent a more suitable instrument for handling pavement condition and quality information, in a user-friendly software environment. The potentialities of the modern survey technologies may be integrated and optimized in a BIM process, involving in parallel both design and maintenance.

Pavement deformation is a critical issue in the design of pavement structures and the related mixture. Asphalt concretes may be very sensitive to this problem, in compliance with the viscoelastic behaviour of the adopted bitumen. To improve the material performance, many attempts have been made to introduce in the mixture other materials as “modifiers” or “additives” for increasing the permanent deformation resistance and the elastic modulus of the material. Among the different possible materials, polymers determined significant improvements in the road pavement performance. In this paper, the authors tested the adoption of a specifically engineered polymeric compound, in order to evaluate its effects on a generic asphalt mixture. Several tests were used to prove the effectiveness of the modification. Tests were performed not only in the laboratory, but also in an actual pavement section of the International Airport of Palermo in Sicily. Tests results prove that a proper mix-design can assure a decrease in the permanent deformations, remarkable growth of the material modulus with a reduced bitumen percentage, with economical savings. Finally, regarding fatigue resistance, the modified mixture with low bitumen content assures performance comparable to the control mix containing higher bitumen percentage. Then, the proposed application can be very useful to improve pavement performance even when using softer binder, easier to find in the Italian context.

The development of the road construction sector determines the consequences on consumption of non-renewable resources, energy expenditure and environmental pollution. Recent sustainability issues have highlighted the importance of efficient design and quality-oriented techniques in this sector, due to the huge amount of materials involved in construction and maintenance activities. Thus, it is necessary to properly quantify the environmental impacts of asphalt mixtures used for pavement construction, considering the whole life cycle of the products. Life cycle assessment (LCA) represents the most appropriate methodological framework for assessing the environmental burdens of a product, from raw material acquisition to final disposal. A common problem for LCA is the lack of primary data useful to calculate the product eco-profile, for a specific production process. In this context, there is generally limited reliable and accurate data regarding the asphalt plant production phase, which represents the most critical phase. Consequently, the aim of this paper is to perform an environmental/energy audit of an asphalt plant and, further, to collect and analyze primary data useful for the definition of the eco-profile of 1 metric ton of hot mix asphalt (HMA), following a &ldquo, gate to gate&rdquo, approach, including transport. The asphalt production is examined in a Sicilian batch-mix plant, representing one of the most commonly used for asphalt production in the Italian context. The results are of interest for asphalt mixture producers, contractors, transportation agencies and researchers seeking to quantify asphalt pavement environmental impacts in Italy, based on context-related foreground data.

In order to guarantee safety and driving comfort and to maintain an efficient railway infrastructure, the first step is to carefully monitor the track geometry and wear level of the materials constituting the superstructure. To that end diagnostic trains are widely used on main lines, in that they can detect several geometric track parameters and rail wear, but under no circumstances they can yet detect ballast gradation. Due to the practical implications for the planning of maintenance operations on the railway network, this article presents a “DIP” digital image processing technique for measuring the transverse profile and corrugations of the rails as well as ballast gradation. The research was carried out in the laboratory on samples of worn-out rails taken from operational railway lines and in situ in the case of ballast analyses. For the latter, the reliability of the results obtained was assessed by comparison with available results yielded by traditional testing methods. It is shown that the proposed technique can be used not only for laboratory analyses, but most conveniently for high-efficiency in situ surveys, along with the methods traditionally adopted by the railway managing authorities thus contributing to lowering the maintenance cost associated with rail inspection.

This work explores the influence of climate changes on the proper selection of asphalt binder for pavement construction purposes, according to the Performance Grade (PG) defined in the SUPERPAVE specifications. Based on temperature data at national level, it is possible to obtain thematic maps for the whole Italian territory, which is extremely useful for technicians and pavement engineers for selection of asphalt binder for road construction purposes. Furthermore, the statistical significant temperature trends’ knowledge enables deriving thematic maps which allows to include the effects of climate change in the asphalt binder design. It is argued that, due to climate change, the binders to be selected may be different from those commonly selected at the design stage of the infrastructure, since likely higher temperature determine more demanding constraints. The comparison among the PG grades necessary for covering the needs for construction in the different regions of Italy also call for highly performing binders, such as those obtained via specific modification with polymers. This will also imply the need for even more performing materials, in terms of mechanical properties and durability, to be used for modification of neat asphalt as well as the need for defining new specification and testing methods, specifically valid for these modified materials.

The aim of this work is to carry out a comparative analysis of environmental impacts for different scenarios of a typical local road. Life Cycle Assessment (LCA) is the modeling tool used to quantify and characterize comparative environmental impacts. In carrying out this specific application of the LCA, different road construction techniques were considered with regards to the whole structure and compared in order to identify the best alternative in terms of environmental sustainability. So far, in fact, typical LCA frameworks of roads have focused on recycled materials for pavement layers only, thus neglecting study of the materials used in the embankment or in the subgrade. In this study, these materials were included too, in order to prove the environmental benefit of using a sustainable technique such as in situ stabilization of fine soils with lime (typically dumped clayey soils) in order to reduce the need for virgin material for embankment and subgrade construction. When using different percentages of recycled materials (such as reclaimed asphalt pavement – RAP) in the bituminous layer or in the foundation, the analysis of the functional unit studied shows a significant reduction of energy consumption and pollutant emissions mainly due to transportation of materials involved, in this way increasing the environmental performance of the road. Another important consideration is that the use of fine soils stabilized with lime “in situ”, instead of dumping it, not only is a good technical solution for improving soil mechanical properties, but it also produces a reduction of energy consumption and of pollutant emissions. It is noticeable that this technique results in a significant reduction of pollutant emissions due the transportation of involved materials, increasing the environmental performance of the road.

"Published online: June 29, 2017", The mechanical performance of a typical surface course mixture, modified with two different plastic wastes, both via the wet and dry processes, was evaluated in this study. Water sensitivity, rutting resistance, stiffness modulus, and fatigue cracking resistance tests were used. The results obtained indicated that the polymer-modified mixtures showed similar or improved performance when compared with that of a conventional control mixture produced with a harder virgin grade bitumen, not always available, or available at higher costs, in several countries. Thus, modifying asphalt mixtures with these plastic wastes can be an economical and ecological alternative for paving works. Moreover, the mixtures produced via the dry process showed increased water sensitivity and stiffness modulus properties. This holds out new possibilities for use of polymer-modified mixtures, especially in developing countries, because it widens the possibility of using locally available bitumen, of variable quality, for producing mixtures with higher performance. This can be achieved at real scale with no major extra costs because the dry process does not require modification of typical asphalt plants., This work is funded by ERDF funds through the Operational ompetitiveness Program – COMPETE and by National funds by FCT – Portuguese Foundation for Science and Technology in the scope of Project FCOMP-01-0124-FEDER-020335 (PTDC/ECM/119179/2010)., info:eu-repo/semantics/publishedVersion

The paper presents some experimental results collected on samples recovered from an experimental embankment obtained by compacting a lime-treated clay. Samples were collected soon after the in situ compaction and they were cured in controlled environmental conditions for at least 18 months. Mercury intrusion porosimetry tests (MIP) were carried out on freeze-dried specimens to characterize the microstructure of the material. In order to assess the durability of the improved material, laboratory tests focused on the effects of cyclic variations of the degree of saturation on the water retention properties and the volumetric behaviour of the stabilized clay. Collected results show that the lime-treated clay undergoes an almost irreversible volumetric behaviour; this irreversible contraction is associated to severe drying processes .

The macroscopic mechanical behaviour of dense sands originates to a great extent from their microstructural characteristics such as the coordination number, the grain contact and the packing density indexes. The study of intergranular contacts and the reckoning of these indexes may be carried out on planar images of the grains either by means of time-consuming visual inspection assisted by CAD or by automatic image analysis. An innovative method for the automatic determination of microstructural characteristics of sands based on image analysis of thin section is proposed. Tests performed on a locked sand show that the proposed method is much more effective, convenient and faster than the usual visual inspection technique. Therefore, it can be considered an extremely useful tool for calibrating predictive models for arrangements of granular media based on computer simulations.

Bearing in mind the need to answer one of the most frequent needs for civil construction, in general, and major project such as road infrastructures in particular, this paper presents the results of a laboratory experimental study in order to evaluate the performance improvement that is possible to achieve when modifying road bitumen with CRM (Crumb Rubber Modifier) from discarded tire rubber (TR), using a Wet Process. The environmental advantage is double, since the aim of the research is to obtain high performance road bitumen thanks to the re-use of a discarded material, such as the rubber tires, which otherwise would be dumped in scrap-yard. In particular, this experimental study aimed to define a laboratory optimization protocol that allowed to discriminate amongst the different asphalt–rubber blends, in relation to the different content of rubber, as well as to the blending times, with the possibility of carefully controlling the production temperature throughout the production process. In order to do this, simple and widespread laboratory equipments and procedures have been adopted, such as the Brookfield rotational viscometer, capable of ensuring the representativeness of the final product to be tested. After the optimization study, a comparison was made between the conventional and rheological properties of the optimized rubber–asphalt blend with those of two commercially available PMBs, modified with synthetic rubber type Styrene–Butadiene–Styrene, with two different level of modification: a medium and a high level of polymer, respectively termed as “Medium” and “High” in this study. This comparison allows one to appreciate to what extent control of the modification process is able to affect the properties of the final product and shows that the preliminary optimization of the mixing parameters carried out with the proposed protocol allows one to obtain a rubber–bitumen blend with improved performances, above all reduced temperature susceptibility, as proved by an increase in the Superpave™ high temperature performance grading, up to a two grade jump, which it is possible to obtain only for SBS modified bitumen with high content of polymer. Therefore, this study proves that, thanks to the appropriate re-use of crumb rubber form scrap tires, with the proposed optimization protocol it is possible obtain improved bitumen with high content of recycled materials that, with respect to specific needs of regions with warm climates such as the Mediterranean area, can be considered as “high-performance blends”.

Interpretation of NDTdata is crucial in any Airport Pavement Management System (APMS), in order to implement strategies to maintain airport pavementssince they allow to estimate their remaining life and related maintenance needs and activities. In this paper, the AntColony Optimization algorithmwasused for backcalculation of pavement moduli from surface deflection data. The algorithm’s performances are illustrated and improvement in prediction quality is demonstrated both in terms of goodness of fitness and computational effort. Moreover, it is proved that the proposed algorithm is also able to predict layer thicknesses, taking into account their variation too.

Prediction of asphalt mixtures’ behavior during their service life is a challenge due to its complexity and sensitivity to environmental and loading conditions. It has been proved that, when subjected to loading conditions comparable with most pavement operating conditions, asphalt mixtures behave as linear visco-elastic (LVE) materials. Traditionally the LVE behavior of bituminous material is modeled via creep/recovery functions. In the past, several rheological models constituted by elastic and viscous elements arranged in series or in parallel (analogical models) have been proposed and specified for both bitumen and asphalt mixtures. The corresponding constitutive laws always involve first order derivatives of time with exponential type solutions but problems in setting parameters arise when both the creep and recovery behavior have to be modeled. In this paper it is shown that experimental creep data follow a power decay law, rather than an exponential one. As a consequence, a simple fractional model is here proposed for predicting creep/recovery behavior of asphalt mixtures with a small number of parameters and low computational efforts with respect to the classical analogical models. The proposed model is then calibrated by a best fitting procedure on experimental data from creep and creep/recovery tests carried out on asphalt mixtures under different load and temperature conditions.

By fitting experimental data from static creep/recovery carried out on pure bitumen, it is shown that the fractional model proposed enables the description of both creep and recovery behaviour with fewer parameters than those needed by other models in the literature. In particular, the model is fitted to experimental data of complex modulus |G*| and phase angle δ° obtained from Dynamic Mechanical Analysis. Lastly, it is demonstrated that when the fractional model is used, complex modulus isotherms for a range of frequencies can be created simply starting from isochronals at f = 1Hz.

An image analysis technique for automatic traffic sign detection and classification is proposed. This analysis makes it possible, after proper training, to detect, recognize and classify vertical road signs from video frames acquired on a moving vehicle equipped with cameras, as well as to identify anomalies with respect to road sign regulations (positioning and visibility). The experimental results show that this technique allows one to correctly detect and classify almost all vertical signs and, mainly in extra-urban environment, it can be considered as highly reliable, apart from being really versatile and user-friendly for road inventory and road maintenance purposes.

When selecting the appropriate materials for constructing road infrastructures, an important way for minimizing both the economical and environmental impact is to make use of lime for treating soils that are not suitable for road or railways construction.Advances in lime stabilization technique allowed the successful use of this technique also for improving the bearing capacity of the subgrade, with noticeable savings on both aggregate and disposal charges.In this paper a review of internationally adopted design methods for soil-lime mixture is presented, in order to compare testing methods and requirements of the adopted criteria, as discussed in Part 2.

The mechanical properties of bituminous mixture strongly depend on the gradation of the aggregate that represents the mineral skeleton of the mixture, since for open and gap-graded mixtures, stresses due to vehicles in movement on the pavement are mainly transmitted through their contacts. Internal structure of bituminous mixture is, therefore, of great interest for road and infrastructure engineering and it is appropriate to study it with recently developed image analysis method. The purpose of this study was to finalize an effective analysis of asphalt section image for automatically extracting aggregate gradation without the need of separation of the bitumen from the aggregate. This paper proves that, thanks to the synergic use of different segmentation methods of the digital images taken on slices of cores from the pavement, it is possible to obtain a reliable gradation of the mineral skeleton of the mixture. The proposed methodology allows one to estimate the aggregate gradation that, otherwise, it would be necessary to establish via specially equipped laboratory, undertaking time-consuming tests that also imply health risks for the operators, due to the use of solvents and other hazardous materials.

The paper deals with a specific laboratory study aiming at perfectioning recycled asphalt with high mechanical performance, for surface and structural layers of flexible pavements. The aim of the research was to combine in the same material the maximum possible quantity of recycled asphalt (RA), coming from degraded asphalt layers, together with high structural performance of the recycled mixtures obtained (mainly stability, load spreading properties, rutting and fatigue resistance) that should not be lower, or possibly better than those offered by traditional asphalt mixture, made with virgin binder and aggregate. For this purpose, innovative recycled mixtures, close-graded and with high mechanical performance, characterized by high content of recycled asphalt (up to 50%) and designed for surface, binder and base layers were investigated in a laboratory study. The results of physical and mechanical characterization tests show that, by controlling the homogeneity of recycled material and by using new bitumen with adequate rheological properties, it is possible to obtain paving mixtures with high content of recycled materials that, in relation to their intended use (surface, binder or base layer), can be considered as “high-performance mixtures”.

The characterization of unbound materials in the mechanistic–empirical pavement design guide (MEPDG), also known as the 2002 design guide, is reviewed, and this characterization is applied to Minnesota subgrades. The main emphasis is on the collection of k1-, k2-, and k3-parameters for Minnesota fine-grained soils and the procedure for the interpretation of the resilient modulus test to provide an input to the multilayer elastic theory (MLET) analysis (Level 2 input). This is an important aspect of adaptation of the MEPDG, because the guide recommends measurement of resilient moduli from laboratory testing, but the procedure does not specify how to interpret the test data to obtain an input for an MLET analysis. The resilient modulus test results from 23 samples collected from several Minnesota locations were used to provide information for the nonlinear finite element program and multilayer elastic theory program. The obtained elastic moduli were compared with the MEPDG recommended ranges for subgrade modulus of elasticity based on the soil classification (Level 3 inputs). The MEPDG Level 3 ranges were found to be reasonable.

The characterization of unbound materials in the mechanistic–empirical pavement design guide (MEPDG), also known as the 2002 design guide, is reviewed, and this characterization is applied to Minnesota subgrades. The main emphasis is on the collection of k1-, k2-, and k3-parameters for Minnesota fine-grained soils and the procedure for the interpretation of the resilient modulus test to provide an input to the multilayer elastic theory (MLET) analysis (Level 2 input). This is an important aspect of adaptation of the MEPDG, because the guide recommends measurement of resilient moduli from laboratory testing, but the procedure does not specify how to interpret the test data to obtain an input for an MLET analysis. The resilient modulus test results from 23 samples collected from several Minnesota locations were used to provide information for the nonlinear finite element program and multilayer elastic theory program. The obtained elastic moduli were compared with the MEPDG recommended ranges for subgrade modulus of elasticity based on the soil classification (Level 3 inputs). The MEPDG Level 3 ranges were found to be reasonable.

The work presented in this paper offers a contribution to understand to what extent different discretization modes for describing a whole day can affect the estimation of in-service durability of a flexible pavement, in relation with concomitant traffic flow fluctuations. Calculation of the stress–strain state was carried out with an elastic multi-layer model, and performance laws were implemented for verification of the major distress mechanisms that are able to affect the prediction of a flexible pavement’s service life. Results from the prediction of the fatigue life allow one to conclude that no big mistakes are made when evaluating the total damage by describing climatic conditions via daily average temperatures to be assigned to seasonal periods, as in routine design practice. The situation is completely different with regard to the estimation of damage for cumulated permanent deformation in bituminous layers: there is evidence for underestimation of the total rut depth, when calculated assuming a simple daily variation,as happens in the ordinary pavement design practice. A correct estimation of rut depth produced by accumulation of permanent deformation in bituminous mixtures cannot, in fact, leave out of consideration an accurate analysis and an equally correct superposition of the hourly variation in temperature and traffic.

As detailed in Part 1, the most common Italian Technical Specifications refer to different design methodologies for design of lime-soil mixtures, some being quite different from those internationally adopted. Therefore, it seemed appropriate to the Authors to compare these methodologies, via a wide experimental program.It is shown that the Italian methodology of the National Road Agency is different not only from those used in Italy, but also from the main international standards. The experimental results highlight that a revision of that methodology is needed in order to bring it into line with what is prescribed by the European standard.

Il presente contributo riferisce dell´esperienza del Nucleo della Sicilia —Area Valutazione progetti, in merito alla redazione della relazione tecnica di accompagnamento all´APQ per il Trasporto delle Merci e per la Logistica in Sicilia. Partendo dalle Disposizioni contenute nella delibera CIPE n.20/2004 e dalle indicazioni della nota di indirizzo Rete NUVV dic/2004 in proposito, il gruppo di lavoro ha proceduto alla necessaria acquisizione delle informazioni e dei dati relativi a ciascun singolo intervento previsto in APQ, ricostruendo i processi e le procedure, come pure la sequenza tecnico-procedurale con la quale si sono sviluppate le proposte (analisi del fabbisogno, individuazione degli obiettivi, definizione degli interventi). Alla luce delle scelte programmatorie esistenti, e tendendo debitamente conto della relazione tra gli strumenti programmatici, primi tra tutti quelli propri della programmazione regionale, il ruolo del Nucleo ha consistito principalmente nella individuazione di primi stralci funzionali per gli interventi che garantiscono la piena funzionalità della rete proposta in APQ al fine di realizzare opere rispondenti alla domanda del breve-medio periodo con possibilità di facili successive espansioni già contenute in sede progettuale. In tal senso, gli interventi individuati in APQ sono, per la quasi totalità dei casi, limitati a primi stralci funzionali al fine di procedere, durante le fasi successive, al monitoraggio della domanda e, quindi, al dimensionamento della offerta in modo coerente ed ottimale, garantendo, in tal modo, la ottimizzazione degli investimenti pubblici e la redditività per il soggetto gestore