Design of eco-sustainable bituminous mixtures for road pavements

In the civil engineering sector and in particular in road construction, attention is increasingly being focused on the need for "sustainable development", which reflects the growing trend, on the one hand, to reduce the amount of materials taken to landfills and, on the other hand, to conserve and reuse non-renewable resources (suitably treated) instead of raw materials that should be preserved in nature. The aim of this thesis was to enhance the conservation of local natural resources by reusing secondary raw materials such as Reclaimed Asphalt Pavement (RAP), Jet grouting waste (JW) and plastic waste (PW) in the construction of sustainable infrastructures. The different sizes of each material have led to investigate the mechanical behaviour of different scales of the mixture; in particular, laboratory tests have focused on the rheological behaviour of bituminous mastics when JW and PW are adopted as filler, while static and dynamic tests focused on hot and cold bituminous mixtures when JW and RAP are used as aggregates. With the aim to create a complete procedure supporting the decision makers in the comparative analysis of the designed bituminous mixtures as base layer of a flexible pavement, taking into account not only the mechanical variables linked to the performance of the mixtures, but also in terms of environmental sustainability, an LCA was developed. Finally, to identify the most appropriate bituminous mixture solution, a sensitivity analysis was implemented

Analytical Assessment of Effective Maintenance Operations on At-Grade Unsignalized Intersections

This chapter describes a methodological structure to support and improve the decision-making process for redesigning the geometric configurations of substandard sites and thus reduce crash risk factors on at-grade three-leg and four-leg intersections with stop-control on minor roads and single-lane roundabouts belonging to a two-lane rural road network located in Southern Italy. Starting from an initial evaluation of the risk level at each investigated site and adopting a procedure developed by the Italian National Research Council based on an estimated crash rate level, a more precise hierarchy of intersections with “black” rankings was developed. In addition, new geometric configurations for the most hazardous sites were suggested based on a statistical comparison in terms of safety and Level of Service (LoS). The effectiveness of the strategies was validated by computing the expected LoS and safety by adopting an empirical Bayesian analysis and performance functions centered on a revised Highway Safety Manual procedure reflecting the context of the study

Design Criteria for Improving Safety Performance of Rural Intersections

This paper, on the one hand, aims to identify significant crash risk factors at unsignalized three-leg intersections connecting rural two-lane two-way roads and minor roads with a STOP control on the approaches (3ST) and, on the other, to make adjustments to the Highway Safety Manual (HSM) procedure, fine-tuning its Safety Performance Function (SPF) based on observation of the local context. Over an 8-year period of study, a total of 240 crashes on 35 3ST intersections were observed, with no geometric-infrastructure adjustments or changes in the Annual Average Daily Traffic (AADT) and surrounding context noted at the intersections investigated. To obtain reliable results, the study period was divided into two groups: (a) 5 years to calibrate a new SPF, and (b) the remaining 3, not included in the first dataset, were used to validate the results. A negative binomial regression model was adopted to calibrate the new SPF. It was found that the AADT on the major and minor roads, the intersection skew angle, the co-occurrence of left and right-turn lanes on the major roads, and lighting seriously affect the crash scenario. Document type: Articl

Rheological Properties Comparing Hot and Cold Bituminous Mastics Containing Jet Grouting Waste

The use of reclaimed asphalt pavement is a practice that is adding significant environmental value to road technologies, not only due to the reduction of materials sent to landfill but also because of the mechanical properties of the reclaimed asphalt (RA) that can be reused. This research focuses on the rheological properties of hot and cold bituminous mastics made up as follows: (1) hot mastics mixed with limestone filler (LF) and bitumen, (2) hot mastics, made from bitumen mixed with jet grouting waste (JW), a mixture of water, cement, and soil derived from land consolidation work in underground tunnels, and (3) hot mastics mixed with LF and JW as filler and bitumen. Three different ratios (0.3, 0.4, and 0.5) of filler per unit of neat bitumen (B50/70) were studied. The same number was used for mixing cold mastics, by using an appropriate laboratory protocol designed since the adoption of a cationic bituminous emulsion. A total of 18 mastics were prepared and investigated. The comparison was carried out using the frequency sweep (FS) test, analysing shear modulus G∗, applying the multistress creep and recovery (MSCR) test (40°C and 60°C) as well as the delta ring and ball (ΔR&B) test, focusing on two main issues: (1) the stiffening effect caused by the filler type used for mixing each mastic, and (2) a comparison, in terms of stiffening effects and nonrecoverable creep compliance (Jnr) of hot and cold mastic performance to highlight JW reuse in mastics. The results showed that the best G∗ performance at test temperatures higher than 30°C is given by cold mastic after 28 days of curing time when JW is added to LF and bitumen. The lowest Jnr value was 40°C and 60°C for the same mastic

hot mix asphalt with fly ashes for dense graded surface layers of rural roads

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Additional procedures for characterizing the performance of recycled polymer modified asphalt mixtures

Great efforts have been made in recent years to improve the mechanical properties of asphalt mixtures by replacing conventional mix components with innovative ones or by adding materials such as polymers. Hence, the innovative-sustainable road materials to be investigated through laboratory tests require articulated procedures, the research here presented aims to provide an experimental-methodological approach to analyse the mechanical performance of untraditional hot asphalt mixtures made up using a polymer compound of recycled plastics. Three Asphalt Concrete 20 (AC20) Hot Asphalt Mixtures (HMA) were analysed by measuring base properties (i.e., indirect tensile strength and moisture damage) and advanced features (i.e., stiffness, fatigue, cracking and rutting resistance). As a result, the addition of polymer compound using dry process might lead firstly to change the laboratory mixing procedure than the traditional hot limestone asphalt solutions. The main benefits derived from the adoption of this innovative technology compared to the conventional ones are as follows: a) an improvement of resistance to moisture damage (at 15 ◦C); b) a suitable stiffness at 10, 20 and 40 ◦C; c) an increment of the cracking resistance (at 10 ◦C) and d) a good rutting resistance in terms of rut depth (at 60 ◦C)

Verifying the Mechanical Performance of Cold and Hot Asphalt Mastics Containing Jet Grouting Waste as a Filler

In the road construction sector, the CO2 emissions that affect global warming are, in most cases, from the asphalt mixtures production activities that are carried out at high temperature (above 160 °C). The research here presented aims to investigate the physical-mechanical properties of asphalt mastics made up using jet grouting waste (JW) as a filler produced through both cold (40–50 °C) and hot mixing process. The first step focused primarily on examining the effects of optimal blending time and curing time of the mastics. The second step focused on the investigation of the rheological properties using a dynamic shear rheometer and carrying out a frequency sweep test at temperatures ranging from 0 to 50 °C with increments of 10 °C, and a multiple stress creep and recovery (MSCR) test under 0.1 and 3.2 kPa load levels at temperatures of 40 and 50 °C. Four cold asphalt mastic solutions were analyzed and then compared to three hot traditional ones, keeping constant, on the one hand, the binder weight and filler over binder weight ratio (0.5), and, on the other hand, changing the type and amount of filler. The compositions of the hot and cold asphalt mastics were as follows: (a) 33% limestone filler (LF) plus 67% bitumen (concerning the cold mixing process, the bitumen content refers to the amount of bitumen into the bitumen emulsion), (b) 33% JW plus 67% bitumen, (c) 16.5% LF plus 16.5% JW and 67% bitumen. The fourth solution designed only for cold asphalt mastic was made up of 33% Portland cement (PC) plus 67% bitumen (referring to the amount of bitumen in the bitumen emulsion). The main findings showed that the optimal performance was achieved at high test temperature by cold and hot asphalt mastics made up adding LF and JW filler, which showed a pronounced elastic behavior. Moreover, the cold asphalt mastic solution made up of LF and JW filler showed better performance than the mastic made up using PC, reaching over 40% increase of the shear modulus and 30% lower non-recoverable creep compliance values at all test temperatures

BIM-LCA Integration Framework for Sustainable Road Pavement Maintenance Practices

The latest advancements in road asphalt materials and construction technologies have increased the difficulty for engineers to select the appropriate pavement design solution with consideration of life cycle assessment (LCA) methodology. On the other hand, infrastructure building information modeling (BIM) tools allow practitioners to efficiently store and manage large amounts of data, supporting decision making in road asphalt pavement design and management. This research contributes to setting up a dynamic LCA tool for the specific evaluation of designed road asphalt pavement solutions involving alternative materials and advanced recycling technologies; the tool is structured to minimize the need of input data by the designer, that are usually unknown during the early design stage, and automate the entire LCA calculation process to reduce the designer efforts and avoid any errors during data transcription. A traditional BIM workflow was integrated with additional user-defined property sets to simultaneously compute the environmental impact of the entire life cycle of the asphalt pavement, and dynamically update the result basing on the design thickness of the pavement layers, the specific features of materials and an external database of several life cycle impact category indicators that can be edited and updated gradually during more advanced design stage. The proposed BIM-LCA aims to be a practical and dynamic way to integrate environmental considerations into road pavement design, encouraging the use of digital tools in road industry and ultimately supporting a pavement maintenance decision-making process oriented toward circular economy

INDIRECT TENSILE STRENGTH METHOD FOR DEFINING A PROPER PRACTICE OF ASPHALT MIXTURES DESIGN

This paper shows the results of a laboratory investigation of indirect tensile strength test effects on bituminous mixtures characterization. In particular, the research focusses, in the first analysis, on the procedure of Marshall mix design, where 4 different mixtures of hot mix asphalt (HMA) were prepared at different bitumen contents between 3.5% and 4.25% by total aggregate weight at 0.25% increments. In the second phase, bituminous specimens made-up by gyratory compactor in compliance with Marshall optimization were tested to evaluate their indirect tensile strength. It was ascertained how the air voids percentage and indirect tensile strength can change by varying the number of revolutions during gyratory compaction and the height of specimens. A one-way ANOVA test was finally carried out to verify whether statistically significant differences exist in terms of mechanical properties when the number of revolutions and the specimen size change. This research may help to provide administrations with fast laboratory procedures to use in situ for all activities related to acceptance of mixtures