1,720,982 research outputs found
Laboratory mechanical characterisation of cold recycled mixtures produced with different RAP sources
No full textCold Recycled Mixtures (CRM) are composed of high amounts of Reclaimed Asphalt Pavement
(RAP) together with bitumen emulsion. As additional binder, some ordinary cement is
normally employed. Since RAP aggregates represents almost the entire solid structure, it is
important to fully characterise Cement-Bitumen Treated Materials (CBTM) produced with
different RAP materials. This work focuses the characterisation at small strain level, investigating
the stiffness modulus at three testing temperatures; at the failure point, measuring the
Indirect Tensile Strength; and studying the fracture behaviour, in Semi-Circular Bending Test
configuration. From the results, it is possible to confirm the influence of different RAP materials,
also characterised by different aggregates Nominal Maximum Size. As a consequence,
a reliable RAP classification can allow a better prediction of the final CBTM mechanical
properties
Influence of low production temperatures on compactability and mechanical properties of cold recycled mixtures
Full text linkIn cold regions, the production of Cement-Bitumen Treated Materials (CBTM) represents an issue in terms of annual time available for production. The objective of this research is to study the influence of different combinations of production temperatures for mixing, compacting and curing (developed in two steps) on the mechanical properties of CBTM produced with two sources of bitumen emulsion. Workability, compactability, indirect strength and other additional tests were involved in the analysis. Findings highlighted the critical effect of transportation and compaction temperatures on CBTM workability. Moreover, the emulsion source significantly affects the mixture strength when produced at low temperatures
Use of fine aggregate matrix to analyze the rheological behavior of cold recycled materials
Full text linkNowadays, one of the main challenges to a wider application of cold recycling techniques is the lack of reliable information on the mechanical behavior of cold recycled materials (CRM). In this context, measurement and modelling of the complex modulus of CRM mixtures may give an important contribution to the design and analysis of pavements including cold recycled layers. In this study, we analyzed the rheological behavior of CRM mixtures produced using bitumen emulsion and cement through the study of their fine aggregate matrix (FAM). Starting from a fixed CRM mixture composition, we compared different FAM mortars, focusing on the effect of water and air content. Then, we selected a composition as representative of the FAM in the mixture and investigated the evolution of both materials during a fixed curing period. Next, we measured the complex modulus of the CRM mixture and FAM at two curing stages and applied a rheological model to simulate and compare their behavior. Results showed that the properties of CRM mixtures are comparable to those of FAM mortars produced using all the binding agents (bitumen emulsion and cement) and a fraction of the voids contained in the mixture. Despite the huge difference in volumetric compositions, the FAM mortar controlled the curing and the thermo-rheological behavior of the CRM mixture, while the coarse reclaimed asphalt aggregate fraction and the voids mainly affected the asymptotic properties (equilibrium and glassy moduli) and the non-viscous dissipation component
Thermo-rheological modelling of cement-bitumen treated materials in the small strain domain
Full text linkCold recycled materials (CRM) have been introduced as structural materials in road pavement structures thanks to their significant economical and environmental benefits. Among them, cement-bitumen treated materials (CBTM) are often employed because of both contributions given by bitumen (in form of emulsion) and cement. The first confers a bituminous behaviour, whereas the second ensures good short-term performance otherwise penalized by the presence of water. Water plays a fundamental role in providing workability of the mixture at the atmospheric production temperatures. Due to such peculiarities, CBTM mixtures require attention when rheological modelling is performed in the small strain domain. This paper provides an overview on the most common rheological model applied to bituminous mixtures (2S2P1D) and the main issues related to the application to CBTM mixtures are highlighted. Afterwards, another model is proposed from the literature, the DBN model, and applied to three mixtures. The mixtures were prepared to assess the effect of the bitumen emulsion used, as well as the type of curing conditions. Results showed that the DBN model seems to be an excellent tool for not only CBTM rheological modelling in the small strain domain and it is recommended for applications in wider experimental programs
Visco-Elasto-Plastic Characterization in the Small Strain Domain of Cement Bitumen-Treated Materials Produced at Low Temperatures
No full textIn the framework of recycling techniques employed in maintenance and rehabilitation projects for the road industry, cement bitumen-treated materials (CBTMs) provide good performance as well as economic and environmental benefits. Because these materials are produced with bitumen emulsion at atmospheric temperature, the environmental factors during production are extremely important to guarantee the quality of the final product. This paper focuses on the stiffness of CBTMs produced and conditioned at low temperatures, and cured in two different conditions (sealed and unsealed). The mixtures were evaluated in terms of rheological properties using complex modulus (E*) tests performed 1 year after production. Results were modeled with an adapted version of the Di Benedetto-Neifar (DBN) model for plastic dissipation for small cycles (PDSC), accordingly called DBNPDSC. Results showed that the curing conditions, as well as the low production temperatures, significantly changed the rheological properties of the material. In fact, mixing or compacting the mixtures at 5°C compared with 25°C resulted in a loss in stiffness of around 30% in the small strain domain. This model is a good tool to describe, in the small strain domain, such material behavior, which shows plastic nonviscous phenomena
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Effect of RAP Source on Compactability and Behavior of Cold-Recycled Mixtures in the Small Strain Domain
No full textCold recycled materials (CRMs) are products of modern recycling techniques that are used in maintenance and rehabilitation of pavement structures with significant economical and environmental benefits. CRM mixes are produced at ambient temperature using bitumen emulsion or foamed bitumen as a binding agent, and the aggregate phase is composed mainly of reclaimed asphalt pavement (RAP). This paper investigated the compactability of two RAP sources and their effects on the behavior of CRM mixtures tested in the small strain domain. The compactability was studied using experimental results and the compressible packing model (CPM). Complex modulus tests of CRM mixtures were conducted, and the results were modeled using the Di Benedetto-Neifar (DBN) model. Findings showed that in CRM mixtures with the same gradation and formulation, one RAP source required almost half of the compaction energy of the other source to reach the design air voids content. The rheological analysis results highlighted the impact of the RAP source on the behavior of the CRM mixes in the small strain domain
Effect of gradation on volumetric and mechanical properties of cold recycled mixtures (CRM)
No full textIn recent times, recycling using cold bituminous mixtures has become one of the most interesting techniques in pavement engineering from sustainability aspect. This study focuses on the clarification of the steps concerned with the cold mixture mix design to determine the initial aggregate gradation of the mixture. The study has been developed involving procedures followed in Canada and Italy. In both the cases, three different gradations, normally employed in the production of traditional bituminous mixtures, were compared. The effect conferred by the gradation type has been studied in terms of workability, compactability and mechanical properties. Results show that in both the procedures the gradation influenced the workability and the compaction behaviour of the mixtures studied. At the same time, in terms of mechanical properties, the gradation influenced the strength of the final mixture in only one of the procedures applied
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