Search results for "Strade"
showing 10 items of 396 documents
A simple interpretation of the effect of the polymer type on the properties of PMBs for road paving applications
2018
Abstract 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…
An automated procedure for computing the packing properties of dense and locked sands by image analysis of thin sections
2014
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 us…
Performance of asphalt mixes with high recycling rates for wearing layers
2016
The corresponding paper presents selected results of a research on the feasibility of going toward 100% recycling of asphalt pavements into surface courses through an increasing percentage of RA within the mixes. The research is carried out within a two-year CEDR Transnational Road Research project, AllBack2Pave, led by the Technische Universitaet Dresden (Germany), together with the University of Nottingham (UK) and the University of Palermo (Italy), and finalised in January 2016. The main objectives of the project are - to establish, through laboratory tests on binders and asphalt mixes, whether the use of high rates of RA is feasible in developing mixes with high level of durability, and…
Linear and nonlinear fractional hereditary constitutive laws of asphalt mixtures
2016
The aim of this paper is to propose a fractional viscoelastic and viscoplastic model of asphalt mixtures using experimental data of several tests such as creep and creep recovery performed at different temperatures and at different stress levels. From a best fitting procedure it is shown that both the creep one and recovery curve follow a power law model. It is shown that the suitable model for asphalt mixtures is a dashpot and a fractional element arranged in series. The proposed model is also available outside of the linear domain but in this case the parameters of the model depend on the stress level.
Influence of bio-based additives on RAP clustering and asphalt binder rheology
2017
The use of high Reclaimed Asphalt Pavement (RAP) content in Hot Mix Asphalt (HMA) allows developing innovative materials for the construction and/or rehabilitation of sustainable infrastructures. The chemo-physical phenomena occurring during production of HMA containing high RAP content should be investigated and considered for the mix design optimization. In fact, when additives are used as rejuvenators of the aged bitumen, these phenomena can be affected causing significant variations in the mixture characteristics. This paper aims at studying the influence of two bio-based additives specifically on RAP clustering, phenomena which can significantly affect the performance of high-content R…
Experimental validation of a fractional model for creep/recovery testing of asphalt mixtures
2012
Abstract 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 in…
Quality control of manufacturing and hot storage of crumb rubber modified binders
2020
The ultimate performance of crumb rubber modified (CRM) binders is linked to the accurate control of the properties during manufacturing and hot storage. However, due to their complexity, asphalt technologists find the characterisation of these materials still challenging. In this study, the adoption of a Dual Helical Ribbon (DHR), a novel mixing/measuring device for rotational viscometers, is proposed for the real-time monitoring of CRM binders during manufacturing and hot storage. According to the laboratory results, manufacturing periods of 45-60 min at 195 degrees, as well as storage temperatures not exceeding 150 degrees C, are recommended for this type of modified binders. (C) 2019 El…
Laboratory mix design of asphalt mixture containing reclaimed material
2014
This paper presents a study on the production of asphalt test specimens in the laboratory containing reclaimed asphalt. The mixtures considered were stone mastic asphalt concrete mixtures containing up to 30% of reclaimed asphalt. Specimens were compacted to the reference density obtained from the Marshall mix design. Gyration compaction method was used for preparing specimens for the experimental programme, while coring and cutting methods and X-ray computed tomography (CT) were used to investigate the change in properties within the specimens and to validate the selected methodology. The study concluded that gyratory compaction is suitable to produce homogeneous test specimens also for mi…
Effect of mixing time on reclaimed asphalt mixtures: An investigation by means of imaging techniques
2015
This paper presents an application of imaging techniques to investigate the distribution of reclaimed asphalt and air voids within gyratory compacted specimen. Stone Mastic Asphalt specimens containing reclaimed asphalt, were produced at five different laboratories participating in the collaborative project Re-Road: University of Nottingham, Belgium Road Research Centre, Danish Road Directorate, TU Braunschweig and Laboratoire Centrale de Ponts et Chaussees (now IFSTTAR). This study applies the X-ray Computed Tomography and Optical Microscopy techniques to view the internal structure of the specimen with particular focus on the air voids and reclaimed asphalt distributions within the specim…
Tyre rubber-modified bitumens development: the effect of varying processing conditions
2013
Tyre rubber-modified binders (TR-MBs), produced through McDonald’s wet process and used worldwide (e.g. asphalt rubber), have been demonstrated to provide various benefits to pavements and, moreover, they represent a good opportunity for recycling tyre rubber (TR). However, this technology is still struggling to be fully adopted in Europe, mainly because of their poor stability during high temperatures storage, which leads to high initial costs in modifying existing asphalt plants. Storage stable TR-MBs are proving to be a great option and their development could be the key to spread the recycling of TR within paving applications in Europe. This paper aims to enrich this field of research b…