1,721,016 research outputs found
Advanced testing on theoretical evaluation of bituminous mixtures for flexible pavements
No full textMechanical behaviour of cement-bitumen treated materials containing different amounts of reclaimed asphalt
No full textCold recycling techniques have become one of the main sustainable solutions in road construction and maintenance. The use of reclaimed asphalt (RA) as a constituent material for bound mixtures offers two main advantages: it eliminates problems concerning disposal and it allows natural resources to be preserved. Among the most widespread recycled mixtures, the use of cement–bitumen-treated materials (CBTM) for subbase courses has rapidly increased over the last 10 years. This paper deals with the influence of RA content on the mechanical characteristics of CBTM. Several mixtures were produced by combining different dosages of binders (cement and bituminous emulsion) and RA contents. The behaviour of recycled mixtures was evaluated and compared in terms of indirect tensile strength, water sensitivity and stiffness modulus. In addition, the effects of temperature on the stiffness properties were investigated. Experimental results showed that the RA content did not significantly affect the compactability and the strength properties of CBTM. The presence of RA determined an increase in mix deformability and thermodependence, but the effect can be inhibited by increasing cement dosage. The findings offer good prospects for increasing the use of RA and encourage administrations to employ this material as an effective construction solution
Effect of ageing process on bitumen and rejuvenated bitumen
Full text linkIn the last few decades, highway agencies and the paving companies have invested huge efforts on increasing the amount of reclaimed asphalt (RA) to be introduced in the production of new asphalt concrete (AC). This technique, so-called hot recycling of RA, offers several economical and environmental advantages tightly related to the replacing of natural materials, such as aggregates and bitumen, with recycled one. Indeed, the hot recycling of RA implies a reduction of the virgin aggregate and bitumen supply to produce AC. Additionally, hot recycling allows decreasing the amount of RA disposal. However, when a high amount of RA is hot recycled, the mechanical properties of aged bitumen must be considered for an appropriate mix design. In this case, recycling additives are used to achieve good mechanical performance.
This paper deals with the effect of ageing and of a specific rejuvenator on mechanical properties of a paving grade bitumen. Moreover, the effect of ageing on mechanical properties of the rejuvenated bitumen is investigated. The results showed that the stiffening effect of ageing can be reduced or restored by the use of the rejuvenator. In addition, the ageing process affects the rejuvenated bitumen as well as it does for paving grade bitumen
Mechanical behaviour of cement-bitumen treated materials containing different amounts of reclaimed asphalt
No full textCold recycling techniques have become one of the main sustainable solutions in road construction and maintenance. The use of reclaimed asphalt (RA) as a constituent material for bound mixtures offers two main advantages: it eliminates problems concerning disposal and it allows natural resources to be preserved. Among the most widespread recycled mixtures, the use of cement–bitumen-treated materials (CBTM) for subbase courses has rapidly increased over the last 10 years. This paper deals with the influence of RA content on the mechanical characteristics of CBTM. Several mixtures were produced by combining different dosages of binders (cement and bituminous emulsion) and RA contents. The behaviour of recycled mixtures was evaluated and compared in terms of indirect tensile strength, water sensitivity and stiffness modulus. In addition, the effects of temperature on the stiffness properties were investigated. Experimental results showed that the RA content did not significantly affect the compactability and the strength properties of CBTM. The presence of RA determined an increase in mix deformability and thermodependence, but the effect can be inhibited by increasing cement dosage. The findings offer good prospects for increasing the use of RA and encourage administrations to employ this material as an effective construction solution
Eco-sustainable solutions for the maintenance of the road pavements in the Republic of San Marino
No full textIn the last decade, climatic changes have caused intense natural phenomena such as heavy precipitations, dry and hot weather, river flood waves, sea level increase and fluctuations that impact on the social life, significantly. All over the world, governments are now asked to stimulate and to adopt new tools to preserve natural resources and to reduce atmospheric pollutions. Therefore, new complex aspects have to be considered also in management and maintenance of road network matching policies, investment strategies and engineered solutions. Since 2016, the San Marino state-owned enterprises for public works (Azienda Autonoma di Stato per i Lavori Pubblici) and for public utilities (Azienda Autonoma di Stato per i Servizi Pubblici), in collaboration with the University of the Republic of San Marino, have gradually introduced eco-sustainable techniques for the maintenance of road pavements and utility trenches, involving local construction enterprises and mix plants. This paper describes the approach and the specifications for eco-sustainable road materials such as cold and hot recycled asphalt concrete, cement treated recycled materials and cold surface treatments. These materials are used in San Marino for road pavements and in the utility trenching
Strato in misto cementato per pavimentazioni stradali
No full textImpiego di materiali fibrati per la realizzazione dei sottofondi stradali, allo scopo di ridurre la manutenzione
Pavement management system for local governments: case study in the Republic of San Marino
No full textLocal governments manage large and heterogeneous road networks with limited budgets, human resources and often they cannot easily access or apply technology and methodologic innovations. For these reasons local governments need a tailored pavement management system (PMS) to plan activities, investments and to achieve efficient solution in a multi-year prospective. The PMS must identify a rational and cost-effective maintenance planning through a systematic process that considers technical, economical, social and environmental impacts. Tools and procedures have to be specifically determined taking into consideration the real potentialities of the local governments.
The adopted PMS in the Republic of San Marino has been based on a tight coordination among national institutions and stakeholders operating in the territory. This paper shows the principles, procedures and tools developed and used in the Republic of San Marino
Characterization of Water Sensitivity of Asphalt Mixtures with Coaxial Shear Test
No full textThe CoAxial Shear Test (CAST) performs fatigue test under simultaneous action of dynamic loading, temperature cycles and water, and modulus test on wet or dry specimen. Both a dense graded and an open graded mixture were studied at different air void content. The water sensitivity of both mixtures was determined by comparing fatigue performance of dry and wet tests. Additionally, the effects of water action, temperature and loading cycles were also investigated by comparison of modulus test before (undamaged specimen) and after (damaged specimen) each fatigue test. The introduced Water Sensitivity Index for fatigue test confirms that water damage in asphalt pavements is considerably related to air voids. Finally, the modulus test analysis allowed explaining also the different consequences of environmental factors on viscoelastic properties of asphalt mixtures by using the Standard Linear Solid model. © 2008 Lavoisier
Recycling Techniques and Environmental Issues relating to the Widening of an High Traffic Volume Italian Motorway
No full textOn the last few decades, the use of recycled materials has become important because of the limited availability of good aggregates and the difficulties and excessive disposal costs for milled materials. This study provides an environmental evaluation of a specific rehabilitation project involving several recycling techniques on one of the main Italian motorways. Three rehabilitation options are evaluated and compared in terms of their environmental impact, with particular emphasis on the construction of the subbase course. In the end, the definitive design involved different recycling techniques, including cold in-place recycling (CIPR) with bituminous emulsion and cement for the subbase layer, stabilization of the soil with lime for the embankment, the use of reclaimed asphalt in the production of hot mix asphalt, and the use of crushed cement concrete for the cement treated layers. All of these recycling methods allow the saving of the virgin aggregates, and a reduction in materials transportation and pollutant emissions coming from both the production plant and the means of transport
Flow analysis during Resin Transfer Molding of thick structures
No full textThe Resin Transfer Molding (RTM) process is widely investigated as a powerful method to fabricate aerospace structure. So far RTM
applications concern thin laminates and very little work on thick composites can be found in the literature.
Nevertheless, an investigation of thick composites is necessary in order to extend the RTM advantages to primary structure. To
achieve fast, repeatable and reliable process one needs to acquire some predictive modeling capability to simulate the resin flow within the mold during the injection. This capability is
readily available for RTM process modeling, but it has to be extended to the fabrication of thick structures. We present experimental and numerical studies to determine a corrective factor of the preform permeability to take into account the effects of the transverse resin flow through the thickness in 2-D simulations. Numerical studies were compared with experimental cases
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