4 research outputs found
Microstructural self-healing of bituminous materials: Combined experimental and numerical study
Bituminous materials form a class of materials that possess the intrinsic ability to selfheal. This self-healing capability is evidenced by the observation that the service life of these materials ‘in the field’ exceeds the service life as predicted by standard mechanical laboratory tests. This mismatch between laboratory prediction and field service life is usually accounted for by applying a shift or healing factor. In this contribution we demonstrate a model that is based on the observation that bitumen possesses a microstructure on the micrometre length scale, as can be observed by atomic force microscopy (AFM). On this scale bitumen can be regarded as a two-phase material, where the phases have a distinct stiffness. . One of the phases has a very typical appearance and is often referred to as ‘bee-phase’ [1-3]. The interface between the phases can be regarded as a manifold that is defined by stiffness gradient in the material. From mechanical considerations damage will initiate within this manifold. Modest variations in thermodynamic conditions (thus without melting the material) will already lead to rearrangement of phases, and a new damage initiation manifold, meanwhile the accumulated damage is erased. Starting from two experimental microstructural arrangements, one before and one after phase rearrangement, a finite element mesh is produced. For both phases a viscoelastic constitutive model is implemented. The interface manifold is treated equally, but is allowed to acquire damage, as are the other phases, to a lesser extent. In this way, using experimental observations as a starting point, it is demonstrated that the effect of healing in bituminous materials can be treated micromechanically, and leads to quantitative results. This opens the way to quantify the healing potential of a bituminous material upon its microstructure. Optimal manifolds to accommodate the healing behaviour can then be derived. The experimental challenge will be to engineer the interface manifold in accordance with the desired healing potential of the material.Structural EngineeringCivil Engineering and Geoscience
Effect of using of reclaimed asphalt and/or lower temperature asphalt on the availability of the road network
There is a need for a method for assessing the results from changes in the potential durability of road materials due to the inclusion of reclaimed and secondary component materials in the manufacture of new road materials. Such changes will have an effect on the cost of the construction maintenance, both financially to the client and environmentally to society in general, and any savings may be transitory. A site trial has been laid of mixtures with and without reclaimed asphalt and work started to assess their durability from early-life properties. The trials are being monitored for their initial performance whilstlaboratory trials are concentrating on the combined effect of ageing and moisture damage on the performance of asphalt mixtures on the trial. All three strands are being used to develop life-cycle analysis models to customise them for the effect of using alternative component materials on the availability of the network and their overall financial and environmental cost, both initial and whole-life. The costs will be identified as being direct (of the construction and maintenance) and indirect (on society in general, such as congestion).Structural EngineeringCivil Engineering and Geoscience
Effects of reclaimed asphalt and warm mix asphalt on the availability of the road network
This repot reviews the EARN project, which was undertaken under CEDR Call2012 in order to investigate the effects of using reclaimed asphalt (RA) and/or lower temperature asphalt on the road network. The work consisted of a review of existing data on service lifetime and availability of road materials and structures, a site trial to evaluate varying proportions of RA, experimental evaluation of moisture damage and ageing in asphalt mixtures and development of an impact assessment model. The site trial involved four different mixtures containing varying proportions of RA and warm mix additive and was monitored for international roughness index, mean profile depth, corrected SCRIM Coefficient, indirect stiffness modulus, water sensitivity and indirect tensile strength, the latter with and without artificial ageing. The monitoring was extended to 40 months with two extensions to the project, when monitoring of the binder mechanical and other properties were also made.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Pavement Engineerin
Effect of using of reclaimed asphalt and/or lower temperature asphalt on the availability of the road network
The use of reclaimed asphalt, secondary component materials and/or additives and lower temperature asphalt are being increasingly used in order to improve the sustainability of asphalt production. The use of reclaimed asphalt reduces the need for virgin materials whilst lower temperature asphalts have reduced CO2 emissions, increased sustainability, improved working conditions for construction and maintenance crews, reduced noise level on the work sites, extended paving season and provided financial benefits from lower production and transport costs. However, there is uncertainty about the ageing and durability performance of these technologies because there is limited information available on their long-term performance. Changes in durability will affect the availability of the road network for highway authorities. CEDR commissioned a European project to assess these uncertainties. A site trial was commissioned on one of the Irelands busiest motorways (M3), comprising stone mastic asphalt mixtures containing varying proportions of the reclaimed asphalt with some using warm mix technology. The site has been monitored regularly over a full calendar year for the material performance. A suite of laboratory tests have been undertaken concentrating on the combined effect of ageing and moisture damage on the performance of asphalt mixtures on the site trial. The findings have been used to develop life-cycle analysis models to customise them for the effect of using alternative component materials on the availability of the network and their overall financial and environmental cost, both initial and whole-life. The costs identified are both direct (of the construction and maintenance) and indirect (on society in general, such as congestion). The paper describes the model and the assurance that can be given to the assumptions made within the model from the research findings. Comparative sensibility studies are included.Structural EngineeringCivil Engineering and Geoscience