![]() Hereafter, the reclaimed and wasted asphalt will be indicated as RAP, although both acronyms are widely used. In other countries, notably in the USA and Australia, the removed asphalt materials for road pavements are known as Reclaimed Asphalt Pavement (RAP) to differentiate it from other reclaimed materials that incorporate bituminous binder, e.g. In detail, the EN 13108-8 standard defines the Reclaimed Asphalt (RA) as the processed material in the form of milled or the ripped up slabs from existing bituminous road layers and the asphalt mixtures from surplus, rejected or failed productions. Generally, standards and guidelines that regulate the handling and the inclusion of the waste asphalt material in other bituminous products consider both origins. The wasted asphalt mixtures during the start-up, transition between mixes and clean-out operations together with the rejected mix from a project have to be accounted for in the total amount of recyclable bituminous materials, adding it to the major quantity of the removed asphalt concrete from existing pavements. Nevertheless, the use of removed asphalt concrete has to be evaluated also from a cost efficiency perspective, since it significantly reduces the overall costs of new bituminous products. The encouragement of its use reflects the worldwide trend to face the existing environmental issues by trying to increase the efficient use of resources and reduce carbon emission. The recycle and/or the re-use of removed bituminous mixture is an example of the sustainable development in the infrastructures sector. Indeed, some studies have revealed the possible multi-recycling aspect of the removed asphalt concrete, that is, the capacity of the material in being treated with multiple recycling processes without losing its properties and performing some valorisation actions when required. Eventually, the downgrading of the removed bituminous mixture into a lower value product (i.e., aggregates for unbound layer) may be appropriate after several re-uses and recycling processes. The value of removed asphalt concrete is maximized by re-using it in the same engineering applications at the top of the recycling hierarchy and not in being down-cycled as simple aggregates. However, the latter option does not exploit the full potential of the material as the former does, since it ignores the aged bituminous binder that coats the recycled aggregates. of aged bituminous binder, it can be re-used in new asphalt mixtures, reducing the demand for virgin aggregates and bitumen, or as recycled aggregates to produce unbound layers of pavements. Since it consists of valuable non-renewable resources, i.e., approximately 95% wt. The asphalt concrete removed from an existing road pavement is a fully recyclable material for construction. The economic and environmental benefits are also discussed. This manuscript aims to summarize the state-of-the-art of use of RAP aggregates in new asphalt mixtures. The amount of RAP in asphalt concretes can be significantly increased by applying good management practices of the RAP, either processed or not, as well as novel production technologies and advanced mix design approaches. However, the common practices of many countries still limit the RAP content to a 15–20% wt., on average, in the recycled asphalt mixes. Several studies have revealed positive responses of the recycled asphalt mixtures with high or very high content of RAP. ![]() of RAP were used in USA and Europe, respectively, as aggregates for Hot, Warm and Cold Asphalt Mixtures and for unbound layers. The RAP material represents one of the most re-used construction products worldwide in 2018, approximately 88% wt. ![]() Therefore, the use of RAP for the production of new asphalt formulations at the top of the recycling hierarchy is preferable instead of being down-cycled in low-value applications. Thanks to the use of RAP material in new asphalt products, the USA saved 4.1 million tons of virgin binder and 78 million tons of virgin aggregates in 2018. Being composed of two valuable non-renewable resources, i.e., aggregates and bituminous binder, its conscious use can ensure the sustainability of asphalt pavement construction. Reclaimed Asphalt Pavement (RAP) material mainly consists of removed asphalt concretes from existing infrastructures and, to a minor extent, of wasted or rejected mixes during the production processes. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |