نوع مقاله : پژوهشی اصیل (کامل)
کلیدواژهها
موضوعات
عنوان مقاله English
نویسنده English
Pavement distresses are the major concern in asphalt pavement industry. Permanent deformation is one of the most common types of pavement distresses. This kind of distress which is caused by repeated traffic loading at high temperatures appears mainly in upper layers of asphalt pavements in form of longitudinal depressions in wheel paths and small changes on the sides of the wheel paths. This phenomena not only leads to pavement structural failure, but it results in reduced service life of pavements and affects safety of road users. Over the past decades, pavement researchers have taken different approaches to improve rheological properties of bitumen and promote performance of asphalt mixtures. Application of additives such as Crumb Rubber (CR) in asphalt layers is one of the most economic approaches that results also is reduced environmental pollution. Crumb Rubber has been experienced in asphalt mixtures as an effective modifier for several decades. Despite numerous advantages of the application of crumb rubber in asphalt mixtures, there is still no extensive use of it in road pavements worldwide. This might be related to problems such as increased production cost of Crumb Rubber Modified (CRM) mixes, early aging due to high temperature at mixing and laying down faces and eventual coagulation of rubber particles in mixes, as well as phase separation of the CRM modified binder. In order to overcome the above mentioned negative issue, one of the latest methods of CRM modified mix Production is the application of Processed Crumb Rubber (PCR) instead of the application of commonly methods of wet processing. This type of crumb rubber is a combination of fine rubber powder, soft bitumen, minerals and hydrated lime, which are mixed in a short time processing. Processed crumb rubber can easily be added to asphalt mixes in dry mode mixing and improves performance of asphalt mixes. Lower Processed crumb rubber -Bitumen mixing time reduces problems of coagulation of rubber particles and have several advantages. Due to the fact that the Processed Crumb Rubber approach is relatively new, it is necessary to carry out comprehensive laboratory research works in order to evaluate characteristics of bitumen and performance of asphalt mixtures. In this research, rutting resistance of Crumb Rubber and Processed Crumb Rubber modified asphalt mixtures of a dense and a gap graded mix was evaluated. With this regard, Marshall Mix Design was modified in order to use the Processed Crumb Rubber in dry method. Hamburg Wheel-Track and repeated axial load tests were carried out to investigate rutting resistance of the modified mixes. Hamburg Wheel-Track test was performed in dry and saturated conditions and repeated axial load was assessed under stresses of 150 kPa and 300 kPa. The results were compared on samples containing conventional bitumen and wet processed crumb rubber. Although, the results showed that using both crumb rubber additives increased resistance of mixes against rutting, samples contains 25% Processed Crumb Rubber showed the highest resistance against permanent deformation. Moreover, application of Processed Crumb Rubber in stone mastic asphalt mixes showed superior performance against permanent deformation due to better stone to stone contact and higher amounts of Processed Crumb Rubber bitumen in mixes.
کلیدواژهها English
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