Effect of crumb rubber gradation on a rubberized cold recycled mixture for road pavements

a r t i c l e i n f o Cold recycling technique represents the most environmental friendly solution for pavement rehabilitation nowadays. In fact, this technique allows the use of the highest percentage of reclaimed asphalt avoiding the energy consumption related to aggregates heating required by the traditional hot mix asphalt design. The mix design represents a key phase of the cold mix production. The study of workability and compactability properties combined with a deep laboratory investigation is required. The idea of introducing crumb rubber in the cold mixtures was developed based on the concept of maximizing the valorization of recycled materials together with the goal of achieving high performance. In the present research project, two different gradations of crumb rubber, processed with the traditional grading method, have been adopted for the production of a cold recycled mixture stabilized with bitumen emulsion and cement. The spring-back effects of the rubber particles, which occur after compaction, together with the Indirect Tensile Strength and the Indirect Tensile Stiffness Modulus have been studied. The results show that the gradation of the adopted crumb rubber sensibly affects the compaction and mechanical properties of the cold recycled mixture. The public, industry and governments recently raised their interests in green design and engineering in order to achieve and guaranty better environmental quality and sustainable development. Pavements construction is one of the largest consumers of natural resources [1] but their environmental loading can be sensibly reduced if recycled materials are incorporated in both new and maintenance road project [2]. In Europe and the United States [3], recycled materials used in construction are normally classified as industrial by-products, such as steel slag and coal fly ash; road by-products, such as reclaimed concrete pavement materials and reclaimed asphalt pavement materials; or demolition by-products, such as crushed concrete, tiles, and bricks [4]. Most of these material groups can be valorized during pavement construction and rehabilitation. At the present time, the use of reclaimed asphalt with the cold recycling technique represents one of the primary ways to rehabilitate pavements, toward a sustainable development, that combines the reduction in virgin aggregates and energy consumption. In 2008 the importance of asphalt recycling was supported by the EU Waste Framework Directive 2008/98/EC, where a recycling target of 70% for non-hazardous construction and demolition waste (that includes asphalt waste) was defined to be achieved by 2020 [5]. The cold recycling technique is the …