Effect of RAP on the properties of recycled asphalt mixtures based on bitumen foam

Recycling asphalt pavements through cold and hot methods is an effective solution for repairing, enhancing, or reconstructing pavements. In simple terms, recycling involves the reuse of existing pavement materials that have reached the end of their service or design life. Over the past two decades, increased awareness of environmental issues, depletion of high-quality stone resources, growing traffic volumes, and the challenges, including inefficiencies, of traditional repair and improvement methods have prompted road construction authorities to leverage the potential of existing pavement materials and employ more effective rehabilitation strategies. Among the available solutions, cold recycling stands out as an attractive option due to its environmental and economic advantages. With advancements in machinery, this method can efficiently modify and reuse surface layers of materials in a single step, without damaging the underlying substrate and maintaining its structural integrity. The introduction of bitumen foam as a stabilizing agent marks a new approach in cold recycling. Bitumen foam can be mixed in situ with various materials, such as new high-quality aggregates, recycled materials, and even sandy soils with significant plasticity, thereby addressing some challenges faced by contractors when using other stabilizers.In situ cold recycling of worn asphalt surfaces utilizing bitumen foam has recently emerged as a highly effective method for pavement improvement and repair, replacing traditional techniques. During this process, the worn asphalt material is commonly milled to an appropriate depth and blended with base materials. Simultaneously, fresh bitumen is introduced in a manner distinct from conventional practices, applying it in the form of expanded, or “foamed,” bitumen. In certain cases, additives like cement or lime are also employed to enhance the quality of the recycled layer. Ultimately, this research suggests that using RAP materials, considering their superior quality, favorable design outcomes such as reduced bitumen consumption, better uniformity in the gradation of the recycled mixture, and an appropriate filler amount, is advantageous in light of the overall project implementation costs.

کلیدواژه ها:

Cold recycling ، RAP ، bitumen foam