PERFORMANCE EVALUATION OF SUSTAINABLE RECYCLED BASE USING RAP MATERIAL

Abstract

Recycled materials are being investigated as a potential solution for road construction as individuals around the globe become more mindful of the need for sustainable infrastructure in recent years. The focus of this research is driven by the pressing sustainability concerns related to pavement materials and mix design. The practice of utilizing recycled materials (RM) in pavement construction has garnered significant attention due to its eco-friendly nature and eliminating the need for natural aggregate (NA), particularly in the context of flexible (bituminous) pavements. One effective approach involves integrating substantial quantities of Reclaimed Asphalt Pavement (RAP) material into the base and sub-base layers during pavement construction or rehabilitation process due to its increased percentage (up to 100) and ease of construction technology used. Numerous studies have consistently demonstrated the feasibility of reusing RAP as an aggregate in Hot Mix Asphalt (HMA), but there is a restriction of using only up to 50% RAP material in the Indian context (MoRTH-2013). Cold recycling technology, much like hot mix technology, has gained popularity across various countries for effectively rehabilitating damaged bituminous pavements. RAP, stabilized with bitumen emulsion and foamed bitumen, has proven a viable option as a base layer in these applications. However, the problem with the foamed bitumen is to maintain the temperature of bitumen between 160°C-180°C for preparing foamed bitumen. That is why the current study focussed on exploring the potential advantage of using bitumen emulsion instead of foamed bitumen due to it’s ease of handling and environment-friendly behavior. Sustainable recycled base using RAP material is also possible by constructing a cement-treated base (CTB) layer. Hence, the current study also explored the potential of using the RAP material for CTB mixes. Moreover, both the CTB and ETB layer can be constructed and re-constructed at the site only by using the latest techniques of road recyclers, which are capable of pulverizing the existing base or sub-base up to the desired depth precisely and also capable of mixing the cement, cement stabilizer, additives, waste material which are pre-spreaded on the existing damaged layer by homogenously mixing the existing RAP material. The function of the cement, cement stabilizer, fiber, liquid anti-stripping additive and waste material is explored and it is expected to strengthen the existing base layer by using very little or no new aggregate, depending upon the gradation of the existing pavement layer. The widespread belief among experts, and practitioners is that this technique is poised to have a crucial impact on pavement maintenance and rehabilitation in the forthcoming period. This thesis focuses on the performance evaluation of sustainable recycled base using reclaimed asphalt pavement (RAP) material in cement treated base (CTB) and bitumen emulsion-treated base (ETB) layers. The aim of the study is to maximize the use of RAP material in these layers, as dumping such large amounts of RAP material is not environmentally friendly. However, it is difficult to use 100% RAP material in the top/surface layer of pavements due to the practical limitations of using RAP material due to the change in it’s properties.