Impact of binder on properties of foamed bituminous mixtures

Foamed bitumen technology is gaining acceptance across the world as an approach towards sustainable road construction. This technology offers advantages in terms of reduced energy consumption, materials recycling and reduced bitumen requirement. The properties of foamed bitumen mixtures depend on various factors, including the properties of the constituent materials and production conditions. This paper concentrates on the influence of the properties of the binder on the foaming characteristics of bitumen and the properties of foamed bitumen mixtures. Initially, four binders of different grades were evaluated for physical properties and foaming characteristics. The optimum foam content was then used to prepare foamed bituminous mixtures containing recycled asphalt pavement. These mixtures were evaluated for their mechanical properties, including indirect tensile strength, retained tensile strength and resilient modulus. The results from this laboratory study indicate that the properties of foamed bitumen and foamed mixtures are significantly influenced by the physical properties of the binder used, the quantity of binder and the recycled asphalt content. For a particular binder content in the mixture, use of a higher viscosity grade binder resulted in higher indirect tensile strength. A higher recycled asphalt pavement content in the mixture also resulted in higher indirect tensile strength. For all binder grades, a larger resilient modulus was observed for binder content the range of 2·3–2·5%.