Development of Bitumen Selection Criteria for Cold Recycled Bituminous Mixes with Foamed Bitumen

The objective of the present study was to develop bitumen selection criteria for cold recycled bituminous mixes (CRBMs) with foamed bitumen. The criteria were developed by investigating the influence of various factors, such as physical properties of bitumen (specifically viscosity), foam characteristics, and their interaction effect on the performance of CRBMs in terms of moisture damage resistance. CRBMs were prepared using three different types of bitumen and 70% reclaimed asphalt pavement (RAP) content. All compacted and cured CRBMs were tested for moisture damage resistance using the indirect tensile strength (ITS) test before and after conditioning. The test results demonstrated that the physical properties of bitumen significantly affected the moisture damage resistance of CRBMs. The characteristics of the foamed bitumen and its interaction with the physical properties of bitumen were found to be equally influential. Based on these findings, the study recommends that the selection of bitumen for CRBMs should consider both the physical properties of the bitumen and the characteristics of the foamed bitumen. A strong positive correlation was observed between the product of the foam expansion ratio (ERm) and bitumen viscosity (viscosity at 60 degrees C x ERm), and the moisture damage resistance of CRBMs, specifically in terms of the wet indirect tensile strength (ITS-wet). Consequently, it is suggested that the product of ERm and bitumen viscosity can serve as a bitumen selection parameter for CRBMs, where a higher value of the product indicates a more suitable choice of bitumen.