Investigation of Foamed Bitumen Mixes Using Reclaimed Asphalt Pavement Materials for Cold Recycling Technology

Utilization of reclaimed asphalt pavement (RAP) in road construction has become a common practice worldwide. This is in-line with the global objective of sustainable development aimed at lowering the consumption of dwindling sources of virgin aggregates and coming up with viable solutions to deal with RAP materials generated from highway rehabilitation projects. In the present study, an investigation of the laboratory performance of foamed bitumen stabilized material mixes for use in base courses was conducted. A suitable laboratory mix design was developed to evaluate the effect of different proportions of bitumen and Portland cement on properties of cold RAP materials. Cement content was varied at percentages of 0.5, 0.75, and 1.0% while bitumen content was varied at percentages of 1.75, 2.0, and 2.5%. Also, mixes utilizing typical bituminous surfacing materials encountered on paved road networks during road rehabilitation were assessed. RAP materials from pavements comprising thick layers of asphalt concrete and thin layers of surface dressing as well as unbound crushed aggregate made from fresh quarried rock often used for road bases were considered. Optimal values of 1.0% and 2.5% for cement and bitumen contents, respectively, were determined and used to come up with mixes which incorporated different surfacing materials. Mixes developed were analyzed for mechanical properties of indirect tensile strength (soaked and unsoaked), indirect tensile fatigue, elastic modulus and rutting. RAP materials from thin layers of surface dressing were determined as the best performing surfacing material for cold foamed in-place pavement recycling technology.