Chemical and Foaming Analysis on Cold Mix Asphalt Performance with Recycled Asphalt Pavement

Cold-mix asphalt has been developed in recent years by combining foamed asphalt and recycled asphalt pavement (RAP). However, manufacturers struggled due to the less standardized specification. Foaming and mixing performance cannot be accurately controlled and are usually treated with a foaming agent (FA). This research focused on the relationship between the chemical composition of bitumen and its foaming properties. Three groups of AC-20 bitumen and organo-modified siloxanes based FA with water content of 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0% and 4.5%. were analyzed. Chemical components of different bitumen types were evaluated using the Gaestel colloidal index (CI). The half-life (HL), expansion ratio (ER), Foam index (FI), and bubble surface area index (SAI) were used to evaluate the workability of the binders and discuss the effects of the values on the performance of the mixture. The CI observation revealed that FA obviously changed the saturates value and greatly improved the foam properties in terms of stability and expansion. FI change was found to be 71% of the change in the CI. Similarly, the resulting FI and SAI reach up to 88% in terms of correlation.