Investigation on the drying and demulsification process of filler–bitumen emulsion paste

The drying and demulsification of bitumen emulsion largely dominate the development of the mechanical properties of emulsion-based mixtures. However, the demulsifying of bitumen emulsion with the effect of filler is seldom studied from the aspect of drying. The emulsion drying and film formation mechanism is employed to study the drying process of filler–bitumen emulsion paste with thin layer. Based on the drying process, the demulsifying effect of bitumen emulsion with the effect of filler is quantificationally studied. The drying process of filler–bitumen emulsion paste can be accurately divided into three stages by the gravimetric and electrical methods. The key parameters of drying process, including the particle volume fraction of the initial unstabilized state, the continuous film state, and the fast coalesced state (ϕcrit1, ϕcrit2 and ϕm), are calculated to reveal the drying and demulsification process of filler–bitumen emulsion paste. Results show that the addition of cement mainly reduces the evaporation rate of the second stage compared to limestone powder, especially for the period when bitumen emulsion is from the initial unstabilized state to the fast coalesced state. This phenomenon is attributed to that the demulsifying effect of bitumen emulsion can reduce the evaporation rate of filler–bitumen emulsion paste. Besides, compared to the effect of limestone powder, bitumen droplets are more quickly coalesced with the effect of cement when bitumen emulsion is unstable.