Method for controlling mean droplet size in the manufacture of phase inversion bituminous emulsions

The most important factors related to the manufacture of phase inversion bitumen in water emulsions are discussed in this paper. The distribution and average droplet diameter of an emulsion depends on formulation variables such as the volume fraction, the concentration and type of surfactant and the temperature of the dispersed phase employed, the type of bitumen used, and mechanical variables as the rotational speed and time used. The emulsions for this study are prepared according to the High Internal Phase Ratio (HIPR) procedure, which requires that the initial dispersion is conducted with internal phase fractions higher than the critical packing (phi > 0.74). The bitumen used in this paper are 15/25, 35/50, 50/70 and 70/100. This procedure allows the manufacture of high concentration emulsions, with a small average droplet size, and narrow particle size distribution. Results show that both the droplet size and the particle size distribution obtained can be controlled by changing the parameters of the formulation. Specially one of the most important parameters to consider in the emulsion formulation if we want to obtain the smallest mean droplet size is the penetration grade bitumen used, such as the results presented in this paper.