Contribution to the study of relationship between characteristics and performances of bitumen emulsions

The characteristics governing the properties of emulsions in general are binder type and content, particle size distribution and aqueous phase composition. All these parameters are interlinked and it is often difficult to distinguish the exact contribution of each of them to the properties of an emulsion. This paper presents the results of a study aimed establishing relationships between characteristics and properties of cationic bitumen emulsions. A series of emulsions was prepared, with strictly identical formulae, but the manufacturing process was controlled to produce different particle size distributions. To start with, the breaking index of the emulsions was correlated with the median diameter of the particles. Then it has been shown that the viscosity of bitumen emulsions increased as the standard deviation decreased, irrespective of the emulsion series concerned. The behaviour of the emulsions on the road was assessed by measuring the cohesion build up of surface dressing made with emulsions of the same formulae but with different intrinsic characteristics. The rate of cohesion building up of the surface dressing gets faster as the standard deviation of the emulsions gets lower. This study shows the effect of the parameters characterising emulsion grading curves (median diameter and standard deviation) on viscosity and rate of cohesion building. By controlling these two very important properties for surface dressing, their behaviour in the field can be improved.