Viscoelastic properties and stability of highly concentrated bitumen in water emulsions

The influence of bitumen concentration, presence of electrolytes, mean droplet diameter and distribution, storage temperature and length of the ethylene oxide chains, on the dynamic shear rheology, of concentrated bitumen in water emulsions, stabilized by nonyl phenol ethoxylated surfactants, was investigated. Emulsions showed a viscoelastic behavior when the bitumen concentration was increased above 60% (v/v). All the emulsions exhibited an increase in the shear modulus when the mean droplet diameter was decreased at a constant volume fraction of bitumen, or when the bitumen volume fraction was increased at a constant mean droplet diameter. The shear modulus became greater when the number of ethylene oxide units in the non-ionic surfactant increased. In all cases studied, the storage temperature and the presence of magnesium nitrate in the aqueous phase promoted a decrease in the values of the viscoelastic parameters. Results are explained on the base of the interaction between the surfactant molecules, adsorbed on adjacent bitumen droplets.