The relevance HLB of surfactants on the stability of asphalt emulsion

In this study, 13 non-ionic surfactants were selected; they have been used in wide range of HLB from 4 to 17.6. Asphalt emulsions with individual and some mixtures of surfactants were done. The stability of emulsions was determined via three physical means, batch settling time, particle size analysis and rheological characterization. The optimum stability of w/o emulsions was obtained at HLB range 4–6 with 30% water (dispersed phase). But the maximum stability of o/w emulsions was exhibited at HLB range 10–13, with 70% asphalt (dispersed phase). Five mixtures of surfactants (1:1 molar ratio) with HLB range 11.2–11.7 were formulated. The results reveal that, the mixtures with narrow range of HLB enhance the stability of asphalt emulsions and they exhibited long course of stability (95–155 days). The effect of carbon numbers in the hydrocarbon chain length of the surfactant on the stability of emulsions was classified for Tween 81, G1089 and Tween 85 with narrow HLB range (10–11). The data clears that; the increase of the carbon number in the chain length of surfactant enhances the stability of asphalt emulsions. The rheological parameters shows that, the increase of the carbon numbers in the alkyl chain length acts to increase the viscosity and the stability of asphalt emulsions which hindrance the coalescence rate. By analysis of the data obtained, it has been founded that, there is no discrepancy between the stability of asphalt emulsions related to HLB of the surfactants (emulsifiers), which was determined from the batch settling test and the particle size analysis.