Determining the quality of asphalt emulsions using particle size and zeta potential analysis

Asphalt binder emulsions have proven to be an environmentally friendly, energy efficient, and cost-effective alternative to hot asphalt binder mixtures [1].  They are typically used for roadway resurfacing where they are employed as an adhesive for post-applied aggregate chip.   They are typically composed of bitumen, water, and an emulsifying agent or surfactant and must give the required stability and application characteristics for optimum performance.  For example, the structural layers must have adequate mechanical properties to make them less susceptible to early-life damage.  

The main component of asphalt emulsions is asphalt cement which constitutes 50-75 percent of the emulsion content.  Its properties are critically important since they influence emulsion behavior and performance on the road [1].  Water is the next component and can affect the properties of the emulsion if minerals or other materials are present.  One of the most influential components is the emulsifier or surfactant, and more specifically its chemical structure.  The emulsifier can determine whether the emulsion is cationic, anionic, or non-ionic.  Furthermore, the chemical compatibility of the emulsifier with the asphalt cement greatly affects the emulsions’ stability.  The physical properties of asphalt emulsions can also be modified using additives such as polymers or fillers. There are many reasons to modify asphalt emulsions, including; improved resistance to permanent deformation at high temperature; increased low temperature flexibility; improved fatigue resistance; increased tensile strength; and reduced temperature susceptibility.   

Malvern Panalytical has several tools that can provide valuable metrics for production and characterization of asphalt emulsions.  The two tools discussed in this application note are the Mastersizer and the Zetasizer., which can both be used to determine droplet/particle size, and in the case of the Zetasizer to measure the Zeta potential of emulsions also.


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