Homogeneity of filler distribution within asphalt mix – A microscopic study

• Three fillers (limestone dust, granite dust and rhyolite dust) are chosen based on their surface charge.
• These fillers are separately used to make asphalt mix.
• Limestone is used as aggregates for all the asphalt mix samples.
• Analyses of SEM images suggest that the fillers are homogeneously distributed within asphalt mix.
• This homogeneity of distribution is independent of possible surface charge of filler particles.

In the present work distribution of filler particles within asphalt mix is studied using scanning electron microscope (SEM). Three different fillers namely, limestone dust, granite dust and rhyolite dust are used for making separate asphalt mix samples. Images are captured at two locations within the asphalt binder film, (i) close to the aggregate surface and (ii) away from the aggregate surface, typically at the middle of the binder film. Images are analyzed for (i) each location and (ii) each of the type of fillers. Image analysis results suggest that the fillers are homogenously distributed within the asphalt binder film and the distribution is not affected by the nature of possible surface charge of the filler particles.