Abstract:
Bitumen and aggregates are the main constituents of asphalt; their physical and chemical
properties have a direct influence on the performance of the mixture. Adhesion between
mineral aggregates and bitumen is an important criterion for predicting the performance of
asphalt pavements to resist common distresses. Lack of bonding can lead to significant
asphalt pavement failure. The objective of this study was to investigate the application of
zeta potential analysis for the prediction of adhesion between bitumen and stone
aggregate based on their surface charge. The adhesion behaviour of four (4) aggregate
sources (dolomite, dolerite, andesite, and quartzite) to a 70/100pen grade bitumen was
studied. The adhesion of the bituminous binder to stone aggregate was determined with
the conventional Rolling Bottle test method used at the CSIR. The zeta potential for
macroscopic solid surfaces of aggregates with similar physical properties and bitumen was
measured using an electrokinetic analyser at different pH levels. The results predicted that
dolomite aggregates had better adhesion when compared to dolerite, andesite, and
quartzite aggregates. The Rolling Bottle results are ranked in a way consistent with the
zeta potential predictions when the isoelectric point (IEP) is used. The characterization of
the aggregate surface chemistry in the zeta potential vs pH curves has provided a better
insight into the behaviour of aggregates in different pH conditions. The location of the IEP
as per the characterization allows for a better prediction of aggregate-bitumen adhesion
behaviour. The content of Fe2O3 and CaO present in the aggregates (i.e., dolomite and
dolerite) results in better adhesion than the aggregates with a higher content of SiO2 (i.e.,
quartzite and andesite). The study shows that the zeta potential analysis has the potential
to predict the adhesion of bituminous binder to stone aggregate.
