Bitumen-aggregate adhesion: a predictive study based on zeta potential analysis using the streaming potential technique

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.