Aggregate–binder adhesiveness assessment and investigation of the influence of morphological and physico-chemical properties of mineral aggregates

Aggregate–binder adhesiveness in asphalt mixtures is affected by the physico-chemical properties of aggregates and asphalt binder. The objective of this paper is to analyse how aggregate morphological and physico-chemical properties affect the aggregate–binder adhesiveness measured by different techniques. Two aggregate sources (granitic and phonolitic) combined with two asphalt binders (a neat binder and the same binder modified by an anti-stripping agent) were used. Grounded plastic bags were also used as an additive to improve aggregate–binder interface properties. The adhesiveness test used follows ABNT 12583 (similar to static water storage according to EN 12697-11B) and subsequent digital image processing (DIP), developed in a previous work. Absorption was measured by a classical immersion weighting procedure (DNER 081), while angularity and texture were determined using the Aggregate Image Measurement System (AIMS). Aggregate’s chemical composition was investigated by X-Ray Fluorescence. Moisture-induced damage resistance was determined by the modified Lottman test (ABNT 15617). Asphalt Bond Strength (ABS) tests were performed with different water conditioning times. DIP allowed correlating adhesiveness to different parameters, such as angularity, texture, porosity and oxide content of the aggregate, and also to moisture-induced damage test results and the ABS test results. Results show that the granitic aggregate presented better adhesiveness with both the neat binder and the binder with anti-stripping agent. The mixture with grounded plastic bags also had better adhesiveness when compared to the control mixture. Aggregate’s angularity, texture and porosity do not appear to affect aggregate–binder adhesiveness, whereas Fe2O3 and CaO content presented excellent correlations with the adhesiveness test analysed by DIP. The asphalt film dislocation test analysed by DIP also presented strong correlation with the moisture-induced damage test. It seems possible to establish a reliable limit for DIP results in this simple test to prevent mixtures of being susceptible to moisture damage.