Use of Atomic Force Microscopy for Evaluation of the Adhesion Mechanism of Bituminous Binder Modified with Nano Hydrated Lime

Abstract

The durability of flexible pavements is affected by the presence of moisture, which leads to failure of bitumen-aggregate bonds. The failure of the bond has been explained by various mechanisms. The use of hydrated lime (HL) has been found to improve this bond and reduce moisture damage. However, a unique mechanism leading to the improvement in the bond requires further research and has motivated the introduction of nanotechnology in its determination. The present study is based on the use of synthesized NHL in varying percentages to modify bituminous binder. Atomic force microscopy (AFM) was carried out on the base and modified binders to evaluate bond strength and bond length of the modified bituminous binder, and unique observations were made. The peak force corresponding to bond strength is found to increase up to 10% with the addition of NHL, after which saturation is observed. The distance corresponding to this peak force, however, keeps on increasing with incremental usage of NHL. This observation was attributed to an increase in charge density due to addition of inorganic NHL.