Rheological and adhesive properties of nanocomposite bitumen binders based on hydrophilic or hydrophobic silica and modified with bio-oil

Abstract

Improved adhesive and cohesive properties of bitumen blends with bio-oil and two types of silica nanoparticles having either hydrophilic or hydrophobic surface were studied. The morphology of the modified bitumen and its rheological properties at normal and elevated temperatures were also investigated in detail. The addition of 5–20 wt% bio-oil leads to the appearance of a small yield stress in the bitumen melt and a reduction in the loss tangent for the cooled mixture. At the same time, the addition of 5% bio-oil is the most optimal, as it results in an increase of the thermodynamic work of adhesion and the measured adhesive strength of the bitumen binder to the silicate surface by 16–21%. The addition of silica nanoparticles in quantities up to 15 wt% causes a more significant increase in the yield stress as well as an even greater improvement in the stiffness and elasticity of the bitumen binder at normal temperature. Moreover, the nanoparticles increase the cohesive strength of the bitumen binder up to 60% and bidirectionally change its adhesion characteristics, depending on the nature of their surface. At a concentration of 15 wt%, the hydrophobic silica doubles the adhesion of the binder to steel, whereas the hydrophilic one conversely halves it.