Enhancing shear-thinning behavior in asphalt binders through organophilic clay modification

Abstract

This study investigates the influence of shear rate on the non-Newtonian flow behavior of asphalt binders modified with 1–5% organophilic nano clay by weight. Asphalt binders exhibit shear-thinning characteristics, where viscosity decreases with increasing shear rate, enhancing elasticity and reducing temperature sensitivity. Two penetration-grade bitumen samples (60/70 and 80/100) from Attock Refinery Limited (ARL), Pakistan, were modified using the melting method as per ASTM D6606. Rotational viscometer tests (ASTM D4402) were conducted at 135°C, over shear rates from 3.4 to 34 s⁻¹. Viscosity dropped by nearly 60% with increasing shear rate, with the 5% nano clay blend exhibiting the highest viscosity (385.5 cp (mPa·s)) at low shear rates. All concentrations demonstrated improved flow behavior, with 5% yielding the most significant effect. These findings highlight the potential of organophilic nano clay to improve binder rheology, indicating enhanced resistance to rutting and deformation, critical for pavement applications. Further field-scale research is recommended to evaluate long-term performance, mix workability and economic feasibility.