Enhancing Performance of Gilsonite-Modified Binders and Mixtures via Optimization of Nanoclay Content: Analysis and Response Surface Methodology

Abstract

Improving the durability and performance of asphalt binders is critical for extending pavement life spans and reducing maintenance costs. Gilsonite, a natural modifier, offers promising benefits but suffers from increased viscosity and reduced low-temperature flexibility, which limit its practical applications. This study addresses these challenges by incorporating nanoclay into Gilsonite-modified binders to optimize their properties. Three types of binders were prepared and evaluated: Gilsonite-modified binder (G15, containing 15% Gilsonite), Gilsonite-modified softer binder with 10% Gilsonite (Sb_G10), and Gilsonite-modified softer binder combined with nanoclay (Sb_G10/Nc) at different nanoclay percentages (4.3% and 5.0%). The response surface methodology (RSM) was applied to optimize nanoclay content under different climatic conditions, with models validated by experimental data. Rheological and viscoelastic tests showed that adding nanoclay improves stiffness and thermal resistance but requires limiting Gilsonite content to maintain adequate low-temperature flexibility. Using RSM, optimal nanoclay contents were identified for different climates: 4.3% for standard, 5.0% for hot, and 3.1% for cold conditions. Performance evaluation of asphalt mixtures reinforced these findings, demonstrating that mixtures with Sb_G10/Nc formulations exhibited enhanced mechanical properties and durability, and G15 mixtures offered strong resistance suitable for high-traffic applications. The Sb_G10/Nc4.3 mixture was also highlighted for its balanced performance and lower environmental impact. This study connects binder modification with mixture performance, providing practical guidance for sustainable, high-performance asphalt pavement design.