A thermodynamic framework for multisolid wax precipitation and reversible hardening in asphalt binders

Asphalt binders undergo low-temperature wax precipitation and reversible hardening governed by coupled paraffinic crystallisation and matrix structural evolution. This study develops a reduced thermodynamic framework, coupling a distributed paraffinic pseudocomponent population with an asphaltene-mediated structural variable. The model integrates equilibrium precipitation, compatibility-dependent phase partitioning, local stability, nonisothermal evolution and calorimetric, spectroscopic and rheological response mappings. Predictions based on literature-informed and physically prescribed parameters are benchmarked semi-quantitatively against reconstructed literature trends. The predicted wax precipitation temperature rises from 63.2 °C for sample A to 74.2 °C for sample B, whose peak cooling response is approximately 30% higher. Increasing the cooling rate from 0.5 to 4.0 °C/min reduces crystallinity at −20 °C from 0.39 to 0.05 wt.% for sample A and from 0.72 to 0.11 wt.% for sample B. Precipitation and hardening depend jointly on paraffinic distribution, aromatic content, residual-liquid compatibility and structural coupling.HighlightsGeneral thermodynamic framework for wax precipitation in asphalt binders.Distributed paraffinic population replaces single-wax idealisation.Structural coupling links precipitation and reversible hardening.Nonisothermal evolution is connected to measurable observables.Framework supports population partitioning and stability analysis.