Influence of fly ash on the resilient mechanical performance of cold mix asphalt using the stress-temperature superposition principle

Cold mix asphalt (CMA) is a lower-temperature and lower-energy alternative to hot mix asphalt, yet further improvement of its mechanical performance remains needed. This study evaluated the compactability and resilient mechanical behaviour of CMA mixtures incorporating Class C and Class F fly ashes as substitutes for limestone filler. Three CMA mixtures were fabricated using a Superpave Gyratory Compactor, assessing how filler type affects compaction and volumetric properties. Mechanical performance was characterised via dynamic triaxial testing at 5, 15, 25, and 35°C to analyse the stress- and temperature-dependent resilient modulus (Mr). Fly ash improved compactability and increased Mr across all conditions. However, fly ash-modified mixtures exhibited greater stress sensitivity at lower temperatures, possibly due to partial bonding from premature emulsion breaking. The stress-temperature superposition principle was applied to develop Mr* master curves, supporting the potential of tailored fly ash use to enhance CMA performance for sustainable pavement applications.