Temperature effects on the compressive strength of recycled asphalt pavement stabilised with polyurethane foam and disposable face mask fibers

This paper investigates the effects of temperature on the compressive strength (UCS) of recycled asphalt pavement (RAP) mixed with face masks fibres (DFM) and stabilised with expanding polyurethane foam (EPF). For this context, an experimental programme was carried out on the RAP aggregates incorporating varying DFM contents (0%, 0.6% and 1%) and EPF = 6%, 8%, and 10%. The specimens were subjected to UCS testing at three different temperatures (T = −10°C, 25°C, and 50 °C). The obtained results indicate that the temperature of (T = 25°C) consistently serves as the thermal optimum, delivering the highest peak axial stress, whereas both elevated (T = 50°C) and subzero (T = −10°C) conditions result in a pronounced decline in stress, regardless of EPF and DFM content. This highlights a strong coupling between temperature, fibre reinforcement (DFM), and EPF dosage in controlling the mechanical response of the mixtures. Indeed, the finding confirm clearly that the mixture with EPF = 8% and DFM = 0.6% achieves optimal mechanical performances at the ambient temperature (T = 25°C). Furthermore, a consistently strong correlation (R2 = 0.94) exists between secant modulus (E50) and UCS across all composites, independently of tested temperature parameter, underscoring the reliability of this correlation as a mechanical performance indicator of investigated materials.