Evaluation of the nonlinear viscoelastic behaviour of Fluid Mastic Asphalt Mixture (FMA) with a wide range of asphalt contents using the multiple stress creep recovery test

Objectives Fluid mastic asphalt mixture (FMA) is a novel hot-mix asphalt mixture with near-zero air voids and a wide range of asphalt contents. However, its nonlinear viscoelastic behaviour remains insufficiently characterised. This study aimed to investigate the effects of asphalt content and stress on the nonlinear viscoelastic response of FMA.Methods Multiple stress creep recovery (MSCR) tests were conducted at 55 °C on FMA-13 with asphalt contents of 6%, 7%, 8%, 9%, and 10%, with AC-13 serving as a reference. Schapery’s nonlinear viscoelastic theory was employed to identify the parameters g1, g2, and α s. Their relationships with asphalt content and stress were analysed, and exponential predictive models were developed.Findings FMA-13 (6%) exhibited greater total creep strain and recoverable strain than AC-13. Parameters g1 and α s were relatively insensitive to stress, whereas g2 decreased rapidly before stabilizing. With increasing asphalt content, g1 increased, while g2 and α s decreased. The established models effectively captured the variations in these parameters and enabled the prediction of recoverable creep strain.Novelty This study establishes a theoretical framework for characterising the nonlinear viscoelastic behaviour of FMA over a wide range of asphalt contents, providing a basis for evaluating its deformation recovery performance.