INVESTIGATION OF TERTIARY FLOW BEHAVIOR OF BITUMEN STABILISED MATERIALS WITH BITUMEN EMULSION

Cold recycling technology is gaining popularity as a sustainable way of rehabilitating existing asphalt pavements. Bitumen Stabilised Materials with bitumen emulsion (BSMs) are cold recycling mixtures (CRMs) that contain RAP, virgin aggregates, bitumen emulsion, water, and active filler and exhibit a combination of mechanical properties of both granular and viscoelastic materials. However, the BSMs' mechanical performance in terms of viscoelasticity remains insufficiently explored. This study aimed to synthesize and adapt dynamic creep test methods, commonly used for HMA mixes, for characterizing tertiary flow behavior of BSMs. Tests were conducted on BSM mixtures with 50% and 70% RAP content, bitumen emulsion amount in the 4.5%-6.4% range, and 1% cement addition. The designed BSM series were also differentiated in terms of volumetric properties. Permanent deformation (PD) response of Bitumen Stabilised Materials was evaluated based on the analysis of the accumulated permanent strain curves obtained in repeated load tests. The experimental data were fitted to the Francken model, using an originally developed Python calculation script, to determine the Flow Number (FN) values for BSMs under specified loading stress and testing temperature conditions. The study showed that the specification of the Flow Number dynamic creep test parameters for testing BSMs requires an individual approach depending on the composition and volumetric properties of the mixture. With appropriately selected test conditions, the permanent deformation of BSMs can be evaluated by means of fitting the accumulated permanent strain curve to the Francken model and estimating Flow Number values.