SUSTAINABLE DIKE REVETMENTS: INDICATORS FOR MULTI-YEAR PERFORMANCE TRACKING

Dike revetments are a crucial part of infrastructure in low-lying regions worldwide, providing essential protection against flooding and rising sea levels. As the asphalt industry advances toward circular and climate-resilient solutions, seven dike sections with asphalt surfacing containing varying recycled content (0 to 70%), filler-to-binder ratios (0.48 to 2.4), and three binder grades were constructed in 2019. The sections have since been monitored to evaluate their long-term performance and support maintenance planning. This research presents insights from multi-year field monitoring to demonstrate how rheological indicators can support the assessment of ageing sensitivity in asphalt dike surfacing and inform responsible recycling strategies. Field cores were collected at construction and after five years of service. Bitumen and fillers were extracted and recombined to produce mastics reflecting field-representative proportions. Dynamic shear rheometer testing across multiple temperatures and frequencies enabled the construction of master curves and the extraction of performance indicators, including crossover frequency (fc), crossover modulus (|Gc*|), and the rheological (R) index. A statistically significant decrease in fc was observed, indicating increased stiffness and reduced stress-relaxation capacity with ageing. In contrast, R-index and |Gc*| exhibited only marginal changes, reflecting their limited sensitivity to incremental ageing. Overall, the indicators showed consistent ageing-related trends, although their ability to distinguish between ageing levels varied across parameters. Additionally, the magnitude of stiffness evolution was strongly influenced by the combined effects of recycled content, filler-to-binder ratio, binder grade, and site-specific exposure conditions. The findings highlight that while recycled materials offer circularity benefits, their proportion must be carefully managed to avoid compromising the durability of dike revetments. This research is envisioned to pave the way for indicators that can assist in establishing material thresholds and support sustainable maintenance planning.