Material and environmental performance of breakwaters with varying slopes and concrete armor types

Global climate change and resource scarcity have intensified the need for sustainable and resilient coastal protection. Breakwaters, which dissipate wave energy and mitigate shoreline erosion, traditionally rely on large natural stones or mass concrete armor units. However, the increasing unavailability of suitably sized natural stones and significant carbon emissions associated with concrete production present critical challenges for sustainable design. This study aimed to investigate the design efficiency of rubble mound breakwaters armored with three types of concrete units (tetrapods, tribars, and dolos) across three slope configurations (1 : 1.5, 1 : 2, and 1 : 3). The methodology involved calculating the required armor unit weight and quantity using Hudson's equation, determining the crest geometry, and estimating the total embodied carbon emissions per meter length of breakwater based on a cradle-to-gate life cycle assessment approach. The results show that while gentler slopes reduce individual armor unit weight, they increase the number of units required per area, leading to higher total material use and embodied carbon. Among the armor types, dolos consistently exhibited the highest material efficiency and lowest embodied carbon because of their superior stability coefficient, although they require more units for placement. These findings highlight the trade-offs between slope geometry, armor type, and environmental performance, emphasizing the importance of integrated design approaches for optimizing material consumption and carbon footprint in sustainable breakwater construction.