A new protocol to evaluate the behaviour and durability of marine structures

Abstract

Sustained mechanical and environmental loadings on offshore structures result in creep phenomena. Creep and relaxation significantly affects the development of strains and stresses, thus they influence the durability of structures. Creep originates from the behaviour of the phases within the cement matrix. Seawater modifies the phases composition of cement matrix because of the variety of ions and their possible interactions with cement hydration products. This, in turn, affects the mechanical behaviour of structures, including creep. For durability and safety purposes, the design of offshore structures should consider the possible coupling between cement hydration, seawater exposure, and creep. Therefore, there was a need to develop a new protocol to evaluate the behaviour and durability of marine structures. As part of this new protocol, a new rig has been developed to evaluate the creep of cement-based materials immersed in seawater. The obtained results show that the short-term creep of structures in seawater is faster than in tap water. In the long term, even though multiple phases are microscopically formed due to seawater attack, the positive and negative effects of these phases formation and dissolution lead to almost similar creep development in seawater. This protocol can be used to assess the chemo-mechanical durability of multiple structural materials in order to develop low carbon materials. Additionally, it could improve the design of offshores structures by estimating the maximum permissible load based on the rigidity of structures and their chemical degradation level.