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Description
The microstructural evolution of cementitious materials strongly governs their durability and transport properties. In marine environments, these properties are of particular importance for the long-term durability of reinforced concrete structures, particularly for floating offshore wind turbines (FOWTs). Concrete used for FOWTs is expected to enable long service lives with reduced maintenance requirements in aggressive marine environments compared to steel support structures. Moreover, concrete foundations offer opportunities for incorporating low-carbon and supplementary cementitious materials. However, the long-term performance of such materials in continuous seawater exposure remains insufficiently understood, particularly with respect to microstructural evolution and transport mechanisms.
In this context, this study investigates the influence of curing medium (freshwater and seawater) on pore structure development and ionic transport in cement-based materials. It focuses on decoupling the effects of extended curing time from chloride exposure in seawater. The studied concrete mixture was prepared with Portland cement, limestone and calcined clay in line with low carbon construction objectives. Mercury intrusion porosimetry was employed to characterize pore size distribution and total porosity starting from early age (7 days) to long term.
The results reveal a specific evolution of porosity and microstructure with hydration time: a relatively constant porous volume and a significant refinement of the pore network. For both curing conditions, modal pore diameter shifts toward smaller size between 7 and 28 days indicating progressive filling of capillary pores thanks to pozzolanic reaction. However, samples exposed to seawater exhibit a shift toward finer pores compared to freshwater cured specimens. This behavior suggests that different solid phases are formed in marine environment. It is attributed to the combined effects of hydration advancement and interaction with seawater ions. The latter promotes the precipitation of secondary phases and partial pore blocking leading to reduce pore connectivity and to form less permeable microstructure. These analyses were confirmed by additional microstructural investigations using thermogravimetric analysis and X-ray diffraction.
In addition, complementary transport measurements reveal a pronounced decrease in the diffusion coefficient over time accompanied with an increase in electrical resistivity. Meanwhile, variations in water porosity remain limited. Collectively, these changes contribute to a time dependent modification of transport properties involved in chloride induced corrosion of concrete structure exposed to seawater.
| Country | France |
|---|---|
| Green Housing & Porous Media Focused Abstracts | This abstract is related to Green Housing |
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