Effect of Oyster Adhesion on the Performance of Marine Concrete

Given the insufficient understanding of the mechanism by which oysters influence marine concrete, this study investigates the impact of oyster attachment on concrete performance. The results demonstrate that oyster colonization significantly enhances the overall performance of concrete. At the macroscopic level, oyster attachment delays the alkalinity loss and mechanical property deterioration of concrete. At 480 days, the pH values of the attachment and unattached groups decreased by 26.89% and 32.77%, respectively, compared to those at day 0, indicating that oyster attachment contributed to mitigating alkalinity loss in concrete by 5.88%. With regard to compressive strength, the attachment group exhibited a reduction of 4.65%, whereas the unattached group showed a significantly greater decline of 38.24% relative to the initial value at day 0, resulting in a contribution rate of oyster attachment toward maintaining compressive strength of 33.59%. In terms of durability, oyster attachment markedly enhanced resistance to chloride ion penetration and freeze-thaw cycles. At 480 days, the electric flux in the attachment group at the 0–50 mm depth was 19.91% lower than at day 0, while that of the unattached group increased by 77.17%, yielding a contribution rate of 97.08% for oyster attachment in reducing electric flux. After 480 days of exposure, the mass loss rates due to freeze-thaw cycling were recorded as 1.41% and 1.98% for the attachment and unattached groups, respectively, suggesting that the presence of oyster shells and biologically secreted adhesives effectively reduced freeze-thaw damage. Microstructural analysis revealed that oysters secrete biological colloids to form a dense, approximately 2-mm-thick filling layer, which efficiently seals surface pores and, together with the oyster shell, creates a physical barrier. This barrier inhibits the ingress of corrosive species such as SO 4 2 − and CO 2 , as well as the leaching of OH − , thereby suppressing the formation of detrimental compounds like ettringite and calcium carbonate. This study elucidates the beneficial protective role of oyster attachment on concrete through biomaterial interactions and offers a novel bionic strategy for enhancing the durability of marine concrete structures.