No abstract

Civil engineers have a responsibility to take measures to protect marine biodiversity by selecting more bioreceptive construction materials in the design of marine infrastructure, for better biodiversity conservation. In this study, it was shown that pre-carbonation of cementitious materials accelerates their bacterial colorization by lowering the pH of their surface. It has been shown both in the laboratory and in-situ tests that the bacterial colonization of cementitious materials is influenced by the pH and the type of cement. By comparing the bacterial colonization of Portland cement mortars, CEM I, and slag cement, CEM III, mortars, it was found that the CEM III mortars are more bioreceptive than the CEM I mortars. This study presented and verified a novel experimental laboratory approach which can be used to evaluate the bacterial colonization (bioreceptivity) of cementitious materials in marine environment. The approach could be taken up in future recommendations to enable engineers to eco-design more eco-friendly marine infrastructure and develop green-engineering projects.

Coastal marine ecosystems provide essential benefits and services to humanity, but many are rapidly degrading. Human activities are leading to significant land take along coastlines and to major changes in ecosystems. Ecological engineering tools capable of promoting large-scale restoration of coastal ecosystems are needed today in the face of intensifying climatic stress and human activities. Concrete is one of the materials most commonly used in the construction of coastal and marine infrastructure. Immersed in seawater, concretes are rapidly colonized by microorganisms and macroorganisms. Surface colonization and subsequent biofilm and biofouling formation provide numerous advantages to these organisms and support critical ecological and biogeochemical functions in the changing marine environment. The new challenge of the 21st century is to develop innovative concretes that, in addition to their usual properties, provide improved bioreceptivity in order to enhance marine biodiversity. The aim of this study is to master and clarify the intrinsic parameters that influence the bioreceptivity (biocolonization) of cementitious materials in the marine environment. By coupling biofilm (culture-based methods) and biofouling (image-analysis-based method and wet-/dry-weight biomass measurement) quantification techniques, this study showed that the application of a curing compound to the concrete surface reduced the biocolonization of cementitious materials in seawater, whereas green formwork oil had the opposite effect. This study also found that certain surface conditions (faceted and patterned surface, rough surface) promote the bacterial and macroorganism colonization of cementitious materials. Among the parameters examined, surface roughness proved to be the factor that promotes biocolonization most effectively. These results could be taken up in future recommendations to enable engineers to eco-design more eco-friendly marine infrastructure and develop green-engineering projects.

L'activité humaine sur le littoral a un impact majeur sur l'environnement et sur la biodiversité sous-marine. La démarche d'éco-conception permet d'intégrer les objectifs environnementaux à la conception structurelle des ouvrages qui sont aptes à remplir leurs fonctions techniques et une fonction environnementale de support de la biodiversité. L'éco-conception des ouvrages est une approche globale et systémique qui est initiée par le client au moment du programme et qui se poursuit lors de la conception puis jusqu'à la phase d'exécution. A la demande de l'Office Environnemental de la Corse, cette méthodologie a été appliquée au projet expérimental de récifs artificiels et de corps morts du Ricantu dans la baie d'Ajaccio. Les ouvrages immergés ont pour but de proposer des habitats destinés aux espèces cibles à forte valeur ajoutée pour la pêche. Cet article décrit la démarche suivie pour éco-concevoir les ouvrages à construire 1) méthodologie suivie, 2) essais préliminaires en laboratoire pour évaluer les paramètres prioritaires, 3) réalisation d'ouvrages à l'échelle 1. La relation écosystème-ouvrage, le design des formes et des matériaux ont été investigués avec des objectifs de biomimétisme affirmés. Le suivi scientifique des ouvrages expérimentaux depuis près de 2 ans offre un retour d'expérience concret indispensable à la consolidation de la méthodologie à adopter dans le but de concevoir des ouvrages éco-conçus durables.