La bioréceptivité de matériaux cimentaires dans l’eau de mer : mécanismes, facteurs agissants et conséquences

Le beton est un materiau composite complexe, dont les differents composants lui permettent de s’adapter a des usages tres differents grâce a ses caracteristiques physicochimiques adaptables a des cahiers des charges tres varies. Ses performances mecaniques, sa durabilite exceptionnelle et son cout modere justifient l’utilisation large de ce materiau dans la construction des ouvrages maritimes. Immerge dans l’environnement marin, le beton est susceptible d’etre colonise par les differents organismes marins qui se regroupent ensemble sur la surface sous leur forme sessile nommee biofilm/biofouling. Cette colonisation forme le point de depart de differentes interactions biologiques pouvant avoir lieu entre le materiau et son environnement marin (biodeterioration/bioprotection). Le cycle et la vitesse de colonisation vont dependre des conditions environnementales comme de la nature du substrat (composition, proprietes physico-chimiques du support…) ainsi que des proprietes de microorganismes concernes. Dans le but d’etudier la bioreceptivite du beton dans l’environnement marin, cet article se focalise successivement sur les parametres du milieu marin qui influent sur sa colonisation et sur les organismes concernes. Les caracteristiques intrinseques du beton qui sont susceptibles d’influencer la bioreceptivite et les mecanismes conduisant a la formation du biofilm et a la biocolonisation des betons sont decrits. Enfin, le sujet de l’effet positif (bioprotection) ou negatif (biodeterioration) des organismes vivants sur le beton est evoque. Bioreceptivity of cementitious materials in seawater: mechanisms, acting factors and consequences Abstract: Concrete is a complex composite material; whose different components allow it to adapt to very different uses due to its physicochemical characteristics adaptable to very varied conditions. Its mechanical performance, exceptional durability and moderate cost explain the wide use of this material in the construction of marine structures. Submerged in the marine environment, the concrete will be colonized by various marine organisms that gather together on the surface in their sessile form called biofilm/biofouling. This colonization is the starting point for different biological interactions that may occur between the material and its marine environment (biodeterioration/bioprotection). The cycle and the rate of colonization will depend on environmental conditions such as the nature of the substrate (composition, physicochemical properties of the support, etc.) as well as the properties of the concerned microorganisms. In order to study the bioreceptivity of concrete in the marine environment, this paper focuses successively on the characteristics of the marine environment that affect the colonization of the concrete and the concerned organisms. Then, the intrinsic parameters of concrete that can influence bioreceptivity are listed and described. The same goes for the mechanisms leading to the biofilm formation and the biocolonisation of concretes. Finally, the subject of the positive (bioprotection) or negative (biodeterioration) effect of the biofilm formation on concrete is discussed. Key words: Concrete, Marine environment, Biocolonization, Biofilm/Biofouling, Bioreceptivity/Biodeterioration.