Bioreceptivity Of Cementitious Materials In River Water And Technique Of Biodeterioration Assessment By Indentation

Living microorganisms can colonize the surface of cementitious materials by forming biofilms which causes, in some cases, biodeterioration of the material. A study of the bioreceptivity of a concrete structure in contact with a river freshwater (the Lauch, Alsace) by means of bacterial cultures on selective agar media, showed the presence of sulfur-oxidizing bacteria (BSO), sulfate-reducing (SRB) and thiosulphate-reducing (BTR). Known to be involved in the biodeterioration of cementitious materials, the presence of these bacteria involves a potential risk of biodeterioration. The thickness affected by the biodeterioration is generally limited (in the order of millimeter). Thus, to study the biodeterioration from a mechanical point of view, an indentation technique is under development. Results on both sound and chemically surface attacked material, with a Vickers tip and a maximum load of 20 N, show that the measurement scale is adapted to the thicknesses commonly affected, in terms of penetration depths. Elastic modulus values of cement pastes have little dispersion and are comparable to literature data. Elastic moduli measured on the cement pastes deteriorated surface show a sharp drop compared to the sound material.