Effects of bioadmixture on cement paste surface by dynamic contact angle measurement

International audienceSustainability is nowadays a crucial subject in concrete field. Many parameters are involved in the deterioration process of concrete. Furthermore alteration or deterioration of concrete can be accelerated by the growing of micro-organisms on their surfaces. This work consists on studying a new type of admixture which should reduce biocontamination of cementitious surfaces in order to avoid their alteration. This bioadmixture is produced using extracellular matrix of some bacteria. To realize this study, the bioreceptivity - i.e. the ability of a material to be colonized by living organisms – should be evaluated. However, for porous and complex material as concrete, it’s very difficult to characterize bioreceptivity. This phenomenon depends on many factors as the roughness, the porosity, the chemical composition, as well as the rate of cement hydration. These different parameters were studied for cement (CEM I) pastes samples with different rate of bioadmixture. The affinity of water with cement pastes surface was also studied by the measurement of the dynamic contact angle. These tests were performed to compare the behavior of dry cement pastes with and without bioadmixture when a drop of water is deposited on the sample surface. An original technique for analyzing the penetration compared to spreading has been developed while avoiding time constraint. It highlighted that bioadmixture promotes spreading of the drop and reduces the phenomenon of penetration into the material