Biodeterioration of cementeous matrix by fungi // Biodeterioration d'une matrice cimentaire par les champignons

International audienceBiodeterioration mechanisms are complex and not yet absolutely understood. To control and to act efficiently against deterioration by fungi, it is necessary to have a better understanding of those mechanisms. The aim of this paper is to present different stages taken into account for the setting up of a laboratory accelerated test of biodeterioration of cementeous matrix by fungi. Indeed in natural environment, biodeterioration takes place after several years. Incubation tests performed on non weathered and weathered specimens underline the importance of pH surface on fungi development. Best solution for the moment appears to be carbonation and leaching of specimens for matrix weathering and inoculation with spores suspension of specimen covered by a thin agar-agar film. Les mécanismes de la biodeterioration sont complexes et pas encore totalement compris. Afin de contrôler et d'agir efficacement contre la biodétérioration par les champignons, il est nécessaire d'avoir une meilleure compréhension de ces mécanismes. Le but de cet article est de présenter les différents étapes intervenant dans la mise au point d'un test accéléré de laboratoire sur la biodétérioration d'une matrice cimentaire par les champignons. En effet, en environnement naturel, la biodétérioration s'établie après plusieurs années. Les tests d'incubations réalisés sur des éprouvettes non vieillies et vieillies soulignent l'importance du pH de surface sur le développement fongique. Actuellement la meilleure solution semble être pour le vieillissement de la matrice : la carbonatation et lixiviation des éprouvettes, et l'inoculation par une suspension de spore d'éprouvettes recouvertes d'un fin film de gélose

Biodétérioration d'une matrice cimentaire par les champignons : influence du vieillissement accéléré sur le développement fongique // Biodeterioration of cementeous matrix by fungi: Influence of accelerated weathering on fungal development.

National audienceLes micro-organismes ont la capacité de se développer sur les matériaux de construction et sont susceptibles de dégrader les fonctions des matériaux, d'abréger leur durée de vie et d'en modifier l'aspect esthétique. La biodétérioration est associée aux mécanismes physique, chimique et esthétique. Elle est amplifiée par les facteurs environnementaux tels que la pollution atmosphérique ou les cycles gel-dégel, par exemple. Pour contrôler et lutter efficacement contre la biodétérioration des matériaux de construction, il est nécessaire d'avoir une meilleure compréhension de ces mécanismes. L'objectif de cette étude est de mettre au point un essai accéléré de laboratoire pour étudier la biodétérioration d'une pâte de ciment par deux souches de champignons "Alternaria alternata" et "Aspergillus niger". L'influence du mode de conservation et le vieillissement des éprouvettes sont étudiés : certains échantillons sont carbonatés afin de réduire le pH de la matrice. Les premiers résultats obtenus montrent que la carbonatation n'est pas suffisante pour permettre un développement fongique. En revanche, la carbonatation couplée à une lixiviation permet d'obtenir de meilleurs résultats. En parallèle, des essais sont réalisés afin d'optimiser l'étape d'inoculation des échantillons. // Micro-organisms can grow on building materials. They are liable to degrade materials properties: from an alteration of aesthetic aspect to a reduction of its service life. Biodeterioration is associated to chemical, physical and aesthetic mechanisms. Biodeterioration is enhanced by environmental factors such as air pollution or freeze/thaw cycles. To control and to act efficiently against biodeterioration of buildings materials it is necessary to have a better understanding of those mechanisms. The aim of this study is to set up an accelerated laboratory test in order to study biodeterioration of a cement paste by two fungal strains: "Alternaria alternata" et "Aspergillus niger" Influence of conservation and weathering of specimens is studied: some samples are carbonated in order to reduce matrix pH. First results show that carbonation isn't sufficient to trigger fungal development. Carbonation associated to leaching give better results. Tests are performed too, in order to optimize inoculation stage

Accelerated weathering of cementitious matrix for the development of an accelerated laboratory test of biodeterioration

International audienceCement based materials are porous, may contain organic adjuvants, and thus possesses an important primary bioreceptivity. To preserve constructions from fungal colonization and to act efficiently against fungal biodeterioration, it is necessary to have a better understanding of biodeterioration mechanisms and its effects on materials properties. An accelerated laboratory test which allows us to compare the growth of three fungal strains and the aesthetic biodeterioration of a cementitious matrix was developed. As the surface pH of the fresh cement specimen is too high to allow fungal growth (pH ~12), accelerating weathering of the matrix, consisting of the combination of carbonation and leaching, was performed to reduce the matrix alkalinity. XRD analyses and SEM observations pointed out that the matrix surface is progressively covered by a calcium carbonate layer as the weathering increases. Results point out that the microbial growth occurs on matrix with a surface composition more like a limestone than a cementitious one

Accelerated laboratory test to study fungal biodeterioration of cementitious matrix

International audienc

Biodétérioration d'une matrice cimentaire par des champignons : Mise au point d'un test accéléré de laboratoire

229 pagesMicro-organisms (bacteria, cyanobacteria, fungi, algae) can grow on building materials. They are liable to degrade materials properties: from an alteration of aesthetic aspect to a reduction of its service life. Biodeterioration is associated to chemical, physical and aesthetic mechanisms. To control and to act efficiently against biodeterioration of buildings materials, it is necessary to have a better understanding of those mechanisms.The aim of this study is to develop an accelerated laboratory test to study the biodeterioration of cementitious matrix by fungi.The study of biodeterioration involves a pluridisciplinary approach. Firstly, this work was considered from a biological point of view. Hence, optimum parameters for a rapid fungal development were determined. Then, attention was paid to the matrix preparation, to make it favourable for fungal growth. Finally, these two approaches were combined to study microbial development on the matrix prepared. The accelerated laboratory test developed permits to obtain a rapid fungal growth on cement specimens. The results point out that in the present study the microbial growth is promoted with the accelerated weathering of the matrix. It plays a major role. No microbial growth is noticed on nonweathered specimens. From a biodeterioration point of view, the test developed permits to observe and to points out aesthetical and physical biodeterioration mainly. Results point out the necessity to have not only microscopic observations to study the microbial development. While this shows the aesthetical biodeterioration of specimens, it underestimates the real extent of the microbial colonization. The PAS staining reveals microbial growth on and within the matrix. The SEM observations permit to identify characteristic bacterial shapes.Les micro-organismes (bactéries, cyanobactéries, champignons, algues) peuvent se développer sur les matériaux de construction. Ils sont capables de dégrader les propriétés du matériau : de l'altération de l'aspect esthétique jusqu'à une réduction de sa durabilité. La biodétérioration est associée aux mécanismes chimiques, physiques et esthétiques. Une meilleure compréhension des mécanismes impliqués dans la biodétérioration permettra de mieux lutter contre les dommages engendrés et à terme de prévenir le développement de ces micro-organismes.Le but de cette étude est de développer un test accéléré de laboratoire pour étudier la biodétérioration d'une matrice cimentaire par des champignons. L'étude de la biodétérioration nécessite une approche pluridisciplinaire. Dans un premier temps, ce travail a été abordé d'un point de vue purement « micro-organismes ». Cela a permis d'identifier et de définir les paramètres optimums de culture et croissance fongique. Dans un second temps, l'attention s'est portée sur la préparation d'une matrice cimentaire compatible avec le développement fongique. Enfin, les deux approches ont été combinées permettant l'étude de la croissance des micro-organismes sur le matériau.Le test développé a permis d'obtenir un développement fongique rapide sur des éprouvettes en ciment. Les résultats obtenus ont notamment mis en évidence le rôle fondamental joué par le pH de surface sur le développement microbien. Les résultats montrent qu'il ne peut y avoir de développement microbien sans un vieillissement préalable du matériau. D'un point de vue de la biodétérioration, le test développé a permis d'observer et de mettre en évidence la biodétérioration esthétique et physique principalement. Les résultats ont également montré la nécessité de ne pas se limiter aux observations au microscope pour étudier la biodétérioration. Bien que ces observations mettent en évidence la biodétérioration esthétique, elles sous-estiment l'étendue réelle de la colonisation microbienne. La coloration PAS révèle l'étendue de la colonisation microbienne sur et dans la matrice. De plus, les observations au MEB ont permis d'identifier des formes caractéristiques de bactéries, confirmant les observations au stéréomicroscope et après coloration

Biodétérioration d'une matrice cimentaire par des champignons (mise au point d'un test accéléré de laboratoire)

Le but de cette étude est de développer un test accéléré de laboratoire pour étudier la biodétérioration d une matrice cimentaire par des champignons. Dans un premier temps, ce travail a été abordé d un point de vue purement micro-organismes . Cela a permis de définir les paramètres optimums de culture fongique. Dans un second temps, l attention s est portée sur la préparation d une matrice cimentaire compatible avec le développement fongique. Enfin, les deux approches ont été combinées permettant l étude de la croissance des micro-organismes sur le matériau. Le test développé a permis d obtenir un développement fongique rapide sur des éprouvettes en ciment. Les résultats obtenus ont mis en évidence le rôle fondamental joué par le pH de surface sur le développement microbien. D un point de vue de la biodétérioration, le test développé a permis d observer la biodétérioration esthétique et physique. Ce travail a permis de disposer d un panel de techniques analytique complémentaires.The aim of this study is to develop an accelerated laboratory test to study the biodeterioration of cementitious matrix by fungi. Firstly, this work was considered from a biological point of view. Hence, optimum parameters for a rapid fungal development were determined. Then, attention was paid to the matrix preparation, to make it favourable for fungal growth. Finally, these two approaches were combined to study microbial development on the matrix prepared. The accelerated laboratory test developed permits to obtain a rapid fungal growth on cement specimens. The results point out that in the present study the microbial growth is promoted with the accelerated weathering of the matrix. It plays a major role. The test developed permits to observe aesthetical and physical biodeterioration. This work allows us to have complementary analytical methods to study biodétérioration.ST ETIENNE-ENS des Mines (422182304) / SudocSudocFranceF

A Bacteria-Based Self-Healing Cementitious Composite for Application in Low-Temperature Marine Environments

The current paper presents a bacteria-based self-healing cementitious composite for application in low-temperature marine environments. The composite was tested for its crack-healing capacity through crack water permeability measurements, and strength development through compression testing. The composite displayed an excellent crack-healing capacity, reducing the permeability of cracks 0.4 mm wide by 95%, and cracks 0.6 mm wide by 93% following 56 days of submersion in artificial seawater at 8 °C. Healing of the cracks was attributed to autogenous precipitation, autonomous bead swelling, magnesium-based mineral precipitation, and bacteria-induced calcium-based mineral precipitation in and on the surface of the bacteria-based beads. Mortar specimens incorporated with beads did, however, exhibit lower compressive strengths than plain mortar specimens. This study is the first to present a bacteria-based self-healing cementitious composite for application in low-temperature marine environments, while the formation of a bacteria-actuated organic–inorganic composite healing material represents an exciting avenue for self-healing concrete research

Data of "Optimization of concrete mix designs toward the bond properties of steel reinforcement in self-healing concrete by Taguchi method"

Dataset for the hardened properties of self-healing concrete and the bond properties of steel reinforcement in self-healing concrete used for the optimization via Taguchi metho

Performance requirements to ensure the efficiency of bacteria-based self-healing concrete

Abstract: Self-healing concrete has been the subject of great scientific interest over the last ten years. Various research groups worldwide have been working on different healing agent concepts, with bacteria-based healing agents being one of the most popular. Bacterial spores together with organic mineral precursor compounds are immobilized and protected in capsules. Once a crack is created, the bacterial spores turn from a dormant to an active state and start to metabolize the organic compounds, resulting in the production of calcium carbonate crystals. Those crystal formations are able to bridge the open cracks. Many studies have proven the enhanced healing performance of bacteria-based self-healing cementitious materials in comparison to the ordinary ones. However, they do not explicitly designate which performance conditions should be satisfied in order to verify the functionality of the embedded healing agent. This study presents and explains why there are three requirements needed to ensure the performance of a bacteria-based healing agent. Those requirements are the presence of mineral formation inside the crack, the reduced crack permeability and the evidence of bacterial activity in the mortar. In this study, the requirements are studied on mortar specimens through: i) microscopic observations on crystals found inside the cracks, ii) crack water permeability tests and iii) oxygen concentration measurements

Low power plasmon-soliton in realistic nonlinear planar structures,

International audienceWe study the propagation of nonlinear waves in layered nonlinear dielectric/linear dielectric/metal planar structures. We develop vector models that describe the light propagation in such configurations and allow to obtain both one- and two-dimensional solutions. We compute the nonlinear dispersion relation, the field profiles, and estimate losses. We use our models to design realistic structures, in terms of linear and nonlinear properties, which support soliton waves with a plasmon tail at low peak power around or below 1GW/cm2. These results open the way for potential observation of such states in chalcogenide waveguides associated with silica and metal films. In the proposed structures, the nonlinearity confines the field in both transverse directions. A recordable plasmonic part of the field extends in air