Proceedings pro123-1 : Final Conference of RILEM TC 253-MCI: Microorganisms-Cementitious Materials Interactions Volume 1

Title: Final Conference of RILEM TC 253-MCI: Microorganisms-Cementitious Materials Interactions Volume 1 Edited by: Alexandra Bertron and Henk Jonkers e-ISBN: 978-2-35158-206-0 ISBN: 978-2-35158-207-7 (Set) ISBN: 978-2-35158-209-1 (Volume1) Pages: 288 Publication date: 2018

Infrastructures and buildings are exposed to microorganisms in a variety of contexts. Structures exposed to aggressive aqueous media containing microorganisms (waste water, soft water, fresh water, ground water, sea water, agricultural or agro-industrial environments, etc.), often concrete structures, can suffer deterioration that can be detrimental (loss of alkalinity, erosion, spalling of the concrete skin, corrosion of rebars, loss of water- or airtightness...). The deleterious effect of microorganisms, mainly bacteria and fungi, on the cementitious matrix has been found to be linked, on the one hand, with the production of aggressive metabolites (e.g. acids, CO2, and/or sulphur compounds) but also, on the other hand, with some specific, physical and chemical effects of the microorganisms themselves through the formation of biofilm on the surface. Moreover, the intrinsic properties of the cementitious matrix (physical properties, mineralogical and/or chemical composition) can also influence the biofilm characteristics.
These deteriorations lead to a significant increase in the cost of repairing structures and to loss of production income, but may also lead to pollution issues resulting from waste water leakage to the environment for example.
Also, building facades, and notably concrete external walls, can be affected by biological stains, which alter aesthetical quality of the construction, sometimes very quickly, and lead to significant cleaning costs.
In indoor environments, proliferation of bacteria and fungi on building materials is responsible for health problems through the production of microbial volatile organic compounds, allergens and toxins. The bio-receptivity of construction materials conditions the proliferation of microorganisms on their surfaces. This is a significant issue as the economic and societal consequences of bacterial proliferation inside buildings are very important.
However, in some cases, microorganisms can have beneficial effects on cementitious materials when they are used for example as a way to protect and/or repair concrete in applications such as bacteria-based engineering protective systems. New formulations of cementitious materials, incorporating selected bacteria and suitable chemical precursors, are developed with the aim to fill micro-cracks in concrete and thus improve the durability properties. Moreover, concrete with enhanced bio-receptivity are being developed, e.g. with the aim of using the buildings’ envelope to provide a higher surface of green areas (living wall systems), or to reduce the impact of marine works (artificial reefs).
More and more research efforts are devoted to these topics related to cementitious materials- microorganisms interactions within local, trans-regional on international initiatives by multidisciplinary research teams involving scientists in material science, civil engineering, microbiology, microbial ecology, and bioprocess, etc. Significant progress is made, but important scientific and technical obstacles are remaining.
RILEM 253-MCI Technical Committee (2014-2019) aimed to implement concerted approaches and comparison of research outcomes to move toward a better understanding of the phenomena and furthermore, to standardization (of test methods for example) and/or certification.
The TC was organized into four Working Groups, each group tackling a major aspect of these phenomena:
Biodeterioration / microorganisms-cement-based materials interactions in different contexts: sewers, water treatment, agricultural environments, tunnels, marine environment, nuclear waste storage, etc. and the impact on the materials’ properties (biodeterioration) and/or the structures’ performances (durability, safety, etc.)
Microbial stains on building materials and protection of materials; building materials with improved bio-receptivity (vegetal walls, reefs, etc.)
Proliferation of microorganisms (bacteria, fungi) on building materials in indoor conditions and health issues.
Bacteria-based engineering protective systems for cementitious materials (biodeposition, bacteria-based self-healing systems, etc.).
RILEM TC 253-MCI met as a Committee for the first time in May 2014, and since then the committee has held a further 10 plenary meetings, and organized an International Workshop in Delft in June 2016. Besides, numerous informal communications have been held over the years between the members of the working groups.
The TC is involved in the production of some deliverables. These will comprise a comprehensive State of the Art Report (STAR) in published book form, expected to be published next year. This Report will essentially be a compilation and synthesising of reports of the working groups. This conference is also a TC deliverable. Further, it is hoped to produce a shorter report providing a summary and practical applications, for publication in the RILEM Journals.
This conference represents the final major event of the TC. It seeks to bring together a wide range of experts – researchers, practitioners, regulators, and infrastructure managers – to share experiences and new scientific information on these problems. We are pleased that the conference has attracted 55 papers and 15 posters, which will be presented over two days in Toulouse in June 2018. These communications were organized in 4 sessions, matching the different tasks of the 253-MCI working groups: (1) Biodeterioration and microorganisms- cementitious materials interactions in various contexts, (2) Microbial stains on building materials and protection of external walls; building materials with improved bio-receptivity, (3) Proliferation of microorganisms on indoor building materials and (4) Bacteria-based engineering protective systems for cementitious materials. A Young Researcher Competition is also organized, with the aim to identify and encourage talented young scientists on these emerging topics. All the papers have been rigorously peer-reviewed by experts, primarily members of the technical committee who have specific expertise in the areas considered. Thus, we believe the conference volumes will be a valuable addition to the literature on these subjects.
We wish to acknowledge the Convenors of the Working Groups for the work they have done to facilitate the broader work of the TC, and of course the contributions of the members of the working groups.

Contents

Session 1: Microorganisms-cementitious materials interactions in different contexts - Biodeterioration