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CALCIUM CARBONATE PRECIPITATION OF ALKALIPHILIC BACTERIA ON ORDINARY PORTLANDITE CEMENT WITH A VISION ON RECYCLED CONCRETE AGGREGATES APPLICATION



Author(s): H. Martinez Hernandez, M. Gueguen Minerbe, Y. Pechaud and T. Sedran
Paper category: Proceedings
Book title: CO2STO2019 - International Workshop CO2 Storage in Concrete
Editor(s): Assia Djerbi, Othman Omikrine-Metalssi, Teddy Fen-Chong
ISBN:
e-ISBN: 978-2-35158-232-9
Publisher: RILEM Publications SARL
Publication year: 2019
Pages: 127-137
Total Pages: 11
Language : English


Abstract: Recycled concrete aggregates (RCA) can substitute natural aggregates in concrete with the
disadvantage of needing a major quantity of cement and water as consequence of their
moderate quality. The objective of this study is to precipitate calcium carbonate crystals over
RCA by consuming atmospheric CO2 with a green and sustainable process achieved by
microorganisms (MO), improving the mechanical and durability properties of RCA.
Bio-carbonation is the result of the metabolism of MO, which must possess three main
characteristics; the ability to precipitate calcium carbonate, grow under alkaline conditions
(between 11 and 13 pH) and to form complex colonies known as biofilm.
In this study, a selection of bacteria isolated from RCA was done with the aim to obtain the
species with the capacity to grow in alkaline conditions and to form biofilm. Even if these
bacteria are not able to precipitate calcium carbonate crystals, we could fusion their
characteristics of growth with other bacteria that perform calcium carbonate synthesis such as
Bacillus Halodurans.
Microbiological techniques were employed to perform isolation and selection of wild species.
An incubation process over a mortar disks was performed to observe the possible behaviour
of bacteria to colonize a surface. As result, three wild bacteria species growing in liquid nutrient
broth pH 11 were obtained. The isolated bacteria grew under a matrix made of nutritive agar
culture over a mortar at pH 13 through biofilm formation. Spherical structures (possibly calcium
carbonate crystals) of around 20 – 30 micrometres appeared near to the zones were bacteria
developed.
The experimental design of this study opens a new gate of research that seeks an evolution in
the use of concrete before and after its life span having as aim a tangible contribution in the
reduction of atmospheric CO2 generating RCA of high quality.
Keywords. Bio carbonation, bacteria, metabolism, biofilm, calcareous rocks and calcium
carbonate crystals.


Online publication : 2019
Publication type : full_text
Public price (Euros) : 0.00


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