Browsing by Author "Belie, N. de"

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    Bacteria-based concrete
    (Elsevier, 2018) Belie, N. de; Wang, J.; Bundur, Zeynep Başaran; Paine, K.; Civil Engineering; BUNDUR, Zeynep Başaran
    Several strains of bacteria can induce the precipitation of calcium carbonate, if the appropriate conditions, sufficient nutrients and a calcium source are provided. The metabolic pathway that is followed by the bacterial strain will dictate the type of nutrients to be selected. This precipitation ability has been investigated during recent decades to improve the mechanical properties and durability of construction materials. Starting with applications for the consolidation of natural stones in weathered cultural heritage buildings and the consolidation of sandy soils, the research efforts have moved towards applications in concrete. When bacteria are mixed into fresh concrete, viable cell numbers rapidly decrease with time. Still, positive effects on concrete strength have been reported. To improve the survival rate of bacteria in concrete, various encapsulation and immobilization strategies have been explored and bacterial spores have been used instead of vegetative cells. Furthermore, added nutrients may impair concrete properties and may also be encapsulated for this reason. Encapsulated bacterial spores have shown the ability to self-heal cracks in concrete and first in-situ applications have been launched.
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    Impact of air entraining admixtures on biogenic calcium carbonate precipitation and bacterial viability
    (Elsevier, 2017) Bundur, Zeynep Başaran; Amiri, Ali; Ersan, Y. C.; Boon, N.; Belie, N. de; Civil Engineering; BUNDUR, Zeynep Başaran; Amiri, Ali
    The applications of self-healing in cement-based materials via biomineralization processes are developing quickly. The main challenge is to find a microorganism that can tolerate the restricted environment of cement paste matrix (i.e. very high pH, lack of oxygen and nutrients, small pore size etc.). The focus of this work was to determine the possible use of an ammonium salt-based air-entraining admixture (AEA) as a protection method to improve the survival of incorporated Sporosarcina pasteurii cells in cement-based mortar. Bacterial cells were directly added to the mortar mix with and without nutrients. Nutrients should be provided to keep the microorganisms viable even at early ages (i.e. 7 days). Surface charge of the bacterial cells and in vitro biogenic calcium carbonate (CaCO3) precipitation were not affected by the incorporation of AEA. However, introducing AEA did not influence the viability in mortar samples, which might be attributed to the type and chemistry of AEA used.