Browsing by Author "Sonmez, Merve"

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Citation - WoS: 11
Citation - Scopus: 13
Production and Compatibility Assessment of Denitrifying Biogranules Tailored for Self-Healing Concrete Applications
(Elsevier Sci Ltd, 2022) Sonmez, Merve; Ersan, Yusuf Cagatay
Microbial granules have been mostly used for wastewater treatment. Recently, biogranules consisting nitrate-reducing microorganisms have appeared as a unique healing agent providing simultaneous self-healing of cracks and corrosion inhibition of rebar in concrete. Yet, information about the production process and microbial activity of these biogranules as well as their compatibility with cementitious materials remains unknown. This study presents the biogranule production procedure in detail and evaluates the compatibility of the produced biogranules with the cementitious composites. In the form of biogranules, bacteria doses varying between 0.25% and 3.00% w/w cement were incorporated into mortar and the variations in fresh and hardened properties of mortars were evaluated with respect to abiotic mortars. Biogranules were also tested for their compatibility with concrete at minimum and the defined maximum tolerable doses. Biogranules with a NOx-N reduction activity of 0.10 g NOx-N.g(-1) bacteria.d(-1) and organic carbon oxidation activity of 1.50 g HCOO-.g(- 1) bacteria.d(-1) were produced successfully by using minimal medium. It was found out that biogranules enable bacteria incorporation into mortar up to a dose of 2.50% w/w cement without compromising fresh and hardened properties of cementitious composites. It was revealed that the compatibility of the biogranules was due to the mineral layer surrounding the biogranules which prevented interaction between the cement matrix and the microbial content. The thickness of the protective mineral layer around the granules was varying between 50 and 300 mu m depending on the granule size. Net yield for concrete compatible biogranule production was determined as 0.05 g bio-granule.g(-1)HCOO-.
Citation - Scopus: 8
Production of Concrete Compatible Biogranules for Self-Healing Concrete Applications
(EDP Sciences, 2019) Sonmez, Merve; Erşan, Yusuf Çaǧatay
Recently, cost-efficient nitrate reducing biogranules were suggested as an alternative to axenic microbial cultures for development of microbial self-healing concrete. In a marine environment, biogranule containing microbial self-healing concrete showed simultaneous self-healing of cracks and immunisation against rebar corrosion. Yet, information about the production strategy of these biogranules and their compatibility with a mortar matrix is limited. This study presents the production of biogranules and their compatibility with mortar specimens when incorporated at dosages between 0.36% to 4.30% w/w cement (0.25% to 3% of bacteria w/w cement). In-house produced biogranules composed of 70% bacteria and 30% of minerals w/w of biogranule were used for the compatibility tests. In test mortars, calcium formate (CF) and calcium nitrate (CN) were used as regular nutrient admixtures, and nutrient content was set identical in every batch. Up to 2.9% incorporation, biogranules had no significant influence on the fresh properties of mortar. More than 2.9% incorporation caused poor workability and a 26% decrease in 3-Day compressive strength of biomortar specimens. Overall, the biogranules produced are compatible with a cementitious matrix up to 2.9% w/w cement, and even up to 3.6% if early age strength is not essential, which makes biogranules one of the most compatible microbial healing agents among the suggested agents in the literature. © 2021 Elsevier B.V., All rights reserved.