Browsing by Author "Ersan, Yusuf Cagatay"

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Compatibility and Biomineralization Oriented Optimization of Nutrient Content in Nitrate-Reducing-Biogranules-Based Microbial Self-Healing Concrete
(MDPIST ALBAN-ANLAGE 66, CH-4052 BASEL, SWITZERLAND, 2021) Kardogan, Beyza; Sekercioglu, Kadir; 0000-0003-4128-0195; AGÜ, Mühendislik Fakültesi, İnşaat Mühendisliği Bölümü; Ersan, Yusuf Cagatay
Microbially induced calcium carbonate precipitation (MICP) can be mentioned among the popular approaches to develop a self-healing concrete. The production of dissolved inorganic carbon through microbial activity is the main precursor for MICP in concrete and it is limited by the bioavailability of the nutrients. When nutrients are added to the mortar as admixtures, their bioavailability becomes more significant for crack repair because nutrients disperse in the mortar and considerable fraction stays far from a single crack. Therefore, the determination of bioavailability of nutrients and its variation with the initial nutrient content and crack age is essential to optimize a recipe for bacteria-based self-healing concrete. This study presents the optimum nutrient content defined for nitrate-reduction-based self-healing bioconcrete. In the tests, calcium nitrate (CN) and calcium formate (CF) were combined with a CF:CN w/w ratio of 2.50. Mortar properties and bioavailability of nutrients were analysed at different nutrient doses. Moreover, the bioavailability of nutrients at different crack ages changing between 3 and 56 days was monitored. Finally, resuscitation, microbial activity and the MICP performance of nitrate reducing biogranules were tested at defined nutrient bioavailabilties. The optimum nutrient content was determined as 7.00% (CF 5.00% and CN 2.00%). The leaching rates of formate ions were twice the leaching rate of the nitrate ions at similar initial concentrations, which led to a bioavailable HCOO-/NO3-N ratio of 23 g/g in cracked mortar. Under optimum nutrient conditions, the CaCO3 precipitation yield of nitrate reducing biogranules was recorded as 1.5 g CaCO3/g HCOO- which corresponded to 68% C precipitation efficiency.
The effects of aerobic/anoxic period sequence on aerobic granulation and COD/N treatment efficiency
(ELSEVIER, 2013) Erguder, Tuba Hande; Ersan, Yusuf Cagatay; 0000-0002-9669-171X; 0000-0003-4128-0195; AGÜ, Mühendislik Fakültesi, İnşaat Mühendisliği Bölümü; Ersan, Yusuf Cagatay
The effects of period sequence (anoxic–aerobic and aerobic–anoxic) on aerobic granulation from suspended seed sludge, and COD, N removal efficiencies were investigated in two sequencing batch reactors. More stable granules with greater sizes (1.8–3.5 mm) were developed in R1 (anoxic–aerobic sequence). Yet, no significant difference was observed between the reactors in terms of removal efficiencies. Under optimum operational conditions, 92–95% COD, 89–90% TAN and 38–46% total nitrogen removal efficiencies were achieved. The anoxic–aerobic period sequence (R1) resulted in almost complete denitrification during anoxic periods while aerobic–anoxic sequence (R2) led to nitrate accumulation due to limited-carbon source and further granule disintegration. NH3–N concentration of 15–28 mg/L was found to inhibit COD removal up to 30%. This study also revealed the inhibitory sulfide production during anoxic periods. Sulfate concentration of 52.6–70.2 mg/L was found to promote sulfate reduction and sulfide generation (0.24–0.62 mg/L) which, together with free-ammonia, inhibited TAN oxidation by 10–50%.
Life cycle assessment of lightweight concrete containing recycled plastics and fly ash
(TAYLOR & FRANCIS LTD, 2-4 PARK SQUARE, MILTON PARK, ABINGDON OR14 4RN, OXON, ENGLAND, 2020) Ersan, Yusuf Cagatay; Gulcimen, Sedat; Imis, Tuba Nur; Saygin, Osman; Uzal, Nigmet; 0000-0003-4128-0195; AGÜ, Mühendislik Fakültesi, İnşaat Mühendisliği Bölümü
Researchers put significant effort to decrease the environmental impact of concrete by using industrial by-products as an alternative binder. However, the considerable environmental impact still exists due to the consumption of natural resources as aggregates. Natural aggregates are the most used resources by volume in the construction sector. Therefore, it is necessary to investigate by-products as an alternative to natural aggregates as well. This study presents the environmental impact of lightweight concrete (LWC) produced by replacing natural aggregates with recycled waste plastic (polyethylene) (RWP) and partially replacing Portland cement with Class F fly ash (FA). Life Cycle Assessment (LCA) was performed to compare a conventional LWC, containing pumice as natural aggregate and Portland cement as a binder, with green LWC, containing 30% RWP as pumice replacement and 20% FA as cement replacement. These scenarios were evaluated in terms of global warming potential, abiotic depletion, ozone layer depletion, terrestrial ecotoxicity, photochemical oxidation, acidification and eutrophication. LCA was coupled with mechanical tests at 7 days and 28 days. RWPs were found to be an environment-friendly replacement material for natural lightweight aggregates with an overall decrease in all CML-IA impacts except eutrophication. Tested green mix design also provided sufficient strength for nonstructural applications.
Overlooked Strategies in Exploitation of Microorganisms in the Field of Building Materials
(SPRINGER-VERLAG SINGAPORE PTE LTD, 152 BEACH ROAD, #21-01/04 GATEWAY EAST, SINGAPORE, 189721, SINGAPORE, 01.09.2019) Ersan, Yusuf Cagatay; 0000-0003-4128-0195; AGÜ, Mühendislik Fakültesi, İnşaat Mühendisliği Bölümü
Resource efficiency reports released in the last decade point out construction industry as one of the key sectors that needs improvement in terms of ecological sensitivity. Being aware of this unfavorable reputation of construction industry, researchers embarked on replacing the ongoing conventional methods with more sustainable and environmentally friendly ones. One of the approaches for the latter is incorporating microorganisms into construction industry. Popularly investigated strategies can be listed as biocementation, biomasonry, biorepair, and bioconsolidation. Most of these processes are the outcome of a single approach, namely microbial-induced calcium carbonate precipitation (MICP) which was mostly investigated by means of axenic cultures and through one single microbial process, ureolysis. The state of the art about the latter is close to saturation. Moreover, approaching from the ecological wisdom perspective it can be said that some promising microbial strategies to achieve green building materials were overlooked and drawing attention to these strategies became necessary. This review study reveals the overlooked promising microbial strategies in the field of construction biotechnology. The context mainly discusses the potential of five overlooked microbial strategies: (i) heterotrophic and autotrophic MICP pathways, (ii) microbial strategies for surface treatment, (iii) microbial-induced corrosion inhibition, (iv) microbial sequestration of greenhouse gases, and (v) microbial- produced polymers, for their application in the field of construction materials. Further suggestions aim to integrate the microbial resource management approach and non-axenic cultures into the relevant fields of research for the development of environmentally friendly building materials.
Production and compatibility assessment of denitrifying biogranules tailored for self-healing concrete applications
(ELSEVIER SCI LTD, 2022) Sonmez, Merve; Ersan, Yusuf Cagatay; 0000-0003-4128-0195; AGÜ, Mühendislik Fakültesi, İnşaat Mühendisliği Bölümü; Ersan, Yusuf Cagatay
Microbial granules have been mostly used for wastewater treatment. Recently, biogranules consisting nitratereducing 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 μm depending on the granule size. Net yield for concrete compatible biogranule production was determined as 0.05 g biogranule.g− 1 HCOO⁻.
Self-Healing Performance of Biogranule Containing Microbial Self-Healing Concrete Under Intermittent Wet/Dry Cycles
(Self-Healing Performance of Biogranule Containing Microbial Self-Healing Concrete Under Intermittent Wet/Dry Cycles, 2021) Ersan, Yusuf Cagatay; 0000-0003-4128-0195; AGÜ, Mühendislik Fakültesi, İnşaat Mühendisliği Bölümü; Ersan, Yusuf Cagatay
Development of self-sensing and self-healing concrete is essential to minimize the labour-intensive monitoring and repair activities conducted for the maintenance of concrete structures. A type of self-healing concrete can be achieved by using microbial agents that induce calcium carbonate precipitation inside a concrete crack. Recently, biogranules consist of nitrate reducing microorganisms were presented as a new generation microbial healing agent and biogranule containing specimens revealed decent healing performance under completely submerged conditions. However, their performance under intermittent wetting conditions, a common case for various concrete structures, remains unknown. This study presents the self-healing performance of biogranule containing biomortar specimens under intermittent wet/dry conditions. In-house produced biogranules were incorporated into mortar specimens at a dose of 1.45% w/w cement (1.00% of bacteria w/w cement) and self-healing performance of cracked specimens were investigated under alternating wet/dry conditions for a crack width range of 50 to 600 um. Upon alternating wet/dry treatment for 4 weeks, cracks up to a 400 um crack width were effectively healed in biomortar specimens. Their water tightness regain was 44% better than control specimens due to their enhanced healing performance. Overall, non-axenic biogranules appear to be useful in development of self-healing bioconcrete for applications under spraying or intermittent wetting conditions.