Civil Engineering

Permanent URI for this collectionhttps://hdl.handle.net/10679/312

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Automated flow rate control of extrusion for 3D concrete printing incorporating rheological parameters
(Elsevier, 2024-04) Ahi, Oğulcan; Ertunç, Özgür; Bundur, Zeynep Başaran; Bebek, Özkan; Civil Engineering; Mechanical Engineering; ERTUNÇ, Özgür; BUNDUR, Zeynep Başaran; BEBEK, Özkan; Ahi, Oğulcan
The use of inline quality assessment technologies is of great importance in meeting the consistent extrusion requirements of 3D concrete printing (3DCP) applications. This paper presents a system to regulate extrusion speed and maintain the flow rate at a target value during 3DCP processes. The system is based on a new equation that combines printing parameters and the material's rheological properties in the printing process. The proposed control strategy is designed to effectively function with various cement-based mixtures. Validation tests demonstrate that the proposed system can maintain an instantaneous flow rate within a certain range and eventually achieve a constant flow rate. During operation, the flow rate is consistently maintained around the targeted value with an average error rate of 6.7 percent. The flow rate control mechanism shows promise as a reliable and efficient solution for achieving precise and constant flow rates, regardless of the cement mix design used.
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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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Bio-derived rheology modifying agents for cement-based materials
(Springer, 2020) Azima, M.; Bundur, Zeynep Başaran; Civil Engineering; BUNDUR, Zeynep Başaran
In recent few years, significant development has been made in concrete technology to accommodate the requirements of high-performance concrete. Rheology Modifying Agents (RMAs) (such as superplasticizers) and Viscosity Modifying Agents (VMAs) have been developed as two alternative admixtures to obtain the required workability. However, these admixtures not only increased the environmental impacts of concrete production but also increased the unit cost of concrete. Following these concerns, several studies have been focusing on exploring more sustainable approaches in concrete production such as the use of bio-based admixtures in concrete production. Throughout the literature, bio-based polysaccharides (cellulose, chitosan, etc.) were found to be highly effective as VMAs. Long chain molecules of these polysaccharides stick to the water molecules, decrease their relative motion and forms a gel, so increase the yield stress and plastic viscosity. This behaviour reduces the bleeding and segregation, which results in robust highly workable concrete. The interest in this study was motivated by the vital demand to introduce a greener and more sustainable VMA to improve the rheological properties of cement paste. To this end, bacterial cells proposed as VMAs for cement-based materials. The bacterial cells were directly incorporated into the mix of water without any additional intervention. The rheological measurements were implemented to evaluate the influence of cells on apparent viscosity and yield strength. In addition, the use of superplasticizers and fly ash on the performance of biological VMA were also investigated. Our results showed that the apparent viscosity and yield stress of the cement-paste mix were increased with the addition of the microorganisms. Moreover, bacterial cells were found to be compatible with the use of both fly ash and superplasticizers.
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Biomineralization in self-healing cement-based materials: investigating the temporal evolution of microbial metabolic state and material porosity
(American Society of Civil Engineers, 2017) Bundur, Zeynep Başaran; Bae, S.; Kirisits, M. J.; Douglas Ferron, R.; Civil Engineering; BUNDUR, Zeynep Başaran
The potential for self-healing of concrete via biomineralization processes in which microorganisms influence mineral precipitation is promising. To embed microorganisms within a cement-based material, key challenges are to find a microorganism that can tolerate the highly alkaline conditions, survive the mixing process, and remain viable with limited access to nutrients. The focus of this work is to determine the metabolic state of unencapsulated Sporosarcina pasteurii, inoculated vegetatively, in a cement-based matrix over time and to examine its ability to remediate internal cracks and reduce porosity. Viable S. pasteurii was found in hardened mortar samples that were as old as 330 days, and 48% of the viable cells detected were vegetative. A greater fraction of the inoculated cells remained viable in mortar as compared to cement paste, which is promising because mortar is a better representation of the composite nature of concrete than cement paste. Furthermore, as compared to neat paste and neat mortar, addition of the vegetative cell culture to bacterial paste and bacterial mortar resulted in reduced porosity. Bacterial mortar also demonstrated increased strength recovery as compared to neat mortar. The reduction in porosity and increase in mechanical regains demonstrated by the bacterial mortar suggest improved durability and service life for bioconcrete as compared to traditional concrete.
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Biomineralized cement-based materials: impact of inoculating vegetative bacterial cells on hydration and strength
(Elsevier, 2015-01) Bundur, Zeynep Başaran; Kirisits, M. J.; Ferron, R. D.; Civil Engineering; BUNDUR, Zeynep Başaran
Biomineralization in cement-based materials has become a point of interest in recent years due to the possibility that such an approach could be used to develop a self-healing cement-based system. The objective of this study was to investigate the impact of vegetative cells of Sporosarcina pasteurii on the hydration kinetics and compressive strength of cement-based materials. The hydration kinetics were greatly influenced when a bacterial solution consisting of urea-yeast extract nutrient medium and vegetative cells was used to prepare bacterial cement pastes; specifically, severe retardation was observed. In addition, an increase in calcium carbonate precipitation, particularly calcite, occurred within the bacterial pastes. Furthermore, after the first day of hydration, the bacterial mortar displayed compressive strength that was similar to or greater than the compressive strength of the neat mortar.
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Calcium sulfoaluminate cement and supplementary cementitious materials-containing binders in self-healing systems
(Elsevier, 2023-08) Acarturk, B. C.; Sandalcı, Ilgın; Hull, N. M.; Bundur, Zeynep Başaran; Burris, L. E.; Civil Engineering; BUNDUR, Zeynep Başaran; Sandalcı, Ilgın
Creation of more durable concrete is one pathway to achieving improved sustainability and carbon footprint over a concrete structure's life. Microbially induced calcite precipitation has been shown to densify concrete microstructure and fill cracks, reducing moisture transport. One challenge associated with the longevity of bacterial-concrete systems is the high pH environment of the cement paste. Herein, two approaches to address this challenge were investigated: (i) sustainable binder systems, such as calcium sulfoaluminate (CSA) cement and fly ash substitutions of ordinary portland cement (OPC), which lead to lower pH systems, and (ii) non-axenic bacterial cultures, which may facilitate growth of more alkaline-resistant bacteria. Mechanical properties, water absorption, self-healing ability, and survivability of the bacterial systems were tracked, finding that incorporation of non-axenic bacteria did not result in increased bacteria survivability compared to axenic bacteria. However, both bacteria healed cracks [removed]
Open Access
Çimento-esaslı harçlarda kendiliğinden iyileşmenin sağlanması için 2 bileşenli biyolojik katkı maddesinin geliştirilmesi
(Gazi Üniversitesi, 2021) Tezer, Mustafa Mert; Bundur, Zeynep Başaran; Civil Engineering; BUNDUR, Zeynep Başaran; Tezer, Mustafa Mert
Purpose: Throughout the literature, studies showed that among several alternatives such as diatomaceous earth (DE), metakaolin, zeolites and expanded clay could be suitable for protection of the bacteria based on their effects on compressive strength and setting, in particular DE was found to be effective in self-healing of cracks. A correct choice of the protection barrier and application methodology are of crucial for further development of self-healing concrete. This study presents a comparative study on the possible use of a mineral additive (DE) and a porous lightweight aggregate (pumice) as a protective barrier for bacterial cells. Theory and Methods: To obtain a two-phase bio additive, half of the minerals were saturated with a nutrient medium consisting of urea, corn-steep liqueur (CSL) and calcium acetate and the cells with immobilized to the other half without nutrients. Screening of the healing process was done with stereomicroscopy imaging, ultrasonic pulse velocity (UPV) analysis and water absorption testing. Results: Cracks with an average width of 0.4 mm in 28-day old mortar specimens were almost completely filled by bio-based precipitate depending on the curing regime. Cracks were sealed even in sample including relatively smaller dosage of nutrients and bacterial cells in presence of moisture. Moreover, the duration of crack healing was approximately 21 days, which was almost half of the duration to remediate the cracks when cells were directly incorporated to the mix. Conclusion: With this approach, the cracks on mortar surface were sealed and the water absorption capacity of the socalled self-healed mortar decreased compared to its counterpart cracked mortar samples.
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A comparative evaluation of sepiolite and nano-montmorillonite on the rheology of cementitious materials for 3D printing
(Elsevier, 2022-10-03) Aydın, Eylül Mina; Kara, Ahmet Burhan; Bundur, Zeynep Başaran; Özyurt, N.; Bebek, Özkan; Gulgun, M. A.; Civil Engineering; Mechanical Engineering; BUNDUR, Zeynep Başaran; BEBEK, Özkan; Aydın, Eylül Mina; Kara, Ahmet Burhan
Through the last decade, methods of digital manufacturing of concrete gained a significant interest compared to conventional concrete. The main challenge in additive manufacturing (3D printing) is to design a highly thixotropic cementitious system. This study aims to investigate the use of sepiolite as a rheology modifier as a novel approach to improve the thixotropic behavior and adapt cementitious systems to 3D printing. To understand the influence of sepiolite on rheological properties, a comparative evaluation with nano-montmorillonite was established. The effectiveness of clay addition was also investigated in fly-ash amended cement-based materials. The rheological analysis was done on cement-paste samples containing both clays in terms of their effects on thixotropy, structural build-up, and recovery. A preliminary printability assessment was done with a lab scale printer having a ram extruder. The results show that the incorporation of clays increased the dynamic yield stress and time-dependent evolution of static yield stress. Moreover, the addition of clays improved the thixotropic behavior of cement-based systems, particularly those containing fly-ash. Herein, the sepiolite was found to be more effective compared to nano-montmorillonite in terms of improving thixotropy, structural build-up and recovery. The results showed that use of fly-ash enhances the printability of the mix for the specified extruder and the samples containing 1% nano-montmorillonite or 0.5% sepiolite can be printed. The positive effects of sepiolite were attributed to opposing surface charges of the clay layers and its micro-fibrous microstructure. The findings in this study enabled an in-depth understanding of the rheology and printability of fly-ash amended clay containing printable cement-based mortars.
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Crack remediation in mortar via biomineralization: effects of chemical admixtures on biogenic calcium carbonate
(Elsevier, 2018-11-30) Amiri, Ali; Azima, Mahzad; Bundur, Zeynep Başaran; Civil Engineering; BUNDUR, Zeynep Başaran; Amiri, Ali; Azima, Mahzad
Limited research on biomineralization in cement-based systems suggested that self-healing of surface cracks could be obtained by triggering biogenic calcium carbonate (CaCO3) precipitation within the cracks. While this is encouraging, there is not enough information regarding the influence of admixtures on crack remediation and durability of the biogenic CaCO3 against weathering conditions. In this study, the microorganisms were introduced to mortar with their growth medium, which included corn steep liquor (CSL) and urea. With this approach, the cracks on mortar surface were sealed with the CaCO3 and the water absorption capacity of the so-called self-healed mortar decreased compared to its counterpart cracked mortar samples. The biogenic CaCO3 precipitate was found to be durable against freeze-thaw; however the precipitate was unstable under rain water and light. While the addition of air entraining agents (AEA) did not influence the self-healing ability of cells, use of superplasticizers improved the self-healing ability in terms of crack sealing, water absorption, and durability of the precipitate.
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Design of energy-efficient white portland cement mortars for digital fabrication
(Springer, 2020) Kurt, S.; Atalay, Yiğit Alper; Aydın, Ozan Eray; Avcıoğlu, B.; Yıldırım, T.; Göktepe, G. B.; Emir, S.; Bundur, Zeynep Başaran; Paksoy, H. Ö.; Civil Engineering; Bos, F. P.; Lucas, S. S.; Wolfs, R. J. M.; Salet, T. A. M.; BUNDUR, Zeynep Başaran; Atalay, Yiğit Alper; Aydın, Ozan Eray
Additive manufacturing, i.e. three-dimensional (3D) printing technology has many advantages over traditional processes and the related technology is continuously improving. This study aims to develop an energy- efficient White Portland cement (WPC) mortar mix suitable for 3D printing applications. The mortar mix contained a blended binder content using Çimsa Recipro50 calcium aluminate cement (CAC) along with Çimsa Super WPC (sWPC). Microencapsulated Phase Change Materials (mPCMs) added to the mix enhance thermal performance through latent heat storage capability. The CAC used in the study has an alumina content of at least 50% Mineralogical analysis of the CAC and sWPC binder were characterized by the XRD-Rietveld method. In terms of material design for 3D printing, printable mortars must be workable enough to be extruded (extrudability) and retain its shape with little or no deformation after extrusion (buildability). In this study, the printability of mortar was evaluated through workability loss, open time, green strength, and early-age compressive strength. Results showed that use of sWCP and CAC composite enables a thixotropic behavior, which is required for 3D printing. The designed mortar mixes can enable high flowability necessary for successful extrusion and have high green strength at fresh state to maintain stable printing. The results also showed that the use of mPCMs can influence printability while improving buildability.
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Designing redundant cable-driven parallel robots for additive manufacturing using end-effector compliance index
(IEEE, 2023) Kara, Burhan; Qureshi, Muhammad Sarmad; Bundur, Zeynep Başaran; Bebek, Özkan; Civil Engineering; Mechanical Engineering; BUNDUR, Zeynep Başaran; BEBEK, Özkan; Kara, Burhan; Qureshi, Muhammad Sarmad
This paper presents a methodology for optimizing cable anchor points for cable-driven parallel robots (CDPRs) for specific additive manufacturing tasks. Much of a CDPR's workspace is generally not used for printing tasks. The unused workspace of the CDPR can be sacrificed to gain greater control to fulfill the printing task. In this paper, the CDPR is designed for a specific task to achieve the best printing results. To find the optimum robot size, the stiffness of the end-effector and mean cable tension are analyzed. The end-effector compliance index (ECI) is proposed to assess the stiffness of the end-effector within the workspace. The ECI uses cable directions to determine the compliance of a given robot pose. From simulation results, a relation to get optimum CDPR frame size is achieved for both suspended and constrained type CDPRs. The proposed method can be used to design low-cost cable-driven robots for additive manufacturing.
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End-of-life materials used as supplementary cementitious materials in the concrete industry
(MDPI, 2020-04) Nicoara, A. I.; Stoica, A. E.; Vrabec, M.; Rogan, N. S.; Sturm, S.; Ow-Yang, C.; Gulgun, M. A.; Bundur, Zeynep Başaran; Ciuca, I.; Vasile, B. S.; Civil Engineering; BUNDUR, Zeynep Başaran
A sustainable solution for the global construction industry can be partial substitution of Ordinary Portland Cement (OPC) by use of supplementary cementitious materials (SCMs) sourced from industrial end-of-life (EOL) products that contain calcareous, siliceous and aluminous materials. Candidate EOL materials include fly ash (FA), silica fume (SF), natural pozzolanic materials like sugarcane bagasse ash (SBA), palm oil fuel ash (POFA), rice husk ash (RHA), mine tailings, marble dust, construction and demolition debris (CDD). Studies have revealed these materials to be cementitious and/or pozzolanic in nature. Their use as SCMs would decrease the amount of cement used in the production of concrete, decreasing carbon emissions associated with cement production. In addition to cement substitution, EOL products as SCMs have also served as coarse and also fine aggregates in the production of eco-friendly concretes.
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Evaluation of self-healing of internal cracks in biomimetic mortar using coda wave interferometry
(Elsevier, 2016-05) Liu, S.; Bundur, Zeynep Başaran; Zhu, J.; Ferron, R. D.; Civil Engineering; BUNDUR, Zeynep Başaran
Calcium carbonate biomineralization is a bio-chemical process in which calcium carbonate precipitation is obtained by leveraging the metabolic activity of microorganisms. Studies have shown that biomineralization can be used to repair surface cracks in cement-based materials. One of the challenges in determining whether biomineralization is a feasible option for internal crack repair pertains to how to monitor and quantify self-healing of internal microcracks. In this study, mortar samples with and without microcracks and microorganisms were cured in different environments until 50 days. Coda wave interferometry measurements, a nondestructive method that is very sensitive to small changes in material, were conducted on these samples to evaluate the extent of self-healing during the entire curing period. Compressive strength tests were performed after 7 and 28 days of curing. The results indicated that the cracked mortar samples with microorganisms showed significantly higher strength development and higher relative velocity change than samples without microorganisms.
Open Access
Fly-ash evaluation as potential EOL material replacement of cement in pastes: Morpho-structural and physico-chemical properties assessment
(MDPI, 2022-04-24) Vasile, B. S.; Nicoara, A. I.; Surdu, V. A.; Ene, V. L.; Neacsu, I. A.; Stoica, A. E.; Oprea, O.; Boierasu, I.; Trusca, R.; Vrabec, M.; Miklavic, B.; Sturm, S.; Ow-Yang, C.; Gulgun, M. A.; Bundur, Zeynep Başaran; Civil Engineering; BUNDUR, Zeynep Başaran
The main objective of the study was to produce alternative binder materials, obtained with low cost, low energy consumption, and low CO2 production, by regenerating end-of-life (EOL) materials from mineral deposits, to replace ordinary Portland cement (OPC). The materials analyzed were ash and slag from the Turceni thermal power plant deposit, Romania. These were initially examined for morphology, mineralogical composition, elemental composition, degree of crystallinity, and heating behavior, to determine their ability to be used as a potential source of supplementary cementitious materials (SCM) and to establish the activation and transformation temperature in the SCM. The in-situ pozzolanic behavior of commercial cement, as well as cement mixtures with different percentages of ash addition, were further observed. The mechanical resistance, water absorption, sorptivity capacity, resistance to alkali reactions (ASR), corrosion resistance, and resistance to reaction with sulfates were evaluated in this study using low-vacuum scanning electron microscopy.
Open Access
Immobilization of bacterial cells on natural minerals for self-healing cement-based materials
(Frontiers Media, 2021-04-13) Sandalcı, Ilgın; Tezer, M. M.; Bundur, Zeynep Başaran; Civil Engineering; BUNDUR, Zeynep Başaran; Sandalcı, Ilgın
Recent research in the field of concrete materials showed that it might be possible to develop a smart cement-based material that is capable of remediating cracks by Microbial-induced calcium carbonate precipitation (MICP). The early remediation of microcracks enables the design of cement-based systems with an elongated service life with a sustainable approach. However, the main challenge of the application is to extend the viability of the cells against the restrictive environment of cement-paste. These cells have to tolerate the highly alkaline conditions of cement paste, survive the mixing process, and remain viable even when access to nutrients is limited. This paper summarizes a novel study undertaken to investigate the self-healing efficiency of Sporosarcina pasteurii (S. pasteurii) cells immobilized on zeolite and sepiolite minerals having the same particle size. This manuscript reports an extensive experimental study to understand the factors influencing the efficiency of immobilization barriers, such as composition and reactivity. To obtain the bio-additive, the bacterial cells were immobilized without nutrients and additional nutrients were only provided during the curing stage after crack initiation. Screening of the healing process was done with ultrasonic pulse velocity (UPV) testing and stereomicroscopy. Further evaluation on performance was done by evaluating the decrease in water absorption capacity. The healing precipitate was characterized through Environmental Scanning Electron Microscope (ESEM) and Fourier-Transform infrared spectroscopy (FTIR). With this approach, the cracks on mortar surface were sealed and the water absorption capacity of the so-called self-healed mortar decreased compared to its counterpart cracked mortar samples. Sepiolite was found to be a more suitable bedding for the microorganisms compared to zeolite, therefore samples containing sepiolite exhibited a higher performance in terms of crack healing. The results showed that while vegetative cell immobilization on locally available materials is a simple and economically feasible approach the healing capacity of bacterial cells can be hindered due to the reactivity of the mineral.
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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.
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Influence of Sporasarcina pasteurii cells on rheological properties of cement paste
(Elsevier, 2019-11-20) Azima, Mahzad; Bundur, Zeynep Başaran; Civil Engineering; BUNDUR, Zeynep Başaran; Azima, Mahzad
Nowadays with the developments in the concrete materials technology, researches started to focus on highly flowable mixes with improved rheological properties. These highly flowable mixes generally require use of viscosity modifying agents (VMAs) to reduce bleeding and segregation. VMAs are water-soluble polymers that can be produced from acrylic polymers and polysaccharide-based biopolymers obtained from cellulose, starch or bacterial fermentation. Through the literature, nopal mucilage, brown algae and bacterial cell walls were proposed as alternatives to these bio-based admixtures. However, these alternatives also require extra processing which results again with a higher unit cost. This paper summarizes the rheological properties of a cement paste including bacterial cells. The main goal of this study was to investigate the influence of Sporasarcina pasteurii (S. pasteurii) cells on viscosity and yield stress of cement-based materials. The bacterial cells were directly incorporated to the mix water and influence of cells on viscosity and yield strength was evaluated by rheological tests. In addition, the influence of bacteria dosage, water to cement ratio (w/c), use of superplasticizers and fly ash on performance of biological VMA were investigated. Our results showed that the apparent viscosity and yield stress of the cement-paste mix were increased with the addition of the microorganisms. Moreover, the provided biological VMA was found to be compatible with the use of fly ash and superplasticizers depending on the w/c of cement paste.
Open Access
Two-part bio-based self-healing repair agent for cement-based mortar
(International Center for Numerical Methods in Engineering, 2020) Tezer, Mustafa Mert; Bundur, Zeynep Başaran; Civil Engineering; BUNDUR, Zeynep Başaran; Tezer, Mustafa Mert
Factors affecting durability of concrete structures are generally associated with each other. Due to its brittle nature, concrete can crack under stress and these cracks are one of the main reasons for a decrease in service life in concrete structures. Therefore, it is crucial to detect and recover microcracks, then to repair them as they were developed to wider cracks. Recent research in the field of concrete materials suggested that it might be possible to develop a smart cement-based material that is capable of remediate cracks by triggering biogenic calcium carbonate (CaCO3) precipitaton. This paper summarizes a study undertaken to investigate the self-healing efficiency of Sporosarcina pasteurii (S. pasteurii) cells immobilized on both diatomaceous earth and pumice, to remediate flexural cracks on mortar in early ages (28 days after mixing). To obtain a two-phase bio additive, half of the minerals were saturated with a nutrient medium consisting of urea, corn-steep liqueur(CSL) and calcium acetate and the cells with immobilized to the other half without nutrients. Screening of the healing process was done with ultrasonic pulse velocity (UPV) testing and stereomicroscopy. With this approach, the cracks on mortar surface were sealed and the water absorption capacity of the so-called self-healed mortar decreased compared to its counterpart cracked mortar samples.
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Use of biomineralisation in developing smart concrete inspired by nature
(Inderscience, 2015) Zhang, B.; Bundur, Zeynep Başaran; Mondal, P.; Ferron, R. D.; Civil Engineering; BUNDUR, Zeynep Başaran
Recently, interest has focused on leveraging the biological functions of microorganisms to develop smart cement-based materials. This paper provides an overview of the calcium carbonate biomineralisation process in nature and presents a review of the work conducted by various groups around the world on biogenic calcium carbonate formation as it relates to the hydration, microstructure, properties, and performance of cement-based materials. Promises and concerns of applying biomineralisation in cement-based materials are also discussed, and directions for future research are explored.
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Use of corn-steep liquor as an alternative carbon source for biomineralization in cement-based materials and its impact on performance
(Elsevier, 2018-03-20) Amiri, Ali; Bundur, Zeynep Başaran; Civil Engineering; BUNDUR, Zeynep Başaran; Amiri, Ali
Early age microcracks are generally the primary cause for a decrease in service life of cement-based structures. Recent studies suggested that it might be possible to develop a smart cement-based material that could self-heal microcracks. The use of microbial induced calcium carbonate precipitation (MICP) in cement-based materials is a novel approach to trigger self-healing and it has become an interesting field of research. MICP is a biochemical process where calcium carbonate (CaCO3) precipitation is obtained via metabolic pathways for microorganism and MICP via urea hydrolysis is the most common approach used in cement-based materials. Through the literature the most commonly used nutrient media for urea hydrolysis was composed of yeast extract and urea. However, use of yeast extract as a carbon source not only resulted with a severe retardation of initial setting and it increases the cost of the application. This study investigates the suitability of corn steep liquor (CSL) as an alternative replacement of yeast extract. CSL was found to be a suitable alternative for MICP applications without compromising bacterial growth, ability to promote CaCO3 precipitation. In addition, use of a nutrient medium including CSL and urea did not have such an adverse effect on initial set and compressive strength as compared to a urea and yeast extract medium. (C) 2018 Elsevier Ltd. All rights reserved.

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