The Experts below are selected from a list of 1551 Experts worldwide ranked by ideXlab platform
Willy Verstraete - One of the best experts on this subject based on the ideXlab platform.
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A mirobial based system developed for self-healing concrete cracks
2020Co-Authors: Jianyun Wang, Nele De Belie, Willy VerstraeteAbstract:Concrete has a relatively low tensile strength which makes it prone to cracking. Without immediate and proper treatment, cracks tend to expand further and eventually require costly repair. Engineering structural elements in such a way, that they would respond to crack formation with an autonomous self-healing action, would therefore be highly desirable. Based on previous experience with microbial induced calcium carbonate precipitation for consolidation of concrete and stone, the use of Bacteria as self-healing agent is tested. Diatomaceous earth (DE) was used as the carrier to protect Bacteria since the Bacterial activity decreases a lot in the high pH concrete environment. Fist the ureolytic activity of the Bacteria after being Immobilized in DE, was tested at neutral pH and in a cement suspension which was used to mimic the high pH environment inside concrete. The DE Immobilized Bacteria were shown to remain active in cement suspension and decompose a significant amount of the urea (60 %) that was provided as a nutrient. Un-Immobilized Bacteria almost lost all ureolytic activity in the cement suspension. By means of light microscopy, it was observed that cracks of width 0.15 mm to 0.17 mm in the specimens added with DE Immobilized Bacteria, were completely filled by the precipitation. The precipitation was primarily confirmed tob e CaCO3 based on the results of Energy Dispersive Spectrum analysis. The addition of diatomaceous earth did not decrease the tensile and compressive strength of the specimens.
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Use of silica gel or polyurethane Immobilized Bacteria for self-healing concrete
Construction and Building Materials, 2012Co-Authors: Jianyun Wang, Kim Van Tittelboom, Nele De Belie, Willy VerstraeteAbstract:Cracks in concrete are the main reason for a decreased service life of concrete structures. It is therefore more advisable and economical to restrict the development of early age small cracks the moment they appear, than to repair them after they have developed to large cracks. A promising way is to pre-add healing agents to the concrete to heal early age cracks when they appear, i.e. the so-called self-healing approach. In addition to the more commonly studied polymeric healing materials, Bacterial CaCO3precipitation also has the potential to be used for self-healing. It is more compatible with the concrete matrix and it is environment friendly. However, Bacterial activity decreases a lot in the high pH (>12) environment inside concrete. In this research, the possibility to use silica gel or polyurethane as the carrier for protecting the Bacteria was investigated. Experimental results show that silica gel Immobilized Bacteria exhibited a higher activity than polyurethane Immobilized Bacteria, and hence, more CaCO3precipitated in silica gel (25% by mass) than in polyurethane (11% by mass) based on thermogravimetric analysis. However, cracked mortar specimens healed by polyurethane Immobilized Bacteria had a higher strength regain (60%) and lower water permeability coefficient (10-10-10-11m/s), compared with specimens healed by silica gel Immobilized Bacteria which showed a strength regain of only 5% and a water permeability coefficient of 10-7-10-9m/s. The results indicated that polyurethane has more potential to be used as a Bacterial carrier for self-healing of concrete cracks. © 2011 Elsevier Ltd. All rights reserved.
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Diatomaceous earth as a protective vehicle for Bacteria applied for self-healing concrete
Journal of Industrial Microbiology and Biotechnology, 2012Co-Authors: J.y. Wang, Willy VerstraeteAbstract:Crack repair is crucial since cracks are the main cause for the decreased service life of concrete structures. An original and promising way to repair cracks is to pre-incorporate healing agents inside the concrete matrix to heal cracks the moment they appear. Thus, the concrete obtains self-healing properties. The goal of our research is to apply Bacterially precipitated CaCO₃ to heal cracks in concrete since the microbial calcium carbonate is more compatible with the concrete matrix and more environmentally friendly relative to the normally used polymeric materials. Diatomaceous earth (DE) was used in this study to protect Bacteria from the high-pH environment of concrete. The experimental results showed that DE had a very good protective effect for Bacteria. DE Immobilized Bacteria had much higher ureolytic activity (12-17 g/l urea was decomposed within 3 days) than that of un-Immobilized Bacteria (less than 1 g/l urea was decomposed within the same time span) in cement slurry. The optimal concentration of DE for immobilization was 60% (w/v, weight of DE/volume of Bacterial suspension). Self-healing in cracked specimens was visualized under light microscopy. The images showed that cracks with a width ranging from 0.15 to 0.17 mm in the specimens containing DE Immobilized Bacteria were completely filled by the precipitation. Scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) were used to characterize the precipitation around the crack wall, which was confirmed to be calcium carbonate. The result from a capillary water absorption test showed that the specimens with DE Immobilized Bacteria had the lowest water absorption (30% of the reference ones), which indicated that the precipitation inside the cracks increased the water penetration resistance of the cracked specimens.
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Use of silica gel or polyurethane Immobilized Bacteria for self-healing concrete
Construction and Building Materials, 2012Co-Authors: Jianyun Wang, Kim Van Tittelboom, Willy VerstraeteAbstract:Abstract Cracks in concrete are the main reason for a decreased service life of concrete structures. It is therefore more advisable and economical to restrict the development of early age small cracks the moment they appear, than to repair them after they have developed to large cracks. A promising way is to pre-add healing agents to the concrete to heal early age cracks when they appear, i.e. the so-called self-healing approach. In addition to the more commonly studied polymeric healing materials, Bacterial CaCO 3 precipitation also has the potential to be used for self-healing. It is more compatible with the concrete matrix and it is environment friendly. However, Bacterial activity decreases a lot in the high pH (>12) environment inside concrete. In this research, the possibility to use silica gel or polyurethane as the carrier for protecting the Bacteria was investigated. Experimental results show that silica gel Immobilized Bacteria exhibited a higher activity than polyurethane Immobilized Bacteria, and hence, more CaCO 3 precipitated in silica gel (25% by mass) than in polyurethane (11% by mass) based on thermogravimetric analysis. However, cracked mortar specimens healed by polyurethane Immobilized Bacteria had a higher strength regain (60%) and lower water permeability coefficient (10 −10 –10 −11 m/s), compared with specimens healed by silica gel Immobilized Bacteria which showed a strength regain of only 5% and a water permeability coefficient of 10 −7 –10 −9 m/s. The results indicated that polyurethane has more potential to be used as a Bacterial carrier for self-healing of concrete cracks.
Jianyun Wang - One of the best experts on this subject based on the ideXlab platform.
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A mirobial based system developed for self-healing concrete cracks
2020Co-Authors: Jianyun Wang, Nele De Belie, Willy VerstraeteAbstract:Concrete has a relatively low tensile strength which makes it prone to cracking. Without immediate and proper treatment, cracks tend to expand further and eventually require costly repair. Engineering structural elements in such a way, that they would respond to crack formation with an autonomous self-healing action, would therefore be highly desirable. Based on previous experience with microbial induced calcium carbonate precipitation for consolidation of concrete and stone, the use of Bacteria as self-healing agent is tested. Diatomaceous earth (DE) was used as the carrier to protect Bacteria since the Bacterial activity decreases a lot in the high pH concrete environment. Fist the ureolytic activity of the Bacteria after being Immobilized in DE, was tested at neutral pH and in a cement suspension which was used to mimic the high pH environment inside concrete. The DE Immobilized Bacteria were shown to remain active in cement suspension and decompose a significant amount of the urea (60 %) that was provided as a nutrient. Un-Immobilized Bacteria almost lost all ureolytic activity in the cement suspension. By means of light microscopy, it was observed that cracks of width 0.15 mm to 0.17 mm in the specimens added with DE Immobilized Bacteria, were completely filled by the precipitation. The precipitation was primarily confirmed tob e CaCO3 based on the results of Energy Dispersive Spectrum analysis. The addition of diatomaceous earth did not decrease the tensile and compressive strength of the specimens.
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Use of silica gel or polyurethane Immobilized Bacteria for self-healing concrete
Construction and Building Materials, 2012Co-Authors: Jianyun Wang, Kim Van Tittelboom, Nele De Belie, Willy VerstraeteAbstract:Cracks in concrete are the main reason for a decreased service life of concrete structures. It is therefore more advisable and economical to restrict the development of early age small cracks the moment they appear, than to repair them after they have developed to large cracks. A promising way is to pre-add healing agents to the concrete to heal early age cracks when they appear, i.e. the so-called self-healing approach. In addition to the more commonly studied polymeric healing materials, Bacterial CaCO3precipitation also has the potential to be used for self-healing. It is more compatible with the concrete matrix and it is environment friendly. However, Bacterial activity decreases a lot in the high pH (>12) environment inside concrete. In this research, the possibility to use silica gel or polyurethane as the carrier for protecting the Bacteria was investigated. Experimental results show that silica gel Immobilized Bacteria exhibited a higher activity than polyurethane Immobilized Bacteria, and hence, more CaCO3precipitated in silica gel (25% by mass) than in polyurethane (11% by mass) based on thermogravimetric analysis. However, cracked mortar specimens healed by polyurethane Immobilized Bacteria had a higher strength regain (60%) and lower water permeability coefficient (10-10-10-11m/s), compared with specimens healed by silica gel Immobilized Bacteria which showed a strength regain of only 5% and a water permeability coefficient of 10-7-10-9m/s. The results indicated that polyurethane has more potential to be used as a Bacterial carrier for self-healing of concrete cracks. © 2011 Elsevier Ltd. All rights reserved.
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Use of silica gel or polyurethane Immobilized Bacteria for self-healing concrete
Construction and Building Materials, 2012Co-Authors: Jianyun Wang, Kim Van Tittelboom, Willy VerstraeteAbstract:Abstract Cracks in concrete are the main reason for a decreased service life of concrete structures. It is therefore more advisable and economical to restrict the development of early age small cracks the moment they appear, than to repair them after they have developed to large cracks. A promising way is to pre-add healing agents to the concrete to heal early age cracks when they appear, i.e. the so-called self-healing approach. In addition to the more commonly studied polymeric healing materials, Bacterial CaCO 3 precipitation also has the potential to be used for self-healing. It is more compatible with the concrete matrix and it is environment friendly. However, Bacterial activity decreases a lot in the high pH (>12) environment inside concrete. In this research, the possibility to use silica gel or polyurethane as the carrier for protecting the Bacteria was investigated. Experimental results show that silica gel Immobilized Bacteria exhibited a higher activity than polyurethane Immobilized Bacteria, and hence, more CaCO 3 precipitated in silica gel (25% by mass) than in polyurethane (11% by mass) based on thermogravimetric analysis. However, cracked mortar specimens healed by polyurethane Immobilized Bacteria had a higher strength regain (60%) and lower water permeability coefficient (10 −10 –10 −11 m/s), compared with specimens healed by silica gel Immobilized Bacteria which showed a strength regain of only 5% and a water permeability coefficient of 10 −7 –10 −9 m/s. The results indicated that polyurethane has more potential to be used as a Bacterial carrier for self-healing of concrete cracks.
Ke Zhang - One of the best experts on this subject based on the ideXlab platform.
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Bacterial community dynamics and enhanced degradation of di n octyl phthalate dop by corncob sodium alginate Immobilized Bacteria
Geoderma, 2017Co-Authors: Ke Zhang, Qiang Chen, Wei Chen, Jia Chen, Lin Ji, You MoAbstract:Abstract A Bacterial strain designated as ETG-101, capable of utilizing DOP as source of carbon and energy, was isolated from activated sludge. According to the 16 s rRNA gene sequences, strain ETG-101 was identified as Burkholderia sp. Analysis of DOP degradation intermediates indicated that strain ETG-101 could completely degrade DOP via de-esterification pathway that transforms di-esters to monoesters, where DOP was transferred to M-n-O-P which in turn metabolized to phthalic acid (PA) and eventually entered into tricarboxylic acid (TCA) cycle. Further, strain ETG-101 was Immobilized into complex carriers (corncob and sodium alginate). The environmental factors tests demonstrated that the Immobilized cells had broader range of pH and temperature than free cells. Carrier and entrapment media significantly affected the efficiency of DOP removal in soil. Corncob-sodium alginate (SA) Immobilized cells had the highest DOP removal rate of 78.1% in soil, which was 60-fold and 2.3-fold more increase in DOP removal rate compared to corncob and free cells, respectively. The Bacterial quantity and community structure dynamics in soil were also investigated by the real-time quantitative PCR (q-PCR) and Illumina Miseq sequencing. The results revealed that inoculation of free cells into soil significantly reduced the Bacterial quantity of soil and altered the Bacterial community structure, whereas the introduction of Immobilized cells to soil increased the total Bacterial quantity and slightly changed the Bacterial community composition. As the acclimatization, Sphingomonas and Rhodocyclus gradually disappeared when free cells were inoculated to soil. Burkholderia along with Acinetobacter , Bacteroides and Arthrobacter were the predominant genera in both free and Immobilized cells systems, which were probably responsible for DOP biodegradation in soil system. Corncob-sodium alginate Immobilized Bacteria significantly enhanced DOP biodegradation in soil and had little impact on soil biodiversity. Therefore this immobilization method has potential in DOP-contaminated soil remediation.
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Degradation of quinclorac by corncob, bamboo charcoal, canola meal adsorption-sodium alginate Immobilized Pseudomonas stutzeri PFS-4
Journal of Applied Ecology, 2017Co-Authors: Ke Zhang, Qiang Chen, Wei Chen, Jia Chen, Sang GeAbstract:To enhance the degradation of quinclorac in soil and water, corncob, bamboo charcoal, canola meal and sodium alginate were used as complex carriers to immobilize previously isolated Bacterial strain Pseudomonas stutzeri PFS-4. Orthogonal experiment was conducted to optimize immobilization condition, and the degradation efficiency of quinclorac by Immobilized Bacteria and free Bacteria in water and soil were further investigated. The results indicated that the optimal conditions for immobilization were: alginate concentration 4%, proportion of adsorption carrier (corncob: bamboo charcoal: canola meal=1:2:1), calcium chloride 3%, crosslinking time 4 h. Immobilized Bacteria and free Bacteria could effectively degrade 91.4% and 72.8% of quinclorac (800 mg·L-1) after 6 d inoculation at 30 ℃ and pH 7.0. The removal rates of quinclorac by Immobilized Bacteria and free Bacteria were affected in actual wastewater and soil treatments, but the quinclorac removal rate remained at 84.2% in soil and 74.3% in water, respectively. The results also demonstrated that the carrier and entrapment media significantly affected the quinclorac removal in soil, and the degradation rate of quinclorac in soil was significantly positively correlated with turnover frequency. Therefore, the approach of corncob, bamboo charcoal, canola meal adsorption-sodium alginate Immobilized P. stutzeri PFS-4 possesses application potential in in situ remediation of quinclorac contaminated water and soil due to its buffering to adverse conditions.
Kim Van Tittelboom - One of the best experts on this subject based on the ideXlab platform.
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Use of silica gel or polyurethane Immobilized Bacteria for self-healing concrete
Construction and Building Materials, 2012Co-Authors: Jianyun Wang, Kim Van Tittelboom, Nele De Belie, Willy VerstraeteAbstract:Cracks in concrete are the main reason for a decreased service life of concrete structures. It is therefore more advisable and economical to restrict the development of early age small cracks the moment they appear, than to repair them after they have developed to large cracks. A promising way is to pre-add healing agents to the concrete to heal early age cracks when they appear, i.e. the so-called self-healing approach. In addition to the more commonly studied polymeric healing materials, Bacterial CaCO3precipitation also has the potential to be used for self-healing. It is more compatible with the concrete matrix and it is environment friendly. However, Bacterial activity decreases a lot in the high pH (>12) environment inside concrete. In this research, the possibility to use silica gel or polyurethane as the carrier for protecting the Bacteria was investigated. Experimental results show that silica gel Immobilized Bacteria exhibited a higher activity than polyurethane Immobilized Bacteria, and hence, more CaCO3precipitated in silica gel (25% by mass) than in polyurethane (11% by mass) based on thermogravimetric analysis. However, cracked mortar specimens healed by polyurethane Immobilized Bacteria had a higher strength regain (60%) and lower water permeability coefficient (10-10-10-11m/s), compared with specimens healed by silica gel Immobilized Bacteria which showed a strength regain of only 5% and a water permeability coefficient of 10-7-10-9m/s. The results indicated that polyurethane has more potential to be used as a Bacterial carrier for self-healing of concrete cracks. © 2011 Elsevier Ltd. All rights reserved.
You Mo - One of the best experts on this subject based on the ideXlab platform.
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Bacterial community dynamics and enhanced degradation of di n octyl phthalate dop by corncob sodium alginate Immobilized Bacteria
Geoderma, 2017Co-Authors: Ke Zhang, Qiang Chen, Wei Chen, Jia Chen, Lin Ji, You MoAbstract:Abstract A Bacterial strain designated as ETG-101, capable of utilizing DOP as source of carbon and energy, was isolated from activated sludge. According to the 16 s rRNA gene sequences, strain ETG-101 was identified as Burkholderia sp. Analysis of DOP degradation intermediates indicated that strain ETG-101 could completely degrade DOP via de-esterification pathway that transforms di-esters to monoesters, where DOP was transferred to M-n-O-P which in turn metabolized to phthalic acid (PA) and eventually entered into tricarboxylic acid (TCA) cycle. Further, strain ETG-101 was Immobilized into complex carriers (corncob and sodium alginate). The environmental factors tests demonstrated that the Immobilized cells had broader range of pH and temperature than free cells. Carrier and entrapment media significantly affected the efficiency of DOP removal in soil. Corncob-sodium alginate (SA) Immobilized cells had the highest DOP removal rate of 78.1% in soil, which was 60-fold and 2.3-fold more increase in DOP removal rate compared to corncob and free cells, respectively. The Bacterial quantity and community structure dynamics in soil were also investigated by the real-time quantitative PCR (q-PCR) and Illumina Miseq sequencing. The results revealed that inoculation of free cells into soil significantly reduced the Bacterial quantity of soil and altered the Bacterial community structure, whereas the introduction of Immobilized cells to soil increased the total Bacterial quantity and slightly changed the Bacterial community composition. As the acclimatization, Sphingomonas and Rhodocyclus gradually disappeared when free cells were inoculated to soil. Burkholderia along with Acinetobacter , Bacteroides and Arthrobacter were the predominant genera in both free and Immobilized cells systems, which were probably responsible for DOP biodegradation in soil system. Corncob-sodium alginate Immobilized Bacteria significantly enhanced DOP biodegradation in soil and had little impact on soil biodiversity. Therefore this immobilization method has potential in DOP-contaminated soil remediation.
