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Nele De Belie - One of the best experts on this subject based on the ideXlab platform.

  • Application of microorganisms in concrete: a promising sustainable strategy to improve concrete durability
    Applied Microbiology and Biotechnology, 2016
    Co-Authors: Jianyun Wang, Nico Boon, Yusuf Cagatay Ersan, Nele De Belie
    Abstract:

    The beneficial effect of microbially induced carbonate precipitation on building materials has been gradually disclosed in the last decade. After the first applications of on historical stones, promising results were obtained with the respect of improved durability. An extensive study then followed on the application of this environmentally friendly and compatible material on a currently widely used construction material, concrete. This review is focused on the discussion of the impact of the two main applications, bacterial surface treatment and bacteria based Crack Repair, on concrete durability. Special attention was paid to the choice of suitable bacteria and the metabolic pathway aiming at their functionality in concrete environment. Interactions between bacterial cells and cementitious matrix were also elaborated. Furthermore, recommendations to improve the effectiveness of bacterial treatment are provided. Limitations of current studies, updated applications and future application perspectives are shortly outlined.

  • microbially induced caco3 precipitation through denitrification an optimization study in minimal nutrient environment
    Biochemical Engineering Journal, 2015
    Co-Authors: Yusuf Cagatay Ersan, Nele De Belie, Nico Boon
    Abstract:

    Abstract So far, researchers investigated microbially induced CaCO3 precipitation (MICP) for soil reinforcement, self-Repairing concrete and Ca2+ removal from industrial waste streams. Reported MICP yields were mainly achieved under nutrient-rich conditions. However, creating the tested nutrient-rich conditions in intended applications is both an economical and a practical issue. Therefore, investigation of MICP in more realistic conditions is necessary. This study presents optimization of MICP through denitrification in minimal nutrient conditions. To optimize their MICP performances, we isolated two strains, Pseudomonas aeruginosa and Diaphorobacter nitroreducens, by following an application oriented selection procedure. Upon performance optimization, in 2 days, D. nitroreducens and P. aeruginosa precipitated 14.1 and 18.9 g CaCO3/g NO3-N, respectively. Repetitive CaCO3 precipitation was also achieved from a single inoculum in both 2 days and 3 weeks intervals. Selected strains and the process were further evaluated for three MICP applications: (1) Ca2+ removal from paper mill wastewater (2) soil reinforcement, (3) Crack Repair in concrete. Overall, denitrification was found to be an effective process to remove Ca2+ from paper mill wastewater. P. aeruginosa and D. nitroreducens could be introduced as potential candidates for soil and concrete applications due to their enhanced precipitation yields, resilience and performance under minimal nutrient conditions.

  • The efficiency of self-healing concrete using alternative manufacturing procedures and more realistic Crack patterns
    Cement and Concrete Composites, 2015
    Co-Authors: Kim Van Tittelboom, Eleni Tsangouri, Danny Van Hemelrijck, Nele De Belie
    Abstract:

    During the last years, more and more research has been devoted to self-healing in cementitious materials. While most research is still done on carefully prepared small-scale mortar samples with predefined Cracks, the healing efficiency should be investigated after exposure of the capsules to the concrete mixing and casting process and for random appearing Cracks. In the current study, the resistance of brittle encapsulation materials, containing polyurethane, against the mixing and manufacturing process of concrete was studied. Different methods to protect the capsules were proposed and evaluated. In addition, realistic Crack patterns were created in beams with embedded capsules. Non-destructive testing techniques such as digital image correlation, acoustic emission analysis and X-ray radiography were used to evaluate the survivability of the capsules upon mixing and the breakability of the capsules upon Crack formation. Evaluation of the Crack Repair efficiency by performing water permeability tests showed some improvement in water tightness due to self-healing, but the water ingress into the Cracks was not completely prevented.

  • Effect of chemical composition of polymeric precursors on the healing capability of cementitious materials
    2015
    Co-Authors: Maria Adelaide Pereira Gomes De Araújo, Sandra Van Vlierberghe, Peter Dubruel, Nele De Belie
    Abstract:

    Cracking in concrete is frequently a concern since these Cracks can provide easy entry channels for the penetration of aggressive liquids and gases into the concrete, leading to deterioration. The Repair of these Cracks is, therefore, indispensable. However, manual Crack Repair is expensive and difficult when Cracks are not visible or accessible. Thus, the design of concrete with self-healing properties would be highly beneficial to improve its durability. One of the Crack Repair approaches makes use of capsules sequestering polymer-based healing agents. The self-healing mechanism is triggered upon Crack formation, leading to release and reaction of the healing agent in the zone of damage. In the present work, we aimed at determining the most suitable polymer backbone to be applied for self-healing of cementitious materials. For this purpose, several key prerequisites such as viscosity, curing time and mechanical properties of different polymeric precursors including siloxane-, urethane-, epoxy- and polyester-based have been evaluated. To assess the effect of high alkalinity on the degradation of the polymerized healing agents, stability tests have been performed. The results indicate that different healing agent solutions show adequate curing time, viscosity and mechanical properties. The various healing agent solutions were manually injected into Cracks of mortar samples to evaluate their sealing capability and strain capacity.

  • microbial self healing concrete denitrification as an enhanced and environment friendly apporach
    5th International conference on Self-Healing Materials (ICSHM 2015), 2015
    Co-Authors: Yusuf Cagatay Ersan, Nico Boon, Nele De Belie
    Abstract:

    ID No : 43 ABSTRACT Concrete tends to Crack due to its relatively low tensile strength which jeopardizes the good condition of steel reinforcement bars. Concrete Cracks start at micro level and facilitate ingression of corrosive substances such as SO4 , Cl, O2. Corrosion of the rebar may result in failure of the structure. Self-healing concrete can provide Crack Repair immediately after Crack initiation. One of the self-healing mechanisms is the use of bacteria to induce CaCO3 precipitation in the Crack environment. So far two different bio-chemical pathways, aerobic oxidation of lactate and ureolysis were used for microbial self-healing concrete. Despite the reported successful results, there are critical drawbacks of these two metabolic pathways to be improved such as oxygen limited performances, toxic byproducts, odor and negative effects on mechanical properties of concrete. To overcome these issues, we proposed an alternative pathway based on microbial NO3 reduction (denitrification) which also leads to CaCO3 precipitation.Concrete tends to Crack due to its relatively low tensile strength which jeopardizes the good condition of steel reinforcement bars. Concrete Cracks start at micro level and facilitate ingression of corrosive substances such as SO4 , Cl, O2. Corrosion of the rebar may result in failure of the structure. Self-healing concrete can provide Crack Repair immediately after Crack initiation. One of the self-healing mechanisms is the use of bacteria to induce CaCO3 precipitation in the Crack environment. So far two different bio-chemical pathways, aerobic oxidation of lactate and ureolysis were used for microbial self-healing concrete. Despite the reported successful results, there are critical drawbacks of these two metabolic pathways to be improved such as oxygen limited performances, toxic byproducts, odor and negative effects on mechanical properties of concrete. To overcome these issues, we proposed an alternative pathway based on microbial NO3 reduction (denitrification) which also leads to CaCO3 precipitation. We tested two axenic NO3 reducing cultures, Pseudomonas aeruginosa and Diaphorobacter nitroreducens for microbial self-healing through denitrification. Bacterial agents were encapsulated within expanded clay particles (0.5-2mm) and tested for multiple Crack closure (Crack range 100-500 μm) in mortar specimens under wet and wet/humid conditions. Under wet conditions, specimens with bacteria could completely close the Cracks up to 250 μm in 2 weeks and 350 μm in 4 weeks. After 4 weeks, for 235 ± 35 μm original Crack width, mortar prisms containing P. aeruginosa and D. nitroreducens absorbed 47% and 51% less water than reference specimen, respectively. Overall, the denitrification pathway was found to be as effective as existing methods while it is more environment-friendly.

Shunzhi Qian - One of the best experts on this subject based on the ideXlab platform.

  • use of genetically modified bacteria to Repair Cracks in concrete
    Materials, 2019
    Co-Authors: Zhigang Zhang, Yuanzhao Ding, Yiwei Weng, Shunzhi Qian
    Abstract:

    In this paper, we studied the Crack-Repair by spraying bacteria-based liquid around the Cracks in concrete. To enhance the Repair efficiency and speed up the Repair process, the transposon mutagenesis method was employed to modify the genes of Bacillus halodurans and create a mutant bacterial strain with higher efficiency of calcium carbonate productivity by catalyzing the combination of carbonate and calcium ion. The efficiency of Crack-Repairing in concrete by spraying two kinds of bacterial liquid was evaluated via image analysis, X-ray computed tomography (X-CT) scanning technology and the sorptivity test. The results show that the Crack-Repair efficiency was enhanced very evidently by spraying genetically modified bacterial-liquid as no microbiologically induced calcite precipitation (MICP) was found within the Cracks for concrete samples sprayed using wild type bacterial-liquid. In addition, the Crack-Repair process was also shortened significantly in the case of genetically modified bacteria.

Kim Van Tittelboom - One of the best experts on this subject based on the ideXlab platform.

  • use of neutron radiography and tomography to visualize the autonomous Crack sealing efficiency in cementitious materials
    Materials and Structures, 2013
    Co-Authors: Kim Van Tittelboom, Peter Vontobel, F H Wittmann, Nele De Belie
    Abstract:

    Penetration of moisture into building materials is at the origin of several damage mechanisms. In the case of cement-based materials Crack formation is a common problem and highly accelerates the ingress of water and aggressive substances. Crack Repair may be needed, however, Repair works are expensive and in some cases Cracks are even not accessible. Therefore, in this research we aim at autonomous Crack sealing. Upon Crack appearance, damage is sealed autonomously by the release of encapsulated agents. Visualization of the water uptake by means of neutron radiography for samples with manually and autonomously sealed Cracks showed that in both cases ingress of water into the Crack can be prevented depending on the type of agent. The efficiency of three different agents was examined and it was shown that the use of polyurethane or a water repellent agent were most promising. Neutron tomography scans demonstrated that poor results were obtained when encapsulated methyl methacrylate was used, since one component of the agent hardened inside the capsules before Crack appearance. From the results we can conclude that autonomous sealing of Cracks is feasible and that neutron radiography and tomography are suitable non-destructive test techniques to visualize the autonomous Crack sealing efficiency.

  • acoustic emission analysis for the quantification of autonomous Crack healing in concrete
    Construction and Building Materials, 2012
    Co-Authors: Kim Van Tittelboom, Nele De Belie, Frank Lehmann, C Grosse
    Abstract:

    Abstract As half of the annual construction budget is spent on remediation of existing structures, self-healing of concrete, which is very sensitive to Cracking, would be highly desirable. In this research, encapsulated healing agents were embedded in the concrete matrix in order to obtain self-healing properties. Upon Cracking, the capsules break and the healing agent is released, resulting in Crack Repair. The efficiency of this Crack healing technique was evaluated by means of mechanical tests and by using acoustic emission analysis. It was shown that due to autonomous Crack Repair, more than 80% of the original strength and stiffness can be regained. Events with an energy higher than the energy related to concrete Cracking indicated breakage of the capsules. Upon reloading of beams with untreated Cracks, the released energy was lower compared to beams with healed Cracks. From this study it was shown that AE is a suitable technique to evaluate self-healing of Cracks in concrete.

  • Self-healing efficiency of cementitious materials containing tubular capsules filled with healing agent
    Cement & Concrete Composites, 2011
    Co-Authors: Kim Van Tittelboom, Patric Jacobs
    Abstract:

    Abstract It has been estimated that, in Europe, 50% of the annual construction budget is spent on rehabilitation and Repair of the existing structures [1] . Therefore, autonomous Crack healing of concrete, a construction material that is highly susceptible to Cracking, would be desirable. In this research, an encapsulated healing agent was embedded in the mortar matrix to obtain self-healing properties. Upon Crack appearance, the capsules break and the healing agent is released, causing Crack Repair. By means of Computed Tomography and visual observation of the Crack faces, filling of the Cracks with healing agent was observed. It was seen that more than 50% of the original strength and stiffness could be regained after self-healing. It was also found that the water permeability could be reduced by a factor 102 to 104 due to autonomous Crack healing. As a consequence, the proposed technique may be used for partial restoration of concrete properties after Cracking.

Zhigang Zhang - One of the best experts on this subject based on the ideXlab platform.

  • use of genetically modified bacteria to Repair Cracks in concrete
    Materials, 2019
    Co-Authors: Zhigang Zhang, Yuanzhao Ding, Yiwei Weng, Shunzhi Qian
    Abstract:

    In this paper, we studied the Crack-Repair by spraying bacteria-based liquid around the Cracks in concrete. To enhance the Repair efficiency and speed up the Repair process, the transposon mutagenesis method was employed to modify the genes of Bacillus halodurans and create a mutant bacterial strain with higher efficiency of calcium carbonate productivity by catalyzing the combination of carbonate and calcium ion. The efficiency of Crack-Repairing in concrete by spraying two kinds of bacterial liquid was evaluated via image analysis, X-ray computed tomography (X-CT) scanning technology and the sorptivity test. The results show that the Crack-Repair efficiency was enhanced very evidently by spraying genetically modified bacterial-liquid as no microbiologically induced calcite precipitation (MICP) was found within the Cracks for concrete samples sprayed using wild type bacterial-liquid. In addition, the Crack-Repair process was also shortened significantly in the case of genetically modified bacteria.

Al-karawi Hassan - One of the best experts on this subject based on the ideXlab platform.

  • Fatigue Crack Repair by TIG-remelting
    'Informa UK Limited', 2021
    Co-Authors: Al-karawi Hassan, Manai Asma, Al-emrani Mohammad, Von Bock Und Polach R. U.franz
    Abstract:

    Fatigue is one of the most detrimental problems that often limit the service life of steel bridges. Because of that, different post-weld treatment methods have been studied to extend the fatigue life and Repair any existing Cracks resulted from the traffic loading. The aim of this paper is to study the fatigue life extension of Cracked structures by means of Tungsten Inert Gas (TIG) remelting. Fatigue tests were conducted at a stress ratio of 0.29 on a transverse attachment of 16 mm, thick-walled specimens. The specimens were instrumented with multiple strain gauges along the weld to detect the strain drop caused by Crack growth. The specimens were pre-fatigued until a Crack of around 1 mm- deep was obtained at the weld toe. After Crack detection, the weld toes were treated by TIG-remelting to remove any existing Cracks and to reduce the local stress concentration. The weld parameters were controlled so that the fusion depth was always larger than the Crack depth. A substantial fatigue life extension could be achieved and the testing led to ran-out after 10 million cycles, which was attributed to the improvement in geometry and residual stress. Weld toe radius was measured before and after treatment by a laser scanner. Hole drilling was used to measure the residual stresses in as-welded state and after TIG-remelting. In this paper, a fatigue damage model is also presented. It is shown that the model gives a good prediction of the effect of TIG-treatment in Repairing fatigue loaded welded details

  • Fatigue Crack Repair in welded structures via tungsten inert gas remelting and high frequency mechanical impact
    Elsevier Science, 2020
    Co-Authors: Al-karawi Hassan, Bock Und Polach, Rüdiger Ulrich Franz Von, Al-emrani Mohammad
    Abstract:

    Rehabilitation of welded structures has gained increasing attention lately. This paper aims at investigating the efficiency of Tungsten Inert Gas (TIG)-remelting and TIG-remelting followed by High Frequency Mechanical Impact treatment (TIG-HFMI) in fatigue life extension. Fatigue tests were carried out on as-welded and Cracked specimens after treatment. The lives of the treated specimens increased remarkably by the two methods (TIG and TIG-HFMI). Many of the treated specimens ran-out after 10 million cycles of loading and failed at the clamping location when tested at a higher stress range. The improvement in compressive residual stresses, hardness values and weld toe radii were the reasons behind the life extension. These factors were used for fatigue life estimation in as-welded and TIG-treated specimens using the base metal S[sbnd]N curve. Moreover, the test results together with results from previous tests in the literature demonstrated that these methods can be useful for Crack retrofitting as for new structures.The authors are grateful to the road administration (Trafikverket) and the innovation system agency in Sweden Vinnova (Infra Sweden 2030) who financed the whole project

  • Fatigue life extension in existing steel bridges. High-Frequency Mechanical Impact treatment and Tungsten Inert Gas remelting in life extension and fatigue Crack Repair of welded steel structures
    2020
    Co-Authors: Al-karawi Hassan
    Abstract:

    This thesis investigates the performance of improved welds with two post-weld treatment methods for application on existing structures. High-Frequency Mechanical Impact (HFMI) treatment and Tungsten Inert Gas (TIG) remelting were used for fatigue life extension of welded structures. Axial fatigue testing was conducted on transversal non-load-carrying attachment treated via the investigated methods. Furthermore, more than 250 test results on different treated welded details were collected, sorted and analysed. HFMI-treatment was found to give a significant fatigue life extension even with the presence of Cracks up to 2.25 mm. On the other hand, the efficiency of TIG-remelting was also proven when the Crack was completely eliminated after remelting. Even if a small part of the Crack remains after remelting, fair fatigue life could be expected. However, it is recommended to use HFMI-treatment or TIG-remelting only when the Crack inspection is negative before and after treatment respectively.Complimentary studies showed that the investigated methods induced compressive residual stress, increased the smoothness of the weld toe, increased the local hardness and changed the angular distortion status locally. Moreover, TIG-remelting changed the microstructure in both the fusion zone and the heat-affected zone. HFMI-treatment changed the Crack orientation, induced compressive plasticity at the Crack tip and caused Crack narrowing or even closure. However, these effects were less significant for deeper Cracks. Moreover, some practical aspects of the treatment application were investigated. Unlike treating new structures, TIG-electrode should be placed at the weld toe to secure that the maximum fusion depth corresponds to the Crack plane. On the other hand, HFMI-indentor should be slanted more toward the base metal than the weld to avoid unintentional Crack opening. Moreover, the IIW recommendations for both HFMI-treatment inclination and indentation depth could be extended to Cracked structures. The aforementioned investigated parameters (i.e. residual stress, distortions, local hardness and toe\u27s smoothness) were incorporated in fatigue life predictions for both treatment methods. The base metal S-N curve was used to predict the life of specimens treated via TIG-remelting, while Paris law was used to track the Crack propagation of HFMI-treated details. The results corresponded well with fatigue test results. Combining TIG-remelting with HFMI-treatment resulted in welds with higher fatigue strength because of the combined effects of Crack closure via TIG-remelting and compressive plasticity via HFMI-treatment