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1
Chen, How-Ji, Ching-Fang Peng, Chao-Wei Tang, and Yi-Tien Chen. "Self-Healing Concrete by Biological Substrate." Materials 12, no. 24 (December 8, 2019): 4099. http://dx.doi.org/10.3390/ma12244099.
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At present, the commonly used repair materials for concrete cracks mainly include epoxy systems and acrylic resins, which are all environmentally unfriendly materials, and the difference in drying shrinkage and thermal expansion often causes delamination or cracking between the original concrete matrix and the repair material. This study aimed to explore the feasibility of using microbial techniques to repair concrete cracks. The bacteria used were environmentally friendly Bacillus pasteurii. In particular, the use of lightweight aggregates as bacterial carriers in concrete can increase the chance of bacterial survival. Once the external environment meets the growth conditions of the bacteria, the vitality of the strain can be restored. Such a system can greatly improve the feasibility and success rate of bacterial mineralization in concrete. The test project included the microscopic testing of concrete crack repair, mainly to understand the crack repair effect of lightweight aggregate concrete with implanted bacterial strains, and an XRD test to confirm that the repair material was produced by the bacteria. The results show that the implanted bacterial strains can undergo Microbiologically Induced Calcium Carbonate Precipitation (MICP) and can effectively fill the cracks caused by external concrete forces by calcium carbonate deposition. According to the results on the crack profile and crack thickness, the calcium carbonate precipitate produced by the action of Bacillus pasteurii is formed by the interface between the aggregate and the cement paste, and it spreads over the entire fracture surface and then accumulates to a certain thickness to form a crack repairing effect. The analysis results of the XRD test also clearly confirm that the white crystal formed in the concrete crack is calcium carbonate. From the above test results, it is indeed feasible to use Bacillus pasteurii in the self-healing of concrete cracks.
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Lenting and Orlowsky. "Self-Healing of Cracked Textile Reinforced Concrete Layers." Proceedings 34, no. 1 (November 18, 2019): 20. http://dx.doi.org/10.3390/proceedings2019034020.
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Sustainable maintenance of existing steel-reinforced concrete structures becomes more important. Using non-reinforced sprayed mortar to maintain these structures often leads to cracks in this repair layer due to the alteration of crack widths in the ordinary structure. The water impermeability as well as the durability of the sprayed mortar will be reduced due to the described cracks. This presentation shows a solution for the described problem. The use of carbon yarns with a special inorganic coating as reinforcement in sprayed mortars leads to a self-healing of the arising cracks. Due to the inorganic coating applied on carbon yarns the excellent bond between mortar and yarn results in a fine distributed crack image with crack width below 0.1 mm. It is shown that these cracks heal themselves. Consequently we can provide a mainly mineral protection layer for existing steel reinforced concrete structures which is impermeably to water based solutions. The presentation focuses on the material development and characterization.
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Luo, Mian, Kang Jing, Jingquan Bai, Ziqi Ding, Dingyi Yang, Haoliang Huang, and Yongfan Gong. "Effects of Curing Conditions and Supplementary Cementitious Materials on Autogenous Self-Healing of Early Age Cracks in Cement Mortar." Crystals 11, no. 7 (June 27, 2021): 752. http://dx.doi.org/10.3390/cryst11070752.
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The autogenous healing potential of cement-based materials is affected by multiple factors, such as mix composition, crack width, pre-cracking age and external environmental conditions. In this study, the effects of curing conditions and supplementary cementitious materials (SCMs) on autogenous self-healing of early age cracks in cement mortar were investigated. Three curing conditions, i.e., standard curing, wet–dry cycles and incubated in water, and two SCMs, i.e., fly ash (FA) and blast furnace slag (BFS) with various contents (cement replacement ratio at 0%, 20%, and 40%) were examined. A single early age crack (pre-cracking age of 3 days) with a width of 200~300 μm was generated in cylindrical mortar specimens. Autogenous crack self-healing efficiency of mortar specimens was evaluated by performing a visual observation and a water permeability test. Moreover, microstructure analysis (XRD, SEM and TG/DTG) was utilized to characterize the healing products. The results indicated that the presence of water was essential for the autogenous self-healing of early age cracks in cement mortar. The efficiency of self-healing cracks was highest in specimens incubated in water. However, no significant self-healing occurred in specimens exposed to standard curing. For wet–dry cycles, a longer healing time was needed to obtain good self-healing compared to samples incubated in water. SCMs type and content significantly affected the autogenous self-healing ability of early age cracks. The self-healing efficiency of early age cracks decreased with increases in FA and BFS content. BFS mortars exhibited greater recovery in relation to water penetration resistance compared to the reference and FA mortars. Almost the same regain of water tightness and a lower crack-healing ratio after healing of 28 days in FA mortars were observed compared to the reference. The major healing product in the surface cracks of specimens with and without SCMs was micron-sized calcite crystals with a typical rhombohedral morphology.
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Abro, Fahad ul Rehman, Abdul Salam Buller, Tariq Ali, Zain Ul-Abdin, Zaheer Ahmed, Noor Ahmed Memon, and Ali Raza Lashari. "Autogenous Healing of Cracked Mortar Using Modified Steady-State Migration Test against Chloride Penetration." Sustainability 13, no. 17 (August 24, 2021): 9519. http://dx.doi.org/10.3390/su13179519.
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Concrete is a popular building material all over the world, but because of different physiochemical processes, it is susceptible to crack development. One of the primary deterioration processes of reinforced concrete buildings is corrosion of steel bars within the concrete through these cracks. In this regard, a self-healing technique for crack repair would be the best solution to reduce the penetration of chloride ions inside concrete mass. In this study, a rapid chloride migration (RCM) test was conducted to determine the self-healing capacity of cracked mortar. With the help of the RCM test, the steady-state migration coefficient of cracked and uncracked specimens incorporating expansive and crystalline admixtures was calculated. Based on the rate of change of the chloride ion concentrations in the steady-state condition, the migration coefficient was calculated. Furthermore, bulk electrical conductivity tests were also conducted before and after the migration test to understand the self-healing behavior. It was evident from the test results that the self-healing of cracks was helpful to reduce the penetration of chloride ions and that it enhanced the ability of cracked mortar to restrict the chloride ingress. Using this test method, the self-healing capacity of the new self-healing technologies can be evaluated. The RCM test can be an acceptable technique to assess the self-healing ability of cement-based materials in a very short period, and the self-healing capacity can be characterized in terms of the decrease of chloride migration coefficients.
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Ekaputri, J. J., M. S. Anam, Y. Luan, C. Fujiyama, N. Chijiwa, and D. H. E. Setiamarga. "Application of GGBFS and Bentonite to Auto-Healing Cracks of Cement Paste." Journal of Advanced Civil and Environmental Engineering 1, no. 1 (April 30, 2018): 38. http://dx.doi.org/10.30659/jacee.1.1.38-48.
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Cracks are caused by many factors. Shrinkage and external loading are the most common reason. It becomes a problem when the ingression of aggressive and harmful substance penetrates to the concrete gap. This problem reduces the durability of the structures. It is well known that self – healing of cracks significantly improves the durability of the concrete structure. This paper presents self-healing cracks of cement paste containing bentonite associated with ground granulated blast furnace slag. The self-healing properties were evaluated with four parameters: crack width on the surface, crack depth, tensile strength recovery, and flexural recovery. In combination with microscopic observation, a healing process over time is also performed. The results show that bentonite improves the healing properties, in terms of surface crack width and crack depth. On the other hand, GGBFS could also improve the healing process, in terms of crack depth, direst tensile recovery, and flexural stiffness recovery. Carbonation reaction is believed as the main mechanism, which contributes the self-healing process as well as the continuous hydration progress.
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Bonilla, Luis, Marwa Hassan, Hassan Noorvand, Tyson Rupnow, and Ayman Okeil. "Evaluation of Self-Healing Efficiency of Reinforced Concrete Beams with Calcium Nitrate Microcapsules." Transportation Research Record: Journal of the Transportation Research Board 2629, no. 1 (January 2017): 63–72. http://dx.doi.org/10.3141/2629-09.
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The self-healing efficiency of cementitious materials was improved by developing several strategies to provide and deliver the products (healing agents) needed for cracks to self-repair. This study evaluated the self-healing efficiency of microcapsules filled with calcium nitrate in reinforced and unreinforced concrete beams. The structural behavior and healing efficiency were evaluated by measuring and then comparing the initial stiffness, peak strength, and deformation with posthealing measurements. Furthermore, as part of this study, crack monitoring was conducted to evaluate crack healing over time. Then characterization analysis was carried out with energy dispersive X-ray spectroscopy to quantify the healing components in the cracked areas. Results showed that the air content in samples containing microcapsules was two times higher than that in the control samples. Furthermore, addition of microcapsules lowered the flexural strength of concrete beams compared with that of the control samples. A positive stiffness recovery was recorded for all groups, with and without microcapsules or steel. Control samples showed the lowest stiffness recovery; however, the use of steel with microcapsules presented a superior healing efficiency and improved stiffness recovery significantly by 38%. Results from image analysis showed that crack widths did not completely heal for the control samples, while using microcapsules allowed the cracked widths to heal more efficiently. The best observed performance was for the microcapsules–steel group, which yielded 100% healing of the cracks.
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VijayaSekhar, K., Swati Ghosh Acharyya, Sanghamitra Debroy, V. Pavan Kumar Miriyala, and Amit Acharyya. "Self-healing phenomena of graphene: potential and applications." Open Physics 14, no. 1 (January 1, 2016): 364–70. http://dx.doi.org/10.1515/phys-2016-0040.
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AbstractThe present study investigates the self healing behavior of both pristine and defected single layer graphene using a molecular dynamic simulation. Single layer graphene containing various defects such as preexisting vacancies and differently oriented pre-existing cracks were subjected to uniaxial tensile loading till fracture occurred. Once the load was relaxed, the graphene was found to undergo self healing. It was observed that this self healing behaviour of cracks holds irrespective of the nature of pre-existing defects in the graphene sheet. Cracks of any length were found to heal provided the critical crack opening distance lies within 0.3-0.5 nm for a pristine sheet and also for a sheet with pre-existing defects. Detailed bond length analysis of the graphene sheet was done to understand the mechanism of self healing of graphene. The paper also discusses the immense potential of the self healing phenomena of graphene in the field of graphene based sub-nano sensors for crack sensing.
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Huyang, George, and Jirun Sun. "Clinically Applicable Self-Healing Dental Resin Composites." MRS Advances 1, no. 8 (2016): 547–52. http://dx.doi.org/10.1557/adv.2016.86.
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ABSTRACTSelf-healing is one of the most desired material properties. Herein, we present the design and development of a new self-healing dental composite (SHDC) that can heal micro-cracks autonomously. The SHDC has two functional components in addition to contemporary dental composites: healing powder (HP) and healing liquid (HL) encapsulated in silica microcapsules. The autonomous healing is triggered by micro-cracks which fracture microcapsules in their propagation path and release the HL. As a consequence, the released HL dissolves and reacts with the HP, and then fill the micro-cracks with a cement-like new material. This 3-step crack-release-heal process prevents micro-cracks from causing restoration failure, thus improving the service life of dental restorative material. The mechanical performance of the SHDC prepared were evaluated in terms of elastic modulus and fracture toughness, which were in the upper level compared to commercial dental restorative materials, and the self-healing capability was confirmed through fracture toughness recovery test. In addition, the SHDCs were made with clinically-tested, biocompatible materials, which makes them readily applicable as medical devices.
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Nellesen, A., M. von Tapavicza, J. Bertling, A. M. Schmidt, G. Bauer, and T. Speck. "Self-Healing in Plants as a Model for Self-Repairing Elastomer Materials." Polymers from Renewable Resources 2, no. 4 (November 2011): 149–56. http://dx.doi.org/10.1177/204124791100200402.
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Polymer based elements are frequently subject to high mechanical load. It is well known, that such components can spontaneously break although the mechanical stress has not reached the average maximum load. These fatigue fractures are caused by micro-cracks. A smart approach would be to implement a self-healing function that is able to heal a crack in an early stage and thus avoid crack propagation. Fraunhofer UMSICHT and the Plant Biomechanics Group Freiburg together with co-operation partners develop biomimetic self-healing elastomers having the capability to repair micro-cracks automatically without any intervention from outside.
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Yoo, Kyung Suk, Seung Yup Jang, and Kwang-Myong Lee. "Recovery of Chloride Penetration Resistance of Cement-Based Composites Due to Self-Healing of Cracks." Materials 14, no. 10 (May 12, 2021): 2501. http://dx.doi.org/10.3390/ma14102501.
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This study proposed a method of applying coating on uncracked surfaces of test specimens in the electrical migration–diffusion test for the evaluation of the chloride penetration resistance of cracked cement-based composites. It was shown that, by applying the proposed method, the recovery of the chloride penetration resistance from self-healing of cracks can be evaluated more accurately because the application of surface coating reduces the test time and the error introduced by over-simplification. Based on observations of the self-healing-induced recovery of chloride penetration resistance, a phenomenological model for predicting the progress of crack self-healing in cement-based composites was suggested. This model is expected to evaluate the chloride penetration resistance more accurately in actual concrete structures with cracks.
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Negrini, Alberto, Marta Roig-Flores, Eduardo J. Mezquida-Alcaraz, Liberato Ferrara, and Pedro Serna. "Effect of crack pattern on the self-healing capability in traditional, HPC and UHPFRC concretes measured by water and chloride permeability." MATEC Web of Conferences 289 (2019): 01006. http://dx.doi.org/10.1051/matecconf/201928901006.
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Concrete has a natural self-healing capability to seal small cracks, named autogenous healing, which is mainly produced by continuing hydration and carbonation. This capability is very limited and is activated only when in direct contact with water. High Performance Fibre-Reinforced Concrete and Engineered Cementitious Composites have been reported to heal cracks for low damage levels, due to their crack pattern with multiple cracks and high cement contents. While their superior self-healing behaviour compared to traditional concrete types is frequently assumed, this study aims to have a direct comparison to move a step forward in durability quantification. Reinforced concrete beams made of traditional, high-performance and ultra-high-performance fibre-reinforced concretes were prepared, sized 150×100×750 mm3. These beams were pre-cracked in flexion up to fixed strain levels in the tensioned zone to allow the analysis of the effect of the different cracking patterns on the self-healing capability. Afterwards, water permeability tests were performed before and after healing under water immersion. A modification of the water permeability test was also explored using chlorides to evaluate the potential protection of this healing in chloride-rich environments. The results show the superior durability and self-healing performance of UHPFRC elements.
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Danner, Tobias, Ulla Hjorth Jakobsen, and Mette Rica Geiker. "Mineralogical Sequence of Self-Healing Products in Cracked Marine Concrete." Minerals 9, no. 5 (May 10, 2019): 284. http://dx.doi.org/10.3390/min9050284.
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Self-healing of cracked concrete beams after 25 years of marine exposure was investigated. The extent of self-healing and the chemical and mineralogical composition of the self-healing products were characterized, and mechanisms proposed. There was no effect of varying silica fume (4%, 12%) and fly ash content (0%, 20%) on the mineralogy and chemistry of the self-healing products and the extent of self-healing. Crack widths smaller than 0.2 mm appeared closed. With increasing crack depth, a sequence of changing mineralogy of self-healing products was found. In the outer part of the crack (0–5 mm depth from the exterior surface) only calcite was precipitated followed by brucite layers from 5–30 mm depth. The brucite was occasionally intermixed with calcite. At crack depths >30 mm only ettringite was observed. It is hypothesized that the mineralogical sequence observed with increasing crack depth occurs due to an increasing pH of the solution inside the crack with increased crack depth. Self-healing of cracks in marine exposed concrete is proposed to happen through precipitation of ions from seawater partly in reaction with ions from the cement paste in the outer part of the crack and through dissolution and reprecipitation of ettringite at larger crack depths.
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Ando, Kotoji, Koji Takahashi, Wataru Nakao, Toshio Osada, and Kae Iwanaka. "New Technology for Increasing Through-Life Reliability of Ceramics Components Using Self-Crack-Healing Ability." Journal of Powder Technology 2013 (June 13, 2013): 1–11. http://dx.doi.org/10.1155/2013/937312.
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Structural ceramics are superior to metallic materials in terms of their high-temperature strengths and critical heat proof temperatures. However, compared to metallic materials, ceramics exhibit lower fracture toughness, so they are more sensitive to flaws such as pores and cracks. The shortness considerably decreases the component reliability. To overcome the shortness, in this study, special attention is paid to structural ceramics with self-crack-healing ability. There are several advantages for using a material with self-crack-healing ability. (1) After an efficient machine operation, the materials are able to self-heal the cracks introduced by the machining. (2) The materials are able to self-heal the cracks introduced during service and recover the strength completely at healing temperature. However, ways of organizing the available knowledge to increase the through-life reliability of ceramics components have not been extensively studied. The authors propose a new concept and the corresponding flowchart. This new concept is a promising technique for increasing the through-life reliability of ceramics components with excellent self-crack-healing ability.
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Amer Ali Algaifi, Hassan, Suhaimi Abu Bakar, Abdul Rahman Mohd Sam, and Ahmad Razin Zainal Abidin. "Crack-healing in cementitious material to improve the durability of structures: Review." MATEC Web of Conferences 250 (2018): 03005. http://dx.doi.org/10.1051/matecconf/201825003005.
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One of the most commonly used materials in the field of construction is concrete. Nevertheless, there are strong inclinations for concrete to form cracks, which would then allow the penetration of both aggressive and harmful substances into the concrete. Subsequently, this will decrease the durability of the affected structures. Thus, the ability for cracks to heal themselves in the affected cementitious materials is in demand to prolong the life of any structure. Autogenous self-healing is one approach to overcome smaller crack widths (macrocracks). Nowadays, crack width-healing is of great importance. Having said that, both polymers and bacteria are the most common approach to enhance autogenous self-healing and bond crack faces. Crack width-healing of up to 0.97 mm was achieved via bacteria-based self-healing. In this paper, the mechanisms of these approaches and their efficiency to heal crack were highlighted. Both bacteria-and polymers-based self-healing are promising techniques for the future. However, long term studies are still required before real applications can be made.
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Nakao, Wataru. "Second Step Approach for Self Healing Ceramics." Materials Science Forum 638-642 (January 2010): 2133–37. http://dx.doi.org/10.4028/www.scientific.net/msf.638-642.2133.
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Self healing of surface cracks is the most effective function to ensure the structural integrity for ceramic components, because even minute surface crack give rise to a large strength decrease because of its high sensitivity to flaws. The present author and coworkers succeeded that the degraded strength due to cracking can be completely recovered by self crack healing ability driven by the high temperature oxidation of silicon carbide. Then, the mechanism and the effect of the self-healing were investigated. The most attractive feature of the self healing is to be able to respond to the damage caused during service. Thus, enhancement in self healing velocity has been necessary to actualize the self healing ceramics. In the present study, nanometer sizing the disperse silicon carbide particle was attempted to achieve the purpose. Alumina composites containing various shapes of silicon carbide nanometer sized particles were synthesized from mullite, aluminum and carbon powders. From the strength recovery behaviors of these alumina/ silicon carbide composites, the following aspects were derived. Silicon carbide particles nanometer sizing can heal completely the surface cracks at lower temperature and shorter time.
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Sun, Xichen, Jie Chen, Siyi Lu, Miaomiao Liu, Siyu Chen, Yifei Nan, Yang Wang, and Jun Feng. "Ureolytic MICP-Based Self-Healing Mortar under Artificial Seawater Incubation." Sustainability 13, no. 9 (April 25, 2021): 4834. http://dx.doi.org/10.3390/su13094834.
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Ureolytic microbial-induced calcium carbonate precipitation (MICP) is a promising green technique for addressing sustainable building concerns by promoting self-healing mortar development. This paper deals with bacteria-based self-healing mortar under artificial seawater incubation for the sake of fast crack sealing with sufficient calcium resource supply. The ureolytic MICP mechanism was explored by morphology characterization and compositional analysis. With polyvinyl alcohol fiber reinforcement, self-healing mortar beams were produced and bent to generate 0.4 mm width cracks at the bottom. The crack-sealing capacity was evaluated at an age of 7 days, 14 days, and 28 days, suggesting a 1-week and 2-week healing time for 7-day- and 14-day-old samples. However, the 28-day-old ones failed to heal the cracks completely. The precipitation crystals filling the crack gap were identified as mainly vaterite with cell imprints. Moreover, fiber surface was found to be adhered by bacterial precipitates indicating fiber–matrix interfacial bond repair.
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Xu, Jing, Xianzhi Wang, Junqing Zuo, and Xiaoyan Liu. "Self-Healing of Concrete Cracks by Ceramsite-Loaded Microorganisms." Advances in Materials Science and Engineering 2018 (June 24, 2018): 1–8. http://dx.doi.org/10.1155/2018/5153041.
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Protective carrier is essential for the self-healing of concrete cracks by microbially induced CaCO3 precipitation, owing to the harsh conditions in concrete. In this paper, porous ceramsite particles are used as microbial carrier. Heat treatment and NaOH soaking are first employed to improve the loading content of the ceramsite. The viability of bacterial spores is assessed by urea decomposition measurements. Then, the self-healing efficiency of concrete cracks by spores is evaluated by a series of tests including compressive strength regain, water uptake, and visual inspection of cracks. Results indicate that heat treatment can improve the loading content of ceramsite while not leading to a reduction of concrete strength by the ceramsite addition. The optimal heating temperature is 750°C. Ceramsite particles act as a shelter and protect spores from high-pH environment in concrete. When nutrients and spores are incorporated in ceramsite particles at the same time, nutrients are well accessible to the cells. The regain ratio of the compressive strength increases over 20%, and the water absorption ratio decreases about 30% compared with the control. The healing ratio of cracks reaches 86%, and the maximum crack width healed is near 0.3 mm.
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Yin, Tao, Min Zhi Rong, and Ming Qiu Zhang. "Self-Healing of Cracks in Epoxy Composites." Advanced Materials Research 47-50 (June 2008): 282–85. http://dx.doi.org/10.4028/www.scientific.net/amr.47-50.282.
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To provide epoxy based composites with self-healing ability, two-component healing system consisting of urea-formaldehyde walled microcapsules containing epoxy (30~70µm in diameter) and CuBr2(2-MeIm)4 (the complex of CuBr2 and 2-methylimidazole) latent hardener was synthesized. When cracks were initiated or propagated in the composites, the neighbor micro-encapsulated epoxy would be damaged and released. As the latent hardener is soluble in epoxy, it can be well dispersed in epoxy composites during composites manufacturing, and hence activate the released epoxy wherever it is. As a result, repair of the cracked sites is completed through curing of the released epoxy. The present work indicated that the plain weave glass fabric laminates using the above self-healing epoxy as the matrix have been provided with self-healing capability.
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Ekaputri, Januarti Jaya, Fahmi Firdaus Alrizal, Iqbal Husein, Triwulan, and Mohd Mustafa Al Bakri Abdullah. "An Application of Rice Husk Ash (RHA) and Calcium Carbonate (CaCo3) as Materal for Self-Healing Cement." Key Engineering Materials 673 (January 2016): 3–12. http://dx.doi.org/10.4028/www.scientific.net/kem.673.3.
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Self-healing cement is a novel topic in concrete technology. Concrete is created to have its own ability to heal cracks. Crack closure is due to the material deposition of the gap so causing the crack closed. Materials used in this paper is mortar composition with ordinary portland cement replaced by calcium carbonate (CaCO3) and rice husk ash. There are three testing presented in this paper. The first is compressive test to determine the compression applied to mortar for initial cracks. The second is an ultrasonic pulse velocity (UPV) test to observe the depth of cracks and density of each composition. The third is macroscopic investigation to observe cracks wide in each mixture. The maximum compressive strength of 22.46 MPa shown by specimens made with 10% rice husk ash and 10% calcium carbonate cement. By the end of healing process, it reached 23.18 MPa. It was also shown that in crack depth decreased from 38 mm to 16 mm. From this analysis, it can be concluded that rice husk ash (RHA) and calcium carbonate (CaCO3) can be utilized as self-healing concrete materials.
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DONG, BIQIN, NINGXU HAN, MING ZHANG, XIANFENG WANG, HONGZHI CUI, and FENG XING. "A MICROCAPSULE TECHNOLOGY BASED SELF-HEALING SYSTEM FOR CONCRETE STRUCTURES." Journal of Earthquake and Tsunami 07, no. 03 (September 2013): 1350014. http://dx.doi.org/10.1142/s1793431113500140.
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In the study, a novel microcapsule technology based self-healing system for concrete structures has been developed. Through situ-polymerization reaction, the microcapsule is formed by urea formaldehyde resin to pack the epoxy material, which is applied to cementitious composite to achieve self-healing effect. The experimental results revealed that the self-healing efficiency of the composite can be accessed from the recovery of the permeability and strength for the cracked cementitious specimens as the healing agent in the microcapsule acting on the cracks directly. Scanning electronic microscope (SEM/EDX) results show that the epoxy resin is released along with the cracking of the cementitious composite and prevent from cracks continued growth. Further studies show that the self-healing efficiency is affected by the pre-loading of composite, particle size of microcapsule, aging duration of healing agent and so on.
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Farhadi, Sasan, and Shervin Ziadloo. "Self-Healing Microbial Concrete - A Review." Materials Science Forum 990 (May 2020): 8–12. http://dx.doi.org/10.4028/www.scientific.net/msf.990.8.
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The cracks naturally exist in concrete and make it weak to the deleterious environment, ending with structure degradation. According to this fact, concrete requires to be improved and remediated. Self-healing methods are considered as a helpful way to mitigate the propagation and development of the cracks in the concrete. Bio-mineralization methods can heal the concrete by using bacteria suchlike Bacillus subtilis and Bacillus pasteurii, which can seal the cracks by CaCO3 precipitation. The literature represents the MICP method of using bacteria in concrete, which can improve the concrete durability by increasing the compressive strength. Furthermore, the different kinds of bacteria used in the concrete structure and the methods of employing as a self-healing agent review. Moreover, it illustrates B. Pasteurii and B. Sphaericus has more efficient results between other bacteria due to increasing the compressive strength and lifespan of the concrete.
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Jones, A. S., J. D. Rule, J. S. Moore, N. R. Sottos, and S. R. White. "Life extension of self-healing polymers with rapidly growing fatigue cracks." Journal of The Royal Society Interface 4, no. 13 (December 19, 2006): 395–403. http://dx.doi.org/10.1098/rsif.2006.0199.
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Self-healing polymers, based on microencapsulated dicyclopentadiene and Grubbs' catalyst embedded in the polymer matrix, are capable of responding to propagating fatigue cracks by autonomic processes that lead to higher endurance limits and life extension, or even the complete arrest of the crack growth. The amount of fatigue-life extension depends on the relative magnitude of the mechanical kinetics of crack propagation and the chemical kinetics of healing. As the healing kinetics are accelerated, greater fatigue life extension is achieved. The use of wax-protected, recrystallized Grubbs' catalyst leads to a fourfold increase in the rate of polymerization of bulk dicyclopentadiene and extends the fatigue life of a polymer specimen over 30 times longer than a comparable non-healing specimen. The fatigue life of polymers under extremely fast fatigue crack growth can be extended through the incorporation of periodic rest periods, effectively training the self-healing polymeric material to achieve higher endurance limits.
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Dinh Vu, Huy, and Makoto Nanko. "Self-Healing Behavior of Y2SiO5 Toughened by SiC Particles." Key Engineering Materials 728 (January 2017): 149–54. http://dx.doi.org/10.4028/www.scientific.net/kem.728.149.
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Crack-healing effectiveness of Y2SiO5-based composites dispersed with 5 vol% SiC particles was investigated. Dense specimens of 5 vol% SiC/Y2SiO5 were fabricated by pulsed electric current sintering technique. Surface cracks were introduced by using a Vickers indenter to be a crack length of approximately 200 μm. Self-healing performance of SiC/Y2SiO5 composites via high-temperature oxidation in air was studied as a function of heat treatment temperature. As a result, surface cracks disappeared perfectly after heat treatment at 1300°C for 6 h in air.
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Tolba, Emad, Shunfeng Wang, Xiaohong Wang, Meik Neufurth, Maximilian Ackermann, Rafael Muñoz-Espí, Bothaina M. Abd El-Hady, Heinz C. Schröder, and Werner E. G. Müller. "Self-Healing Properties of Bioinspired Amorphous CaCO3/Polyphosphate-Supplemented Cement." Molecules 25, no. 10 (May 19, 2020): 2360. http://dx.doi.org/10.3390/molecules25102360.
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There is a strong interest in cement additives that are able to prevent or mitigate the adverse effects of cracks in concrete that cause corrosion of the reinforcement. Inorganic polyphosphate (polyP), a natural polymer that is synthesized by bacteria, even those on cement/concrete, can increase the resistance of concrete to progressive damage from micro-cracking. Here we use a novel bioinspired strategy based on polyP-stabilized amorphous calcium carbonate (ACC) to give this material self-healing properties. Portland cement was supplemented with ACC nanoparticles which were stabilized with 10% (w/w) Na–polyP. Embedding these particles in the hydrated cement resulted in the formation of calcite crystals after a hardening time of 10 days, which were not seen in controls, indicating that the particles dissolve and then transform into calcite. While there was no significant repair in the controls without ACC, almost complete closure of the cracks was observed after a 10 days healing period in the ACC-supplemented samples. Nanoindentation measurements on the self-healed crack surfaces showed a similar or slightly higher elasticity at a lower hardness compared to non-cracked surfaces. Our results demonstrate that bioinspired approaches, like the use of polyP-stabilized ACC shown here, can significantly improve the repair capacity of Portland cement.
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Danner, Tobias, and Mette Rica Geiker. "Long-term Influence of Concrete Surface and Crack Orientation on Self-healing and Ingress in Cracks – Field Observations." Nordic Concrete Research 58, no. 1 (June 1, 2018): 1–16. http://dx.doi.org/10.2478/ncr-2018-0001.
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Abstract This paper presents results from investigations on the long-term influence of concrete surface and crack orientation on ingress in cracks. Five reinforced concrete structures from Norway exposed to either de-icing salts or seawater have been investigated. Concrete cores were taken with and without cracks from surfaces with vertical and horizontal orientation. Carbonation in cracks was found on all de-iced structures, and a crack on a completely horizontal surface appeared to facilitate chloride ingress. Ingress of substances from seawater was found in all cracks from marine exposure. However, the impact of cracks on chloride ingress was unclear. Horizontal cracks on vertical surfaces appeared to facilitate self-healing.
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Khushnood, Rao Arsalan, Siraj ud din, Nafeesa Shaheen, Sajjad Ahmad, and Filza Zarrar. "Bio-inspired self-healing cementitious mortar using Bacillus subtilis immobilized on nano-/micro-additives." Journal of Intelligent Material Systems and Structures 30, no. 1 (November 3, 2018): 3–15. http://dx.doi.org/10.1177/1045389x18806401.
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Bio-inspired self-healing strategies are much innovative and potentially viable for the production of healable cement mortar matrix. The present research explores the feasibility of gram-positive “Bacillus subtilis” microorganisms in the effective healing of nano-/micro-scale-induced structural and non-structural cracks. The main concern related to the survival of such microorganisms in cementitious environment has been successfully addressed by devising proficient immobilization scheme coherently. The investigated immobilizing media includes iron oxide nano-sized particles, micro-sized limestone particles, and milli-sized siliceous sand. The effect of induced B. subtilis microorganisms immobilized on nano-micro-additives was analyzed by the quantification of average compressive resistance of specimens (ASTM C109) and healing evaluation. The healing process was mechanically gauged by compressive strength regain of pre-cracked specimens after the healing period of 28 days. The pre-cracking load was affixed at 80% of ultimate compressive stress “[Formula: see text]” while the age of pre-cracking was kept variable as 3, 7, 14, and 28 days to precisely correlate healing effectiveness as the function of cracking period. The healing mechanism was further explored by examining the healed micro-crack using field emission scanning electron micrographs, energy dispersive x-ray spectrographs, and thermogravimetry. The results revealed that B. subtilis microorganisms contribute extremely well in the improvement of compressive strength and efficient healing process of pre-cracked cement mortar formulations. The iron oxide nano-sized particles were found to be the most effective immobilizer for preserving B. subtilis microbes till the generation of cracks followed by siliceous sand and limestone particles. The micro-graphical and chemical investigations endorsed the mechanical measurements by evidencing calcite precipitation in the induced nano-/micro-cracks as a result of microbial activity.
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Richardson, Alan Elliott, Brabha Nagaratnam, Kathryn Ann Coventry, Dominic Brandy, and Leon Amess. "CRACK HEALING IN CEMENTITIOUS MATERIALS INCLUDING TESTS METHODS." Journal of Green Building 15, no. 1 (January 1, 2020): 37–54. http://dx.doi.org/10.3992/1943-4618.15.1.37.
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ABSTRACT If concrete is crack free, deleterious substances can be avoided entering the body of the material, that may corrode the rebar or encourage freeze/thaw damage. This paper examines a self healing system of cementitious materials. Microbial induced calcite precipitation was used to heal cracks in concrete with calcite using bacillus bacteria in alkaline conditions to generate a calcite filling material. Self healing of cracked prisms was determined using a water flow and absorption test and the results were expressed to record the healing as a percentage. The findings of the tests showed that a significant degree of self healing had taken place after 56 days after inducing a crack to the concrete prisms and the water flow test was appropriate to determine the degree of self healing taking place. Limitations of this process are such that the process requires a biological laboratory to create the spore impregnated aggregate. Once the aggregate is prepared, the batching process is essentially the same as any normal concrete. A practical use of this system could be developed using cover panels of self healing material to act as permanent formwork, thus placing the healing ingredients where they are needed at a minimum cost. The system has huge potential for the creation of a self repairing sustainable infrastructure.
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Prošek, Zdeněk, Pavla Ryparová, and Pavel Tesárek. "Application of Bacteria as Self-Healing Agent for the Concrete and Microscopic Analysis of the Microbial Calcium Precipitation Process." Key Engineering Materials 846 (June 2020): 237–42. http://dx.doi.org/10.4028/www.scientific.net/kem.846.237.
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Cracks affect the durability of concrete by increasing its permeability. Self-healing materials can begin repairing themselves immediately after creating a crack. This is a big advantage of self-healing materials. In this study, effect of self-healing agents based on calcium carbonate precipitation for concrete is monitored for three months. Bacillus pseudofirmus was chosen as a self-healing agent and was tested on old cement pastes. Calcium precipitation was analyzed by scanning electron microscope with Energy-dispersive X-ray spectroscopy. The effect of added spontaneous calcination, culture media, bacteria and Ca2+ was monitored.
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Mohammadi, Mojtaba, Carol Youssef-Namnoum, Maxime Robira, and Benoit Hilloulin. "Self-Healing Potential and Phase Evolution Characterization of Ternary Cement Blends." Materials 13, no. 11 (June 3, 2020): 2543. http://dx.doi.org/10.3390/ma13112543.
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The autogenous self-healing of cementitious material micro-cracks might lead to the service-life extension of structures. However, most of its aspects are still unknown. This paper investigates the self-healing capacity of ternary cement blends including metakaolin (MK), ground granulated blast-furnace slag (BFS), limestone (LS), and siliceous filler (F). Morphology and healing precipitation patterns were studied through the optical microscopy of artificial micro-cracks, global healing product mass monitoring, and XRD and TGA used to identify and quantify mineral formation. The self-healing potential index is introduced based on the mass measurements. It was found that the formulation containing 10% MK presented the highest healing potential at an early age (<28 days), while the formulations containing 20% BFS with 10% LS/F showed a higher healing potential at an older age (cracked after 28 days of curing). Calcite, C-S-H, and portlandite were found to be the main healing products alongside specific formulation-dependent compounds, and it was observed that the calcite’s relative quantity generally increased with time. Finally, the evolution of the self-healing product phases was accurately monitored through XRD and TGA measurements.
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Camara, Letícia, Mayara Wons, Ian Esteves, and Ronaldo Medeiros-Junior. "Monitoring the Self-healing of Concrete from the Ultrasonic Pulse Velocity." Journal of Composites Science 3, no. 1 (February 2, 2019): 16. http://dx.doi.org/10.3390/jcs3010016.
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Concrete has the ability to naturally heal its cracks, in a process called self-healing. This article aimed to analyze the self-healing of concretes, evaluating the influence of fly ash and the age of occurrence of cracks. Concrete specimens were submitted to cracking at 7 and 28 days. Subsequently, the samples were exposed to 12 wetting and drying cycles in order to favor the self-healing process. The phenomenon was evaluated through the ultrasonic pulse velocity testing, performed weekly on the specimens from the molding stage until the end of all cycles. The concretes showed a decrease in ultrasonic pulse velocity at the time they were cracked. This is due to the greater difficulty in the propagation of ultrasonic waves in the voids formed during cracking. This drop was higher for concrete with fly ash. Also, the results show that the fly ash concretes presented a more expressive self-healing process when cracked at 28 days, which may be related to the presence of pozzolanic reactions and the presence of more anhydrous particles. The concretes without fly ash had self-healing when they were cracked at 7 days. This is explained by the high hydration rate characteristic of ordinary Portland cement.
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Roig-Flores, Marta, and Pedro Serna. "Concrete Early-Age Crack Closing by Autogenous Healing." Sustainability 12, no. 11 (June 1, 2020): 4476. http://dx.doi.org/10.3390/su12114476.
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Autogenous healing is mainly produced by continuing hydration or carbonation. The aim of this research is to quantify the crack closing produced by autogenous healing for early-age concrete. This healing was evaluated for two crack size levels, 0.1 mm and 0.4 mm, under three healing conditions: water immersion, a humidity chamber, and wet/dry cycles. Crack closing was evaluated after 7, 14, 28 and 42 days under healing conditions. The internal status of the cracks was verified visually and using phenolphthalein. The results show that specimens stored in the humidity chamber did not experience healing, while specimens under wet/dry cycles and water immersion achieved the complete closing of small-sized cracks (under 0.15 mm). Autogenous healing showed higher speed under wet/dry cycles but higher final efficiency under water immersion. However, the inspection of the interior of the specimens showed that self-closing occurred mostly on the surface, and carbonation in the crack faces was only noticed very near the specimen’s surface. Additionally, this study proposes a preliminary strategy to model autogenous healing in concrete in terms of crack closing.
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Tomczak, Kamil, Jacek Jakubowski, and Przemysław Fiołek. "Method for Assessment of Changes in the Width of Cracks in Cement Composites with Use of Computer Image Processing and Analysis." Studia Geotechnica et Mechanica 39, no. 2 (June 27, 2017): 73–80. http://dx.doi.org/10.1515/sgem-2017-0017.
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Abstract Crack width measurement is an important element of research on the progress of self-healing cement composites. Due to the nature of this research, the method of measuring the width of cracks and their changes over time must meet specific requirements. The article presents a novel method of measuring crack width based on images from a scanner with an optical resolution of 6400 dpi, subject to initial image processing in the ImageJ development environment and further processing and analysis of results. After registering a series of images of the cracks at different times using SIFT conversion (Scale-Invariant Feature Transform), a dense network of line segments is created in all images, intersecting the cracks perpendicular to the local axes. Along these line segments, brightness profiles are extracted, which are the basis for determination of crack width. The distribution and rotation of the line of intersection in a regular layout, automation of transformations, management of images and profiles of brightness, and data analysis to determine the width of cracks and their changes over time are made automatically by own code in the ImageJ and VBA environment. The article describes the method, tests on its properties, sources of measurement uncertainty. It also presents an example of application of the method in research on autogenous self-healing of concrete, specifically the ability to reduce a sample crack width and its full closure within 28 days of the self-healing process.
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Buller, Abdul Salam, Fahad ul Rehman Abro, Kwang-Myong Lee, and Seung Yup Jang. "Mechanical Recovery of Cracked Fiber-Reinforced Mortar Incorporating Crystalline Admixture, Expansive Agent, and Geomaterial." Advances in Materials Science and Engineering 2019 (September 22, 2019): 1–14. http://dx.doi.org/10.1155/2019/3420349.
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This research is sought to characterize the stimulated autogenous healing of fiber-reinforced mortars that incorporate healing agents such as crystalline admixtures, expansive agents, and geomaterials. The effects of the healing materials on mechanical performance and water permeability were evaluated experimentally. Furthermore, microscopic and microstructural observations were conducted to investigate the characteristics and physical appearance of healing products within healed cracks. Test results are presented herein regarding index of strength recovery (ISR), index of damage recovery (IDR) and index of dissipation energy gain (IDEG) in relation to crack healing, and reduction of water flow rate. The self-healing capability of the mortars was greater in terms of resisting water flow rather than recovering mechanical performance likely because water flow depends on surface crack sealing, whereas mechanical performance depends on bonding capacity as well as full-depth healing of cracks; thus, mechanical performance may further be improved after longer healing duration.
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Stryszewska, Teresa, and Marta Dudek. "Microstructure of autonomous self-healing concrete." MATEC Web of Conferences 322 (2020): 01022. http://dx.doi.org/10.1051/matecconf/202032201022.
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Over the past years, many research projects in the field of construction have been based on the concept of intelligent materials. One example of such materials is self-healing concrete. This material has the ability to repair the damage that occurs, which in concrete materials means filling/closing the cracks formed. This paper describes autonomous concrete that heals itself thanks to modifications with mineral additives. The study used the basic method of evaluating the effectiveness of the healing process, which is visual observation of the material. For this purpose, tests were performed using optical, digital and electron microscopes. In addition to the observations, a chemical analysis of the composition was performed using the EDS detector mounted on the SEM. The findings indicate the ability of filling cracks with accumulating products of reaction with water.
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Ziegler, Fabiana, Angela Borges Masuero, Daniel Tregnago Pagnussat, and Denise Carpena Coitinho Dal Molin. "Evaluation of Internal and Superficial Self-Healing of Cracks in Concrete with Crystalline Admixtures." Materials 13, no. 21 (November 4, 2020): 4947. http://dx.doi.org/10.3390/ma13214947.
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Reinforced concrete structures are prone to cracking. The development of cementitious matrices with the capacity for self-healing soon after these cracks appear represents savings with inspections and repairs of the structures. Self-healing can be stimulated with the use of crystalline admixtures. Such materials easily react with water and increase the density of C-S-H (hydrated-calcium-silicate), forming insoluble deposits blocking existing pores and cracks. In this research, self-healing in concrete cracks was evaluated using three different crystalline admixtures, submitted to two and six wetting–drying cycles. The efficiency of self-healing was evaluated by optical microscopy and using the chloride diffusion test, which allowed calculating the predicted useful life of the concretes. The results highlight two important findings: (i) in optical microscopy, crystalline admixtures were not efficient in promoting self-healing on the surface of cracks in any of the studied concretes; (ii) the passage of chlorides by diffusion was lower for concretes with crystalline admixtures compared to the reference, showing better internal healing of these materials and, consequently, greater prediction of the concrete’s useful life.
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Richardson, Alan, Leon Amess, Simon Neville, and Christopher Walton. "CRACK HEALING UTILISING BACTERIAL SPORES IN CONCRETE." Journal of Green Building 12, no. 3 (September 2017): 103–14. http://dx.doi.org/10.3992/1943-4618.12.3.101.
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This self repair system is based upon harmless ground borne bacteria as the self-healing agent. The bacteria are activated after the concrete is cracked and the bacterial spores are exposed to moisture and air. The bacterial reproduction process creates a calcite by-product which fills the cracks in the concrete. By sealing the cracks in concrete, an effective barrier to air or liquid borne deleterious materials are formed and as a consequence of this, enhanced durability is achieved in the structure, resulting in lower life cycle costs. The concrete/mortar prisms were cracked and tested for water flow. They were then left for 56 days to heal and were subject to a test for water tightness. Healing was observed and a reduced water flow (74% and 32% healed) measured with the healed samples when compared to the specimens that were cracked and subjected to a water flow test without any healing agent. The number of samples were limited and a larger scale test is recommended for further work; however, this is a proof of concept of the process of healing and testing.
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Cao, Benyi, Livia Ribeiro de Souza, and Abir Al-Tabbaa. "Organic Contaminant-Triggered Self-Healing Soil Mix Cut-Off Wall Materials Incorporating Oil Sorbents." Materials 13, no. 24 (December 18, 2020): 5802. http://dx.doi.org/10.3390/ma13245802.
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Soil mix cut-off walls have been increasingly used for containment of organic contaminants in polluted land. However, the mixed soil is susceptible to deterioration due to aggressive environmental and mechanical stresses, leading to crack-originated damage and requiring costly maintenance. This paper proposed a novel approach to achieve self-healing properties of soil mix cut-off wall materials triggered by the ingress of organic contaminants. Oil sorbent polymers with high absorption and swelling capacities were incorporated in a cementitious grout and mixed with soil using a laboratory-scale auger setup. The self-healing performance results showed that 500 µm-wide cracks could be bridged and blocked by the swollen oil sorbents, and that the permeability was reduced by almost an order of magnitude after the permeation of liquid paraffin. It was shown by micro-CT scan tests that the network formed by the swollen oil sorbents acted as attachments and binder, preventing the cracked mixed soil sample from crumbling, and that the oil sorbents swelled three times in volume and therefore occupied the air space and blocked the cracks in the matrix. These promising results exhibit the potential for the oil sorbents to provide soil mix cut-off walls in organically-contaminated land with self-healing properties and enhanced durability.
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Van Mullem, Tim, Kim Van Tittelboom, Elke Gruyaert, Robby Caspeele, and Nele De Belie. "Development of an improved cracking method to reduce the variability in testing the healing efficiency of self-healing mortar containing encapsulated polymers." MATEC Web of Conferences 199 (2018): 02017. http://dx.doi.org/10.1051/matecconf/201819902017.
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Concrete cracking can result in a significant reduction of the durability and the service life due to the ingress of aggressive agents Self-healing concrete is able to heal cracks without external intervention, thereby mitigating the need for manual repair. In the assessment of the healing efficiency of self-healing concrete the to-be-healed crack width is an important parameter and different researchers have emphasised that the variability of the crack width significantly hampers an accurate assessment of the healing efficiency. With two new crack control techniques the variability of the crack width was reduced in order to decrease the variability on the calculated healing efficiency. This paper reports on the application of these techniques for the assessment of self-healing mortar containing encapsulated polyurethane. The healing potential was investigated by looking at the degree of sealing using a water flow test setup. It was observed that by using a crack control technique the variability on the crack width can indeed be reduced. Nonetheless, this does not translate in an equivalent reduction on the variability of the healing efficiency. This indicates that other factors contribute to the variability of the healing efficiency.
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Lee, Kwang-Myong, Hyung-Suk Kim, Do-Keun Lee, and Kyung-Joon Shin. "Self-Healing Performance Evaluation of Concrete Incorporating Inorganic Materials Based on a Water Permeability Test." Materials 14, no. 12 (June 10, 2021): 3202. http://dx.doi.org/10.3390/ma14123202.
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Research activities that have focused on the development and understanding of self-healing concrete have proposed various technologies intended to enhance self-healing capacity. The self-healing performance cannot be identified sufficiently with either a single test or a specific parameter because there are a number of factors that influence the performance of self-healing. Thus, it has become necessary to provide standardized test methods that make it possible to verify and compare the performance of self-healing materials. In this paper, self-healing mortars based on inorganic admixtures, which are developed for sealing 0.3 mm cracks with a healing index of 90%, are produced and used to validate the water permeability test and to propose protocols for the evaluation of self-healing performance. The healing performances of three self-healing mortars and a plain mortar as a reference are evaluated with a comparative study. The equivalent crack width, which can be estimated from the water flow rate, is suggested as a rational evaluation index. Finally, a self-healing performance chart is proposed to comprehensively show the healing performance of cement-based materials.
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Xu, Hongyin, Jijian Lian, Maomao Gao, Dengfeng Fu, and Yue Yan. "Self-Healing Concrete Using Rubber Particles to Immobilize Bacterial Spores." Materials 12, no. 14 (July 19, 2019): 2313. http://dx.doi.org/10.3390/ma12142313.
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Bacteria-based self-healing concrete is a construction material used to repair cracks in concrete, in which the bacterial spores are immobilized by bacteria carriers. However, the currently available bacteria carriers are not always suitable due to a complicated procedure or high cost. To develop a more suitable bacteria carrier as well as improve the anti-crack capability of self-healing concrete, in this study we evaluate the feasibility of using rubber particles as a novel bacteria carrier in self-healing concrete. Two types of self-healing concrete are prepared with rubber particles of different sizes to quantify the crack-healing effect. In addition, the fluidity and mechanical properties of the self-healing rubber concrete are compared with those of plain concrete and normal rubber concrete. The experimental results show that the self-healing rubber concrete with a particle size of 1~3 mm has a better healing capacity than the self-healing rubber concrete with a particle size of 0.2~0.4 mm, and the width value of the completely healed crack is 0.86 mm. The self-healing rubber concrete has a higher slump than the plain concrete and normal rubber concrete. According to the strength tests, the compressive strengths of the self-healing rubber concrete are low early on but they exceed those of the corresponding normal rubber concrete at 28 days. Moreover, the self-healing rubber concrete has higher splitting tensile strengths than the plain concrete and a better anti-crack capability. The results of a comparison to the other two representative bacterial carriers indicate that rubber particles have potential to be a widely used bacteria carrier for practical engineering applications in self-healing concrete.
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Song, Dowon, Taeseup Song, Ungyu Paik, Guanlin Lyu, Yeon-Gil Jung, Baig-Gyu Choi, In-Soo Kim, and Jing Zhang. "Crack-Resistance Behavior of an Encapsulated, Healing Agent Embedded Buffer Layer on Self-Healing Thermal Barrier Coatings." Coatings 9, no. 6 (May 31, 2019): 358. http://dx.doi.org/10.3390/coatings9060358.
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In this work, a novel thermal barrier coating (TBC) system is proposed that embeds silicon particles in coating as a crack-healing agent. The healing agent is encapsulated to avoid unintended reactions and premature oxidation. Thermal durability of the developed TBCs is evaluated through cyclic thermal fatigue and jet engine thermal shock tests. Moreover, artificial cracks are introduced into the buffer layer’s cross section using a microhardness indentation method. Then, the indented TBC specimens are subject to heat treatment to investigate their crack-resisting behavior in detail. The TBC specimens with the embedded healing agents exhibit a relatively better thermal fatigue resistance than the conventional TBCs. The encapsulated healing agent protects rapid large crack openings under thermal shock conditions. Different crack-resisting behaviors and mechanisms are proposed depending on the embedding healing agents.
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Gupta, Shivani Gupta, Chhavi Rathi, and Suman Kapur. "Biologically Induced Self Healing Concrete: A Futuristic Solution for Crack Repair." International Journal of Applied Sciences and Biotechnology 1, no. 3 (September 25, 2013): 85–89. http://dx.doi.org/10.3126/ijasbt.v1i3.8582.
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Concrete is a mixture of cement, water, sand and other aggregates in adequate proportions. Its high tensile strength and ability to withstand a vast range of environmental changes makes it the first choice for construction material. One of the major problems associated with concrete is its permeability because penetration of gases and/or liquids from the surrounding environment into the concrete, followed by physical and/or chemical reactions within its internal structure/s leads to irreversible damages. Although cement has autonomous capacity to heal, however cracks <0.2mm width can only self-heal. Biomineralization is one of the best ecofriendly techniques to tackle the problem of cracks in concrete structures. Biologically induced self-healing is beneficial in addressing all the drawbacks of concrete matrix. The most promising technology for producing crack resistant/highly self healing concrete in near future seems to be “BacillaFilla”: genetically modified version of Bacillus subtilis, is a “custom –designed” bacteria to embed deep into the cracks in concrete where they produce a mix of calcium carbonate and a special bacteria glue that hardens to the same strength as of the surrounding concrete. DOI: http://dx.doi.org/10.3126/ijasbt.v1i3.8582 Int J Appl Sci Biotechnol, Vol. 1(3) 2013 : 85-89
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Nugroho, Ananto, Iman Satyarno, and Subyakto Subyakto. "Bacteria as Self-Healing Agent in Mortar Cracks." Journal of Engineering and Technological Sciences 47, no. 3 (July 2015): 279–95. http://dx.doi.org/10.5614/j.eng.technol.sci.2015.47.3.4.
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Zhang, M. Q. "Repeatedly self-healing of wider cracks in polymers." Express Polymer Letters 14, no. 10 (2020): 895. http://dx.doi.org/10.3144/expresspolymlett.2020.73.
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Hill, David. "Self-Healing Concrete Uses Bacteria to Repair Cracks." Civil Engineering Magazine Archive 85, no. 7 (July 2015): 44–45. http://dx.doi.org/10.1061/ciegag.0001016.
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Behnia, Behzad, and Henrique Reis. "Self-healing of thermal cracks in asphalt pavements." Construction and Building Materials 218 (September 2019): 316–22. http://dx.doi.org/10.1016/j.conbuildmat.2019.05.095.
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García, Álvaro. "Self-healing of open cracks in asphalt mastic." Fuel 93 (March 2012): 264–72. http://dx.doi.org/10.1016/j.fuel.2011.09.009.
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Lin, Jianjun, Huisu Chen, Zhong Lv, and Yujiang Wang. "Analytical solution on dosage of self-healing capsules in materials with two-dimensional multi-shaped crack patterns." Science and Engineering of Composite Materials 25, no. 6 (November 27, 2018): 1229–39. http://dx.doi.org/10.1515/secm-2017-0256.
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AbstractThis article presents a numerical method for determining the dosage of pre-embedded capsules in self-healing materials with complex crack patterns. The crack distribution on the surface of materials is simplified into a two-dimensional (2D) multi-shaped geometrical structure composed of triangles, rhombuses, and hexagons with specified area fractions, and further decomposed into three separate mono-shaped crack systems. Then, the dosage of capsules required to heal the cracks in each mono-shaped crack system is computed. According to the area fraction of each mono-shaped polygon in the whole system, the integrated models of crack-hitting probability by the capsules and the capsule dosage for the multi-shaped crack system are derived. The analytical results reveal that the dosage of capsules significantly depends on the spatial distribution of the cracks and the ratio of the capsule length to the crack size. For a certain fixed crack pattern, the size and dosage of capsules will strongly affect crack healing efficiency.
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Qian, Chun Xiang, Mian Luo, Li Fu Ren, Rui Xing Wang, Rui Yang Li, Qing Feng Pan, and Huai Cheng Chen. "Self-Healing and Repairing Concrete Cracks Based on Bio-Mineralization." Key Engineering Materials 629-630 (October 2014): 494–503. http://dx.doi.org/10.4028/www.scientific.net/kem.629-630.494.
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In this paper, three bio-mineralization mechanisms were proposed to repair cement-based materials cracks. The common feature is that the three are all induced by bacterial. A type of bacterial which can decompose urea and release carbonate ions could be applied to repair micro cracks on concrete surface when combining calcium ions. But what need to be noted is that the way of repairing cracks is passive. Some alkaliphilic bacterial spores could be added to concrete when casted and two different types of bacterial were used to realize the function of self-healing. The sources of carbonate ions made them different, the one release carbonate dioxide through its own cellular respiration, the other could transfer carbon dioxide in air to bicarbonate. Coefficient of capillary suction, apparent water permeation coefficient and area repairing rate were applied to characterize the repairing effectiveness. The tests results were that all three bio-mineralization mechanisms showed excellent repair effect to small cracks formed at early ages. When the bacteria were immobilized by ceramsite, the self-healing effect could be improved for the cracks formed at late ages.
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Liu, Jun Cong, Dan Yong Wang, Yi Wei Chen, Shu Hu Li, and Hua Zhen Wei. "Research on the Manufacturing Methods of Self-Healing Microcapsules in Advanced Materials." Advanced Materials Research 968 (June 2014): 44–48. http://dx.doi.org/10.4028/www.scientific.net/amr.968.44.
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s: For the problem that cracks exist when the advanced materials are attacked or shocked, and the cracks are hard to self-healing. The microcapsules are put forward to make great effects on healing the cracks to some extents. The manufacturing methods of microcapsules are reviewed, including Matrix Polymerization, In-situ Polymerization, In-situ Cross-linking, Solvent Evaporation Method. And the conclusion and problems are prospected finally.