Materials

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17 pages, 3942 KiB

Open AccessArticle

Crack Width Evaluation of Cracked Mortar Specimen Using Gas Diffusion Characteristics

by Do-Keun Lee, Kyung-Joon Shin and Kwang-Myong Lee

Materials 2023, 16(2), 586; https://doi.org/10.3390/ma16020586 - 6 Jan 2023

Cited by 1 | Viewed by 965

Several methods have been proposed currently for evaluating the crack width of a mortar specimen. Among these, the water permeability test is widely used to estimate crack width because water permeability is directly related to the average crack width of a specimen through [...] Read more.

Several methods have been proposed currently for evaluating the crack width of a mortar specimen. Among these, the water permeability test is widely used to estimate crack width because water permeability is directly related to the average crack width of a specimen through which water passes. However, the viscosity of water makes precise crack width measurement challenging. The possible inflow (outflow) of foreign (healing) substances could affect the test results. To circumvent this limitation, this study proposes a gas diffusion test using oxygen rather than water as the medium. The proposed method includes a process that could compensate for gas diffusion from specimen parts other than the crack, allowing for a more precise estimation of crack width. The crack width can indeed be estimated with an error of 4% or less. Full article

(This article belongs to the Special Issue Self-Healing Concrete and Cement-Based Materials)

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11 pages, 7185 KiB

Open AccessArticle

The Construction of a Footbridge Prototype with Biological Self-Healing Concrete: A Field Study in a Humid Continental Climate Region

by Ronaldas Jakubovskis and Renata Boris

Materials 2022, 15(23), 8585; https://doi.org/10.3390/ma15238585 - 1 Dec 2022

Cited by 4 | Viewed by 1177

Abstract

Biological self-healing concrete (BSHC) offers a sustainable and economical way of increasing the lifespan of structures vulnerable to cracking. In recent decades, an enormous research effort has been dedicated to developing and optimizing the bacterial healing process. Nevertheless, most studies have been carried [...] Read more.

Biological self-healing concrete (BSHC) offers a sustainable and economical way of increasing the lifespan of structures vulnerable to cracking. In recent decades, an enormous research effort has been dedicated to developing and optimizing the bacterial healing process. Nevertheless, most studies have been carried out under laboratory conditions. To verify the effectiveness and longevity of the embedded healing systems under normal service conditions, field studies on BSHC structures must be performed. In the present study, BSHC beams were designed as a structural part of a prototype footbridge. To select the optimal BSHC mix composition, a series of laboratory tests were also carried out. Laboratory tests have shown that the healing ratio in BSHC elements under rain-simulating healing conditions was several times higher in comparison to control specimens. Based on the laboratory results, the BSHC mix composition was selected and applied for structural bridge beams. To the best of the authors’ knowledge, the present study reports the first application of BSHC in a prototype footbridge. The long-term data gathered on the healing process in a humid continental climate zone will allow the benefits of biological self-healing to be quantitatively evaluated and will pave the way for the further optimization of this material. Full article

(This article belongs to the Special Issue Self-Healing Concrete and Cement-Based Materials)

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14 pages, 6590 KiB

Open AccessArticle

Comparison of Mechanical and Crack-Healing Properties of PE-PVA Hybrid Fiber-Reinforced SHCCs in Natural and Underwater Conditions

by Se-Eon Park, Huy Hoàng Nguyễn, Jeong-Il Choi, Bang Yeon Lee and Yun Yong Kim

Materials 2022, 15(18), 6339; https://doi.org/10.3390/ma15186339 - 13 Sep 2022

Cited by 1 | Viewed by 1121

Abstract

This paper presents a direct comparison of the mechanical and crack-healing properties of strain hardening cementitious composites (SHCC) under water submersion in a laboratory and in a natural environment outdoors. Portland cement, slag, crumb rubber powder, and hybrid polyethylene and polyvinyl alcohol fibers [...] Read more.

This paper presents a direct comparison of the mechanical and crack-healing properties of strain hardening cementitious composites (SHCC) under water submersion in a laboratory and in a natural environment outdoors. Portland cement, slag, crumb rubber powder, and hybrid polyethylene and polyvinyl alcohol fibers were used for the SHCC, and mixture proportions were determined. Specimens were exposed to different environmental conditions. A sequence of experimental tests including those for density, compressive strength, and tensile properties was performed to assess the mechanical properties of the SHCC. To confirm the healing feasibility of the SHCC, crack width reduction, stiffness recovery, and tensile performance at post-healing were adopted. The test results showed that underwater conditions are better than natural conditions in improving both the mechanical and crack-healing properties of SHCC. Specifically, the SHCC cured in natural conditions had a lower compressive strength, tensile strength, and tensile strain capacity than that cured in underwater conditions by 10%, 4%, and 3%, respectively. The SHCC cured in underwater conditions had a healing threshold of crack width of 60 µm, while the SHCC cured in natural conditions had very limited crack-healing capacity. Additionally, stiffness recovery of the SHCC cured in underwater conditions was higher than that cured in natural conditions. Full article

(This article belongs to the Special Issue Self-Healing Concrete and Cement-Based Materials)

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19 pages, 4877 KiB

Open AccessArticle

Fundamental Properties and Self-Healing Performance of Repair Mortar with Solid Capsules Made Using Inorganic Reactive Powder

by Sung-Rok Oh, Kwang-Myong Lee, Sung Choi and Yun-Wang Choi

Materials 2022, 15(5), 1710; https://doi.org/10.3390/ma15051710 - 24 Feb 2022

Cited by 7 | Viewed by 1614

Abstract

Self-healing cement composites are generally produced by using materials such as inorganic powders, bacteria pellets, and microcapsules. Among them, inorganic powder-type healing materials tend to decrease in healing performance over time because they react relatively quickly. Accordingly, this study encapsulated self-healing inorganic reactive [...] Read more.

Self-healing cement composites are generally produced by using materials such as inorganic powders, bacteria pellets, and microcapsules. Among them, inorganic powder-type healing materials tend to decrease in healing performance over time because they react relatively quickly. Accordingly, this study encapsulated self-healing inorganic reactive powders in solid capsules (SC) in order to delay their reaction. The capsule surface was coated with a membrane to prevent moisture from permeating it. SC were utilized to provide the self-healing effect to the repair mortar. SC were mixed at three rates (0%, 5%, and 10%) by the binder mass of the repair mortar. The fundamental properties, including rheology, table flow, strength, and length change, and the self-healing performance of the self-healing repair mortar mixes were investigated. It was found that the rheological and mechanical properties of the repair mortar decreased slightly as the amount of SC increased. On the other hand, for a crack width of 0.25 mm and crack inducing age of 28 days, the healing performance of repair mortar specimens containing SC was at least 20 pt% better than that of plain repair mortar after a healing period of 28 days. Full article

(This article belongs to the Special Issue Self-Healing Concrete and Cement-Based Materials)

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12 pages, 30705 KiB

Open AccessArticle

Microcapsule-Type Self-Healing Protective Coating That Can Maintain Its Healed State upon Crack Expansion

by Ji-Sun Lee, Hyun-Woo Kim, Jun-Seo Lee, Hyun-Soo An and Chan-Moon Chung

Materials 2021, 14(20), 6198; https://doi.org/10.3390/ma14206198 - 19 Oct 2021

Cited by 1 | Viewed by 1516

Abstract

The purpose of this study was to develop a microcapsule-type self-healing coating system that could self-heal cracks and then maintain the healed state even upon crack expansion. Mixtures consisting of a photoinitiator and two methacrylate components, bismethacryloxypropyl-terminated polydimethylsiloxane (BMT-PDMS) and monomethacryloxypropyl-terminated PDMS (MMT-PDMS), [...] Read more.

The purpose of this study was to develop a microcapsule-type self-healing coating system that could self-heal cracks and then maintain the healed state even upon crack expansion. Mixtures consisting of a photoinitiator and two methacrylate components, bismethacryloxypropyl-terminated polydimethylsiloxane (BMT-PDMS) and monomethacryloxypropyl-terminated PDMS (MMT-PDMS), were transformed into viscoelastic semi-solids through photoreaction. The viscoelasticity of the reacted mixtures could be controlled by varying the mass ratio of the two methacrylates. Through a stretchability test, the optimal composition mixture was chosen as a healing agent. Microcapsules loaded with the healing agent were prepared and dispersed in a commercial undercoating to obtain a self-healing coating formulation. The formulation was applied onto mortar specimens, and then cracks were generated in the coating by using a universal testing machine (UTM). Cracks with around a 150-μm mean width were generated and were allowed to self-heal under UV light. Then, the cracks were expanded up to 650 μm in width. By conducting a water sorptivity test at each expanded crack width, the self-healing efficiency and capability of maintaining the healed state were evaluated. The B-M-1.5-1-based coating showed a healing efficiency of 90% at a 150-μm crack width and maintained its healing efficiency (about 80%) up to a 350-μm crack width. This self-healing coating system is promising for the protection of structural materials that can undergo crack formation and expansion. Full article

(This article belongs to the Special Issue Self-Healing Concrete and Cement-Based Materials)

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16 pages, 7020 KiB

Open AccessEditor’s ChoiceArticle

Use of Methylcellulose-Based Pellet to Enhance the Bacterial Self-Healing of Cement Composite

by Indong Jang, Dasom Son, Yongjun Son, Jihyeon Min and Chongku Yi

Materials 2021, 14(20), 6113; https://doi.org/10.3390/ma14206113 - 15 Oct 2021

Cited by 2 | Viewed by 1617

Abstract

In this study, a new type of bacterial carrier using methylcellulose was presented, and its applicability to self-healing concrete has been explored. Methylcellulose, the main component of a 2 mm pellet-shaped carrier, can remain stable in alkaline environments and expand in neutral or [...] Read more.

In this study, a new type of bacterial carrier using methylcellulose was presented, and its applicability to self-healing concrete has been explored. Methylcellulose, the main component of a 2 mm pellet-shaped carrier, can remain stable in alkaline environments and expand in neutral or acidic environments. These properties allow bacteria to survive in the high-alkaline and high-pressure environments of early age concrete, and the number of bacteria increases rapidly in the event of cracks, accelerating crack closure. The results show that the survival rate of bacterial spores inside the mortar was increased, and the pellet provides an enhanced biological anchor suitable for bacterial activity, bacterial growth, and mineral precipitation. Further, the results indicate an improved self-healing efficiency compared with mixing bacteria directly into the cement composite. Full article

(This article belongs to the Special Issue Self-Healing Concrete and Cement-Based Materials)

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17 pages, 3135 KiB

Open AccessArticle

Self-Healing Performance Evaluation of Concrete Incorporating Inorganic Materials Based on a Water Permeability Test

by Kwang-Myong Lee, Hyung-Suk Kim, Do-Keun Lee and Kyung-Joon Shin

Materials 2021, 14(12), 3202; https://doi.org/10.3390/ma14123202 - 10 Jun 2021

Cited by 14 | Viewed by 2991

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Self-Healing Concrete and Cement-Based Materials)

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11 pages, 53109 KiB

Open AccessArticle

Prolonging Bacterial Viability in Biological Concrete: Coated Expanded Clay Particles

by Ronaldas Jakubovskis, Augusta Jankutė, Simona Guobužaitė, Renata Boris and Jaunius Urbonavičius

Materials 2021, 14(11), 2719; https://doi.org/10.3390/ma14112719 - 21 May 2021

Cited by 13 | Viewed by 2017

Abstract

One of the biggest challenges in the development of a biological self-healing concrete is to ensure the long-term viability of bacteria that are embedded in the concrete. In the present study, a coated expanded clay (EC) is investigated for its potential use as [...] Read more.

One of the biggest challenges in the development of a biological self-healing concrete is to ensure the long-term viability of bacteria that are embedded in the concrete. In the present study, a coated expanded clay (EC) is investigated for its potential use as a bacterial carrier in biological concrete. Eight different materials for coatings were selected considering cost, workability and accessibility in the construction industry. Long-term (56 days) viability analysis was conducted with a final evaluation of each coating performance. Our results indicate that healing efficiency in biological concrete specimens is strongly related to viable bacteria present in the healing agent. More viable bacteria-containing specimens exhibited a higher crack closure ratio. Our data suggest that the additional coating of EC particles improves long-term bacterial viability and, consequently, provides efficient crack healing in biological concrete. Full article

(This article belongs to the Special Issue Self-Healing Concrete and Cement-Based Materials)

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20 pages, 11121 KiB

Open AccessArticle

Recovery of Chloride Penetration Resistance of Cement-Based Composites Due to Self-Healing of Cracks

by Kyung Suk Yoo, Seung Yup Jang and Kwang-Myong Lee

Materials 2021, 14(10), 2501; https://doi.org/10.3390/ma14102501 - 12 May 2021

Cited by 11 | Viewed by 1863

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Self-Healing Concrete and Cement-Based Materials)

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