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Self-Healing Concretes

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Manufacturing Processes and Systems".

Deadline for manuscript submissions: closed (31 October 2021) | Viewed by 7204

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Guest Editor
Faculty of Chemistry and Chemical Technology, University of Ljubljana, Ljubljana, Slovenia
Interests: ceramics; concrete; composites; nanomaterials; microstructure
Special Issues, Collections and Topics in MDPI journals

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Dear Colleagues,

Concrete is the most widely used construction material. Many excellent functional properties, such as high compressive strength, common availability, good durability, compatibility with reinforcement bars, low price, rather simple preparation, and the ability to be cast in desired shapes and sizes, make concrete the material of choice for many applications. On the other hand, concrete also has a high tendency to form cracks, which are one of the main cause of concrete deterioration and decrease in durability.

The most efficient ways to treat cracks in concrete are the so-called active treatments. Active treatment techniques, which are also known as self-healing techniques, can be implemented through three main strategies: (i) autogenous healing; (ii) encapsulation of polymeric material; (iii) microbial production of minerals (i.e., calcium carbonate).

In autogenous healing, which is considered as a natural repair process, concrete cracks are filled through the hydration of un-hydrated cement particles or the carbonation of dissolved calcium hydroxide in the presence of moisture or water. Additionally, as a mechanism of self-healing in concrete one must also consider the so-called alkali-carbonate reaction (ACR) in concretes with dolomite aggregate, which also results in calcium carbonate precipitation.

The encapsulation of polymeric material can contribute to filling cracks by the conversion of healing agent to foam in the presence of moisture. Although releasing chemicals from incorporated hollow fibers inside concrete can fill the cracks, polymeric materials do not behave in the same way as concrete compositions, and in some extreme conditions even cause extension of the existing cracks.

Biological healing processes are based on the production of minerals by living organisms through biomineralization, which is a widespread phenomenon in nature. In this process, biominerals are formed through the reaction of metabolic products generated by microorganisms with the surrounding environment. Among various pathways of minerals production through biomineralization such as carbonates, sulfides, silicates, and phosphates, the precipitation of calcium carbonate has drawn interest due to the efficient bonding capacity and compatibility with concrete compositions.

In this Special Issue, modern trends in self-healing concretes preparation, including the healing fundamentals and mechanisms as well as the properties of healed concrete, are highlighted and discussed.

It is my pleasure to invite you to submit a manuscript for this Special Issue. Full papers, communications, and reviews are all welcome.

Assoc. Prof. Marjan Marinšek
Guest Editor

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Keywords

  • concrete
  • self-healing
  • crack filling
  • healing mechanisms
  • microstructure
  • mechanical properties

Published Papers (2 papers)

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Research

26 pages, 7730 KiB  
Article
Evaluation of Methodologies for Assessing Self-Healing Performance of Concrete with Mineral Expansive Agents: An Interlaboratory Study
by Chrysoula Litina, Girts Bumanis, Giovanni Anglani, Marta Dudek, Riccardo Maddalena, Maria Amenta, Stamatoula Papaioannou, Gloria Pérez, José Luis García Calvo, Eloy Asensio, Rubén Beltrán Cobos, Fabiano Tavares Pinto, Algirdas Augonis, Robert Davies, Ana Guerrero, Mercedes Sánchez Moreno, Teresa Stryszewska, Ioannis Karatasios, Jean-Marc Tulliani, Paola Antonaci, Diana Bajare and Abir Al-Tabbaaadd Show full author list remove Hide full author list
Materials 2021, 14(8), 2024; https://doi.org/10.3390/ma14082024 - 17 Apr 2021
Cited by 30 | Viewed by 3505
Abstract
Self-healing concrete has the potential to optimise traditional design approaches; however, commercial uptake requires the ability to harmonize against standardized frameworks. Within EU SARCOS COST Action, different interlaboratory tests were executed on different self-healing techniques. This paper reports on the evaluation of the [...] Read more.
Self-healing concrete has the potential to optimise traditional design approaches; however, commercial uptake requires the ability to harmonize against standardized frameworks. Within EU SARCOS COST Action, different interlaboratory tests were executed on different self-healing techniques. This paper reports on the evaluation of the effectiveness of proposed experimental methodologies suited for self-healing concrete with expansive mineral additions. Concrete prisms and discs with MgO-based healing agents were produced and precracked. Water absorption and water flow tests were executed over a healing period spanning 6 months to assess the sealing efficiency, and the crack width reduction with time was monitored. High variability was reported for both reference (REF) and healing-addition (ADD) series affecting the reproducibility of cracking. However, within each lab, the crack width creation was repeatable. ADD reported larger crack widths. The latter influenced the observed healing making direct comparisons across labs prone to errors. Water absorption tests highlighted were susceptible to application errors. Concurrently, the potential of water flow tests as a facile method for assessment of healing performance was shown across all labs. Overall, the importance of repeatability and reproducibility of testing methods is highlighted in providing a sound basis for incorporation of self-healing concepts in practical applications. Full article
(This article belongs to the Special Issue Self-Healing Concretes)
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23 pages, 8800 KiB  
Article
Self-Sealing Process Evaluation Method Using Ultrasound Technique in Cement Composites with Mineral Additives
by Kamil Tomczak, Jacek Jakubowski and Łukasz Kotwica
Materials 2020, 13(15), 3336; https://doi.org/10.3390/ma13153336 - 27 Jul 2020
Cited by 8 | Viewed by 2745
Abstract
The self-sealing process, associated with chemical and microstructural changes inside damaged cement-based composites, leads to the recovery of the original material integrity. Assessing the magnitude of internal changes in samples using non-destructive techniques to capture only the self-sealing effects is difficult. The challenge [...] Read more.
The self-sealing process, associated with chemical and microstructural changes inside damaged cement-based composites, leads to the recovery of the original material integrity. Assessing the magnitude of internal changes in samples using non-destructive techniques to capture only the self-sealing effects is difficult. The challenge is evaluating the differences between subsequent observations in time and between samples with different properties. This paper proposes a new approach to the use of an ultrasonic technique for self-sealing investigation. The method allows the quantification of material changes strictly related to self-sealing processes, excluding changes caused by the naturally progressing hydration of binders. The applied ultrasonic pulse velocity (UPV) data processing procedure allows the investigation of material changes inside and near the cracks, the effects of stimulating the self-sealing of cement composites with mineral additives, and the assessment of changes over time. An important aspect of the method is the sample preparation procedure and testing conditions that reduce the impact of moisture content on the UPV measurements. New parameters allowing the quantitative characterization of the self-sealing process are proposed. The method was evaluated using cement mortars modified with siliceous fly ash with induced cracks 0 to 750 µm wide, which were then cured in water for 152 days. The maximum degree of effective crack filling as a result of autogenous self-sealing in the tested mortars was determined to range from 33% to 57%. Observations of the microstructure of the crack surface confirmed that apart from the volume of the newly formed products, the density of these products may have a key impact on the ultrasonic measurements of the self-sealing performance. The studies were supplemented by the examination of the compression strength of mortars, mortar sample scanning and computer image processing, and observations using an optical microscope and scanning electron microscope with energy dispersive spectroscopy. Full article
(This article belongs to the Special Issue Self-Healing Concretes)
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