Interactions of fungi with concrete: Significant importance for bio-based self-healing concrete
Graphical abstract
Introduction
Concrete infrastructure suffers from serious deterioration [1], [2], and thus self-healing of harmful cracks without high costs or onerous labor have attracted enormous amount of attention. As for how to endow cementitious materials with self-healing properties, many experimental studies and laboratory investigations have been conducted and generated many innovative strategies during the past decades [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27].
To date, self-healing in concrete has been achieved primarily through three different strategies: autogenous healing, encapsulation of polymeric material, and bacterial production of CaCO3. During the autogenous healing, cracks are filled naturally by means of hydration of unhydrated cement particles and carbonation of dissolved calcium hydroxide as a consequence of exposure to CO2 in the atmosphere [3]. However, this autogenous healing is limited to small cracks (less than 0.2 mm) and requires the presence of water [16]. Encapsulation of polymeric material can fill the cracks in concrete by converting healing agent to foam in the presence of humidity. However, the chemicals released from incorporated hollow fibers behave quite differently from concrete compositions, and they may even cause to further propagate the existing cracks [6].
Due to these drawbacks, the use of the biological repair technique by applying mineral-producing microorganisms becomes highly desirable, as it provides a safe, natural, pollution-free, and sustainable solution to the serious challenge [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27], [28]. When a calcium source is present, CaCO3, the most suitable filler for concrete due to its high compatibility with cementitious compositions, can be produced through various biomineralization processes. This microbial approach is superior to the other self-healing techniques owing to its excellent microcrack-filling capacity, strong bonding between filler and crack, high compatibility with concrete compositions, favorable thermal expansion, and sustainability [27].
Recent research has demonstrated that some ureolytic bacteria, such as Bacillus sphaericus and B. pasteurii, have the ability to precipitate calcium carbonate through urea hydrolysis and thus can be used as a powerful tool to heal the cracks [8], [9], [10], [11], [12]. However, for each carbonate ion two ammonium ions are produced, leading to excessive nitrogen loading to our environment. To avoid this drawback, metabolic conversion of organic compound to CaCO3 has been proposed by Jonkers et al. [18], [19], [20] In this approach, aerobic oxidation of organic acids produces CO2, then leading to the production of CO32− in an alkaline environment. Then the presence of a calcium source results in the precipitation of CaCO3. However, this approach requires high concentrations of calcium source [29], which could possibly lead to buildup of high level of salts in concrete. The third pathway to precipitate CaCO3 is known as dissimilatory nitrate reduction [23]. Mineral production is promoted through oxidation of organic compounds through nitrate reduction by means of denitrifying bacteria. However, it has been shown that the efficacy of denitrification approach is much lower than ureolysis regarding the production of CaCO3 [30].
Section snippets
Fungi-mediated self-healing concrete
While the term “microbe” defines a wide variety of organisms, studies on self-healing concrete are still limited to bacteria [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27]. Of course, using bacteria has many advantages. For example, bacteria are easy to culture and handle in a laboratory setting and are typically harmless to humans [31]. Moreover, collection and isolation of bacteria are not very complex, as during the years
Materials and methods
The following criteria will be used to select the candidates of fungi for self-healing concrete. (1) They should be eco-friendly and nonpathogenic, i.e., pose no risk to human health and are appropriate to be used in concrete infrastructure. Fortunately, fungi that are pathogens are usually pathogenic to plants, and there are comparatively few species that are pathogenic to animals, especially mammals. Among the 100,000 described species of fungi, a little more than 400 are known to cause
Identification of BAG4, PP16-P60, 8D, and CM14-RG38
Strain PP16_P60 was isolated from the pitch pine in the Pygmy Pine Plains of the New Jersey Pine Barrens. It has 100% ITS sequence similarity to Umbeliopsis dimorpha ex-type culture CBS110039 (NR_111664), and thus it is identified as Umbeliopsis dimorpha. BAG4 was recovered from the Sprengel’s sedge samples (Carex sprengelii) collected from a subalphine forest in Canadian Rocky Mountains in the province of Alberta, Canada. The blast result indicates its phylogenetic position in the genus
Concluding remarks and future work
In the current study, a new self-healing concept has been explored, in which fungi were used to promote calcium mineral precipitation to heal cracks in concrete infrastructure. An initial screening of different species of fungi has been conducted. The experimental results showed that, due to the dissolving of Ca(OH)2 from concrete, the pH of the growth medium increased from its original value of 6.5 to 13.0. Despite the drastic pH increase, the microscopic analysis showed that T. reesei
Acknowledgements
Congrui Jin and David G. Davies were funded by the Research Foundation for the State University of New York (SUNY RF) through the Sustainable Community Transdisciplinary Area of Excellence Program (TAE-16083068). Congrui Jin also thanks the support from the Small Scale Systems Integration and Packaging (S3IP) Center of Excellence, funded by New York Empire State Development’s Division of Science, Technology and Innovation. Jada Crump, affiliated with Westchester Community College, Valhalla, NY,
References (102)
- et al.
Permeability and self-healing of cracked concrete as a function of temperature and crack width
Cem. Concr. Res.
(2003) - et al.
From straw in bricks to modern use of microfibres in cementitious composites for improved autogenous healing: a review
Constr. Build. Mater.
(2015) - et al.
Mimicking bone healing process to self-repair concrete structure novel approach using porous network concrete
Procedia Eng.
(2013) - et al.
Microbiological precipitation of CaCO3
Soil Biol. Biochem.
(1999) - et al.
Calcite precipitation induced by polyurethane-immobilized Bacillus pasteurii
Enzyme Microb. Technol.
(2001) - et al.
Bacterial carbonate precipitation improves the durability of cementitious materials
Cem. Concr. Res.
(2008) - et al.
Self-healing efficiency of cementitious materials containing tubular capsules filled with healing agent
Cem. Concr. Compos.
(2011) - et al.
Microbial carbonate precipitation improves the durability of cementitious materials: a review
Ecol. Eng.
(2010) - et al.
Use of bacteria to repair cracks in concrete
Cem. Concr. Res.
(2010) - et al.
Use of silica gel or polyurethane immobilized bacteria for self-healing concrete
Constr. Build. Mater.
(2012)