[Paper Review] Interactions of Fungi with Concrete: Significant Importance for Bio-Based Self-Healing Concrete

Jing Luo, Xiaobo Chen+6 more|arXiv (Cornell University)|Aug 4, 2017

Microbial Applications in Construction Materials85 references14 citations

TL;DR

This study proposes using the fungus *Trichoderma reesei* as a bio-based self-healing agent in concrete, leveraging its ability to survive high-pH environments and precipitate calcite crystals on hyphae. Despite pH rising from 6.5 to 13.0 due to calcium hydroxide leaching, *T. reesei* spores germinated and grew effectively, with XRD and SEM confirming calcite formation, demonstrating strong potential for sustainable crack repair in concrete structures.

ABSTRACT

The goal of this study is to explore a new self-healing concept in which fungi are used as a self-healing agent to promote calcium mineral precipitation to fill the cracks in concrete. An initial screening of different species of fungi has been conducted. Fungal growth medium was overlaid onto cured concrete plate. Mycelial discs were aseptically deposited at the plate center. The 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, Trichoderma reesei (ATCC13631) spores germinated into hyphal mycelium and grew equally well with or without concrete. X-ray diffraction (XRD) and scanning electron microscope (SEM) confirmed that the crystals precipitated on the fungal hyphae were composed of calcite. These results indicate that T. reesei has great potential to be used in bio-based self-healing concrete for sustainable infrastructure.

Motivation & Objective

• To investigate the viability of fungi as self-healing agents in concrete for sustainable infrastructure.
• To assess fungal survival and growth under the highly alkaline conditions typical of cured concrete.
• To evaluate the mineral precipitation capacity of fungi on concrete surfaces.
• To identify fungal species capable of precipitating calcium carbonate in alkaline environments.

Proposed method

• Fungal mycelial discs of various species were aseptically inoculated onto cured concrete plates.
• Fungal growth medium was overlaid on the concrete surface to assess nutrient uptake and pH changes.
• pH of the growth medium was monitored over time to track alkalinity changes due to Ca(OH)2 dissolution from concrete.
• X-ray diffraction (XRD) was used to identify crystalline phases of precipitated minerals.
• Scanning electron microscopy (SEM) was employed to visualize fungal hyphae and mineral deposits.
• *Trichoderma reesei* (ATCC13631) was selected for detailed analysis based on initial screening results.

Experimental results

Research questions

• RQ1 Can fungi survive and grow in the highly alkaline environment created by concrete's Ca(OH)2 leaching?
• RQ2 Which fungal species exhibit the ability to precipitate calcium carbonate under alkaline conditions typical of concrete?
• RQ3 Does fungal growth promote the formation of calcite crystals that could seal concrete cracks?
• RQ4 To what extent does the pH of the growth medium increase due to concrete leaching, and can fungi tolerate this?
• RQ5 Can fungal hyphae serve as nucleation sites for calcite precipitation in concrete?

Key findings

• The pH of the fungal growth medium increased from 6.5 to 13.0 due to Ca(OH)2 dissolution from the concrete substrate.
• *Trichoderma reesei* spores successfully germinated and developed into hyphal mycelium even in the high-pH environment.
• X-ray diffraction (XRD) analysis confirmed that the precipitated crystals on fungal hyphae were composed of calcite.
• Scanning electron microscopy (SEM) revealed that calcite crystals were directly associated with fungal hyphae, indicating their role as nucleation sites.
• The ability of *T. reesei* to grow and precipitate calcite under extreme alkalinity demonstrates its strong potential for use in bio-based self-healing concrete.
• No significant difference in fungal growth was observed with or without concrete, indicating tolerance to the alkaline conditions.