Screening of Fungi for Potential Application of Self-Healing Concrete

Rakenth R Menon,Jing Luo,Zhiyong Liu,Hui Zhou,Ning Zhang,Guangwen Zhou,Congrui Jin,Xiaobo Chen

doi:10.1038/s41598-019-39156-8

Abstract

Concrete is susceptible to cracking owing to drying shrinkage, freeze-thaw cycles, delayed ettringite formation, reinforcement corrosion, creep and fatigue, etc. Continuous inspection and maintenance of concrete infrastructure require onerous labor and high costs. If the damaging cracks can heal by themselves without any human interference or intervention, that could be of great attraction. In this study, a novel self-healing approach is investigated, in which fungi are applied to heal cracks in concrete by promoting calcium carbonate precipitation. The goal of this investigation is to discover the most appropriate species of fungi for the application of biogenic crack repair. Our results showed that, despite the significant pH increase owing to the leaching of calcium hydroxide from concrete, Aspergillus nidulans (MAD1445), a pH regulatory mutant, could grow on concrete plates and promote calcium carbonate precipitation.

Highlights

Cracks themselves may not significantly reduce the load-carrying capacity of concrete in the short run, but they considerably weaken the durability of concrete structures, as they channel in water, oxygen, and carbon dioxide, which could potentially corrode the steel reinforcement
The experimental results of this study showed that, despite the significant pH rise caused by the leaching of calcium hydroxide from concrete, one type of pH regulatory mutants of A. nidulans (MAD1445) could grow on concrete plates
Nidulans (ATCC38163), A. nidulans (MAD0305), A. nidulans (MAD0306), R. oryzae (ATCC22961), P. chrysosporium (ATCC24725), A. terreus (ATCC1012), and A. oryzae (ATCC1011) could not grow in the alkali solution caused by the leaching of calcium hydroxide from concrete

Summary

Introduction

Cracks themselves may not significantly reduce the load-carrying capacity of concrete in the short run, but they considerably weaken the durability of concrete structures, as they channel in water, oxygen, and carbon dioxide, which could potentially corrode the steel reinforcement. Concrete has been the key construction material for reactor containment and biological shielding structures, which are essential components of the nuclear reactors in service worldwide for power generation[1]. Cementitious grouts, mortars, and concrete are often used to provide shielding and encapsulation of various radioactive waste materials from military, research, and power generation applications. Concrete can fix its own cracks mainly through the following three mechanisms: autogenous healing, embedment of polymeric material, and bacteria-mediated CaCO3 precipitation, which have been summarized www.nature.com/scientificreports/. It has been demonstrated that in the environment of concrete, CaCO3 can be precipitated by certain species of bacteria through biologically induced mineralization processes[2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21]. Owing to the limited ability of bacteria to produce large amounts of CaCO3, bacteria can only heal small cracks with crack widths less than 0.8 mm[10,11,12,13,14,15,16,17,18,19,20]

Methods

Results

Conclusion