Corrosion resistance of steel bars in concrete when mixed with aerobic microorganisms

September 20, 2019

This study reports on a novel method for enhancing corrosion resistance via reduced availability of dissolved oxygen in the cathodic reactions which could be obtained through metabolic processes of aerobic Bacillus subtilis natto in the presence of organic carbon sources. In addition, the approach is beneficial in facilitating the formation of calcium carbonate which seals cracks accompanied by the self-healing of concrete.

Corrosion of steel bars in concrete leads to a decrease in the durability of reinforced concrete. The corrosion processes can be explained by electro-chemical reactions taking place in anodic and cathodic regions. The latter reaction requires oxygen and water, which is an electrolyte that can support the flow of electrons.

Dissolved oxygen in pore solution is often a controlling factor determining the rate of the corrosion process of steel bars in concrete. The properties are essentially associated with the permeability of dissolved oxygen in the pore solution. This could be affected by the metabolic activities of aerobic Bacillus subtilis natto mixed in cementitious mixtures. Bacillus subtilis natto is resistant to unfavourable environmental conditions, including salinity and extreme pH, through the formation of an endospore at times of nutritional stress until conditions become favourable.

Electro-chemical measurements were carried out to examine the corrosion processes by the AC impedance method, half-cell potential measurements, and macrocell corrosion measurements using zero-resistance ammeters. Cathodic polarization curves were measured at 28 and 91 days before and after the specimens were exposed to chloride induced corrosion tests through dry and wet cycles.

The results indicate that the rate of oxygen permeability inferred based on limiting current density is substantially lower in the case of mortar specimens mixed with the Bacillus subtilis natto. This can be explained by the fact that the dissolved oxygen is consumed by the oxidation of organic matter, a process initially catalyzed by Bacillus subtilis natto present in mortar mixtures during the monitoring periods. Based on the results obtained, the addition of a culture solution containing Bacillus subtilis natto reacting with dissolved oxygen resulted in higher resistance against corrosion processes, which was confirmed by the results of half-cell potential and microcell and macrocell corrosion current density. There is a strong possibility that the reduced dissolved oxygen in the pore solution through the aerobic processes could enhance corrosion resistance in cracked mortar specimens.
-end-


Ehime University

Related Corrosion Articles from Brightsurf:

Story Tips: Remote population counting, slowing corrosion and turning down the heat
ORNL Story tips: Remote population counting, slowing corrosion and turning down the heat

Cement-free concrete beats corrosion and gives fatbergs the flush
Researchers from RMIT University have developed an eco-friendly zero-cement concrete, which all but eliminates corrosion.

Sunflower oil shows unexpected efficiency in corrosion prevention
Sunflower oil, which is found in almost every home, can be used not only in cooking, everyday life and cosmetology - it will help avoid complications (gas hydrates and corrosion) during oil and gas production.

Waterborne polyurea/urethanes significantly reduce hydrate growth rate in pipelines
A series of inhibitors has appeared with new reagents based on water-soluble polyurethanes.

Sulfonated chitosan studied as potential biodegradable corrosion inhibitor
Hydrate formation has long been a problem for hydrocarbon production in the Arctic.

Does graphene cause or prevent the corrosion of copper? New study finally settles the debate
Graphene has attracted the interest of researchers in recent years because, despite its apparent anti-corrosive properties, its proximity was seen to increase the corrosion of copper.

Current model for storing nuclear waste is incomplete
The materials the United States and other countries plan to use to store high level nuclear waste will likely degrade faster than anyone previously knew, because of the way those materials interact, new research shows.

Marine biology: Acidified oceans may corrode shark scales
Prolonged exposure to high carbon dioxide (acidified) seawater may corrode tooth-like scales (denticles) covering the skin of puffadder shysharks, a study in Scientific Reports suggests.

Finding out the factors that most influence the steel corrosion in reinforced concrete
This process causes structures to deteriorate internally and can even cause buildings to collapse.

Researchers strengthen weakest link in manufacturing strong materials
Industrial and automotive machinery, such as automotive engine parts, contain materials that are, heat-, wear-, and corrosion-resistant.

Read More: Corrosion News and Corrosion Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.