Nitrite producing bacteria inhibit reinforcement bar corrosion in cementitious materials

Yusuf Çağatay Erşan,Nico Boon,Nele De Belie,Kim Van Tittelboom

doi:10.1038/s41598-018-32463-6

Abstract

Chemicals and synthetic coatings are widely used to protect steel against corrosion. Bio-based corrosion inhibition strategies can be an alternative in the arising bioeconomy era. To maintain the good state of steel reinforcement in cracked concrete, microbe-based self-healing cementitious composites (MSCC) have been developed. Yet, proposed strategies involve reasonably slow crack filling by biomineralization and thus risk the possible rebar corrosion during crack healing. Here we upgrade the rebar protection to a higher level by combining MSCC with microbial induced corrosion inhibition. Presented NO3− reducing bacterial granules inhibit rebar corrosion by producing the anodic corrosion inhibitor NO2− and meanwhile heal a 300-µm-wide crack in 28 days. During 120 days exposure to 0.5 M Cl− solution, the rebars in cracked MSCC keep showing open circuit potentials above the critical value of −250 mV and they lose less than 2% of the total rebar material which corresponds to half the material loss in cracked plain mortar. Overall, the obtained rebar protection performance is comparable with that of uncracked mortar and mortar containing chemical inhibitor, hence the microbe-based system becomes an alternative to the traditional methods.

Highlights

Microcracks in reinforced concrete structures, especially in marine environment, facilitate the ingress of substances such as Cl−, SO42−, CO2 and O2 towards the reinforcement bar
The closing of the crack in 28 days improved the aesthetic and functional properties of the activated compact denitrifying core’ (ACDC) containing specimen as compared to those of the positive control. These findings unveiled the necessity of a corrosion inhibition mechanism together with the self-healing functionality to delay rebar corrosion in cracked cementitious composites and to limit its development in the post-healing period
By using NO3− reducing ACDC culture, we developed an advanced microbe-based self-healing cementitious composites (MSCC) that can protect the rebar in cracked mortar up to 4 months while healing a 300 μm wide crack in the first 28 days

Summary

Introduction

Microcracks in reinforced concrete structures, especially in marine environment, facilitate the ingress of substances such as Cl−, SO42−, CO2 and O2 towards the reinforcement bar (rebar). Regardless of the proposed metabolic pathway, MSCC perform better than conventional mortars in terms of water tightness regain[7,9,10]. Such regain in functionality is desired to hinder the ingress of aforementioned aggressive substances and to protect the good state of the rebar[11,12,13]. Especially for applications of MSCC in marine environment, complementary mechanisms that provide corrosion inhibition are necessary to effectively protect rebars from corrosion during microbe-mediated healing of cracks. The formation of mobile iron chloride complexes is hindered

Methods

Results

Discussion

Conclusion