Corrosion prevention in cracked concrete by denitrifying bacterial granules


De Belie N., Erşan Y. Ç., Van Tittelboom K.

7th International Conference on Self-Healing Materials (ICSHM 2019), Yokohama, Japan, 3 - 06 June 2019, pp.109

  • Publication Type: Conference Paper / Summary Text
  • City: Yokohama
  • Country: Japan
  • Page Numbers: pp.109
  • Hacettepe University Affiliated: Yes

Abstract

Cracks in concrete may act as preferential location for ingress of aggressive agents, like chlorides, towards the reinforcement. Precipitation of calcium carbonate by protected bacterial consortia introduced in self-healing concrete will help to heal cracks when they appear. However, complete healing of cracks with a width of several hundreds of micrometres will take a number of weeks. Therefore, the question rises whether this healing mechanism allows to avoid corrosion in a chloride containing environment. Two types of self-protected bacterial granules were integrated in mortar specimens containing a steel rebar. Granules containing ureolytic bacteria did provide crack healing, but could not completely avoid corrosion initiation and propagation.On the other hand, denitrifying granules provided corrosion inhibition, as was noticed from measurements of open circuit potential and gravimetric mass loss of reinforcement bars. The denitrifying granules were able to heal 300 μm wide cracks in one month time. Furthermore, during exposure to chloride solution, the obtained performance regarding reinforcement protection was comparable with that of cracked mortar containing chemical inhibitor or even uncracked mortar. This is a result of nitrite release by the denitrifying granules, which quickly stabilizes the corrosion reaction products and hinders the formation of mobile iron chloride complexes