Concrete compatible biogranules: a novel healing agent for bio-based self-healing concrete


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Sönmez M., Erşan Y. Ç.

International Conference on Cement-Based Materials Tailored for a Sustainable Future, İstanbul, Turkey, 27 - 29 May 2021, pp.302-310

  • Publication Type: Conference Paper / Full Text
  • City: İstanbul
  • Country: Turkey
  • Page Numbers: pp.302-310

Abstract

Recent studies focused on development of self-sensing and self-healing concrete to replace the cost and labour intensive maintenance strategies. For the former, use of microbial healing agents that induce calcite precipitation in the crack is a popular approach. So far, ureolytic axenic cultures were mostly proposed as healing agents. Yet, non-axenic cultures, biogranules in particular, may be advantageous by their enhanced performance and resilience. This study presents the compatibility of nitrate reducing biogranules with the mortar matrix and the self-healing performance of corresponding bacteria-based specimen. In-house produced biogranules were incorporated into mortar mix at dosages varying between 0.35% to 4.30% w/w cement (0.25% to 3.00% of bacteria w/w cement). Due to their self-encapsulated structure, biogranules were added into the mortar mix without using any additional protective carrier. A representative specimen containing 1.40% biogranules was also tested for self-healing under alternating a week-long wet/humid treatment for a crack width range of 50 to 600 μm. Considering fresh and hardened mortar properties, the tolerable biogranule content was determined as 3.60% w/w cement. Due to its optimized design mix, the novel microbial self-healing mortar appeared to be 30% stronger than the plain mortar. Upon alternating wet/humid treatment for 4 weeks, cracks up to a 400 μm crack width were effectively healed. Overall, non-axenic biogranules appear to supersede the axenic cultures in development of self-healing bioconcrete by their self-protected structure, compatibility with matrix and enhanced performance under spraying or intermittent wetting conditions, which pave the way for development of cost-efficient self-healing bioconcrete for a broader range of applications.