Bioimmobilized Limestone Powder for Autonomous Healing of Cementitious Systems: A Feasibility Study

Abstract

For preserving concrete structures and hindering ingress of chemicals through cracks and fissures, repair is inevitable. Microbial calcite precipitation is an intrinsic approach for crack rectification and emulating way of sustainability for reducing anthropogenic greenhouse gases (GHGs) along with conserving the natural resources. In this study,Bacillus subtilisstrain is applied for intrinsic repair of concrete’s cracks because of its high pH endurance and capability of sporulation. For prolonged survival of microorganisms, immobilization technique was employed.B. subtiliswas immobilized through limestone powder (LSP) before adding into cement matrix. Self-healing proficiency ofB. subtiliswas deliberated in terms of mechanical strength regain after cracking at 3, 7, 14, and 28 days. To examine the microstructure and characterization of healing precipitate, micrographical (field emission scanning electron microscopy), chemical (energy dispersive X-ray), and thermal (thermogravimetric analysis) analyses were performed after the healing period of 28 days. The results revealed evident signs of calcite precipitation in nano-/microcracks subsequent to microbial activity. Furthermore, immobilized LSP improved the compressive strength of the analyzed formulations.

Novel biodesign enhancements to at-risk traditional building materials

“…Bacteria immobilised within graphite nano-platelets and light weight aggregates can extend calcite precipitation up to 28 days (Khaliq and Ehsan, 2016). Other protective materials include limestone powder (Shaheen, Khushnood and Ud Din, 2018), iron oxide nanoparticles (Seifan et al, 2018), polyurethane (Bang, Galinat and Ramakrishnan, 2001) and sepiolite (Sandalci, Tezer and Basaran Bundur, 2021) which, subject to availability of nutrients, can extend viability for up to a year. A third method for inclusion into a cement or lime paste is to encapsulate the bacteria or spores within a biodegradable capsule providing a mechanical buffer during application and enclosed nutrients to extend cell viability.…”

“…Encapsulation enables the introduction of nutrients into the capsule to extend bacterial performance (Oyen, 2014;Wang and Soens., 2014) Disadvantages The harsh alkaline environment and limited availability of nutrients results in a high cell mortality and extensive physical damage to any live cells (Jadhav et al, 2018) Additional cost and off-site preparation of bacteria and immobilisation material. Antimicrobial qualities of immobilisation materials may reduce bacterial performance (Shaheen, Khushnood and Ud Din, 2018) The discarded capsules may reduce the integrity of the concrete matrix undermining the benefits of the calcite precipitation. Thick capsule walls may impede cell resuscitation preventing the cells from entering the microfractures…”

Encapsulation Techniques and Test Methods of Evaluating the Bacteria-Based Self-Healing Efficiency of Concrete: A Literature Review

“… Encapsulation in special minerals -diatomaceous earth (DE), zeolite [13,14,26,38]  Encapsulation in nanomaterials -graphene nanoplatelets (GNP), granular activated carbon (GAC), iron-oxide nanoparticles (IONPs) [3,13,29,41,42].  Encapsulation in cementitious materials-Metakaolin-geopolymer coating, limestone powder (LSP), calcium sulphoaluminate powder (CSA), volcanic ash [13,15,30,31,43].  Encapsulation in waste-derived biomass -biochar [16,17] Self-healing of cracks increases the toughness of concrete structures through the autogenous healing properties of cemented materials.…”

“…This healed crack width was largest in comparison to other encapsulation materials. For some bacterial carriers, the healed crack width was not investigated but their effect on bacterial spores were studied [27][28][29][30][31]. Table 2 represents the type of bacterial carrier used by the authors and the corresponding maximum completely healed crack width.…”

Cradle-to-Gate Life Cycle and Economic Assessment of Sustainable Concrete Mixes—Alkali-Activated Concrete (AAC) and Bacterial Concrete (BC)

“…The immobilization and encapsulation of bacteria are known to improve the self-healing efficiency of concrete [51]. Limestone powder [52], iron oxide nano-sized particles [53], crushed brick aggregate [54], graphite nanoplatelets [55], expanded perlite [56], and porous ceramsite particles [57] are used for the immobilization of bacteria in concrete. Though efficient, the shortcoming of protective materials is their varying efficiencies depending on the type.…”