A BIO-BASED RHEOLOGY MODIFYING AGENT INSPIRED FROM NATURE

Abstract


 
 Interaction of microorganisms and building materials, particularly with
 concrete and stone, were a main topic of interest for many researchers.
 Initially, studies focused on degradation of concrete by
 organic acids, produced by microbial acidification such as microbial induced
 corrosion. This was followed by prevention of microorganisms fouling on building
 materials. However, the interaction of microorganisms with materials is not
 necessarily negative. Recent research in the field shows that microorganisms
 can have positive effects on concrete and stone, such as in biological cleaning
 and biocalcification, which resulted with stronger and more durable materials.
 Further, studies revealed that it was possible to develop smart-cement based
 materials that could self-heal microorganisms by leveraging metabolic activity
 of microorganisms. Through the development of this so-called smart bio-based
 mortar, it became possible to improve the fresh state performance of the mix.
 This study focusses on design of a cement-based mortar with improved
 rheological properties with use of Bacillus
 megaterium (B. megaterium) and
 Bacillus subtilis (B. subtilis) cells. The bacterial cells were directly
 incorporated to the mix water and influence of cells on viscosity and yield
 strength was evaluated by rheological tests. In addition, the influence of
 bacteria dosage, water to cement ratio (w/c), use of superplasticizers and fly
 ash on performance of biological VMA were investigated. Our results showed that
 the apparent viscosity and yield stress of the cement-paste mix were increased
 with the addition of the microorganisms. Moreover, B. megaterium cells were found to be compatible with both fly ash
 and superplasticizers however B. subtilis
 were only be able to increase the viscosity when they were incorporated with
 superplasticizers.