Production of Bacteria for Structural Concrete - Biotechnologies and Biomimetics for Civil Engineering - page 307

Fig. 14.1 Pathway of biomineral secretion and precipitation in a bacterial cell (Reprinted with
permission from Sarayu et al. 2014 )

The concrete ecosystem, rich in calcium source, provides favorable condition for
MICP as calcium carbonate precipitation readily occurs in alkaline environments
abundant of the calcium (Ca +2)

and carbonate (CO 2

3 ) ions (Stocks-Fischer et al.
1999 ; Ramachandran et al. 2001 ; Qian et al. 2010a ).

14.3 Why MICP and Microbial Concrete?

Natural processes, such as weathering, faults, land subsidence, earthquakes, and
human activities create fractures and fissures in concrete structures or monuments.
These fractures and fissures are detrimental since they can reduce the service life
of the structure (Achal et al. 2011b ). Such processes often weaken strength, induce
porosity and also give an unattractive appearance, and cracks lead to easy passage
for aggressive environment to reach the reinforcement and initiate corrosion.
There are synthetic agents (epoxy, hydroxyl-epoxy) or latex binding agents (such
as acrylic, polyvinyl acetate, butadiene styrene) or silanes or organic-inorganic
products available in the market to protect or repair damaged concrete structures;
however, suffer from being expensive, and problems associated with different
thermal expansion, degradation with age and the need for constant maintenance.
Appearance of cracks and fissures is an inevitable phenomenon during the aging
process of concrete structures when exposed to weather changes. Such cracking
leads to easy passage for aggressive environment to reach the reinforcement and
initiate corrosion. Moreover, sometimes repair is carried out in the areas where it is
not possible to shut down the plant or it is hazardous for human beings. Hence, in
such situations, a way should be found out to self healing materials that seal the