Production of Bacteria for Structural Concrete - Biotechnologies and Biomimetics for Civil Engineering - page 312

Fig. 14.4 Effect of S. pasteurii on the compressive strength of cement mortar cubes grown in
different media at 3, 7 and 28 days (Reprinted with permission from Achal et al. 2010a )
14.4.3 Microbial Concrete and Permeability
Permeability is an important factor on which concrete durability depends, known
to be property that governs the rate of flow of fluid into porous mortar or concrete.
Such property controls the ingress of moisture, gas or harmful substances to
the concrete structures. Any adverse condition affecting building materials or
structures targets permeation properties easily. Some of commercially available
substances, which can be used to make such surface impermeable, are not suc-
cessfully used due to disadvantages such as, an incompatibility of the protective
layer and the underlying layer due to differences in their thermal expansion
coefficient or disintegration of the protective layer over time and a need for
constant maintenance (Reddy et al. 2012 ).
The ability of MICP to improve impermeability on building material surface
was first observed by Tiano et al. ( 1992 ) when they successfully used organic
matrix macromolecules extracted from Mytilus californianus shells to induce the
precipitation of calcium carbonate within the pores of the stone. The calcite pre-
cipitation resulted in a slight decrease in porosity and water absorption by capil-
larity (Tiano 1995 ), which was reduced about 60 % from the limestone (Tiano
et al. 1999b ). Further, Le Metayer-Levrel et al. ( 1999 ) confirmed bacterial car-
bonatogenesis/biocalcification on the stone surface resulted into permeability
reduction without affecting its aesthetic appearance, with conclusion that biolog-
ical mortars or cement could be used to affix small pieces broken from statues and
to fill small cavities on limestone surfaces. Later Dick et al. ( 2006 ) reported calcite