Bacteria for Concrete Surface Treatment - Biotechnologies and Biomimetics for Civil Engineering - page 328

pH (Burne and Marquis 2000), (2) utilizing it as a nitrogen source (Burne and
Chen 2000 ), and (3) using it as a source of energy. There are many species of
Bacillus reported that produce large amount of urease, further helps in carbonate
deposition and biocementation (De Muynck et al. 2008a , b ; Achal et al. 2009 ).
Sporosarcina pasteurii is another specialist organism that has a different use for
urease, other than nitrogen assimilation. S. pasteurii is a moderately alkaliphilic
organism with a growth optimum at pH 9.25. Urea hydrolysis is the most easily
controlled of the carbonate generating reactions, with the potential to produce high
concentrations of carbonate within a short time. Beside conventional bioremedi-
ation measurement, a number of applications involving bacterial deposition have
been attempted in the area of construction industry.
Bacterial induced carbonate deposition has subsequently led to the exploration
of this process in a variety of fields. A first series of applications is situated in the
field of bioremediation. In addition to conventional bioremediation strategies
which rely on the biodegradation of organic pollutants (Chaturvedi et al. 2006;
Simon et al. 2004). Applications include the treatment of groundwater contami-
nated with heavy metals (Warren et al. 2001 ) and radionucleotides (Fujita et al.
2004 ), the removal of calcium from wastewater (Hammes et al. 2003a , b ). Another
series of applications aims at modifying the properties of soil, i.e., for the
enhancement of oil recovery from oil reservoirs (Nemati and Voordouw 2003 ;
Nemati et al. 2005 ), plugging (Ferris and Stehmeier 1992 ) and strengthening of
sand columns (DeJong et al. 2006 ; Whiffin et al. 2007 ). In recent years, biode-
position has been investigated for its potential to improve the durability of con-
crete materials. The deposition can be divided into processes for the deposition of
a protective surface layer with consolidating and/or waterproofing properties, i.e.,
biodeposition for surface treatment, and processes for the generation of a bio-
logically induced binder, i.e., biocementation for bacterial concrete. Following
section deals with detailed review regarding parameters affecting the durability of
concrete materials and structures.
15.3 Concrete Surface Treatment by Biodeposition
15.3.1 Bioremediation of Concrete Surface Cracks
Concrete materials have been used extensively as worldwide construction mate-
rials. They have been typically characterized by a high-compressive strength and a
relative low-tensile strength. The latter can be offsetted by the application of steel
or other material reinforcements taking over tensile forces. High-tensile stresses
may be result from external loads, imposed deformations (due to confined
shrinkage, temperature gradients, or differential settlement), plastic settlement,
plastic shrinkage, and expansive reactions (e.g., due to alkali silica reaction,
reinforcement corrosion, or sulfate attack). Microcrack formation is a commonly