Basics of Construction Microbial Biotechnology - Biotechnologies and Biomimetics for Civil Engineering - page 38

Fig. 2.6 Spatial types of biocementation: formation of the crust on surface of sand (a), formation
of the biocemented layer of the defined thickness (b), biocementation of monolith (c)
were associated with some infectious diseases (Novakova et al. 2006 ; Taponen
et al. 2008 ). Therefore, the isolated strain was not used for biocementation studies
and applications.
Biocementation can be performed as bulk biocementation through the supply of
bacterial suspension altogether or separately with solutions of calcium and urea by
injection, and using surface percolation (Cheng and Cord-Ruwisch 2012 ; Stabni-
kov et al. 2011 ) or surface spraying (Stabnikov et al. 2011 , 2013a ; Chu et al.
2012a ). Modifying types of the treatment it is possible to form the crust on surface
of soil (Fig. 2.6 a), biocemented layer of defined thickness (Fig. 2.6 b) or bioce-
mented monolith (Fig. 2.6 c).
There are several drawbacks in the conventional MICP process: (1) by-product
of urea hydrolysis is ammonium and ammonia that are toxic substances for
workers, harmful for aquatic environment and atmosphere, and increases the risk
corrosion because of high pH (Pacheco-Torgal and Labrincha 2013a ); (2) the
brittleness of calcite crystals bonding the soil particles; and (3) the cost of calcium
reagent and urea are higher than the cost of conventional cement. Therefore, the
improvements of MICP as well as new types of biocementation have to be
developed to overcome these disadvantages of conventional MICP.