Basics of Construction Microbial Biotechnology - Biotechnologies and Biomimetics for Civil Engineering - page 47

the biocemented structure. This property is well known from the structure of the
natural biominerals such as bones, shells, and corals as well as artificial engi-
neering composite materials (Yao et al. 2011 ; Mayer and Sarikaya 2002 ). How-
ever, the cost of micro- and nano-composites could be too high to be suitable for
construction practice.
One prospective application of biocementation is repair of the cracks in con-
crete and self-healing concrete. The repair of the cracks in the surface layer of
concrete is a major portion of multi-billion maintenance and repair cost of the
concrete structures (Neville 1996 ; FHWA 2001 ). Self-healing concrete is based on
the embedding into concrete the glass or plastic capsules with material, which
could be released after simultaneous cracking of concrete and capsules. One type
of material for self-repair of the concrete proposed to be based on MICP (Ra-
machandran et al. 2001 ; Jonkers 2007 ; Jonkers et al. 2010 ). However, volume of
produced CaCO 3 will be always significantly smaller of the volume of capsule and
the crack to be filled.
2.6 Bioremediation and Biodecontamination
of Construction Site Through Biocementation
When site can be used for construction but is polluted with chemical substances
above permitted levels, microbial remediation of this site could be the cheapest
option in comparison with mechanical or chemical cleaning of the construction
site. Bioremediation can be done using such biogeochemical reactions as oxida-
tion, reduction, and transformation of pollutants to nontoxic or not dissolved
substances. Bioremediation of polluted sites is now well developed area with
hundreds of published research papers, reviews and books as well as a lot of
commercially available biotechnologies and equipment.
Meanwhile, bioremediation of construction sites through biocementation is a
relatively new area. Usually, the aim of these methods of construction biotech-
nology is to prevent the dispersion of hazardous substances from the accidentally
polluted site to environment. It is performed through either biocementation of soil
or formation of biogeochemical barrier. For example, MICP has the ability to co-
precipitate toxic radionuclides 90 Sr, 60 Co and metal contaminants such as Cd and
this can be used to prevent their dispersion in environment (Warren et al. 2001 ;
Fujita et al. 2004 ; Mitchell and Ferris 2005 ). After MICP treatment of sand surface
with the quantity just 15.6 g Ca/m 2 the release of the sand dust and its artificial
pollutants to atmosphere decreased in comparison with control by 99.8 % for dust,
92.7 % for phenantherene, 94.4 % for led nitrate, and 99.8 % for bacterial cells of
Bacillus megaterium due to bioaggregation of the fine sand particles. Bioaggre-
gation treatment of the soil surface could be useful method to prevent the dis-
persion of dust and the dust-associated chemical and bacteriological pollutants in
water, air and soil (Stabnikov et al. 2013a ), so it could be useful in construction