Bacteria for Concrete Surface Treatment - Biotechnologies and Biomimetics for Civil Engineering - page 320

15.1 Introduction
Concrete material is the most widely used in building all over the world. Current
remediation of degraded concrete structures has drawn the attention to the methods
to slow down or even to eliminate concrete degradation. Nowadays a broad range
of organic and inorganic products is applied to the protection of concrete surfaces,
such as a variety of coatings, water repellents, and pore blockers. Synthetic agents
such as epoxies and surface treatments with water repellents such as silanes or
siloxanes or with pore blockers are applied for remediation of these structures.
These conventional surface treatments show, however, beside their pro influences
also a number of disadvantageous aspects, e.g., different thermal expansion
coefficient of the treated layers, degradation over time and the need for constant
maintenance, and environmental pollution (Moon et al. 2007 ; De Muynck et al.
2008a , b ). Organic treatments commonly result in the formation of incompatible
and often harmful surface films. Additionally, because large quantities of organic
solvents are used, they contribute to pollution (Camaiti et al. 1988 ). Inorganic
consolidation may be preferable since stone materials and protective or consoli-
dating materials share some physicochemical affinity (Rodriguez-Navarro et al.
2003 ). Surface cracks and fissures is an inevitable phenomenon during the course
of concrete structures when exposed to weather changes. Shortcomings have
drawn the attention to alternative techniques. It is necessary to develop some new
eco-friendly self-healing techniques to concrete structures to meet various
demands to enhance their durability. Bacterial induced carbonate deposition (i.e.,
biodeposition) treatment was similar as conventional treatments. Promising results
of techniques based on microbial mineralization have lead to several investigations
on the use of bacteria in concrete. Alkali-resistant spore-forming bacteria represent
promising candidates for application in concrete and probably other cement-based
materials (Jonkers et al. 2010 ). The use of stone consolidants aims at re-estab-
lishing the cohesion between grains of deteriorated stone. However, both con-
servation treatments are subject to frequent controversy due to their nonreversible
action and their limited long-term performance. Because of problems related to
incompatibility with the stone, both water repellents and consolidants have often
been reported to accelerate stone decay (Moropoulou et al. 2003 ). Biodeposition
has been proposed as an eco-friendly method to protect decayed building stone.
The method relies on biodeposition formation of a compatible carbonate precip-
itate on limestone, and unlike the lime-water treatment, the carbonate cement
appears to be highly coherent (Le Metayer-Levrel et al. 1999 ).
Bacteria are small, prokaryotic, microorganism that are ubiquitous in terrestrial
and aquatic habitats. Some of them can cause deterioration to construction
materials such as stone and concrete by the weathering action of various physical,
chemical, and biological damage factors at the object site (Warscheid and Braams
2000 ; Gaylarde et al. 2003 ). Actually, some of them are also capable of remedi-
ation of buildings materials. Microbial activity can have strong impact on the
durability of building materials. Some can cause deterioration to construction