Environmental Engineering Reference
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cracks automatically. Recently, a novel technique has been reported that utilizes
microorganisms in remediation of cracks and fissures in natural and man-made
structures by precipitation of calcium carbonate.
On the other hand, the cement industry has for some time been seeking
procedures that would effectively reduce the high energy requirements and envi-
ronmental costs of cement manufacture (Rong and Qian 2012 ). The answer very
much depends up on ''microbial concrete'' that is based on MICP process consists
of three materials, namely, alkalophilic microbes, substrate solution and calcium
ion solution. The great promise of MICP-based microbial concrete has been
demonstrated to enhance the durability of building materials, consolidation of sand
columns, and repair of limestone monuments and concrete (Gollapudi et al. 1995 ;
Tiano et al. 1999a ; Ramachandran et al. 2001 ; De Muynck et al. 2008 ; Qian et al.
2009 ; Achal et al. 2011b ; Rong et al. 2012 ). Microbial concrete can improve the
strength and durability of structures, which are considered to be the requirements
for concrete or any other building materials. A major goal of using microbial
concrete is to ensure the quality parameters or durability of building structures.
14.4 Quality Parameters for Concrete Structures
The quality of any building material depends on three major parameters, (i)
strength, (ii) permeability, and (iii) corrosion. For an efficient microbial concrete it
should produce more compressive strength, less permeability and should not affect
corrosion of any reinforcement (Reddy et al. 2012 ). When MICP came in practice,
the first building material to test was sand where the process of MICP was well
established. Sand is the common material used to make most of the building
materials and structures, thus research to confine a novel methodology with sand is
warranted.
14.4.1 Biosandstone
The process of MICP was proposed as a novel method for cementing loose sands
to produce structural materials, termed as biosandstone (Fig. 14.2 ). It consists only
of alkalophilic urease producing bacteria, substrate solution (urea), calcium source
and sand. A typical set-up for the sand consolidation experiment to develop bio-
sandstone was simplified in Reddy et al. ( 2012 ), where sand (either mixed with
bacterial culture or later injected directly in the column) was plugged through a
plastic column and the cementation fluid (consists of nutrient media with urea and
calcium source) was injected or dropped at specific rate in the column in gravity
free flow direction.
The cementation fluid also contains nutrients that are necessary for the bacterial
growth
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