Civil Engineering Reference
In-Depth Information
also state that the treated concrete had a high resistance to carbonation.
achal et al. (2011b) mention a six times reduction in water absorption due
to the microbial calcite deposition. in a different study the same authors
(achal et al., 2011c) used a phenotypic mutant of
Sporosarcina pasteurii
(bp
M-3) with improved urease activity also reporting a significant reduction in
water absorption, permeability and chloride permeability. li and Qu (2012)
confirm that bacterially mediated carbonate precipitation on concrete surface
reduces capillary water uptake, leading to the carbonation rate constant to
be decreased by 25~40%. nevertheless, the cost of biodeposition treatment
still remains a major drawback to be overcome being dependent on the
price of the microorganisms and the price of the nutrients (5-10
7
per
m
2
), which is far from being cost-efficient (De Muynck et al. 2010). More
recently achal et al. (2011c) used corn steep liquor, an hazardous industrial
effluent, as a nutrient source reporting a biodeposition cost of just (0.3-0.7
7
)
per m
2
.
21.6 Future trends
Further investigation in the field of bacteria based concrete is still needed:
∑ Which calcite-producing bacteria are more efficient in highly alkaline
environments?
∑ can air-entraining agents be effective in preventing bacteria loss associated
with reduction in pore size?
∑ Which is the more eco-efficient encapsulation method?
∑ Will biologically deposited calcite endure the test of time?
∑ Can biomineralization be made cost-efficient?
∑
What are the environmental implications related to the use of corn steep
liquor as a nutrient source?
∑
are there any health implications involved in the use of bacteria?
∑
Which is the life-cycle assessment of biotechconcrete?
21.7 References
Achal, V., Mukherjee, A.; Basu, P.; Reddy, M. S. (2009) Strain improvement of
Sporosarcina pasteurii for enhanced urease and calcite production.
J. Ind. Microb.
Biotechnol
.
36
, 981-988.
Achal, V.; Pan, X.; Ozyurt, N. (2011a) Improved strength and durability of fly ash-amended
concrete by microbial calcite precipitation.
Ecol. Engi
.
37
, 554-559.
Achal, V.; Mukherjee, A.; Reddy, M. (2011b) Microbial concrete: Way to enhance the
durability of building structures.
J. Mater. Civil Eng
.
23
, 730-734.
Achal, V.; Mukherjee, A.; Reddy, M. (2011c) Effect of calcifying bacteria on permeation
properties of concrete structures.
J. Ind. Microbiol. Biotechnol
.
38
: 1229-1234.
Afifudin, H.; Hamidah, M.; Hana, H.; Kartini, K. (2011) Microorganism precipitation in
enhancing concrete properties.
Appl. Mech. Mater
.
99-100
, 1157.
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