Civil Engineering Reference
In-Depth Information
polyurethane immobilized bacteria had lower water permeability coefficient
(10
-10
-10
-11
m/s) compared with specimens healed by silica gel immobilized
bacteria, which showed a water permeability coefficient of 10
-7
-10
-9
m/s
(Fig. 21.4).
21.5 Concrete surface treatment
De Muynck et al. (2008a) compared the durability (concerning capillary water
uptake and gas permeability) of concrete when its surface was treated with
pure and mixed cultures of ureolytic bacteria. They concluded that the type
of bacterial culture and the medium composition had a profound impact on
caco
3
crystal morphology, being that the use of pure cultures resulted in
a more pronounced decrease in the uptake of water. They also concluded
that the durability performance obtained with cultures of the species
B.
sphaericus
was comparable to the ones obtained with conventional water
repellents (silanes, siloxanes). (Fig. 21.5).
De Muynck et al. (2008b) studied different durability parameters
(carbonation, chloride penetration, and freezing and thawing), confirming that
the biodeposition treatment showed a similar protection towards degradation
processes when compared with some of the conventional surface treatments
under investigation. They also mention the need for investigations regarding
the durability of the treatment under acidic media. They further mentioned
that biological generated calcite is less soluble than the one inorganically
R
SG
SG+BS
PU
PU+BS
1.00E-04
1.00E-05
1.00E-06
1.00E-07
1.00E-08
1.00E-09
1.00E-10
1.00E-11
21.4
Water permeability of cracked cylinders. (R = reference, SG =
silica gel, BS = bacterial suspension, PU = polyurethane immobilized
bacteria) (Wang et al., 2012b).
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