Environmental Engineering Reference
In-Depth Information
Fig. 16.11 Relative value of capillary water absorption: a normal concrete and b lightweight
concrete. Reprinted from Kim et al. (
2013
), Copyright (2013), with permission from Elsevier
low, though this value increased at 128 h. This was considered to be attributable to
the distribution of the calcium carbonate precipitation on the concrete. In the cell-
free medium, calcium carbonate crystals formed with a stacked particle mor-
phology on the surface of the concrete (Figs.
16.4
and
16.5
); thus, these particles
could easily become detached during the capillary water absorption test. On the
other hand, although the calcium carbonate crystals precipitated by S. pasteurii
had shapes similar to those that formed in the cell-free medium, their sizes were
much smaller and the crystals were connected to each other (Figs.
16.7
and
16.8
).
Therefore, the relative value of the concrete treated with the medium with
S. pasteurii was more stable than that of the concrete treated with the cell-free
medium.
In addition, regarding the decrease in the capillary water absorption of the
concrete, the efficiency of the bacterial treatment in the present work appears to be
similar to experimental results obtained in similar studies. The surface treatment
by B. sphaericus could reduce the capillary water absorption of cement mortar
by about 50 % (De Muynck et al.
2008b
). Moreover, the surface treatment by
B. pasteurii decreased the capillary water absorption of cement paste by about
50-70 % (Qian et al.
2009
).
16.4 Conclusion
In this chapter, a case study involving the bacterial surface treatment of normal and
lightweight concrete samples was presented. The surfaces of concrete specimens
were
treated
with a
liquid
medium
with and
without bacteria.
Macro- and
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