A Case Study: Bacterial Surface Treatment of Normal and Lightweight Concrete - Biotechnologies and Biomimetics for Civil Engineering - page 362

Fig. 16.8 SEM images of top surface of lightweight concrete treated by the medium with S.
pasteurii measured in 100 lm(a), 10 lm(b), and EDS spectra at point 1 (c) and at point 2 (d).
Reprinted from Kim et al. ( 2013 ), Copyright (2013), with permission from Elsevier
formed after the bulk calcium carbonate crystals were developed, but the crys-
tallization process is not yet known. Moreover, why the different shapes of the
calcium carbonate crystals of the lightweight concrete and of the normal concrete
formed is not known. However, it is considered that changes of pH and calcium
ion concentration on the surface of the concrete by a pozzolanic reaction in the
bottom ash aggregate may have led to this phenomenon (c.f. Zhang and Gjørv
1990 ; Mehta and Monteiro 2006 ; Chindaprasirt et al. 2009 ).
In addition, the calcium carbonate formed by the medium with B. sphaericus
crystallized with pockmark shapes regardless of the type of concrete specimen,
whereas the calcium carbonate crystals formed by the cell-free medium and the
medium with S. pasteurii showed spherical or semi-spherical particle shapes
(Figs. 16.9 and 16.10 ). The calcium carbonate developed by S. pasteurii rapidly
Fig. 16.9 SEM images of top surface of normal concrete treated by the medium with B.
sphaericus measured in 50 lm(a), and EDS spectra at point 1 (b). Reprinted from Kim et al.
( 2013 ), Copyright (2013), with permission from Elsevier