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Volume 4
Trends in Green Chemistry
ISSN: 2471-9889
Page 72
JOINT EVENT
Environmental Chemistry 2018 &
Green Technologies 2018
September 20-22, 2018
September 20-22, 2018 Berlin, Germany
&
7
th
Edition of International Conference on
Green Energy, Green Engineering and Technology
8
th
International Conference on
Environmental Chemistry and Engineering
Control of polymorphism of calcium carbonate compounds in the cementitious materials by pH
control
Heesup Choi
and
Masumi Inoue
Kitami Institute of Technology, Japan
G
enerally, cracking is inherent in reinforced concrete structures and leads to serious damage during its service period.
Repeated occurrence of such damages will lead to the enlargement of the cracks, thereby allowing other deteriorating
elements such as CO
2
and Cl- to further penetrate the concrete, and this can have serious consequences for the concrete
structure. On the other hand, in an environment where there is supply of water, concrete structures display "self-healing," in
which some of cracks close up naturally, and this phenomenon is closely associated with the hydrates that are newly generated
in the areas of crack formation. This study focuses on the type of CaCO
3
crystals generated by the self-healing phenomenon.
CaCO
3
is crystal polymorphism and it is reported that crystal forms can be controlled by the relationship of temperature and
pH. Generally, CaCO
3
consists of the three kinds, such as calcite, vaterite and aragonite for crystal formation. On the other
hand, vaterite is also generated most densely among these, and self-healing can be expected. Therefore, an experiment is made
for the purpose of establishing the conditions to generate vaterite. The supplied saturated Ca(OH)
2
solution is used for the
effective self-healing. Conditions of the pH are managed pH 9.0-12.0. The results showed that self-healing occurred and the
product of the self-healing phenomenon was mostly vaterite to a crystal of CaCO
3
under the condition of pH 9.0. Finally, if
we can develop crack resistant concrete or methods for controlling cracks and self-heal cracked concrete, concrete would last
longer and become a more sustainable construction material than the standard concrete. This would extend the life of concrete
structures and hence potentially lower human CO
2
emissions through improving concrete durability. That is, it is expected that
self-healing of concrete can facilitate the maintenance and management of concrete structures, reduce environmental loads,
and extend the lifespan of concrete structures.
Figure:
The self-healing mechanism of concrete.
Recent Publications
1. Heesup Choi, Masumi Inoue, Risa Sengoku, Hyeonggil Choi (2017) Control of polymorphism of calcium carbonate
compounds produced in cracked part of cementitious materials by self-healing. Journal of applied sciences 7(6):1-16.
2. Heesup Choi, Masumi Inoue, Risa Sengoku, Hyeonggil Choi (2017) Strength recovery of concrete exposed to
freezing-thawing by self-healing of synthetic fiber and cementitious materials. Journal of Advanced Materials Letters
8(10):993-998.
3. Heesup Choi, Masumi Inoue, Hyeonggil Choi, Myungkwan Lim, Tomoya Nishiwaki, Kawajiri Shunzo (2016) The
fundamental study of the crack control by self-healing of PVA fiber reinforced cementitious composites. Journal of
Civil Engineering and Architecture Research 3(9):1680-1688.
Heesup Choi et al., Trends in Green chem 2018, Volume 4
DOI: 10.21767/2471-9889-C2-012