Civil Engineering Reference
In-Depth Information
As dehydration crack is created on concrete surface, a penetrating passage of
outside water to inner concrete has been generated naturally, making frost resistance
and impermeability of concrete weakened drastically.
2. Forming weakness plane of concrete
As dehydration crack is crack that locates at concrete surface, it becomes a
weakness plane naturally, making
flexural strength of concrete decreased.
3. Affecting durability of concrete
As dehydration crack has reduced frost resistance and impermeability of con-
crete directly as well as intensi
ed destroy of other cracks on concrete, it will
decease service life of concrete naturally.
4. Partial short, shadow, small dehydration crack may transform to harmless crack
As length, width, and depth of dehydration crack are different, its detriments will
be variable naturally. According to
field investigation, dehydration crack, whose
length is less than 20 cm, width is less than 1 mm, can be called harmless crack as it
has minimal or even negligible effect on frost resistance, impermeability, and rupture
possibility of concrete. Additionally, this kind of crack will disappear naturally after
a period with the help of self-healing ability.
8.4.3 Prevention and Cure for Dehydration Crack
As it is described above, twenty causes for dehydration crack generation have been
summarized by the author. Prevention for dehydration crack is proposing relevant
solutions basing on these causes.
1. Effect of
floating times
Process of concrete strength enhancement is process of shrinkage.
2. Selecting proper construction time
field will
accelerate dehydration of concrete, which increase possibility of generating crack.
Therefore, adverse factors, such as strong wind and high temperature, should be
avoided in construction.
Big wind speed, high temperature, and small humidity at construction
3. Selecting good raw material
neness, C
3
S and C
3
A content, admixture dosage and kind, etc.,
all have direct effect on generation of dehydration crack. Therefore, cement
selection is important solution for preventing generation of dehydration crack.
Cement type,
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