Civil Engineering Reference
In-Depth Information
(a) High temperature reduced use effect of admixture. According to our experi-
ence, water reducer had the best effect under 28
C and its effect would be
°
greatly reduced when temperature was above 30
C. During the experiment,
°
C in the
third day. That is the reason why use effect of admixture was not obvious.
(b) Water reducer would increase concrete shrinkage, which was proved in during
the experiment. In other place of China, temperature was relatively lower and
air humidity was relatively higher compared with Turpan, and phenomenon of
concrete shrinkage increased by admixture was concealed by better environ-
mental factors; thus, this phenomenon was dif
temperature was all above 30
C in the former 2 days and above 28
°
°
cult to be found. Yet in special
climatic condition of Turpan, this phenomenon would become very notable.
However, we thought that we could not deny radically utilization of admixture,
and considered reasons were as follows: Local night temperature was above 30
C
in experiment at Turpan, while airport scheduled that concrete construction time
was from September to October. According to local meteorological data, night
temperature would decrease to around 25
°
C, and admixture would play a very
good role in reducing W/C at this temperature. In addition, although admixture
increased possibility of dehydration crack generation, the problem could completely
be solved by improving other construction technology. In short, reducing W/C as
much as possible in feasible situation was always the biggest principle of concrete
technique.
°
4. Strength
28-day strength results in the experiment were as follows (strength result of
Duolang cement was omitted).
No addition of admixture and
ber: 5.7 MPa.
Addition of admixture: 5.2 MPa
Addition of admixture and
ber: 5.4 MPa
It could be seen from the results that plain concrete had the highest strength, the
latter was concrete which employed admixture and
ber, and the worst was con-
crete which employed admixture solely.
It could be recognized through analysis that increase of W/C led to detriment to
strength for concrete specimen which employed admixture and
fiber; oversized
shrinkage caused by local special climate also harm strength to some extent. Yet, as
specimen groups were not enough,
final conclusion could not be drawn on these
three kinds of different results.
We believed that what we should concern most was reduction and elimination of
dehydration crack in this airport besides concrete strength. As mentioned previ-
ously, reducing and eliminating dehydration crack was key sign of whether the
airport construction was successful or not. As a result, we should give consideration
to two factors of strength and reducing dehydration crack generation to decide
acceptation or rejection of a kind of material.
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