Civil Engineering Reference
In-Depth Information
cation was usually facing with macroscopic and the vast majority
of situations. As for problem in special situation, as it took a little proportion in the
country, speci
National speci
cation was unable to reach every aspect of a matter and clarify
requirement. This was inevitable. When special situation was met in our project,
how to execute speci
cation reasonably and scienti
cally became an important
technical question for
field engineering technicians.
Turpan was just such a situation. Environment in Turpan was also extreme all
over the world. In such circumstances, it was obviously one-sided or even wrong to
insist mechanically and doctrinally that W/C must meet Civil Aviation requirement
of being no more than 0.45. In summer of Beijing and Xi
an, relative air humidity
was usually above 40 % in sunny weather and over 70 % on rainy days. And
temperature in summer of these two cities could basically maintain below 25
'
C
when construction was arranged at night. Supposing W/C adopted in Beijing and
Xi
°
C
in Turpan, how to satisfy the construction requirement under same condition if
construction unit was demanded to adopt a W/C of 0.45? This did not include gap
brought about by great difference of relative air humidity.
Additionally, according to our past experience, concrete unit water demand
would increase nearly 1 kg if temperature increased every 1
'
an at night was 0.45, and night temperature in summer was always above 30
°
C. If average tem-
perature difference between Beijing and Turpan at night was calculated as 5
°
C, unit
concrete unit water demand of Turpan Airport would also need to increase 5
-
6kg
under same condition. This 5
°
6 kg water was two percents if it was converted to W/
C. That was to say, if W/C of being was 0.45, only W/C of Turpan which reached
0.47 could also ful
-
ll operation requirement of the same construction technology.
Moreover, if vast gap of relative air humidity was taken into consideration, it ought
to be greater than 0.47.
The above analysis was mainly based on our experience, because such com-
parative experience had never been carried out by anybody before and no relevant
datum could be found. It ought to be scienti
c and strict for implementation of
speci
cation to adopt a W/C for construction which was one percent higher than
speci
cation regulation.
3. Admixture
AFJ-6 Hgh high effective retarding reducer (air-entrained type) produced by
Beijing Anjian Century Limited Company was employed in the experiment.
Product of the company was repeatedly employed in Xinjiang and other airports,
and the effect was very good. For example, W/C could be reduced from 0.44 to 0.39
when it was utilized in Urumchi Airport. However, the water-reducing effect was
not obvious in the experiment. More than that, crack quantity of concrete slabs
which employed was the most during the experiment in 3 days. We had studied and
analyzed generation of this phenomenon for many times and believed that it was
resulted in by the following two reasons.
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