Summary Report of Experimental Study on Dehydration Crack Appearing in the Construction of Turpan Civil Airport Cement Concrete Pavement - The Issues and Discussion of Modern Concrete Science - page 240

Used sand was sieved from gravel sand on the same riverbed. It was coarse sand
and had a fineness modulus of about 3.0. Similarly, report or viewpoint which

demonstrated different sand

finenesses had various effects on dehydration crack
generation as had been seen so far, comparative experiment on different neness

sands had not been arranged in this experiment.
Traditional concrete scienti c viewpoints insisted that aggregate was one of the

three main factors (cement paste, interference between cement paste and aggregate,
and aggregate itself) that affected concrete strength. We often made concrete whose
strength was between C30 and C60 (having the right to speak about concrete that
was above C60 due to few making) and mainly employed quali

ed aggregate which

was allowed by speci cation, and we had never found that strength of aggregate

itself had signi cant effect on concrete strength. We attributed it to that coarse

aggregate processing manner had transformed to impact or hammer crusher from
the past jaw crusher, and thus,

flaky and elongated particle content of coarse had
been decreased drastically. Crack generation had great detriment to concrete

strength. Now that current aggregate has no signi cant effect on concrete strength,

so we could assume that diverse aggregates had no effect on dehydration crack
generation.
It was believed by somebody at

field that dehydration crack was more easily to
create when coarser sand was adopted under same condition, as thought by engi-
neers Lin Xingang who was from air force corps and Wang Zhaoyuan who was
from Northwest Civil Aviation supervisor company according to their engineering
experience. However, somebody also held contrary ideas; the author deemed that
coarse sand was more bene cial to volume stability of mortar layer on concrete

surface. It needed to be proved by scienti c research and engineering practice

whether these two viewpoints were correct or not. However, such an experiment
was unable to be conducted at

field due to the lack of condition. Such experiment
even could not be accurately carried out under current concrete level of science and
technology. In the Changjiang River, the waves behind drive on those before, and
we had to wait for the next generation of concrete scienti c and technical workers

to finish that experiment.

2. Cement

Work on cement was relatively few in the experiment, which was the greatest
regret of the experiment. We always insisted that the reason why dehydration and
map crack became more and more serious was due to vast genitive effect of cement
which was produced by modern method, including not only cement

neness, grade,
3-day strength, setting time, mineral admixture dosage, and C 3 A and C 3 S content,
but also adoption of high effective separator and grinding aid in cement production
technology. These above reasons all had serious negative effect on generation of
dehydration crack. We also believed that modern and past cement had qualitative
distinction. Besides positive effect on strength at 28th day, negative effect might all
outweigh positive effect as for other in uence of modern cement on concrete.