Sole of Concrete—Mix Proportion - The Issues and Discussion of Modern Concrete Science - page 20

after hydration. A kind of water reducer and different cementitious material will
possess different process and different paste. A kind of cementitious and different
water reducer will also form different paste. Consequently, cement plaster of the
same W/C will form different hardened cement paste. Obviously, one-dimensional
attribute of W/C has changes after adding water reducer and the W/C can only
become a conception.
However, conception of the W/C law is still an important tool for directing
production and scienti

c research. What we need is how to revise and expand it.
With respect to slump, we must determine an important principle, which is that

the smaller the slump is, the better the concrete frost, permeability, crack, car-
bonation resistance and durability will be.

“

It seems true from appearance, but
actually they have no direct relationship. Only when the other conditions are
constant, smaller slump indicates lower water consumption per cubic; concrete
strength will be improved under the premise of even vibrating and compaction.
There are many methods to decrease water consumption per cubic, such as
employing water reducer. But the question is although water consumption per cubic
is decreased and even slump is decreased, concrete shrinkage, especially early-stage
shrinkage, increases dramatically all the same.
“

”

Cement consumption of high-performance concrete is within the range of 450-
500 kg/m 3 .

”

Generally speaking, cement consumption has no direct relationship
with high-performance concrete. It will be much better if coarse aggregate content
can reach 1,300 kg/m 3 . Yet, coarse aggregate content of current pumped concrete
rarely exceeds 1,100 kg/m 3 .

2. Professor Yan Pei-yu

Mr. Yang had mentioned that three theoretical methods for concrete mix design
were severally “ SSA method, ”“ maximum density method, ” and “ Weymouth gap

grading method, and the old theory for concrete mix design failed to guide the mix

design of modern concrete. However, these three methods mainly involved with
quality and content of concrete aggregate. It was impossible to obtain a concrete
mix to just rely on these three methods. There were more contents needed to include
in theoretical foundation of concrete mix design.
There was no de

”

nite boundary between traditional and modern concrete.
Compared with the concrete produced 10 years ago, material composition and
performance of modern concrete had changed a lot. However, the pursuant basic
theory could be traced to the same origin. As so far, the most important theory basis
for concrete mix design is that void content of porous material was in negative
correlation with its strength, speci cally for concrete, that is, concrete strength was

in negative linear relationship with its water-to-binder ratio. It was impossible for
Mr. Yang to overthrow this theory just basing on his own limited experiences.
Although Table 1.2 had given some examples to show

flexural strength of stiff
concrete had no relationship with water-to-cement ratio, we might discover that
“ ”

proposed by Abrams in 1918 was still stand if the statistics
was carried out within wider range. When concrete strength was low, the

water to cement law

rst
solution to adjust was decreasing water-to-binder ratio rather than increasing