Scientific Foundation of Modern Concrete - The Issues and Discussion of Modern Concrete Science - page 177

(i) Professor He Jin-yun holds the view that sand ratio has little effect on
compressive strength of ordinary concrete, especially when W/C is high
enough [ 7 ].
(ii) Through practices obtained in recent years, the author thinks that no rela-
tionship could be found between sand ratio and strength in high-performance
concrete. That is to say, value of sand ratio has no impact on strength.

(c) W/C problem

Since W/C principle was discovered in 1918, it has always been one of the most
important in concrete field. Nowadays, may experts and scholars have raised dif-

ferent opinions about this principle. Professor Wang Lan insisted W/C principle is
effective in certain range; Mr. Xu Fu-chun believed gel and crystal material cannot
be fully generated and concrete strength fails to satisfy requirement when W/C is
too low; after studying effect of W/C on strength of recycled concrete [ 8 ], Mr. Deng
Xu-hua considered strength would be decreased as W/C lowered [ 9 ]; through
practice over recent years, the author deemed strength of concrete that above C40
had no relationship with W/C when unit water demand is less than 140 kg and W/C
is below 0.36 [ 3 ].

(d) Mix proportion problem
Guiding principle of current Mix Design Speci cation for Ordinary Concrete in
China is still higher sand ratio results in lower concrete strength; lower W/C leads
to high concrete strength, which obviously derive from speci

c area theory of old
concrete. As mentioned above, the mistake is quite notable when concrete mix
proportion of modern concrete is made.
The above 4 questions are basis in foundation of the experience subject of
concrete, which can be called

according to modern popular statement.
Opinions of many experts and scholars on these questions are different greatly from
or even completely opposite to statement in old concrete theories, from which
urgency of amending basic theory can be seen.

“ core value ”

2. Owning to adoption of old concrete theory, we can ' t agree with each other on

many important, leading edge, scienti c questions of modern concrete, and

opinions differ greatly.

c achievement through engineering or experimental
data and gives a conclusion of a question. However, another expert thinks the
scienti

An expert gains a scienti

c payoff gained by predecessor is wrong also through engineering practice
or experimental data. Such phenomenon is no longer a case-by-case in concrete
academia. These questions are listed as follows according to diverse importance.

(a) Expansive agent question
Expansive agent has been applied widely in engineering since it is incented.
The majority believe that expansive agent has signi cant effect on prevention

of concrete crack. Meanwhile, it also has fatal effect on boosting concrete
compaction, preventing permeability and leakage, and increasing frost