Scientific Foundation of Modern Concrete - The Issues and Discussion of Modern Concrete Science - page 178

resistance [ 10 , 11 ]. As a result, expansive agent is necessary concrete com-
ponent in housing structure of slab and beam, post-cast strip, basement, wa-
terwork, etc. However, many experts hold opposed opinions and insist that
there still are many cracking examples of concrete works which employ
expansive agent. They even claim aggressively that cracking become more
serious after employing expansive agent [ 12 , 13 ].
(b) Alkali-aggregate reaction question
Nearly all current scienti

cations regard alkali-
aggregate reaction as priority among priorities or propose it in special chapter,
and demand strictly preventing it in work [ 14

c topic and engineering speci

16 ], which cost lots of man-
power and material resources. However, many experts express their puzzles
that alkali-aggregate reaction has never been seen when doing concrete
engineering for a whole life [ 17 ].
(c) Fiber
Adding

-

fiber especially steel fiber in concrete, can greatly increase concrete

flexural capacity, change the characteristic of high strength but low brittleness
of concrete, and improve a lot on resistance to frost and permeability of
concrete. Therefore, this technique has been partly applied in engineering of
airport, wharf, highway and bridge, etc. However, the author has different
opinions about it [ 18 , 19 ], as can be seen in content of Chap. 7 .
(d) High-performance concrete
At present, many people believe that high-performance concrete has the best
durability [ 20 ], but the author thinks high performance may have the poorest
durability as a variety of concrete.
The above questions can be seen in relevant chapters in this topic. In addition,
problem of fly ash, water-reducing agent, etc., a number of experts and
scholars also hold different opinions, and the author will not list them at here.

15.2 Conception of the Second-Period Concrete

Where is the origin of generating the above different views and statements?
The above questions once had brought about numerous sleepless nights. After
persistent pursuing for over 10 years, a conclusion has been drawn. That is concrete
technology has undergone a tremendous change, and many empirical formulas are
out of time and unadapted. When adopting old theory and empirical formula to
solve modern concrete problem, error will be created inevitably. Thus, our urgent
task is establishing new a theoretical foundation and empirical formula which are
adapted to new technologies of modern concrete rather than quarreling on old
things.
In the section of this chapter, the author has proposed new conception of con-
crete in the second stage with great courage.
We will start analyzing on how many differences are there between modern and
past concrete technologies.