Scientific Foundation of Modern Concrete - The Issues and Discussion of Modern Concrete Science - page 188

15.4 Cause Analysis

Why could we always find a close relationship zone, disorder relationship zone,

opposite relationship zone between any two related factors in concrete? Why there
is

“ ”

three-stages principle in concrete? As we all know, there are four main

materials constituting concrete, they are coarse aggregate, ne aggregate, cement,

and water. We momentarily call them four elements. Now we make a funny
assumption, if any one of the four elements was removed by us artificially, fatal
negative effect might bring about to concrete performance, and concrete would
become strange for lacking this element. At this time if we add this element to
concrete from o gradually, various concrete performances will be signi cantly

improved with the incased of dosage. This factor and other related factor in concrete
manifest close linear relationship, like AB section in Fig. 15.9 . When dosage of this
element reaches certain amount, which is equal to a balance is attained after B point
in Fig. 15.9 . Then, various concrete performances are not only related with this
element but also with many other elements as concrete is made up by multiple
factors. Relationship between W/C and strength discussed previously is like this.
When we do not add water and W/C is 0, concrete must be a loose object and its
strength is certainly 0. When W/C increases from 0 to 0.3, strength is proportional
to W/C. Strength if concrete with higher W/C is accordingly higher. When W/C is
between 0.3 0.4, relationship between W/C and strength becomes complex, but it

maintains basic relationship that higher W/C decrease strength. When W/C
increases to 0.4, 0.5 or even higher, much surplus water exists in concrete a when
part of water needed by cement hydration is satis

-

ed. Now, W/C is in accordance
with Bolomey formula and is inversely proportional to strength, namely higher
W/C leads to lower concrete strength. These are basic principle of “ three stages ”

proposed by the author.
We will further illustrate this principle via analogy. It just like a man eats
dumpling when he is hungry. A man can eat 30 dumplings every time. The

rst 20
dumplings are in the most urgently needed period, and hunger status would be
eased if eating a more dumpling, which is equivalent to AB section in Fig. 15.9 .
From the 20 to 30 dumplings is feeling numb period or a more complex period.
Some parts of various body organs feel good, while some parts feel bad, so it would
not be more if eating a more dumpling, or would not be less if eating a less
dumpling, which is equivalent to BC section in Fig. 15.9 . Feeling becomes just
opposite after eating 30 dumplings, body feeling would become much worse is
every a more dumplings was eaten, which is equivalent to CD section in Fig. 15.9 .
Principle of concrete is like eating dumplings, and it can be divided into feeling
good period, feeling numb period, and feeling opposite period, which respectively
equivalent to AB, BC, and CD sections in Fig. 15.9 . Taking relationship between
W/C and crack for example, when W/C is above 0.5, concrete crack will be sig-
ni

cantly recued with continuous decrease of W/C and W/C is the unique main
factor for generation of crack. Other factors have some effects, but the effects are all
so minimal that they can be ignored. As correlation between W/C and crack is quite