Breeding and False Setting, Which Is Better? - The Issues and Discussion of Modern Concrete Science - page 79

Fig. 6.11 Comprehensive
relationship between final
setting time of cement and
breeding as well as false
setting

6.3 Detriment of Breeding and False Setting

1. Detriment of breeding

It is analyzed by somebody that breeding has formed a channel inside concrete,
which affects frost resistance, impermeability, and durability a lot. The author don

' t

agree with the viewpoint for two reasons: firstly, many projects existed breeding

phenomenon twenty years ago (mainly due to high W/C and coarser cement), but
their durability were wholly very good whether in the south or in the north; secondly,
projects done by us which had emerged serious breeding, such as Altay Airport in
Xinjiang, Kashgar Airport, Xining Airport, Heihe Airport in Heilongjiang, etc., their
durability are still in good condition.
Projects which had generated breeding have very good durability yet, what

'

s the

reason? stronger self-

healing ability (mechanism of self-healing can be checked up in Chap. 10 of the
topic).

① probability of generating false setting is quite low; ②

2. Detriment of false setting

Detriment of false setting on project is serious, mainly for three aspects in the
following.

(1) Amplifying possibility of cracking. False setting leads to extremely rapid
water loss of concrete suddenly and oversize shrinkage. Therefore, cracking
usually associates with false setting simultaneous in ordinary project. False
setting inside concrete brings about sightless cracks, which decreases flexural

strength greatly and intensity fracture destruction possibility of beam and
board.
(2) As false setting make it dif

cult for vibration, compaction, together with frost
resistance and impermeability, is weaken.