Civil Engineering Reference
In-Depth Information
Table 4.4
Comparison of the dosages of the conductive admixtures
NCB
(mass/binder %)
CF
(mass/binder %)
Serial number
Plain concrete (concrete
without conductive
admixture)
PC
0
0
Concrete containing NCB
NCB 01
0.1%
0
NCB 02
0.2%
0
NCB 03
0.3%
0
NCB 04
0.4%
0
Concrete containing CF
CF 04
0
0.4%
CF 08
0
0.8%
CF 10
0
1.0%
CF 13
0
1.3%
CF 16
0
1.6%
Concrete containing BF
(NCB and CF)
BF 14
0.1%
0.4%
BF 18
0.1%
0.8%
BF 24
0.2%
0.4%
BF 28
0.2%
0.8%
m and a
length of 6 mm (Fig. 4.2) was between 0.4% and 1.6% by mass of binder
(2.12-8.48 kg/m
3
). Where CF was used (both alone and in combination with
NCB), methyl-cellulose was used as a dispersing agent along with a defoamer
to optimize the dispersion of carbon fi bre in the concrete (Wen and Chung,
2007). Methyl-cellulose and defoamer were not used in the absence of
carbon fi bre. The defoamer dosage was 2.13 kg/m
3
, and the methyl-cellulose
content was between 2.13 and 8.52 kg/m
3
. The series of electric conductive
concrete samples (CF only, NCB only, hybrid use of CF and NCB) and dif-
ferent contents of conductive phases are listed in Table 4.4.
2.12 kg/m
3
). The carbon fi bre content with a diameter of 12-15
μ
4.2.2 Specimen preparation and testing set-up
Mixing was carried out using a mechanical concrete mixer. Methyl-cellulose
was dissolved in water and the defoamer and CF (if applicable) were added
and stirred manually for around two minutes. The methyl-cellulose mixture,
fi ne aggregate, coarse aggregate, cement, fl y ash, water, NCB and superplas-
ticizer were then mixed for fi ve minutes. The mixture was poured into oiled
moulds and an external electric vibrator was used to facilitate compaction
and to decrease the quantity of air bubbles. The specimens were removed
from the moulds after a day and four electrical contacts in the form of
conductive adhesive tape were wrapped around the specimens. Based on
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