Civil Engineering Reference
In-Depth Information
a) The material is heated up to 100°C in a N
2
atmosphere and
purged by N
2
at 100°C.
b) It is heated in an inert atmosphere from 100° to 750°C,
cooled from 750° to 100°C with a flow of nitrogen.
c) It is then subjected to isothermal treatment at 100°C for 5
minutes with air flow.
d) It is heated in a reactive atmosphere from 100° to 1000°C
in air.
Weight loss at 400-450°C in an inert atmosphere was ascribed to
water loss from Ca(OH)
2
, and that at 600-750°C (inert atmosphere) was
caused by the decomposition of CaCO
3
. The loss of weight in the range of
500-740°C in an oxidizing atmosphere signified oxidation of carbon. Table
2 gives the amounts of lime, calcium carbonate, and unburned carbon
determined in six fly ashes by TG.
[16]
Table 2.
TG Estimation of Calcium Carbonate, Calcium Hydroxide, and
Unburned Carbon in Fly Ashes
Fly Ash No.
Ca(OH)
2
, %
CaCO
3
, %
Unburned Carbon, %
1
0.48
0.40
0.09
2
0.16
0.81
2.83
3
——
0.37
2.39
4
——
0.75
4.86
5
0.76
2.26
1.01
6
1.37
3.19
0.70
(Reprinted with permission from Elsevier Science.)
3.0
SILICA FUME
Silica fume is available in a powdered, condensed, or slurry form.
Powdered silica fume is not easy to use in practice because of dust and other
