Environmental Engineering Reference
In-Depth Information
0.12
PC
0.10
0.08
ABSC
0.06
0.04
0.02
0
10 100 1000 10000 100000
Pore radius, (A)
FIGURE 4.3
Cumulative pore volume of portland cement (PC) and alkali-activated slag
cement (ABSC) pastes at 28 days.
4
Cs is a difficult radionuclide to stabilize in radioactive wastes. Cesium leach-
ability from portland cement and alkali-activated slag cements were measured using
a standard semidynamic test in which monolithic samples are suspended in deionized
water in Teflon containers at the testing temperature, these samples are transferred
to other containers with fresh dionized water at specified intervals and the leachate
cesium concentrations are measured.
4
The cesium leachability, L
t
(cm
-1
), at time t
was calculated using the following equation:
L
t
= (a
t
/A) · (F/V)
where:
a
t
- mass of leached Cs
+
at time t (g);
A - total original mass of Cs
+
in the specimens (g);
F - total surface area of the monolithic specimens (cm
2
);
V - volume of the monolithic specimens (cm
3
).
Figure 4.4 shows a higher cesium L
t
(cm
-1
) from portland cement than from alkali-
activated slag cement for 0.5 wt% CsNO
3
loading after 28 days of moist curing at
25°C.
0.30
0.25
0.20
0.15
0.10
0.05
0
0.30
0.25
0.20
0.15
0.10
0.05
0
25
°
C
70
°
C
25
°
C
70
°
C
5 10 15 20 25 30 35 40 45 50
5 10 15 20 25 30 35 40 45 50
Leaching Time (days)
Leaching Time (days)
a b
FIGURE 4.4
Leached fraction of Cs
+
in hardened portland and alkali-activated slag cement
pastes.
4
(a) portland cement pastes, (b) alkali-activated slag cement pastes.
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