Civil Engineering Reference
In-Depth Information
180
Reinforced section
160
Unreinforced section
140
120
100
Reinforcing Bar
80
60
40
20
0
2
4
6
8
10
Distance from the Microwave Exposed Surface (cm)
Figure 3.33
Temperature distribution in reinforced saturated concrete after 5 seconds
of microwave heating at 2.45-GHz frequency and 1.1-MW/m2 incident
power.
Figures 3.33 to 3.35 show the temperature distribution within reinforced
concrete at three different ISM microwave frequencies estimated through
numerical simulation of the representative concrete considered in the pres-
ent chapter. The presence of reinforcing steel bars in concrete usually adds
to the complexity of the analytical models for the estimation of the dis-
tribution of microwaves in concrete. A number of assumptions have been
suggested by various researchers to simplify the interaction between the
microwaves and embedded steel rebars to estimate the energy and thus tem-
perature distribution. The methodology used in such studies as well as the
methodology for estimation of the microwave behaviour in steel-reinforced
concrete is discussed in Chapter 6.
As seen in Figures 3.33 to 3.35, as a result of the increase in microwave
power intensity in the cover concrete caused by reflection by the reinforcing
bars, the presence of reinforcing bars leads generally to a higher tempera-
ture rise within the surface layer of concrete. The effect of the presence of
reinforcing bars on the microwave-assisted demolition process is expected
to decrease with a decrease in the microwave penetration depth. The effect
is especially minimal when the microwave penetration depth is less than
the concrete cover to the embedded reinforcing steel (higher ISM micro-
wave frequencies). The microwave penetration depth may decrease with an
increase in microwave frequency or water content of concrete. As can be
seen in Figures 3.33 and 3.35, the effect of the presence of reinforcing bars
on the temperature distribution generated in saturated concrete for micro-
wave frequencies of 10.6 and 18 GHz is almost negligible.
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