Microwave-assisted selective demolition of concrete - Microwave-Assisted Concrete Technology: Production, Demolition and Recycling - page 93

Figure 3.5 Selective demolition of concrete using expansive chemical agents.
Furthermore, this method is relatively safer than other conventional demo-
lition methods and may be more economical in certain situations.
The main disadvantage of this method is the relatively long time required
for expansion to occur. Furthermore, the drilling of holes itself has to be
done using conventional methods, which is time consuming with the same
disadvantages associated with conventional demolition techniques.
3.3.4 Hydrodemolition
Hydrodemolition is another common method for the selective demolition
of concrete. This method uses high-pressure water jets to delaminate the
selected surface area of the concrete component. Hydrodemolition is particu-
larly suitable for use in concrete repair applications when a particular area
of surface concrete is to be replaced with a new layer of concrete. This is
because, after demolition, the surface of the remaining concrete is usually left
roughened. The rough surface of the concrete substrate enhances the bond
and the composite action between the substrate concrete and the new concrete.
Hydrodemolition is considered to be a relatively fast and efficient method
for the selective demolition of concrete. The use of water in this method can
provide a healthier environment by suppressing the amount of dust gener-
ated. Hydrodemolition is also particularly effective in separating concrete
from the reinforcing bars and other embedded steel elements in concrete.
However, hydrodemolition also has considerable drawbacks and limita-
tions. One of the main drawbacks of hydrodemolition is related to the huge
amount of wastewater produced and the need for wastewater disposal. The
wastewater produced during hydrodemolition contains fine cement particles
with a pH ranging from 11 to 13 and thus requires special measures prior