Microwave-assisted selective demolition of concrete - Microwave-Assisted Concrete Technology: Production, Demolition and Recycling - page 92

Figure 3.4 Handheld hydraulic breaker.
3.3.2 Hydraulic breaker
Handheld hydraulic breakers are also commonly used for the selective
removal of concrete. Such breakers are powered by an auxiliary hydraulic
system that delivers pressurised hydraulic fluids from a hydraulic pump.
A handheld hydraulic breaker is shown in Figure 3.4. In fact, both pneu-
matic and hydraulic breakers are similar in the sense that they both use
fluid power. Pneumatic breakers use an easily compressible gas such as air;
hydraulic breakers use relatively incompressible liquid media such as oils.
Compared to pneumatic breakers, the main advantage of hydraulic breakers
is the fact that, unlike the gases used in pneumatic breakers, the liquid used
in hydraulic breakers do not absorb any of the supplied energy. Hydraulic
breakers are usually capable of providing much higher breaking forces
because of fluid incompressibility, which also minimises spring action.
3.3.3 Expansive agents
Expansive demolition agents are an alternative to conventional mechanical
demolition tools such as hydraulic and pneumatic breakers and explosives.
As shown in Figure 3.5, an array of holes is drilled in selected portions of the
concrete element in order to break up the concrete using expansive agents.
The holes are then filled with a slurry mixture of the expansive demolition
agent and water. The slurry expands gradually and results in relatively high
expansive stresses within the holes, which crack the concrete.
The main advantages of demolition using expansive agents are the reduced
noise and dust pollution as they are silent and do not produce vibration.