Page 28 - Curriculum Visions Dynamic Book

Peaceful explosions
People often associate explosives with death and wanton destruction. However, the vast majority of explosives are used for peaceful purposes, such as to blast rock from quarries or to demolish buildings without damaging the surrounding area.
All explosives decompose to release both gas and heat. It is often thought that, because of this, explosives cause fires. However, explosives are often used to put out fires, such as when burning oil wells have to be capped. Here, the expanding nitrogen gas deprives the burning oil of the oxygen it needs to keep burning and so the flame goes out. At the same time any hot material is thrown clear so it cannot reignite the oil. The oil will then continue to gush, but will not relight.
Explosives used for demolition
Different explosives are suited to different types of building. RDX (see page 27)
is the main explosive used for demolishing skyscrapers with steel frames. Dynamite is used to demolish reinforced concrete buildings.
Most demolition experts use relatively small charges placed in holes drilled into the structure. Demolition aims to achieve a progressive collapse of the structure so that it falls in on itself without creating too much dust.
 A large road bridge is demolished using explosives.
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