HOW BUILDINGS EXPLOSIONS WORK
You can demolish a stone wall with a sledgehammer, and it’s fairly easy to level a five – story buildings using excavators and wrecking balls. But when you need to bring down a massive structure, say a 20 - storey skyscraper, you have to haul out the big guns. Explosive demolition is the preferred method for safely and efficiently demolishing larger structures.
The basic idea of explosive demolition is quite simple: If you remove the support structure of a building at a certain point, the section of the building above that point will fall down on the part of the building below that point. If this upper section is heavy enough, it will collide with the lower part with sufficient force to cause significant damage. The explosives are just the trigger for the demolition. It’s gravity that brings the building down.
Demolition blasters load explosives on several different levels of the building structure falls down on itself at multiple points. When everything is planned and executed correctly, the total damage of the explosives and falling building material is sufficient to collapse the structure entirely, so cleanup crews are left with only a pile of rubble.
In order to demolish a building safely, blasters must map out each element of the implosion ahead of time. The first step is to examine architectural blueprints of the building, if they can be located, to determine how the building is put together. Next, the blaster crew tours the building (several times), jotting down notes about the support structure on each floor. Once they have gathered all the raw data they need, the blasters hammer out a plan of attack. Drawing from past experiences with similar buildings, they decide what explosives to use, where to position them in the building and how to time their detonations. In some cases, the blasters may develop 3D computer models of the structure so they can test out their plan ahead of time in a virtual world.
The main challenge in bringing a building a building down is controlling which way it falls. Ideally, a blasting crew will be able to tumble the building over on one side, into a parking lot or other open area. This sort of blast is the easiest to execute, and it is generally the safest way to go. Tipping a building over is something like felling a tree. To topple the building to the north, the blasters detonate explosives on the north side of the building first, in the same way you would chop into a tree from the north side if you wanted it to fall in that direction.
Usually, a building is surrounded by structures that must be preserved. In this case, the blasters proceed with a true implosion, demolishing the building so that it collapses straight down into its own footprint. This feat requires such a skill that only a handful of demolition companies in the world will attempt it.
APPLICATION ON NANOTECHNOLOGY IN CONSTRUCTION
Nanotechnology can be used for design and construction processes in many areas since nanotechnology generated products have many unique characteristics. These characteristics can, again, significantly fix current construction problems, and may change the requirement and organization of construction process. These include products that are for: • Lighter and stronger structural material composites
• Low maintenance
• Improving pipe joining materials and techniques
• Better properties of cementitious materials
• Reducing the thermal transfer rate of fire retardant and insulation
•Increasing the sound absorption of acoustic absorber
•Increasing the reflectivity of glass The abbreviated list is not an exhaustive list of applications of nanotechnology in constructions. Some of these applications are examined in detail below.
CONCRETE PRODUCTION
Concrete is one of the most common and widely used construction materials. Its properties have been well studied at macro or structural level without fully understanding the properties of the cementitious materials at the micro level. The rapid development of new experimental techniques makes it possible to study the properties of cementitious materials at micro/nano-scale. Research has been conducted to study the hydration process, alkali-silicate reaction (ASR), and fly ash reactivity using nanotechnology. The better understanding of the structure and behavior of concrete at micro/nano-scale could help to improve concrete properties and prevent the illness, such as ASR.