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Demolition Methods


Details of the various methods utilised in demolition and dismantling work:

Pneumatic and Hydraulic Breakers

Often used in concrete demolition projects involving bridge decks, foundations and pavement, hand-held or boom mounted pneumatic and hydraulic breakers are currently the tools of choice.

The amount of work accomplished using these methods depends on the hammer size, strength of the concrete, the amount of steel reinforcing used in the concrete, and working conditions.

Machine-mounted breakers are able to deliver a range of 100 to 20,000 foot-pounds at 300 to 800 blows per minute. Machine-mounted breakers may utilize:
  • A telescoping boom for easy reach and maneuverability
  • Remote control operation
  • Underwater demolition capabilities
  • Some limitations of machine-mounted breakers include the generation of noise, dust and vibration.

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Dismantling

By cutting concrete elements, and then removing them by crane, the demolition of an entire concrete structure may be carried out with a minimum of noise, dust, and impact on surrounding structures.

This may be done by Sawing, Water-Jetting or Thermic Lance, and is a particularly good method of demolishing portions of a structure, especially portions of walls or slabs.
Water-jetting
  • Minimizes dust and eliminates dust and fire hazards
  • Can be used to cut both straight lines and contours
  • Requires the use of an abrasive and water-catching system during the cutting process
Thermic lance
  • Excessive heat causes some deterioration of the concrete adjacent to the cutting
  • Works particularly well in the presence of reinforcing steel
  • Eliminates vibration and dust problems
  • May create smoke and fire hazards

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Pressure Bursting, Mechanical Bursting and Chemical Bursting

Pressure bursting can be used in cases where relatively quiet, dust-free, controlled demolition is preferred.

Both mechanical and chemical pressure bursting split the concrete, either with a splitting machine operating on hydraulic pressure provided by a motor in the case of mechanical bursting, or through the insertion of an expansive slurry into a pre-determined pattern of boreholes in the case of chemical bursting.

The split concrete is then easily removed, either by hand or by crane. Hydraulic and chemical pressure bursting break up concrete structures with a minimum of noise and flying debris. Both methods work by applying lateral forces against the inside of holes drilled into the concrete, and can do virtually any job other demolition methods are capable of. However, rather than shattering the concrete into bits as dynamite and impact tools would, the lateral forces build up over time to crack the concrete into smaller sections.
Mechanical bursting highlights
  • Inexpensive, quiet, no vibration
  • Initial drilling of holes for splitter does produce some noise and vibration
  • Diamond-tipped coring machine greatly reduces noise and vibration during hole drilling, but is much more expensive
  • Controlling crack direction and movement of demolished concrete can be difficult
  • Hand-held or machine-mounted breaker may be needed to expose reinforcing bars for cutting
Chemical bursting highlights
  • More costly method of pressure bursting
  • Can split concrete in a controlled manner
  • In excess of 4300 psi of expansive pressure may be generated to produce concrete cracking within 10 to 20 hours
  • Quiet, no vibration, little or no dust
  • Temperature sensitive : freezing greatly reduces effectiveness

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Explosives

Explosives are generally used for removing large volumes of concrete via insertion of explosive devices in a series of boreholes:
  • Versatile and flexible in terms of work output
  • Vibration and air blast may damage surrounding structures
  • Heightened safety considerations involved when compared to other demolition methods

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Ball and Crane for Demolishing Masonry and Concrete Structures

One of the oldest and most commonly used methods for building demolition, the ball and crane uses a wrecking ball weighing up to 13,500 pounds to demolish concrete and masonry structures. During the process, the ball is either dropped onto or swung into the structure that is to be demolished.

The ball and crane, however, is not suitable for all demolition applications. Some limitations:
  • While the concrete can be broken into rather small pieces, additional work in the form of cutting rebar may be necessary.
  • Only highly skilled and experienced crane operators should be used on ball and crane demolition projects -- smoothness in controlling the swing of the ball is important since missing the target may tip or overload the crane and a mild swing-back may cause the ball to hit the boom.
  • The size of the building that can be demolished with this method is limited by crane size and working room, including proximity to power lines.
  • This form of demolition creates a great deal of dust, vibration and noise.

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Mechanical Demolition & Dismantling

The intricacy of the demolition process is a function of the size and complexity of each project. For the times when explosive demolition is not appropriate, mechanical methods are applied. Small scale demolition projects involving low-rise structures can be carried out using ordinary machinery, methods and equipment. Larger structures and complex projects require more extensive planning as well as specialised procedures, equipment and machinery.

When valued assets are present at the demolition site it is essential to recover these items in order to lessen the cost of demolition to the client. This often involves careful dismantling of plant and equipment to recover the assets for reuse by the client. Alternatively, Amity Contractors will purchase the entire plant and its equipment and carry out a turnkey project involving purchase and removal of the plant and equipment and demolition of the site which leaves the client with a rehabilitated site.

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Please contact us for any kind of demolition and dismantling work for your site.
 
 

Escorts Limited
Dismantling of Menz office and disposal of material

Smithkline Becham
Dismantling of office & disposal of material

Relaxo Footwear Limited
Demolition & disposal of fire damaged three floors building with basement

 
 
 
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