Most contractors, even though not demolition specialists, will have to demolish portions of structures as part of their repair and remodeling business. Knowing which method or combination of methods to use for demolition of reinforced or prestressed concrete structures is essential for a safe and profitable job.
BALL AND CRANE
This is one of the oldest and most commonly used methods for building demolition. A crane uses a wrecking ball, weighing up to 13,500 pounds, which is either dropped onto or swung into the element to be demolished.
Selective or complete demolition of concrete structures is possible by cutting elements and then removing them with a crane. The cutting process may be by sawing, water jetting or thermic lance.
PNEUMATIC AND HYDRAULIC BREAKERS
A common piece of equipment used for demolishing bridge decks, foundations and pavements is a hydraulically or pneumatically operated, boom-mounted breaker. Productivity can vary greatly depending on hammer size, type of concrete, amount of reinforcing and working conditions.
This method of demolition can be classified into two categories, mechanical and chemical bursting. Mechanical bursting is done with a hand-held splitting machine that operates on hydraulic pressure provided by a small motor. Although they are more costly, chemicals may be preferred for pressure bursting. By placing an expansive slurry into boreholes that are located in a predetermined pattern, concrete can be split in a controlled manner for removal.
Blasting methods employ rapidly expanding gases confined within a series of boreholes to produce controlled fractures which provide for easy concrete removal. In general, blasting methods are efficient means of removing large volumes of concrete.