Bursting concrete instead of breaking

The task

Demolishing concrete structures.

The problem

During the renovation of a large warehouse, a temporary concrete retainer was built to support the external walls while the floors were removed and replaced. When the structural work was complete, the retainer, which was 1 m x 1 m in section and ran round the entire 300 m perimeter of the building, had to be removed. Traditionally this is done using small hand-held percussive breakers, as the vibrations from larger plant could damage the building structure. Such small tools have low material removal rates and expose operators to vibration magnitudes in the range of 5 to 20 m/s².

The solution

The main contractor hired a small specialist company to break up the retainer using hydraulic bursting. This involves forcing the concrete apart with a special hydraulic tool inserted into holes specially drilled for the purpose. Although the bursting process itself does not expose the operator to any vibration, in this case the holes were made with a rock drill which would have exposed the operator to vibration magnitudes as high as 15 m/s². The rock drill works fast, so the total daily exposure time was only about 10 minutes, which would give a potential vibration exposure of about 2 m/s² A(8). Vibration exposure could be eliminated altogether by using a clamp-mounted diamond core drill to make the holes. This would take slightly longer than the rock drill.

The cost

The rock drill and bursting method cost approximately 30% more than using breakers. The diamond drill and bursting method cost approximately twice that of using breakers.

The result

• The daily exposure time of the operators is reduced. This method is much quicker than equivalent low impact methods.
• Very low vibration magnitudes are transmitted to the building structure.
• Bursting produces very low noise levels and less dust and flying debris than pneumatic breakers.

Case courtesy of Specialist Services (Cutting and Drilling) Ltd