In concrete repair work usually damaged, deteriorated or defective portion have to be removed and in most cases damaged portions are hardly defined. Most recommendation state that deteriorated or damaged material must be removed completely.
It is very difficult to determine that all such portions are removed or excess amount are removed (i.e. some sound concrete is removed). A recommendation is to continuing removal until aggregate (coarse aggregate) particles are broken down under removal process instead of removal of cement matrix (which is relatively simpler than breaking down of aggregate).
But when low strength concrete is damaged, the aggregate may never fractured under demolition. Here we will learn about milling methods of concrete removal. This method is suitable for removing concrete from both vertical and horizontal surfaces; especially when specific amount from large concrete member.
The depth of removal may range from 3 mm to 100 mm approximately. This method usually produce sound concrete surface free from microcracks.
Usually scarifiers are used in these purposes. It is a cutting tool that uses rotary action with its mass of cutter bits. The rout cutting into concrete surface removes loose fragments of concrete like scaling from blasted surface. Weakened concrete (by any expansive agent) or previously cracked concrete can be successfully removed by this method.
Scarifiers of various sizes are available. Other advantages of this tool are:
- Controlled removal of concrete to defined limit.
- Simple in operation
- Debris produced is relatively small which can be handled easily.
- Both sound and deteriorated concrete containing wire mesh and ties (from formwork) can be removed.
- Applicable for decks, slabs and for mass concrete.
- Broom-mounted cutters can be used to remove concrete from ceiling and walls
Some limitations are as follows:
- Concrete with reinforcement cannot removed
- Removal rate becomes very low when applied to sound concrete
- Noise, dust and vibration are produced
- Concrete having microcracks can be damaged.