Laser Material Processing Division

Laser-assisted Concrete Processing

Importance:

• Laser processing, being non-contact in nature, is capable of remotely performing nuclear decontamination and decommissioning operations with significantly reduced secondary waste generation.
• In many instances radioactive contamination in the concrete lies within a few millimeter thick surface layer and removal of this layer would greatly reduce the volume of the concrete to be disposed.

Objectives: 

• To study the effect of different process parameters like laser power density, size and shape of the laser beam, direction of scanning, laser operation mode (CW or pulsed), composition of the concrete etc. on the efficiency of material removal during CO2 laser beam induced spalling and glazing of concrete surface.
• To extend the process of surface glazing for cutting of 6” thick ground concrete block.
• To study the effect of process parameters on the efficiency of laser beam drilling on a vertical concrete wall.

Highlights:

• Spalling was dominant in cement rich concretes.
• Laser spalling was more dominant in power density range of 40–200 W/cm2.
• Depth of glazed layer increased with laser power and at energy density above 1.5 kJ/cm2.
• At a given laser power, material removal rate was high for large area of the beam.
• At a given laser power density, porosity in the glazed layer decreased with increase in the scan speed.
• By employing the repeated glazing at an optimum scan speed the severance energy for cutting thick concrete sections could be minimized.
• Laser drilling time was minimum at about 20º incidence angle.

Fig. Laser-spalled high density concrete surface.	Fig. Laser-cut 6” thick concrete block with repeated glazing followed by mechanical removal.
Laser-drilled 6" thick concrete block at 200 incidence angle.