Efficiency of concrete removal with a pulsed Nd:YAG laser

The mechanism and efficiency of ablating concrete surfaces with a pulsed Nd:YAG laser were studied. Ablation efficiency and material removal rates were determined as functions of irradiance and pulse overlap. The ablation mechanism was dominated by fragmentation and disaggregation of the concrete. The ablation efficiency was insensitive to peak laser irradiance over a range from 0.2 to 4.4 MW/cm2. Excessive pulse overlap (>60%) caused a significant decrease in ablation efficiency by inducing melting. In concrete samples, the cement phase of the material responds in various ways to the laser energy, including disaggregation, melting, and vaporization, but the aggregate portion (sand and rock) mostly fragments. The ablation effluent therefore consists of both micron-size aerosol particles and chunks of fragmented aggregate material.