Product Code: ICAL08_P146

Laser Concrete Ablation Scaling Effects
Authors:
D.O. Maccallum, Sandia National Laboratories; Albuquerque NM USA
J.T. Norris, Sandia National Laboratories; Albuquerque NM USA
Presented at ICALEO 2008

Surface scabbling of concrete by laser processing has been demonstrated in the literature for large-area problems (~50 mm wide x 10 deep) using physically large, high-power consumption, multi-kW CW laser systems. With large spot diameters (~50 mm) and low power densities (~ 300 W/cm2), large volume thermal stresses are induced which promote concrete cracking. This process is highly power-density and heat-input (J/m) dependent. Too high power densities cause melting and generate potentially toxic fumes by vaporizing the cement matrix material. New applications require concrete removal with more portable, lower power equipment, and low particulate and fume generation. Recent results investigating the process for small-area (~ 2 x 2 mm) removal are examined and discussed. Tests performed were limited to < 700W output power. Ablation via thermal cracking was observed at larger spot sizes but as the spot size approached 10 mm (with constant power density) ablation ceased and melting predominated. Scaling effects involving temperature gradients through the ITZ (Interfacial Transition Zone), the probability of including an ITZ in the beam path at decreasing spot sizes, and the gradient effects on bulk properties between rock and sand zones will be presented and discussed.