Particle size analysis of material removed during CO2 laser scabbling of concrete for filtration design

Abstract

This article examines the particles formed during optimized laser scabbling of concrete in order to help determine an effective filtration strategy for the process. The laser scabbling technique has been developed for noncontact removal of radioactive contaminated surface concrete layers. Surface layer removal is effected using a high power carbon dioxide laser beam to generate stresses in the substrate (caused by temperature gradients and dehydration) which break up the surface. The material removed will be contaminated with radionuclides and its efficient collection must be ensured to prevent the escape of radioactive contaminated particles. The filtration methods selected depend on the size of the particles produced and transport characteristics in an airflow. The particles removed were examined using a laser diffraction particle sizer (for particles below 80 μm physical diameter) and sieving (above 150 μm physical diameter) to determine the particle size distribution. Scanning electron microscope (SEM) analysis was used to identify the components present. The study found that particles removed were constituents of the parent concrete, there were no signs of melting and a small volume fraction (less than 1%) of sub-100 μm physical particle diameter. Particles with aerodynamic diameters under 100 μm are airborne and those between 1 and 30 μm are inhaled into the thoracic and bronchial tracts and lungs. Efficient filtration is required to capture these particles. However, filtration is difficult in the 0.1–1 μm aerodynamic diameter range, which comprises only 0.02% by volume of the removed material. It is considered that laser scabbling of concrete using this method will produce no additional risks than the use of other surface removal mechanisms.

Understanding the scabbling of concrete using microwave energy

“…The particle size distribution of the scabbled material shown in Figure 16 shows that the total quantity of small particulates is relatively low with only 1.6% of the total material ejected passing 106 μm and 80% larger than 1 mm. The use of a CO 2 laser for concrete scabbing was reported by [44]. They found that less than 1% of the liberated material was sub 100 μm which compares well with these results.…”

Heterogeneous oxidation of sulfur dioxide by ozone on the surface of sodium chloride and its mixtures with other components

“…The prepared powders were enough for all the experiments. The diameter distribution of the ground NaCl powder was determined by a Laser Sizer (MasterSizer 2000, Malvern Instruments, U.K.) [ Lobo et al , 2002; Yang et al , 2002] as around 30 μ m. The Brunauer‐Emmett‐Teller (BET) surface area is usually used to represent the surface area of particles [ Brunauer et al , 1938; Knowles and Hudson , 1995]. The BET surface area of the NaCl powders was determined by a measurement instrument of specific surface area and pore size distribution (ASAP2010, Micromeritics, USA) as 0.81 m 2 g −1 .…”

Laser Surface Blasting of Granite Stones Using a Laser Scanning System

“…In order to overcome these drawbacks, laser technology seems to be a good choice since it has already demonstrated its capability to treat different building materials such as concrete, natural stones, tiles, and rocks [5]. For example, some authors have focused on surface texturing of concrete by laser scabbling [6][7][8] or in marble [9]. Regarding granite, a polished surface was laser treated to be transformed into a non-slip surface by generating micro-craters [10,11] on it.…”