Carbon Analysis for Inspecting Carbonation of Concrete Using a TEA CO₂ Laser-Induced Plasma

Abstract

It has been demonstrated that a spectrochemical analysis of carbon using the laser plasma method can be successfully applied to inspect the carbonation of concrete by detecting carbon produced in aged concrete by a chemical reaction of Ca(OH)2 with CO2 gas in environmental air, turning into CaCO3, which induces degradation of the quality of building concrete. A comparative study has been made using a TEA CO2 laser (500-1000 mJ) and a Q-switched Nd-YAG laser (50-200 mJ) to search for the optimum conditions for carbon analysis, proving the advantage of the TEA CO2 laser for this purpose. Also, it was clarified that laser irradiation with suitable defocusing conditions is a crucial point for obtaining high sensitivity in the detection of carbon. Practical experiments on the inspection of carbonation were carried out using both a concrete sample that had been intentionally carbonated by exposure to high concentrations of CO2 gas and a naturally carbonated concrete sample. As a result, good coincidence was observed between the laser method and the ordinary method, which uses the chemical indicator phenolphthalein, implying that this laser technique is applicable as an in situ quantitative method of inspection for carbonation of concrete.

Suppression of self-absorption in laser-induced breakdown spectroscopy using a double pulse orthogonal configuration to create vacuum-like conditions in atmospheric air pressure

“…In our previous publications, which mainly used a single laser in a low pressure surrounding gas, we confirmed that no self-absorption is observed in the emission lines 26 – 40 . We also reported in another publication that the self-absorption effect can be significantly suppressed by applying a double pulse orthogonal configuration in atmospheric He gas.…”

Measurement of Concrete Strength Using the Emission Intensity Ratio between Ca(II) 396.8 nm and Ca(I) 422.6 nm in a Nd:YAG Laser-Induced Plasma

“…The experimental set up used in this work is similar to that used in our previous work except for the laser source. 1 In this experiment, a Nd:YAG laser (Quanta Ray, LAB SERIES, 400 mJ, 5 ns) was operated in the Q-switched mode at a 10 Hz repetition rate with the laser output energy fixed at 50 mJ. The laser beam was focused by a lens (f ¼ 100 mm) through a quartz window onto the sample surface.…”

“…From this point of view, we reported on a new technique for inspecting the carbonation of concrete, which induces its degradation, in terms of TEA CO 2 laser-induced plasma spectroscopy, based on detecting the emission line of C(I) 247.9 nm. 1 On the other hand, concrete hardness (compressive strength) inspection is absolutely important. It is assumed that a laser-induced plasma (LIP) technique could also be used to determine hardness because the plasma characteristics are inherently related to the hardness of the target.…”

Atomic Hydrogen Emission Induced by TEA CO2 Laser Bombardment on Solid Samples at Low Pressure and its Analytical Application

“…The experimental arrangement used in this study is almost similar to that used in our previous work. 15 The TEA CO 2 laser used in this work is a Shibuya SQ-2000 laser, which was developed and constructed by the Shibuya Company for laser marking. The laser light from the TEA CO 2 laser (3 J, 10.6 m, 200 ns), was focused through a ZnSe window onto a sample using a ZnSe lens with a focal length of 100 mm, after the laser energy was reduced to 500 mJ by inserting an aperture in front of the focusing lens.…”